PIC18F23K20/24K20/25K20/26K20/

43K20/44K20/45K20/46K20
Data Sheet
28/40/44-Pin Flash Microcontrollers
with nanoWatt XLP Technology

 2010 Microchip Technology Inc. DS41303G

Note the following details of the code protection feature on Microchip devices:
• Microchip products meet the specification contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.

• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

• Microchip is willing to work with the customer who is concerned about the integrity of their code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.

Information c ontained in t his p ublication regarding d evice Trademarks

applications and the like is provided only for your convenience
The Microchip name and logo, the Microchip logo, dsPIC,
and may be superseded by updates. It is your responsibility to KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART,
ensure that yo ur ap plication me ets wi th yo ur sp ecifications.
rfPIC and UNI/O are registered trademarks of Microchip
MICROCHIP MAKES N O R EPRESENTATIONS OR Technology Incorporated in the U.S.A. and other countries.
WARRANTIES OF AN Y KIN D W HETHER EXPRESS OR
IMPLIED, WR ITTEN O R O RAL, ST ATUTORY OR FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
OTHERWISE, RE LATED T O T HE I NFORMATION, MXDEV, MXLAB, SEEVAL and The Embedded Control
INCLUDING B UT NOT L IMITED T O IT S C ONDITION, Solutions Company are registered trademarks of Microchip
QUALITY, PE RFORMANCE, M ERCHANTABILITY OR Technology Incorporated in the U.S.A.
FITNESS FOR PU RPOSE. Microchip dis claims al l lia bility Analog-for-the-Digital Age, Application Maestro, CodeGuard,
arising f rom t his i nformation an d its use. U se o f Microchip dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,
devices in li fe su pport a nd/or safety ap plications is e ntirely at ECONOMONITOR, FanSense, HI-TIDE, In-Circuit Serial
the buyer’s risk, and the buyer agrees to defend, indemnify and Programming, ICSP, Mindi, MiWi, MPASM, MPLAB Certified
hold h armless M icrochip f rom a ny an d al l da mages, c laims, logo, MPLIB, MPLINK, mTouch, Octopus, Omniscient Code
suits, o r e xpenses re sulting f rom s uch u se. No li censes are Generation, PICC, PICC-18, PICDEM, PICDEM.net, PICkit,
conveyed, im plicitly or ot herwise, under an y M icrochip PICtail, PIC32 logo, REAL ICE, rfLAB, Select Mode, Total
intellectual property rights. Endurance, TSHARC, UniWinDriver, WiperLock and ZENA
are trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated
in the U.S.A.
All other trademarks mentioned herein are property of their
respective companies.
© 2010, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.

Microchip received ISO/TS-16949:2002 certification for its worldwide

headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.

DS41303G-page 2  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
28/40/44-Pin Flash Microcontrollers
with nanoWatt XLP Technology

High-Performance RISC CPU: Extreme Low-Power Management

• C Compiler Optimized Architecture: with nanoWatt XLP:
- Optional extended instruction set designed to • Sleep mode: < 100 nA @ 1.8V
optimize re-entrant code • Watchdog Timer: < 800 nA @ 1.8V
• Up to 1024 bytes Data EEPROM
• Timer1 Oscillator: < 800 nA @ 32 kHz and 1.8V
• Up to 64 Kbytes Linear Program Memory
Addressing Analog Features:
• Up to 3936 bytes Linear Data Memory Addressing
• Up to 16 MIPS Operation • Analog-to-Digital Converter (ADC) module:
• 16-bit Wide Instructions, 8-bit Wide Data Path - 10-bit resolution, 13 External Channels
• Priority Levels for Interrupts - Auto-acquisition capability
• 31-Level, Software Accessible Hardware Stack - Conversion available during Sleep
• 8 x 8 Single-Cycle Hardware Multiplier - 1.2V Fixed Voltage Reference (FVR) channel
Flexible Oscillator Structure: - Independent input multiplexing
• Analog Comparator module:
• Precision 16 MHz Internal Oscillator Block: - Two rail-to-rail analog comparators
- Factory calibrated to ± 1%
- Independent input multiplexing
- Software selectable frequencies range of
31 kHz to 16 MHz • Voltage Reference (CVREF) module
- 64 MHz performance available using PLL – - Programmable (% VDD), 16 steps
no external components required - Two 16-level voltage ranges using VREF pins
• Four Crystal modes up to 64 MHz
Peripheral Highlights:
• Two External Clock modes up to 64 MHz
• 4X Phase Lock Loop (PLL) • Up to 35 I/O Pins plus 1 Input-only Pin:
• Secondary Oscillator using Timer1 @ 32 kHz - High-Current Sink/Source 25 mA/25 mA
• Fail-Safe Clock Monitor: - Three programmable external interrupts
- Allows for safe shutdown if peripheral clock - Four programmable interrupt-on-change
stops - Eight programmable weak pull-ups
- Two-Speed Oscillator Start-up - Programmable slew rate
• Capture/Compare/PWM (CCP) module
Special Microcontroller Features: • Enhanced CCP (ECCP) module:
• Operating Voltage Range: 1.8V to 3.6V - One, two or four PWM outputs
• Self-Programmable under Software Control - Selectable polarity
• Programmable 16-Level High/Low-Voltage - Programmable dead time
Detection (HLVD) module: - Auto-Shutdown and Auto-Restart
- Interrupt on High/Low-Voltage Detection • Master Synchronous Serial Port (MSSP) module
• Programmable Brown-out Reset (BOR): - 3-wire SPI (supports all 4 modes)
- With software enable option - I2C™ Master and Slave modes with address
• Extended Watchdog Timer (WDT): mask
- Programmable period from 4 ms to 131s • Enhanced Universal Synchronous Asynchronous
• Single-Supply 3V In-Circuit Serial Receiver Transmitter (EUSART) module:
Programming™ (ICSP™) via Two Pins - Supports RS-485, RS-232 and LIN
• In-Circuit Debug (ICD) via Two Pins - RS-232 operation using internal oscillator
- Auto-Wake-up on Break
- Auto-Baud Detect

 2010 Microchip Technology Inc. DS41303G-page 3

PIC18F2XK20/4XK20
-

EUSART
Program Memory Data Memory 10-bit CCP/ MSSP
(1) Timers
Device Flash # Single-Word SRAM EEPROM I/O A/D ECCP Master Comp.
SPI 8/16-bit
(bytes) Instructions (bytes) (bytes) (ch)(2) (PWM) I2C™
PIC18F23K20 8K 4096 512 256 25 11 1/1 Y Y 1 2 1/3
PIC18F24K20 16K 8192 768 256 25 11 1/1 Y Y 1 2 1/3
PIC18F25K20 32K 16384 1536 256 25 11 1/1 Y Y 1 2 1/3
PIC18F26K20 64k 32768 3936 1024 25 11 1/1 Y Y 1 2 1/3
PIC18F43K20 8K 4096 512 256 36 14 1/1 Y Y 1 2 1/3
PIC18F44K20 16K 8192 768 256 36 14 1/1 Y Y 1 2 1/3
PIC18F45K20 32K 16384 1536 256 36 14 1/1 Y Y 1 2 1/3
PIC18F46K20 64k 32768 3936 1024 36 14 1/1 Y Y 1 2 1/3
Note 1: One pin is input only.
2: Channel count includes internal fixed voltage reference channel.

DS41303G-page 4  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
Pin Diagrams
28-pin PDIP, SOIC, SSOP
MCLR/VPP/RE3 1 28 RB7/KBI3/PGD
RA0/AN0/C12IN0- 2 27 RB6//KBI2/PGC
RA1/AN1/C12IN1- 3 26 RB5/KBI1/PGM
RA2/AN2/VREF-/CVREF/C2IN+ 4 25 RB4/KBI0/AN11/P1D

PIC18F23K20
PIC18F24K20
PIC18F25K20
PIC18F26K20
RA3/AN3/VREF+/C1IN+ 5 24 RB3/AN9/C12IN2-/CCP2(1)
RA4/T0CKI/C1OUT 6 23 RB2/INT2/AN8/P1B
RA5/AN4/SS/HLVDIN/C2OUT 7 22 RB1/INT1/AN10/C12IN3-/P1C
VSS 8 21 RB0/INT0/FLT0/AN12
OSC1/CLKIN/RA7 9 20 VDD
OSC2/CLKOUT/RA6 10 19 VSS
RC0/T1OSO/T13CKI 11 18 RC7/RX/DT
RC1/T1OSI/CCP2(1) 12 17 RC6/TX/CK
RC2/CCP1/P1A 13 16 RC5/SDO
RC3/SCK/SCL 14 15 RC4/SDI/SDA

40-pin PDIP
MCLR/VPP/RE3 1 40 RB7/KBI3/PGD
RA0/AN0/C12IN0- 2 39 RB6/KBI2/PGC
RA1/AN1/C12IN1- 3 38 RB5/KBI1/PGM
RA2/AN2/VREF-/CVREF/C2IN+ 4 37 RB4/KBI0/AN11
RA3/AN3/VREF+/C1IN+ 5 36 RB3/AN9/C12IN2-/CCP2(1)
RA4/T0CKI/C1OUT 6 35 RB2/INT2/AN8
RA5/AN4/SS/HLVDIN/C2OUT 7 34 RB1/INT1/AN10/C12IN3-
RE0/RD/AN5 8 33 RB0/INT0/FLT0/AN12
PIC18F43K20
PIC18F44K20
PIC18F45K20
RE1/WR/AN6 9 PIC18F46K20 32 VDD
RE2/CS/AN7 10 31 VSS
VDD 11 30 RD7/PSP7/P1D
VSS 12 29 RD6/PSP6/P1C
OSC1/CLKIN/RA7 13 28 RD5/PSP5/P1B
OSC2/CLKOUT/RA6 14 27 RD4/PSP4
RC0/T1OSO/T13CKI 15 26 RC7/RX/DT
RC1/T1OSI/CCP2(1) 16 25 RC6/TX/CK
RC2/CCP1/P1A 17 24 RC5/SDO
RC3/SCK/SCL 18 23 RC4/SDI/SDA
RD0/PSP0 19 22 RD3/PSP3
RD1/PSP1 20 21 RD2/PSP2
RB4/KBI0/AN11/P1D
RA1/AN1/C12IN1-
RA0/AN0/C12IN0-
MCLR/VPP/RE3

RB5/KBI1/PGM
RB7/KBI3/PGD
RB6/KBI2/PGC

28-pin QFN/UQFN(2)

28 27 26 25 24 23 22
RA2/AN2/VREF-/CVREF/C2IN+ 1 21 RB3/AN9/C12IN2-/CCP2(1)
RA3/AN3/VREF+/C1IN+ 2 PIC18F23K20 20 RB2/INT2/AN8/P1B
RA4/T0CKI/C1OUT 3 PIC18F24K20 19 RB1/INT1/AN10/C12IN3-/P1C
RA5/AN4/SS/HLVDIN/C2OUT 4 18 RB0/INT0/FLT0/AN12
VSS 5
PIC18F25K20 VDD
17
OSC1/CLKIN/RA7 6 PIC18F26K20 16 VSS
OSC2/CLKOUT/RA6 7 15 RC7/RX/DT
8 9 10 11 12 13 14
RC0/T1OSO/T13CKI

RC5/SDO
RC1/T1OSI/CCP2(1)

RC4/SDI/SDA
RC2/CCP1/P1A
RC3/SCK/SCL

RC6/TX/CK

Note 1: RB3 is the alternate pin for CCP2 multiplexing.

2: UQFN package availability applies only to PIC18F23K20.

 2010 Microchip Technology Inc. DS41303G-page 5

PIC18F2XK20/4XK20
Pin Diagrams (Cont.’d)

RC1/T1OSI/CCP2(1)
44-pin TQFP

RC2/CCP1/P1A
RC3/SCK/SCL
RC4/SDI/SDA
RC6/TX/CK

RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC5/SDO

NC
44
43
42
41
40
39
38
37
36
35
34
RC7/RX/DT 1 33 NC
RD4/PSP4 2 32 RC0/T1OSO/T13CKI
RD5/PSP5/P1B 3 31 OSC2/CLKOUT/RA6
RD6/PSP6/P1C 4 PIC18F43K20 30 OSC1/CLKIN/RA7
RD7/PSP7/P1D 5 PIC18F44K20 29 VSS
VSS 6 28 VDD
VDD 7
PIC18F45K20 27 RE2/CS/AN7
RB0/INT0/FLT0/AN12 8 PIC18F46K20 26 RE1/WR/AN6
RB1/INT1/AN10/C12IN3- 9 25 RE0/RD/AN5
RB2/INT2/AN8 10 24 RA5/AN4/SS/HLVDIN/C2OUT
RB3/AN9/C12IN2-/CCP2(1) 11 23 RA4/T0CKI/C1OUT
12
13
14
15
16
17
18
19
20
21
22
RA2/AN2/VREF-/CVREF/C2IN+
NC
NC

RB6/KBI2/PGC
RB7/KBI3/PGD

RA3/AN3/VREF+/C1IN+
RB4/KBI0/AN11
RB5/KBI1/PGM

MCLR/VPP/RE3
RA0/AN0/C12IN0-
RA1/AN1/C12IN1-

RC1/T1OSI/CCP2(1)
RC0/T1OSO/T13CKI
RC2/CCP1/P1A
RC3/SCK/SCL
RC4/SDI/SDA
RC6/TX/CK

RD3/PSP3
RD2/PSP2
RD1/PSP1
RD0/PSP0
RC5/SDO

44-pin QFN
44
43
42
41
40
39
38
37
36
35
34

RC7/RX/DT 1 33 OSC2/CLKOUT/RA6
RD4/PSP4 2 32 OSC1/CLKIN/RA7
RD5/PSP5/P1B 3 31 VSS
RD6/PSP6/P1C 4 PIC18F43K20 30 VSS
RD7/PSP7/P1D 5 PIC18F44K20 29 VDD
VSS 6 28 VDD
VDD PIC18F45K20 27 RE2/CS/AN7
7
VDD 8 PIC18F46K20 26 RE1/WR/AN6
RB0/INT0/FLT0/AN12 9 25 RE0/RD/AN5
RB1/INT1/AN10/C12IN3- 10 24 RA5/AN4/SS/HLVDIN/C2OUT
RB2/INT2/AN8 11 23 RA4/T0CKI/C1OUT
12
13
14
15
16
17
18
19
20
21
22
RA2/AN2/VREF-/CVREF/C2IN+
RB3/AN9/C12IN2-/CCP2(1)

RB5/KBI1/PGM
RB4/KBI0/AN11

MCLR/VPP/RE3
RA0/AN0/C12IN0-
RA1/AN1/C12IN1-
NC

RB6/KBI2/PGC
RB7/KBI3/PGD

RA3/AN3/VREF+/C1IN+

Note 1: RB3 is the alternate pin for CCP2 multiplexing.

DS41303G-page 6  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1: PIC18F4XK20 PIN SUMMARY

Comparator

Reference

Interrupts
TQFP Pin

EUSART
QFN Pin
DIL Pin

Analog

Pull-up
Timers
MSSP
ECCP

Basic
Slave
I/O
2 19 19 RA0 AN0 C12IN0- — — — — — — — — —
3 20 20 RA1 AN1 C12IN1- — — — — — — — — —
4 21 21 RA2 AN2 C2IN+ VREF-/ — — — — — — — —
CVREF
5 22 22 RA3 AN3 C1IN+ VREF+ — — — — — — — —
6 23 23 RA4 C1OUT — — — — T0CKI — — — —
7 24 24 RA5 AN4 C2OUT HLVDIN — — SS — — — — —
14 31 33 RA6 — — — — — — — — — — OSC2/
CLKOUT
13 30 32 RA7 — — — — — — — — — — OSC1/CLKIN
33 8 9 RB0 AN12 — — FLT0 — — — — INT0 Yes —
34 9 10 RB1 AN10 C12IN3- — — — — — — INT1 Yes —
35 10 11 RB2 AN8 — — — — — — — INT2 Yes —
36 11 12 RB3 AN9 C12IN2- — CCP2(1) — — — — — Yes —
37 14 14 RB4 AN11 — — — — — — — KBI0 Yes —
38 15 15 RB5 — — — — — — — — KBI1 Yes PGM
39 16 16 RB6 — — — — — — — — KBI2 Yes PGC
40 17 17 RB7 — — — — — — — — KBI3 Yes PGD
15 32 34 RC0 — — — — — — T1OSO/ — — — —
T13CKI
16 35 35 RC1 — — — CCP2(2) — — T1OSI — — — —
17 36 36 RC2 — — — CCP1/ — — — — — — —
P1A
18 37 37 RC3 — — — — — SCK/ — — — — —
SCL
23 42 42 RC4 — — — — — SDI/ — — — — —
SDA
24 43 43 RC5 — — — — — SDO — — — — —
25 44 44 RC6 — — — — TX/CK — — — — — —
26 1 1 RC7 — — — — RX/DT — — — — — —
19 38 38 RD0 — — — — — — — PSP0 — — —
20 39 39 RD1 — — — — — — — PSP1 — — —
21 40 40 RD2 — — — — — — — PSP2 — — —
22 41 41 RD3 — — — — — — — PSP3 — — —
27 2 2 RD4 — — — — — — — PSP4 — — —
28 3 3 RD5 — — — P1B — — — PSP5 — — —
29 4 4 RD6 — — — P1C — — — PSP6 — — —
30 5 5 RD7 — — — P1D — — — PSP7 — — —
8 25 25 RE0 AN5 — — — — — — RD — — —
9 26 26 RE1 AN6 — — — — — — WR — — —
10 27 27 RE2 AN7 — — — — — — CS — — —
1 18 18 RE3(3) — — — — — — — — — — MCLR/VPP
11 7 7 — — — — — — — — — — — VDD
32 28 28 — — — — — — — — — — — VDD
12 6 6 — — — — — — — — — — — VSS
31 29 30 — — — — — — — — — — — VSS
– NC 8 — — — — — — — — — — — VDD
– NC 29 — — — — — — — — — — — VDD
–- NC 31 — — — — — — — — — — — VSS
Note 1: CCP2 multiplexed with RB3 when CONFIG3H<0> = 0
2: CCP2 multiplexed with RC1 when CONFIG3H<0> = 1
3: Input-only.

 2010 Microchip Technology Inc. DS41303G-page 7

PIC18F2XK20/4XK20
TABLE 2: PIC18F2XK20 PIN SUMMARY

Comparator

Reference
Pin QUAD

Interrupts
EUSART
Pin DIL

Analog

Pull-up
Timers
MSSP
ECCP

Basic
Slave
I/O
2 27 RA0 AN0 C12IN0-
3 28 RA1 AN1 C12IN1-
4 1 RA2 AN2 C2IN+ VREF-/
CVREF
5 2 RA3 AN3 C1IN+ VREF+
6 3 RA4 C1OUT T0CKI
7 4 RA5 AN4 C2OUT HLVDIN SS
10 7 RA6 OSC2/
CLKOUT
9 6 RA7 OSC1/
CLKIN
21 18 RB0 AN12 FLT0 INT0 Yes
22 19 RB1 AN10 C12IN3- P1C INT1 Yes
23 20 RB2 AN8 P1B INT2 Yes
24 21 RB3 AN9 C12IN2- CCP2(1) Yes
25 22 RB4 AN11 P1D KBI0 Yes
26 23 RB5 KBI1 Yes PGM
27 24 RB6 KBI2 Yes PGC
28 25 RB7 KBI3 Yes PGD
11 8 RC0 T1OSO/
T13CKI
12 9 RC1 CCP2(2) T1OSI
13 10 RC2 CCP1/
P1A
14 11 RC3 SCK/
SCL
15 12 RC4 SDI/
SDA
16 13 RC5 SDO
17 14 RC6 TX/CK
18 15 RC7 RX/DT
1 26 RE3(3) MCLR/
VPP
8 5 VSS
19 16 VSS
20 17 VDD
Note 1: CCP2 multiplexed with RB3 when CONFIG3H<0> = 0
2: CCP2 multiplexed with RC1 when CONFIG3H<0> = 1
3: Input-only

DS41303G-page 8  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
Table of Contents
1.0 Device Overview ....................................................................................................................................................................... 11
2.0 Oscillator Module (With Fail-Safe Clock Monitor)...................................................................................................................... 27
3.0 Power-Managed Modes ............................................................................................................................................................ 43
4.0 Reset ......................................................................................................................................................................................... 51
5.0 Memory Organization ................................................................................................................................................................ 65
6.0 Flash Program Memory............................................................................................................................................................. 89
7.0 Data EEPROM Memory ............................................................................................................................................................ 99
8.0 8 x 8 Hardware Multiplier......................................................................................................................................................... 105
9.0 Interrupts ................................................................................................................................................................................. 107
10.0 I/O Ports .................................................................................................................................................................................. 121
11.0 Capture/Compare/PWM (CCP) Modules ................................................................................................................................ 143
12.0 Timer0 Module ........................................................................................................................................................................ 155
13.0 Timer1 Module ........................................................................................................................................................................ 159
14.0 Timer2 Module ........................................................................................................................................................................ 167
15.0 Timer3 Module ........................................................................................................................................................................ 169
16.0 Enhanced Capture/Compare/PWM (ECCP) Module............................................................................................................... 173
17.0 Master Synchronous Serial Port (MSSP) Module ................................................................................................................... 193
18.0 Enhanced Universal Synchronous Asynchronous Receiver Transmitter (EUSART) .............................................................. 237
19.0 Analog-to-Digital Converter (ADC) Module ............................................................................................................................. 265
20.0 Comparator Module................................................................................................................................................................. 279
21.0 Voltage References................................................................................................................................................................. 289
22.0 High/Low-Voltage Detect (HLVD)............................................................................................................................................ 293
23.0 Special Features of the CPU................................................................................................................................................... 299
24.0 Instruction Set Summary ......................................................................................................................................................... 315
25.0 Development Support.............................................................................................................................................................. 365
26.0 Electrical Characteristics ......................................................................................................................................................... 369
27.0 DC and AC Characteristics Graphs and Tables...................................................................................................................... 403
28.0 Packaging Information............................................................................................................................................................. 427
Appendix A: Revision History............................................................................................................................................................ 441
Appendix B: Device Differences ....................................................................................................................................................... 442
Index ................................................................................................................................................................................................. 443
The Microchip Web Site .................................................................................................................................................................... 453
Customer Change Notification Service ............................................................................................................................................. 453
Customer Support ............................................................................................................................................................................. 453
Reader Response ............................................................................................................................................................................. 454
Product Identification System ........................................................................................................................................................... 455

 2010 Microchip Technology Inc. DS41303G-page 9

PIC18F2XK20/4XK20

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DS41303G-page 10  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
1.0 DEVICE OVERVIEW 1.1.2 MULTIPLE OSCILLATOR OPTIONS
AND FEATURES
This document contains device specific information for
the following devices: All o f th e devices i n th e PIC18F2XK20/4XK20 family
offer ten d ifferent os cillator op tions, all owing us ers a
• PIC18F23K20 • PIC18F43K20 wide r ange o f ch oices in de veloping a pplication
• PIC18F24K20 • PIC18F44K20 hardware. These include:
• PIC18F25K20 • PIC18F45K20 • Four Crystal modes, using crystals or ceramic
• PIC18F26K20 • PIC18F46K20 resonators
• Two External Clock modes, offering the option of
This fam ily of fers th e ad vantages of a ll PI C18
using two pins (oscillator input and a divide-by-4
microcontrollers – na mely, hig h computational
clock output) or one pin (oscillator input, with the
performance at an economical price – with the addition
second pin reassigned as general I/O)
of high-endurance, Flash program memory. On top of
these fea tures, the PIC18F2XK20/4XK20 fam ily • Two External RC Oscillator modes with the same
introduces d esign en hancements t hat make t hese pin options as the External Clock modes
microcontrollers a log ical ch oice for many hig h- • An internal oscillator block which contains a
performance, power sensitive applications. 16 MHz HFINTOSC oscillator and a 31 kHz
LFINTOSC oscillator which together provide 8
1.1 New Core Features user selectable clock frequencies, from 31 kHz to
16 MHz. This option frees the two oscillator pins
1.1.1 nanoWatt TECHNOLOGY for use as additional general purpose I/O.
All o f t he devices i n t he PIC18F2XK20/4XK20 family • A Phase Lock Loop (PLL) frequency multiplier,
incorporate a ra nge o f features that c an s ignificantly available to both the high-speed crystal and inter-
reduce power c onsumption d uring operation. Ke y nal oscillator modes, which allows clock speeds of
items include: up to 64 MHz. Used with the internal oscillator, the
PLL gives users a complete selection of clock
• Alternate Run Modes: By clocking the controller speeds, from 31 kHz to 64 MHz – all without using
from the Timer1 source or the internal oscillator an external crystal or clock circuit.
block, power consumption during code execution
can be reduced by as much as 90%. Besides its availability a s a cl ock so urce, t he internal
oscillator block provides a stable reference source that
• Multiple Idle Modes: The controller can also run
gives th e fam ily a dditional feat ures for ro bust
with its CPU core disabled but the peripherals still
operation:
active. In these states, power consumption can be
reduced even further, to as little as 4% of normal • Fail-Safe Clock Monitor: This option constantly
operation requirements. monitors the main clock source against a refer-
• On-the-fly Mode Switching: The power- ence signal provided by the LFINTOSC. If a clock
managed modes are invoked by user code during failure occurs, the controller is switched to the
operation, allowing the user to incorporate power- internal oscillator block, allowing for continued
saving ideas into their application’s software operation or a safe application shutdown.
design. • Two-Speed Start-up: This option allows the
• Low Consumption in Key Modules: The internal oscillator to serve as the clock source
power requirements for both Timer1 and the from Power-on Reset, or wake-up from Sleep
Watchdog Timer are minimized. See mode, until the primary clock source is available.
Section 26.0 “Electrical Characteristics”
for values.

 2010 Microchip Technology Inc. DS41303G-page 11

PIC18F2XK20/4XK20
1.2 Other Special Features 1.3 Details on Individual Family
• Memory Endurance: The Flash cells for both
Members
program memory and data EEPROM are rated to Devices in the PIC18F2XK20/4XK20 family are av ail-
last for many thousands of erase/write cycles – up to able in 28-pin and 40/44-pin packages. Block diagrams
10K for program memory and 100K for EEPROM. for the tw o g roups are shown i n Fi gure 1-1 an d
Data retention without refresh is conservatively Figure 1-2.
estimated to be greater than 40 years.
The devices are differentiated from each other in five
• Self-programmability: These devices can write ways:
to their own program memory spaces under inter-
nal software control. By using a bootloader rou- 1. Flash program me mory (8 Kbytes for
tine located in the protected Boot Block at the top PIC18F23K20/43K20 de vices, 16 Kbytes for
of program memory, it becomes possible to create PIC18F24K20/44K20 de vices, 32 Kbytes for
an application that can update itself in the field. PIC18F25K20/45K20 AN D 64 Kbytes for
PIC18F26K20/46K20).
• Extended Instruction Set: The PIC18F2XK20/
4XK20 family introduces an optional extension to 2. A/D channels (11 fo r 28 -pin d evices, 14 fo r
the PIC18 instruction set, which adds 8 new 40/44-pin devices).
instructions and an Indexed Addressing mode. 3. I/O ports (3 bidirectional ports on 28-pin devices,
This extension, enabled as a device configuration 5 bidirectional ports on 40/44-pin devices).
option, has been specifically designed to optimize 4. Parallel Sl ave Port (p resent o nly on 4 0/44-pin
re-entrant application code originally developed in devices).
high-level languages, such as C.
All other features for devices in this family are identical.
• Enhanced CCP module: In PWM mode, this These are summarized in Table 1-1.
module provides 1, 2 or 4 modulated outputs for
controlling half-bridge and full-bridge drivers. The pinouts for all devices are listed in the pin summary
Other features include: tables: Table 1 and Table 2, and I/O description tables:
Table 1-2 and Table 1-3.
- Auto-Shutdown, for disabling PWM outputs
on interrupt or other select conditions
- Auto-Restart, to reactivate outputs once the
condition has cleared
- Output steering to selectively enable one or
more of 4 outputs to provide the PWM signal.
• Enhanced Addressable USART: This serial
communication module is capable of standard
RS-232 operation and provides support for the LIN
bus protocol. Other enhancements include
automatic baud rate detection and a 16-bit Baud
Rate Generator for improved resolution. When the
microcontroller is using the internal oscillator
block, the USART provides stable operation for
applications that talk to the outside world without
using an external crystal (or its accompanying
power requirement).
• 10-bit A/D Converter: This module incorporates
programmable acquisition time, allowing for a
channel to be selected and a conversion to be
initiated without waiting for a sampling period and
thus, reduce code overhead.
• Extended Watchdog Timer (WDT): This
enhanced version incorporates a 16-bit
postscaler, allowing an extended time-out range
that is stable across operating voltage and
temperature. See Section 26.0 “Electrical
Characteristics” for time-out periods.

DS41303G-page 12  2010 Microchip Technology Inc.

 TABLE 1-1: DEVICE FEATURES
 2010 Microchip Technology Inc.

Features PIC18F23K20 PIC18F24K20 PIC18F25K20 PIC18F26K20 PIC18F43K20 PIC18F44K20 PIC18F45K20 PIC18F46K20

Operating Frequency(2) DC – 64 MHz DC – 64 MHz DC – 64 MHz DC – 64 MHz DC – 64 MHz DC – 64 MHz DC – 64 MHz DC – 64 MHz
Program Memory (Bytes) 8192 16384 32768 65536 8192 16384 32768 65536
Program Memory 4096 8192 16384 32768 4096 8192 16384 32768
(Instructions)
Data Memory (Bytes) 512 768 1536 3936 512 768 1536 3936
Data EEPROM Memory 256 256 256 1024 256 256 256 1024
(Bytes)
Interrupt Sources 19 19 19 19 20 20 20 20
I/O Ports A, B, C, (E)(1) A, B, C, (E)(1) A, B, C, (E)(1) A, B, C, (E)(1) A, B, C, D, E A, B, C, D, E A, B, C, D, E A, B, C, D, E
Timers 4 4 44 44 44
Capture/Compare/PWM 1 1 1 1 1 1 1 1
Modules
Enhanced Capture/ 1 1 11 11 11
Compare/PWM Modules
Serial Communications MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced MSSP, Enhanced
USART USART USART USART USART USART USART USART
Parallel Communica- No No No No Yes Yes Yes Yes
tions (PSP)
10-bit Analog-to-Digital 1 internal plus 10 1 internal plus 10 1 internal plus 10 1 internal plus 10 1 internal plus 13 1 internal plus 13 1 internal plus 13 1 internal plus 13
Module Input Channels Input Channels Input Channels Input Channels Input Channels Input Channels Input Channels Input Channels
Resets (and Delays) POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET POR, BOR, RESET
Instruction, Stack Instruction, Stack Instruction, Stack Instruction, Stack Instruction, Stack Instruction, Stack Instruction, Stack Instruction, Stack

PIC18F2XK20/4XK20
Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow Full, Stack Underflow
(PWRT, OST), (PWRT, OST), MCLR (PWRT, OST), (PWRT, OST), MCLR (PWRT, OST), (PWRT, OST), (PWRT, OST), (PWRT, OST), MCLR
MCLR (optional), (optional), WDT MCLR (optional), (optional), WDT MCLR (optional), MCLR (optional), MCLR (optional), (optional), WDT
WDT WDT WDT WDT WDT
Programmable High/ Yes Yes Yes Yes Yes Yes Yes Yes
Low-Voltage Detect
Programmable Brown- Yes Yes Yes Yes Yes Yes Yes Yes
out Reset
Instruction Set 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83 75 Instructions; 83
with Extended with Extended with Extended with Extended with Extended with Extended with Extended with Extended
Instruction Set Instruction Set Instruction Set Instruction Set Instruction Set Instruction Set Instruction Set Instruction Set
enabled enabled enabled enabled enabled enabled enabled enabled
Packages 28-pin PDIP 28-pin PDIP 28-pin PDIP 28-pin PDIP 40-pin PDIP 40-pin PDIP 40-pin PDIP 40-pin PDIP
28-pin SOIC 28-pin SOIC 28-pin SOIC 28-pin SOIC 44-pin QFN 44-pin QFN 44-pin QFN 44-pin QFN
28-pin QFN 28-pin QFN 28-pin QFN 28-pin QFN 44-pin TQFP 44-pin TQFP 44-pin TQFP 44-pin TQFP
DS41303G-page 13

28-pin SSOP 28-pin SSOP 28-pin SSOP 28-pin SSOP

28-pin UQFN
Note 1: PORTE contains the single RE3 read-only bit. The LATE and TRISE registers are not implemented.
2: Frequency range shown applies to industrial range devices only. Maximum frequency for extended range devices is 48 MHz.
PIC18F2XK20/4XK20
FIGURE 1-1: PIC18F2XK20 (28-PIN) BLOCK DIAGRAM
Data Bus<8>
Table Pointer<21>

8 8 Data Latch PORTA

inc/dec logic RA0/AN0
Data Memory RA1/AN1
PCLATU PCLATH RA2/AN2/VREF-/CVREF
21
RA3/AN3/VREF+
20 Address Latch RA4/T0CKI/C1OUT
PCU PCH PCL
RA5/AN4/SS/HLVDIN/C2OUT
Program Counter 12 OSC2/CLKOUT(3)/RA6
Data Address<12> OSC1/CLKIN(3)/RA7
31-Level Stack
Address Latch 4 12 4
BSR FSR0 Access
Program Memory STKPTR Bank
(8/16/32/64 Kbytes) FSR1
FSR2 12
Data Latch
PORTB
RB0/INT0/FLT0/AN12
inc/dec
8 logic RB1/INT1/AN10/C12IN3-
Table Latch RB2/INT2/AN8
RB3/AN9/CCP2(1)/C12IN2-
RB4/KBI0/AN11
ROM Latch Address
RB5/KBI1/PGM
Instruction Bus <16> Decode
RB6/KBI2/PGC
RB7/KBI3/PGD
IR

8
Instruction State machine
Decode and control signals
Control
PRODH PRODL
PORTC
8 x 8 Multiply RC0/T1OSO/T13CKI
3 8 RC1/T1OSI/CCP2(1)
RC2/CCP1
BITOP W RC3/SCK/SCL
8 8 8
RC4/SDI/SDA
Internal RC5/SDO
OSC1(3) Power-up RC6/TX/CK
Oscillator 8 8
Block Timer RC7/RX/DT
OSC2 (3) Oscillator ALU<8>
LFINTOSC Start-up Timer
T1OSI Oscillator Power-on 8
Reset
16 MHz
T1OSO Oscillator Watchdog
Timer
Precision FVR
Single-Supply Brown-out Band Gap
MCLR(2) PORTE
Programming Reset Reference
In-Circuit Fail-Safe
VDD, VSS Debugger Clock Monitor
MCLR/VPP/RE3(2)

BOR Data
EEPROM Timer0 Timer1 Timer2 Timer3
HLVD

FVR
ADC FVR
CVREF Comparator ECCP1 CCP2 MSSP EUSART 10-bit

Note 1: CCP2 is multiplexed with RC1 when Configuration bit CCP2MX is set, or RB3 when CCP2MX is not set.
2: RE3 is only available when MCLR functionality is disabled.
3: OSC1/CLKIN and OSC2/CLKOUT are only available in select oscillator modes and when these pins are not being used as digital I/O.
Refer to Section 2.0 “Oscillator Module (With Fail-Safe Clock Monitor)” for additional information.

DS41303G-page 14  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 1-2: PIC18F4XK20 (40/44-PIN) BLOCK DIAGRAM
Data Bus<8>
Table Pointer<21> PORTA
RA0/AN0
8 8 Data Latch RA1/AN1
inc/dec logic RA2/AN2/VREF-/CVREF
Data Memory RA3/AN3/VREF+
21 PCLATU PCLATH RA4/T0CKI/C1OUT
RA5/AN4/SS/HLVDIN/C2OUT
20 Address Latch
OSC2/CLKOUT(3)/RA6
PCU PCH PCL
OSC1/CLKIN(3)/RA7
Program Counter 12
Data Address<12>
PORTB
31-Level Stack RB0/INT0/FLT0/AN12
Address Latch 4 12 4
RB1/INT1/AN10/C12IN3-
BSR Access
Program Memory STKPTR FSR0 Bank RB2/INT2/AN8
(8/16/32/64 Kbytes) FSR1 RB3/AN9/CCP2(1)/C12IN2-
FSR2 12 RB4/KBI0/AN11
Data Latch
RB5/KBI1/PGM
RB6/KBI2/PGC
inc/dec
8 logic RB7/KBI3/PGD
Table Latch

ROM Latch Address PORTC

Instruction Bus <16> Decode RC0/T1OSO/T13CKI
RC1/T1OSI/CCP2(1)
RC2/CCP1/P1A
IR
RC3/SCK/SCL
RC4/SDI/SDA
8 RC5/SDO
State machine RC6/TX/CK
Instruction
Decode and control signals RC7/RX/DT
Control
PRODH PRODL
PORTD
8 x 8 Multiply RD0/PSP0
3 8 RD1/PSP1
RD2/PSP2
BITOP W
8 RD3/PSP3
8 8
RD4/PSP4
OSC1(3) Internal RD5/PSP5/P1B
Oscillator Power-up
Timer 8 8 RD6/PSP6/P1C
Block RD7/PSP7/P1D
OSC2 (3) Oscillator ALU<8>
LFINTOSC Start-up Timer
T1OSI Oscillator Power-on 8
Reset
16 MHz
T1OSO Oscillator Watchdog PORTE
Timer
Precision RE0/RD/AN5
Brown-out FVR RE1/WR/AN6
MCLR(2) Single-Supply Band Gap
Programming Reset Reference RE2/CS/AN7
In-Circuit Fail-Safe MCLR/VPP/RE3(2)
VDD, VSS Debugger Clock Monitor

BOR Data
EEPROM Timer0 Timer1 Timer2 Timer3
HLVD

FVR
ADC FVR
CVREF Comparator ECCP1 CCP2 MSSP EUSART PSP
10-bit

Note 1: CCP2 is multiplexed with RC1 when Configuration bit CCP2MX is set, or RB3 when CCP2MX is not set.
2: RE3 is only available when MCLR functionality is disabled.
3: OSC1/CLKIN and OSC2/CLKOUT are only available in select oscillator modes and when these pins are not being used as digital I/O.
Refer to Section 2.0 “Oscillator Module (With Fail-Safe Clock Monitor)” for additional information.

 2010 Microchip Technology Inc. DS41303G-page 15

PIC18F2XK20/4XK20

TABLE 1-2: PIC18F2XK20 PINOUT I/O DESCRIPTIONS

Pin Number
Pin Buffer
Pin Name PDIP, Description
QFN Type Type
SOIC
MCLR/VPP/RE3 1 26 Master Clear (input) or programming voltage (input)
MCLR I ST Active-low Master Clear (device Reset) input
VPP P Programming voltage input
RE3 I ST Digital input
OSC1/CLKIN/RA7 9 6 Oscillator crystal or external clock input
OSC1 I ST Oscillator crystal input or external clock source input
ST buffer when configured in RC mode; CMOS otherwise
CLKIN I CMOS External clock source input. Always associated with pin
function OSC1. (See related OSC1/CLKIN, OSC2/CLKOUT
pins)
RA7 I/O TTL General purpose I/O pin
OSC2/CLKOUT/RA6 10 7 Oscillator crystal or clock output
OSC2 O — Oscillator crystal output. Connects to crystal or
resonator in Crystal Oscillator mode
CLKOUT O — In RC mode, OSC2 pin outputs CLKOUT which has 1/4 the
frequency of OSC1 and denotes the instruction cycle rate
RA6 I/O TTL General purpose I/O pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

DS41303G-page 16  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1-2: PIC18F2XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number
Pin Buffer
Pin Name PDIP, Description
QFN Type Type
SOIC
PORTA is a bidirectional I/O port.
RA0/AN0/C12IN0- 2 27
RA0 I/O TTL Digital I/O
AN0 I Analog Analog input 0, ADC channel 0
C12IN0- I Analog Comparators C1 and C2 inverting input
RA1/AN1/C12IN1- 3 28
RA1 I/O TTL Digital I/O
AN1 I Analog ADC input 1, ADC channel 1
C12IN1- I Analog Comparators C1 and C2 inverting input
RA2/AN2/VREF-/CVREF/ 4 1
C2IN+
RA2 I/O TTL Digital I/O
AN2 I Analog Analog input 2, ADC channel 2
VREF- I Analog A/D reference voltage (low) input
CVREF O Analog Comparator reference voltage output
C2IN+ I Analog Comparator C2 non-inverting input
RA3/AN3/VREF+/C1IN+ 5 2
RA3 I/O TTL Digital I/O
AN3 I Analog Analog input 3, ADC channel 3
VREF+ I Analog A/D reference voltage (high) input
C1IN+ I Analog Comparator C1 non-inverting input
RA4/T0CKI/C1OUT 6 3
RA4 I/O ST Digital I/O
T0CKI I ST Timer0 external clock input
C1OUT O CMOS Comparator C1 output
RA5/AN4/SS/HLVDIN/ 7 4
C2OUT
RA5 I/O TTL Digital I/O
AN4 I Analog Analog input 4, ADC channel 4
SS I TTL SPI slave select input
HLVDIN I Analog High/Low-Voltage Detect input
C2OUT O CMOS Comparator C2 output
RA6 See the OSC2/CLKOUT/RA6 pin
RA7 See the OSC1/CLKIN/RA7 pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

 2010 Microchip Technology Inc. DS41303G-page 17

PIC18F2XK20/4XK20
TABLE 1-2: PIC18F2XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number
Pin Buffer
Pin Name PDIP, Description
QFN Type Type
SOIC
PORTB is a bidirectional I/O port. PORTB can be software
programmed for internal weak pull-up on each input.
RB0/INT0/FLT0/AN12 21 18
RB0 I/O TTL Digital I/O
INT0 I ST External interrupt 0
FLT0 I ST PWM Fault input for CCP1
AN12 I Analog Analog input 12, ADC channel 12
RB1/INT1/AN10/C12IN3- 22 19
/P1C
RB1 I/O TTL Digital I/O
INT1 I ST External interrupt 1
AN10 I Analog Analog input 10, ADC channel 10
C12IN3- I Analog Comparators C1 and C2 inverting input
P1C O CMOS Enhanced CCP1 PWM output
RB2/INT2/AN8/P1B 23 20
RB2 I/O TTL Digital I/O
INT2 I ST External interrupt 2
AN8 I Analog Analog input 8, ADC channel 8
P1B O CMOS Enhanced CCP1 PWM output
RB3/AN9/C12IN2-/CCP2 24 21
RB3 I/O TTL Digital I/O
AN9 I Analog Analog input 9, ADC channel 9
C12IN2- I Analog Comparators C1 and C2 inverting input
CCP2(2) I/O ST Capture 2 input/Compare 2 output/PWM 2 output
RB4/KBI0/AN11/P1D 25 22
RB4 I/O TTL Digital I/O
KBI0 I TTL Interrupt-on-change pin
AN11 I Analog Analog input 11, ADC channel 11
P1D O CMOS Enhanced CCP1 PWM output
RB5/KBI1/PGM 26 23
RB5 I/O TTL Digital I/O
KBI1 I TTL Interrupt-on-change pin
PGM I/O ST Low-Voltage ICSP™ Programming enable pin
RB6/KBI2/PGC 27 24
RB6 I/O TTL Digital I/O
KBI2 I TTL Interrupt-on-change pin
PGC I/O ST In-Circuit Debugger and ICSP™ programming clock pin
RB7/KBI3/PGD 28 25
RB7 I/O TTL Digital I/O
KBI3 I TTL Interrupt-on-change pin
PGD I/O ST In-Circuit Debugger and ICSP™ programming data pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

DS41303G-page 18  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1-2: PIC18F2XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number
Pin Buffer
Pin Name PDIP, Description
QFN Type Type
SOIC
PORTC is a bidirectional I/O port.
RC0/T1OSO/T13CKI 11 8
RC0 I/O ST Digital I/O
T1OSO O — Timer1 oscillator output
T13CKI I ST Timer1/Timer3 external clock input
RC1/T1OSI/CCP2 12 9
RC1 I/O ST Digital I/O
T1OSI I Analog Timer1 oscillator input
CCP2(1) I/O ST Capture 2 input/Compare 2 output/PWM 2 output
RC2/CCP1/P1A 13 10
RC2 I/O ST Digital I/O
CCP1 I/O ST Capture 1 input/Compare 1 output
P1A O CMOS Enhanced CCP1 PWM output
RC3/SCK/SCL 14 11
RC3 I/O ST Digital I/O
SCK I/O ST Synchronous serial clock input/output for SPI mode
SCL I/O ST Synchronous serial clock input/output for I2C™ mode
RC4/SDI/SDA 15 12
RC4 I/O ST Digital I/O
SDI I ST SPI data in
SDA I/O ST I2C™ data I/O
RC5/SDO 16 13
RC5 I/O ST Digital I/O
SDO O — SPI data out
RC6/TX/CK 17 14
RC6 I/O ST Digital I/O
TX O — EUSART asynchronous transmit
CK I/O ST EUSART synchronous clock (see related RX/DT)
RC7/RX/DT 18 15
RC7 I/O ST Digital I/O
RX I ST EUSART asynchronous receive
DT I/O ST EUSART synchronous data (see related TX/CK)
RE3 — — — — See MCLR/VPP/RE3 pin
VSS 8, 19 5, 16 P — Ground reference for logic and I/O pins
VDD 20 17 P — Positive supply for logic and I/O pins
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

 2010 Microchip Technology Inc. DS41303G-page 19

PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
MCLR/VPP/RE3 1 18 18 Master Clear (input) or programming voltage (input)
MCLR I ST Active-low Master Clear (device Reset) input
VPP P Programming voltage input
RE3 I ST Digital input
OSC1/CLKIN/RA7 13 32 30 Oscillator crystal or external clock input
OSC1 I ST Oscillator crystal input or external clock source input
ST buffer when configured in RC mode;
analog otherwise
CLKIN I CMOS External clock source input. Always associated with
pin function OSC1 (See related OSC1/CLKIN,
OSC2/CLKOUT pins)
RA7 I/O TTL General purpose I/O pin
OSC2/CLKOUT/RA6 14 33 31 Oscillator crystal or clock output
OSC2 O — Oscillator crystal output. Connects to crystal
or resonator in Crystal Oscillator mode
CLKOUT O — In RC mode, OSC2 pin outputs CLKOUT which
has 1/4 the frequency of OSC1 and denotes
the instruction cycle rate
RA6 I/O TTL General purpose I/O pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

DS41303G-page 20  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
PORTA is a bidirectional I/O port.
RA0/AN0/C12IN0- 2 19 19
RA0 I/O TTL Digital I/O
AN0 I Analog Analog input 0, ADC channel 0
C12IN0- I Analog Comparator C1 and C2 inverting input
RA1/AN1/C12IN0- 3 20 20
RA1 I/O TTL Digital I/O
AN1 I Analog Analog input 1, ADC channel 1
C12IN0- I Analog Comparator C1 and C2 inverting input
RA2/AN2/VREF-/CVREF/ 4 21 21
C2IN+
RA2 I/O TTL Digital I/O
AN2 I Analog Analog input 2, ADC channel 2
VREF- I Analog A/D reference voltage (low) input
CVREF O Analog Comparator reference voltage output
C2IN+ I Analog Comparator C2 non-inverting input
RA3/AN3/VREF+/ 5 22 22
C1IN+
RA3 I/O TTL Digital I/O
AN3 I Analog Analog input 3, ADC channel 3
VREF+ I Analog A/D reference voltage (high) input
C1IN+ I Analog Comparator C1 non-inverting input
RA4/T0CKI/C1OUT 6 23 23
RA4 I/O ST Digital I/O
T0CKI I ST Timer0 external clock input
C1OUT O CMOS Comparator C1 output
RA5/AN4/SS/HLVDIN/ 7 24 24
C2OUT
RA5 I/O TTL Digital I/O
AN4 I Analog Analog input 4, ADC channel 4
SS I TTL SPI slave select input
HLVDIN I Analog High/Low-Voltage Detect input
C2OUT O CMOS Comparator C2 output
RA6 See the OSC2/CLKOUT/RA6 pin
RA7 See the OSC1/CLKIN/RA7 pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

 2010 Microchip Technology Inc. DS41303G-page 21

PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
PORTB is a bidirectional I/O port. PORTB can be
software programmed for internal weak pull-up on
each input.
RB0/INT0/FLT0/AN12 33 9 8
RB0 I/O TTL Digital I/O
INT0 I ST External interrupt 0
FLT0 I ST PWM Fault input for Enhanced CCP1
AN12 I Analog Analog input 12, ADC channel 12
RB1/INT1/AN10/ 34 10 9
C12IN3-
RB1 I/O TTL Digital I/O
INT1 I ST External interrupt 1
AN10 I Analog Analog input 10, ADC channel 10
C12IN3- I Analog Comparator C1 and C2 inverting input
RB2/INT2/AN8 35 11 10
RB2 I/O TTL Digital I/O
INT2 I ST External interrupt 2
AN8 I Analog Analog input 8, ADC channel 8
RB3/AN9/C12IN2-/ 36 12 11
CCP2
RB3 I/O TTL Digital I/O
AN9 I Analog Analog input 9, ADC channel 9
C12IN23- I Analog Comparator C1 and C2 inverting input
CCP2(2) I/O ST Capture 2 input/Compare 2 output/PWM 2 output
RB4/KBI0/AN11 37 14 14
RB4 I/O TTL Digital I/O
KBI0 I TTL Interrupt-on-change pin
AN11 I Analog Analog input 11, ADC channel 11
RB5/KBI1/PGM 38 15 15
RB5 I/O TTL Digital I/O
KBI1 I TTL Interrupt-on-change pin
PGM I/O ST Low-Voltage ICSP™ Programming enable pin
RB6/KBI2/PGC 39 16 16
RB6 I/O TTL Digital I/O
KBI2 I TTL Interrupt-on-change pin
PGC I/O ST In-Circuit Debugger and ICSP™ programming
clock pin
RB7/KBI3/PGD 40 17 17
RB7 I/O TTL Digital I/O
KBI3 I TTL Interrupt-on-change pin
PGD I/O ST In-Circuit Debugger and ICSP™ programming
data pin
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

DS41303G-page 22  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
PORTC is a bidirectional I/O port.
RC0/T1OSO/T13CKI 15 34 32
RC0 I/O ST Digital I/O
T1OSO O — Timer1 oscillator output
T13CKI I ST Timer1/Timer3 external clock input
RC1/T1OSI/CCP2 16 35 35
RC1 I/O ST Digital I/O
T1OSI I CMOS Timer1 oscillator input
CCP2(1) I/O ST Capture 2 input/Compare 2 output/PWM 2 output
RC2/CCP1/P1A 17 36 36
RC2 I/O ST Digital I/O
CCP1 I/O ST Capture 1 input/Compare 1 output/PWM 1 output
P1A O — Enhanced CCP1 output
RC3/SCK/SCL 18 37 37
RC3 I/O ST Digital I/O
SCK I/O ST Synchronous serial clock input/output for
SPI mode
SCL I/O ST Synchronous serial clock input/output for I2C™ mode
RC4/SDI/SDA 23 42 42
RC4 I/O ST Digital I/O
SDI I ST SPI data in
SDA I/O ST I2C™ data I/O
RC5/SDO 24 43 43
RC5 I/O ST Digital I/O
SDO O — SPI data out
RC6/TX/CK 25 44 44
RC6 I/O ST Digital I/O
TX O — EUSART asynchronous transmit
CK I/O ST EUSART synchronous clock (see related RX/DT)
RC7/RX/DT 26 1 1
RC7 I/O ST Digital I/O
RX I ST EUSART asynchronous receive
DT I/O ST EUSART synchronous data (see related TX/CK)
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

 2010 Microchip Technology Inc. DS41303G-page 23

PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
PORTD is a bidirectional I/O port or a Parallel Slave
Port (PSP) for interfacing to a microprocessor port.
These pins have TTL input buffers when PSP module
is enabled.
RD0/PSP0 19 38 38
RD0 I/O ST Digital I/O
PSP0 I/O TTL Parallel Slave Port data
RD1/PSP1 20 39 39
RD1 I/O ST Digital I/O
PSP1 I/O TTL Parallel Slave Port data
RD2/PSP2 21 40 40
RD2 I/O ST Digital I/O
PSP2 I/O TTL Parallel Slave Port data
RD3/PSP3 22 41 41
RD3 I/O ST Digital I/O
PSP3 I/O TTL Parallel Slave Port data
RD4/PSP4 27 2 2
RD4 I/O ST Digital I/O
PSP4 I/O TTL Parallel Slave Port data
RD5/PSP5/P1B 28 3 3
RD5 I/O ST Digital I/O
PSP5 I/O TTL Parallel Slave Port data
P1B O — Enhanced CCP1 output
RD6/PSP6/P1C 29 4 4
RD6 I/O ST Digital I/O
PSP6 I/O TTL Parallel Slave Port data
P1C O — Enhanced CCP1 output
RD7/PSP7/P1D 30 5 5
RD7 I/O ST Digital I/O
PSP7 I/O TTL Parallel Slave Port data
P1D O — Enhanced CCP1 output
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

DS41303G-page 24  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 1-3: PIC18F4XK20 PINOUT I/O DESCRIPTIONS (CONTINUED)
Pin Number Pin Buffer
Pin Name Description
PDIP QFN TQFP Type Type
PORTE is a bidirectional I/O port
RE0/RD/AN5 8 25 25
RE0 I/O ST Digital I/O
RD I TTL Read control for Parallel Slave Port
(see related WR and CS pins)
AN5 I Analog Analog input 5, ADC channel 5
RE1/WR/AN6 9 26 26
RE1 I/O ST Digital I/O
WR I TTL Write control for Parallel Slave Port
(see related CS and RD pins)
AN6 I Analog Analog input 6, ADC channel 6
RE2/CS/AN7 10 27 27
RE2 I/O ST Digital I/O
CS I TTL Chip Select control for Parallel Slave Port
(see related RD and WR)
AN7 I Analog Analog input 7, ADC channel 7
RE3 — — — — — See MCLR/VPP/RE3 pin
VSS 12, 31 6, 30, 6, 29 P — Ground reference for logic and I/O pins
31
VDD 11, 32 7, 8, 7, 28 P — Positive supply for logic and I/O pins
28, 29
NC — 13 12, 13, — — No connect
33, 34
Legend: TTL = TTL compatible input CMOS = CMOS compatible input or output
ST = Schmitt Trigger input with CMOS levels I = Input
O = Output P = Power
Note 1: Default assignment for CCP2 when Configuration bit CCP2MX is set.
2: Alternate assignment for CCP2 when Configuration bit CCP2MX is cleared.

 2010 Microchip Technology Inc. DS41303G-page 25

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 26  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
2.0 OSCILLATOR MODULE (WITH The Oscillator module can be configured in one of ten
primary clock modes.
FAIL-SAFE CLOCK MONITOR)
1. LP Low-Power Crystal
2.1 Overview 2. XT Crystal/Resonator
3. HS High-Speed Crystal/Resonator
The O scillator m odule has a wide va riety o f cl ock
4. HSPLL
High-Speed Crystal/Resonator
sources and selection features that allow it to be used
with PLL enabled
in a wide range of applications while maximizing perfor-
mance and minimizing power consumption. Figure 2-1 5. RC External Resistor/Capacitor with
illustrates a block diagram of the Oscillator module. FOSC/4 output on RA6
6. RCIO External Resistor/Capacitor with I/O
Clock sources ca n be con figured from external
on RA6
oscillators, quartz crystal resonators, ceramic resonators
and R esistor-Capacitor (R C) c ircuits. In a ddition, the 7. INTOSC Internal Oscillator with FOSC/4
system clock source can be configured from one of two output on RA6 and I/O on RA7
internal oscillators, with a choice of speeds selectable via 8. INTOSCIO Internal Oscillator with I/O on RA6
software. Additional clock features include: and RA7
• Selectable system clock source between external 9. EC External Clock with FOSC/4 output
or internal via software. 10. ECIO External Clock with I/O on RA6
• Two-Speed Start-up mode, which minimizes Primary Clock modes are selected by the FOSC<3:0>
latency between external oscillator start-up and bits of t he CONFIG1H C onfiguration R egister. T he
code execution. HFINTOSC and LFINTOSC are factory calibrated high-
• Fail-Safe Clock Monitor (FSCM) designed to frequency and low-frequency oscillators, respectively,
detect a failure of the external clock source (LP, which are used as the internal clock sources.
XT, HS, EC or RC modes) and switch
automatically to the internal oscillator.

FIGURE 2-1: PIC® MCU CLOCK SOURCE BLOCK DIAGRAM

PIC18F2XK20/4XK20
Primary Oscillator LP, XT, HS, RC, EC
OSC2
IDLEN
Sleep HSPLL, HFINTOSC/PLL
4 x PLL Sleep
OSC1
OSCTUNE<6>(1)
Secondary Oscillator T1OSC Peripherals
Main
MUX

T1OSO
T1OSCEN
Enable
T1OSI Oscillator OSCCON<6:4> Internal Oscillator

FOSC<3:0> O SCCON<1:0> 16 MHz CPU

111
8 MHz
Internal 110 Sleep
Oscillator 4 MHz
101
Block Clock
Postscaler

2 MHz
16 MHz Control
MUX

100
Source 1 MHz
16 MHz 011
(HFINTOSC) 500 kHz
31 kHz 010 FOSC<3:0> OSCCON<1:0>
Source 250 kHz
001
Clock Source Option
1 31 kHz
31 kHz (LFINTOSC) 000 for other Modules
0

OSCTUNE<7>
WDT, PWRT, FSCM
and Two-Speed Start-up

Note 1: Operates only when HFINTOSC is the primary oscillator.

 2010 Microchip Technology Inc. DS41303G-page 27

PIC18F2XK20/4XK20
2.2 Oscillator Control 2.2.4 CLOCK STATUS
The OSCCON register (Register 2-1) controls several The OSTS and IOFS bits of the OSCCON register, and
aspects o f the dev ice c lock’s op eration, bo th in ful l the T1RUN b it o f the T1CON re gister, indicate which
power operation and in power-managed modes. clock source is currently providing the main clock. The
OSTS b it i ndicates th at th e O scillator S tart-up T imer
• Main System Clock Selection (SCS) has ti med ou t and the p rimary clock is p roviding th e
• Internal Frequency selection bits (IRCF) device clock. The IOFS bit indicates when the internal
• Clock Status bits (OSTS, IOFS) oscillator b lock has stabilized a nd is p roviding th e
• Power management selection (IDLEN) device cl ock i n H FINTOSC C lock m odes. The IO FS
and O STS S tatus bit s w ill bo th b e s et w hen
2.2.1 MAIN SYSTEM CLOCK SELECTION SCS<1:0> = 00 and HFINTOSC is the primary clock.
The T1RUN bit indicates when the Timer1 oscillator is
The Sy stem Cloc k Se lect b its, SCS<1 :0>, s elect th e
providing the device clock in secondary clock modes.
main clock source. The available clock sources are
When SCS<1:0>  00, only one of these three bits will
• Primary clock defined by the FOSC<3:0> bits of be s et a t a ny tim e. If n one of the se bi ts are set, th e
CONFIG1H. The primary clock can be the primary LFINTOSC is prov iding the clock or the H FINTOSC
oscillator, an external clock, or the internal oscilla- has just started and is not yet stable.
tor block.
• Secondary clock (Timer1 oscillator) 2.2.5 POWER MANAGEMENT
• Internal oscillator block (HFINTOSC and The IDLEN bit of the OSCCON register determines if
LFINTOSC). the d evice go es into Sle ep mode o r on e of the Idl e
The c lock s ource cha nges i mmediately af ter one or modes when the SLEEP instruction is executed.
more of the bits is written to, following a brief clock tran- The u se of the fl ag and c ontrol bits in the OSCCON
sition interval. The SCS bits are cl eared to sel ect the register i s di scussed in m ore d etail in Section 3.0
primary clock on all forms of Reset. “Power-Managed Modes”.

2.2.2 INTERNAL FREQUENCY Note 1: The Timer1 oscillator must be enabled to

SELECTION select the secondary c lock so urce. Th e
Timer1 oscillator is enabled by setting the
The Int ernal Os cillator Frequency Se lect bit s
T1OSCEN b it of the T1 CON re gister. If
(IRCF<2:0>) select the frequency output of the internal
the Timer1 oscillator is not enabled, then
oscillator block. The choices are the LFINTOSC source
the m ain osc illator w ill c ontinue to ru n
(31 kHz), t he H FINTOSC so urce (16 MHz) o r one of
from the previously selected source. The
the freq uencies de rived from the H FINTOSC pos t-
source will then switch to the secondary
scaler (31 .25 kHz to 8 MHz). If the int ernal os cillator
oscillator after the T1OSCEN bit is set.
block is supplying the main clock, changing the states
of th ese b its w ill ha ve an i mmediate c hange on th e 2: It i s rec ommended tha t the Timer1
internal oscillator’s output. On device Resets, the out- oscillator be operating and stable before
put f requency of the in ternal oscillator is s et t o th e selecting the secondary clock source or a
default frequency of 1 MHz. very lo ng delay ma y o ccur while th e
Timer1 oscillator starts.
2.2.3 LOW FREQUENCY SELECTION
When a nominal output frequency of 31 kHz is selected
(IRCF<2:0> = 000), users may choose which internal
oscillator ac ts as th e s ource. Thi s i s done w ith th e
INTSRC bit of the OSC TUNE register. Setting this bit
selects the HFINTOSC as a 31.25 kHz clock source by
enabling the di vide-by-512 ou tput of the H FINTOSC
postscaler. Clearing INTSRC selects LFINTOSC (nom-
inally 31 kHz) as the clock source.
This option allows users to select the tunable and more
precise HFINTOSC as a clock source, while maintain-
ing power savings with a very low clock speed. Regard-
less of t he se tting of I NTSRC, LFINTOSC a lways
remains th e c lock source fo r fea tures s uch a s th e
Watchdog Timer and the Fail-Safe Clock Monitor.

DS41303G-page 28  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 2-1: OSCCON: OSCILLATOR CONTROL REGISTER

R/W-0 R/W-0 R/W-1 R/W-1 R-q R-0 R/W-0 R/W-0
IDLEN IRCF2 IRCF1 IRCF0 OSTS(1) IOFS SCS1 SCS0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’ q = depends on condition
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 IDLEN: Idle Enable bit

1 = Device enters Idle mode on SLEEP instruction
0 = Device enters Sleep mode on SLEEP instruction
bit 6-4 IRCF<2:0>: Internal Oscillator Frequency Select bits
111 = 16 MHz (HFINTOSC drives clock directly)
110 = 8 MHz
101 = 4 MHz
100 = 2 MHz
011 = 1 MHz(3)
010 = 500 kHz
001 = 250 kHz
000 = 31 kHz (from either HFINTOSC/512 or LFINTOSC directly)(2)
bit 3 OSTS: Oscillator Start-up Time-out Status bit(1)
1 = Device is running from the clock defined by FOSC<2:0> of the CONFIG1 register
0 = Device is running from the internal oscillator (HFINTOSC or LFINTOSC)
bit 2 IOFS: HFINTOSC Frequency Stable bit
1 = HFINTOSC frequency is stable
0 = HFINTOSC frequency is not stable
bit 1-0 SCS<1:0>: System Clock Select bits
1x = Internal oscillator block
01 = Secondary (Timer1) oscillator
00 = Primary clock (determined by CONFIG1H[FOSC<3:0>]).

Note 1: Reset state depends on state of the IESO Configuration bit.

2: Source selected by the INTSRC bit of the OSCTUNE register, see text.
3: Default output frequency of HFINTOSC on Reset.

 2010 Microchip Technology Inc. DS41303G-page 29

PIC18F2XK20/4XK20
2.3 Clock Source Modes 2.4 External Clock Modes
Clock Source modes can be classified as external or 2.4.1 OSCILLATOR START-UP TIMER
internal.
(OST)
• External Clock modes rely on external circuitry for
When the Oscillator module is configured for LP, XT or
the clock source. Examples are: Clock modules
HS modes, the Oscillator Start-up Timer (OST) counts
(EC mode), quartz crystal resonators or ceramic
1024 oscillations from OSC1. This occurs following a
resonators (LP, XT and HS modes) and Resistor-
Power-on Reset (POR) and when the Power-up Timer
Capacitor (RC mode) circuits.
(PWRT) has expired (if configured), or a wake-up from
• Internal clock sources are contained internally Sleep. During this time, the program counter does not
within the Oscillator block. The Oscillator block increment and program execution is suspended. The
has two internal oscillators: the 16 MHz High- OST ensures that the oscillator circuit, using a q uartz
Frequency Internal Oscillator (HFINTOSC) and crystal resonator or ceramic resonator, has started and
the 31 kHz Low-Frequency Internal Oscillator is prov iding a stable system clo ck to the Oscillator
(LFINTOSC). module. W hen swi tching be tween cl ock s ources, a
The system clock can be selected between external or delay i s required to al low the ne w cl ock to s tabilize.
internal cl ock sources vi a the S ystem Cl ock S elect These oscillator delays are shown in Table 2-1.
(SCS<1:0>) b its o f the OSCCO N register. Se e In order to minimize latency between external oscillator
Section 2.9 “Clock Switching” for additional informa- start-up a nd c ode ex ecution, the T wo-Speed C lock
tion. Start-up mo de can be se lected (see Section 2.10
“Two-Speed Clock Start-up Mode”).

TABLE 2-1: OSCILLATOR DELAY EXAMPLES

Switch From Switch To Frequency Oscillator Delay
LFINTOSC 31 kHz
Sleep/POR Oscillator Warm-Up Delay (TWARM)
HFINTOSC 250 kHz to 16 MHz
Sleep/POR EC, RC DC – 64 MHz 2 instruction cycles
LFINTOSC (31 kHz) EC, RC DC – 64 MHz 1 cycle of each
Sleep/POR LP, XT, HS 32 kHz to 40 MHz 1024 Clock Cycles (OST)
Sleep/POR HSPLL 32 MHz to 64 MHz 1024 Clock Cycles (OST) + 2 ms
LFINTOSC (31 kHz) HFINTOSC 250 kHz to 16 MHz 1 s (approx.)

2.4.2 EC MODE FIGURE 2-2: EXTERNAL CLOCK (EC)

The Ext ernal C lock ( EC) mode al lows an ext ernally MODE OPERATION
generated logic level as the system clock source. When
operating in this mode , a n ext ernal clock sour ce is Clock from OSC1/CLKIN
connected to the OSC1 input and the OSC2 is available Ext. System
for ge neral p urpose I /O. Fig ure 2-2 s hows th e pi n PIC® MCU
connections for EC mode.
I/O OSC2/CLKOUT(1)
The Oscillator Start-up Timer (OST) is disabled when
EC mode is selected. Therefore, there is no delay in
operation af ter a Power-on R eset (POR ) or wake-up Note 1: Alternate pin functions are listed in
from Sleep. B ecause t he PIC® MCU de sign is fully Section 1.0 “Device Overview”.
static, sto pping t he e xternal cl ock i nput w ill hav e th e
effect of halting the device while leaving all data intact.
Upon res tarting the external cl ock, th e dev ice w ill
resume operation as if no time had elapsed.

DS41303G-page 30  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
2.4.3 LP, XT, HS MODES
Note 1: Quartz crystal characteristics vary according
The LP, XT and HS modes support the use of quartz to ty pe, p ackage and manu facturer. Th e
crystal resonators or ceramic resonators connected to user s hould co nsult t he ma nufacturer d ata
OSC1 and OSC2 (Figure 2-3). The mode selects a low, sheets for specifications and recommended
medium o r h igh ga in setting of the in ternal inverter- application.
amplifier to support various resonator types and speed.
2: Always verify oscillator performance over
LP Oscillator mode selects the lowest gain setting of the the V DD an d t emperature ran ge that i s
internal inverter-amplifier. LP mode current consumption expected for the application.
is the least of the three modes. This mode is best suited
3: For oscillator design assistance, reference
to drive resonators with a low drive level specification, for
the following Microchip Applications Notes:
example, tuning fork type crystals.
• AN826, “Crystal Oscillator Basics and
XT Oscillator mode s elects t he intermediate g ain
Crystal Selection for rfPIC® and PIC®
setting of the internal in verter-amplifier. XT mode
Devices” (DS00826)
current consumption is the medium of the three modes.
This m ode is be st s uited to drive re sonators w ith a • AN849, “Basic PIC® Oscillator Design”
medium drive level specification. (DS00849)
• AN943, “Practical PIC® Oscillator
HS Oscillator mode selects the highest gain setting of the
Analysis and Design” (DS00943)
internal inverter-amplifier. HS mode current consumption
is the h ighest of th e three modes. Th is m ode is be st • AN949, “Making Your Oscillator Work”
suited for resonators that require a high drive setting. (DS00949)

Figure 2-3 a nd Figure 2-4 show ty pical c ircuits for FIGURE 2-4: CERAMIC RESONATOR
quartz crystal and ceramic resonators, respectively.
OPERATION
(XT OR HS MODE)
FIGURE 2-3: QUARTZ CRYSTAL
OPERATION (LP, XT OR
PIC® MCU
HS MODE)
OSC1/CLKIN
PIC® MCU
C1 To Internal
OSC1/CLKIN Logic

C1 RP(3) RF(2) Sleep

To Internal
Logic
Quartz
RF(2) Sleep
Crystal
C2 Ceramic RS(1) OSC2/CLKOUT
Resonator

C2 OSC2/CLKOUT
RS(1) Note 1: A series res istor (R S) may be re quired f or
ceramic resonators with low drive level.
Note 1: A seri es resistor (R S) may be required for 2: The value of RF varies with the Oscillator mode
quartz crystals with low drive level. selected (typically between 2 M to 10 M.
2: The value of RF varies with the Oscillator mode 3: An addit ional p arallel f eedback resis tor (R P)
selected (typically between 2 M to 10 M. may be required for proper cer amic reson ator
operation.

 2010 Microchip Technology Inc. DS41303G-page 31

PIC18F2XK20/4XK20
2.4.4 EXTERNAL RC MODES 2.5 Internal Clock Modes
The external Resistor-Capacitor (R C) m odes su pport The O scillator m odule has tw o ind ependent, int ernal
the u se of an external R C c ircuit. T his al lows th e oscillators that c an be c onfigured o r s elected as th e
designer maximum flexibility in frequency choice while system clock source.
keeping costs to a minimum when clock accuracy is not
required. There are two modes: RC and RCIO. 1. The HFINTOSC (H igh-Frequency Int ernal
Oscillator) is factory calibrated and operates at
2.4.4.1 RC Mode 16 MHz. The frequency of the H FINTOSC can
be us er-adjusted v ia software using the
In RC mode, the RC circuit connects to OSC1. OSC2/ OSCTUNE register (Register 2-2).
CLKOUT outputs the R C oscillator frequency divided
2. The LFINTOSC (Low -Frequency Internal
by 4. This si gnal ma y be used to provide a cl ock for
Oscillator) operates at 31 kHz.
external c ircuitry, s ynchronization, c alibration, t est or
other application req uirements. Fig ure 2-5 sh ows the The system clock speed can be selected via software
external RC mode connections. using the Internal Oscillator Fre quency Sel ect bit s
IRCF<2:0> of the OSCCON register.
FIGURE 2-5: EXTERNAL RC MODES The system clock can be selected between external or
internal clock sources via the System Clock Selection
VDD
PIC® MCU
(SCS<1:0>) bi ts of the O SCCON re gister. Se e
Section 2.9 “Clock Switching” for more information.
REXT
OSC1/CLKIN Internal 2.5.1 INTOSC AND INTOSCIO MODES
Clock The IN TOSC and INTOSCIO m odes co nfigure the
CEXT internal os cillators as th e p rimary cl ock s ource. Th e
VSS FOSC<3:0> bi ts i n t he C ONFIG1H Configuration
register determine w hich m ode i s selected. Se e
FOSC/4 or OSC2/CLKOUT(1) Section 23.0 “Special Features of the CPU” for more
I/O(2) information.
In INTOSC mode, OSC1/CLKIN is available for general
Recommended values: 10 k  REXT  100 k purpose I/O. O SC2/CLKOUT out puts the s elected
CEXT > 20 pF internal oscillator frequency divided by 4. The CLKOUT
signal may be used to prov ide a c lock fo r external
Note 1: Alternate pin functions are listed in circuitry, sy nchronization, ca libration, test or oth er
Section 1.0 “Device Overview”. application requirements.
2: Output depends upon RC or RCIO clock mode. In INTOSCIO mode, OSC1/CLKIN and OSC2/CLKOUT
are available for general purpose I/O.
2.4.4.2 RCIO Mode
2.5.2 HFINTOSC
In RCIO mode, the RC circuit is c onnected to O SC1.
OSC2 becomes an additional general purpose I/O pin. The output of the HFINTOSC connects to a postscaler
and m ultiplexer ( see Figure 2-1). On e of eight
The RC oscillator frequency is a function of the su pply frequencies ca n be selec ted via s oftware us ing the
voltage, the resistor (REXT) and capacitor (CEXT) values IRCF<2:0> bit s of the O SCCON register . See
and the operating temp erature. O ther factors affecting Section 2.5.4 “Frequency Select Bits (IRCF)” for
the oscillator frequency are: more information.
• input threshold voltage variation
The HFINTOSC is enabled when:
• component tolerances
• packaging variations in capacitance • SCS1 = 1 and IRCF<2:0>  000
The user also needs to take into account variation due • SCS1 = 1 and IRCF<2:0> = 000 and INTSRC = 1
to tolerance of external RC components used. • IESO bit of CONFIG1H = 1 enabling Two-Speed
Start-up.
• FCMEM bit of CONFIG1H = 1 enabling Two-
Speed Start-up and Fail-Safe mode.
• FOSC<3:0> of CONFIG1H selects the internal
oscillator as the primary clock
The H F In ternal O scillator (IOFS) bi t o f the O SCCON
register indicates whether the HFINTOSC is stable or not.

DS41303G-page 32  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
2.5.2.1 OSCTUNE Register (PWRT), Watchdog Timer (WDT), Fail-Safe Clock Mon-
itor (FS CM) and periphe rals, ar e not af fected by the
The H FINTOSC is fac tory ca librated b ut c an b e
change in frequency.
adjusted in software by writing to the TUN<5:0> bits of
the OSCTUNE register (Register 2-2). The OSCTUNE register also implements the INTSRC
and PLLEN bits, which control certain features of th e
The de fault v alue o f the TU N<5:0> is ‘ 000000’. Th e
internal oscillator block.
value is a 6-bit two’s complement number.
The INTSRC bit allows users to select w hich internal
When the OSC TUNE regis ter i s mod ified, the
oscillator pr ovides the cl ock so urce when the 31 kHz
HFINTOSC fr equency will be gin shif ting to the new
frequency option is selected. This is covered in greater
frequency. C ode ex ecution continues du ring this shift.
detail in Section 2.2.3 “Low Frequency Selection”.
There is no indication that the shift has occurred.
The PLLEN bit controls the operation of the frequency
OSCTUNE does not af fect the L FINTOSC frequency.
multiplier, PLL, in internal oscillator modes. For more
Operation of features that depend on the LF INTOSC
details a bout the function o f t he PLLEN b it see
clock source frequency , such as the Power-up Timer
Section 2.6.2 “PLL in HFINTOSC Modes”

REGISTER 2-2: OSCTUNE: OSCILLATOR TUNING REGISTER

R/W-0 R/W -0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
INTSRC PLLEN(1) TUN5 TUN4 TUN3 TUN2 TUN1 TUN0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 INTSRC: Internal Oscillator Low-Frequency Source Select bit

1 = 31.25 kHz device clock derived from 16 MHz HFINTOSC source (divide-by-512 enabled)
0 = 31 kHz device clock derived directly from LFINTOSC internal oscillator
bit 6 PLLEN: Frequency Multiplier PLL for HFINTOSC Enable bit(1)
1 = PLL enabled for HFINTOSC (8 MHz and 16 MHz only)
0 = PLL disabled
bit 5-0 TUN<5:0>: Frequency Tuning bits
011111 = Maximum frequency
011110 =
•••
000001 =
000000 = Oscillator module is running at the factory calibrated frequency.
111111 =
•••
100000 = Minimum frequency

Note 1: The PLLEN bit is active only when the HFINTOSC is the primary clock source (FOSC<2:0> = 100X) and
the selected frequency is 8 MHz or 16 MHz. Otherwise, the PLLEN bit is unavailable and always reads ‘0’.

 2010 Microchip Technology Inc. DS41303G-page 33

PIC18F2XK20/4XK20
2.5.3 LFINTOSC 2.5.5 HFINTOSC FREQUENCY DRIFT
The Low-Frequency Internal Oscillator (LFINTOSC) is The factory calibrates the internal oscillator block output
a 31 kHz internal clock source. (HFINTOSC) f or 16 MHz. H owever, this f requency may
The out put o f the LFINTOSC con nects to inte rnal drift as VDD or temperature changes, which can affect the
oscillator block freq uency s election mul tiplexer (s ee controller operation in a var iety of w ays. It is possibl e to
Figure 2-1). Sel ect 31 kHz, via s oftware, usi ng the adjust the HFINTOSC frequency by modifying the value
IRCF<2:0> bit s of th e O SCCON register and the of the TUN<5:0> bits in the OSCTUNE register. This has
INTSRC bit of th e O SCTUNE reg ister. See no effect on the LFINTOSC clock source frequency.
Section 2.5.4 “Frequency Select Bits (IRCF)” for Tuning the HFINTOSC source requires knowing when to
more information. The LFINTOSC is also the frequency make the adjus tment, in w hich directio n it should be
for the Power-up T imer (PWRT), W atchdog T imer made and in some cases, how large a change is
(WDT) and Fail-Safe Clock Monitor (FSCM). needed. Th ree po ssible c ompensation techniques are
The LFINTOSC is enabled when any of the following discussed in the following sections, however other tech-
are enabled: niques may be used.

• IRCF<2:0> bits of the OSCCON register = 000 and 2.5.5.1 Compensating with the USART
INTSRC bit of the OSCTUNE register = 0
An adj ustment m ay be req uired w hen the USART
• Power-up Timer (PWRT) begins to generate framing errors or receives data with
• Watchdog Timer (WDT) errors while in As ynchronous m ode. Framing error s
• Fail-Safe Clock Monitor (FSCM) indicate that the device clock frequency is too high; to
adjust for th is, decrement the value in OSCTUNE to
2.5.4 FREQUENCY SELECT BITS (IRCF) reduce the clock frequency. On the other hand, errors
The output of t he 16 MHz H FINTOSC an d 3 1 kHz in data may suggest that the clock speed is too low; to
LFINTOSC co nnects to a postscaler and multiplexer compensate, in crement O SCTUNE to inc rease the
(see Figure 2-1). The Int ernal Os cillator Fre quency clock frequency.
Select bits IRCF<2:0> of th e OSCCON register select
the output frequency of the internal oscillators. One of 2.5.5.2 Compensating with the Timers
eight frequencies can be selected via software: This technique compares device clock speed to some
• 16 M Hz reference clock. Two timers may be used; one timer is
clocked by the pe ripheral clo ck, w hile the other is
• 8 M Hz
clocked by a fi xed re ference source, s uch as th e
• 4 M Hz Timer1 oscillator.
• 2 M Hz
Both timers are cleared, but the timer clocked by the
• 1 MHz (Default after Reset) reference gen erates int errupts. Whe n an in terrupt
• 500 kHz occurs, th e internally c locked ti mer i s read a nd both
• 250 kHz timers are cleared. If the internally clocked timer value
• 31 kHz (LFINTOSC or HFINTOSC/512) is gre ater th an ex pected, th en the internal osc illator
block is running too fast. To adjust for this, decrement
the OSCTUNE register.
Note: Following any Reset, the IRCF<2:0> bits of
the OSCCON register are set to ‘011’ and 2.5.5.3 Compensating with the CCP Module
the fr equency selection i s s et to 1 MHz. in Capture Mode
The use r can modify the IRCF bit s to A CCP module can use free running Timer1 (or Timer3),
select a different frequency. clocked b y t he i nternal o scillator bl ock a nd a n external
event w ith a k nown pe riod (i .e., A C po wer f requency).
The time of the fi rst e vent is c aptured in th e
CCPRxH:CCPRxL registers and is recorded for use later.
When the second event causes a capture, the time of the
first e vent i s subtracted from th e time of th e second
event. Since the period of the external event is known,
the time difference between events can be calculated.
If th e mea sured t ime is much gr eater tha n t he ca lcu-
lated time, t he i nternal osci llator bl ock is running to o
fast; to compensate, decrement the OSCTUNE register.
If the measured time is much les s than the calculated
time, the internal oscillator block is running too slow; to
compensate, increment the OSCTUNE register.

DS41303G-page 34  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
2.6 PLL Frequency Multiplier 2.6.2 PLL IN HFINTOSC MODES
A Phase Locked Loop (PLL) circuit is provided as an The 4x frequency multiplier can be used with the inter-
option fo r us ers w ho w ish to u se a lo wer fre quency nal o scillator blo ck to p roduce fas ter d evice cl ock
oscillator circuit or to clock the device up to its highest speeds than are norm ally possible w ith an int ernal
rated frequency from the crystal oscillator. This may be oscillator. Whe n ena bled, th e PLL pro duces a cl ock
useful for customers who are concerned with EMI due speed of up to 64 MHz.
to high-frequency crystals or users who require higher Unlike H SPLL mo de, the PLL is controlled through
clock sp eeds f rom an i nternal os cillator. Th ere a re software. T he PL LEN co ntrol bi t of t he O SCTUNE
three conditions when the PLL can be used: register is used to enable or disable the PLL operation
• When the primary clock is HSPLL when the HFINTOSC is used.
• When the primary clock is HFINTOSC and the The PLL is availa ble when the devi ce is configured to
selected frequency is 16 MHz use t he internal osc illator bloc k as it s p rimary cloc k
• When the primary clock is HFINTOSC and the source (FOSC<3:0> = 1001 or 1000). Additionally, the
selected frequency is 8 MHz PLL w ill only func tion w hen t he selected output fre-
quency is either 8 MHz or 16 MHz (O SCCON<6:4> =
2.6.1 HSPLL OSCILLATOR MODE 111 or 110). If both of these conditions are not met, the
PLL is disabled.
The HSPLL mode makes use of the HS mode oscillator
for frequencies up to 16 MHz. A PLL then multiplies the The PLLEN control bit is only functional in those inter-
oscillator output frequency by 4 to produce an internal nal oscillator modes where the PLL is available. In all
clock frequency up to 64 MHz. The PLLEN bit of the other m odes, it i s fo rced to ‘ 0’ an d is ef fectively
OSCTUNE register is active only when the HFINTOSC unavailable.
is the primary clock and is not available in HSPLL oscil-
lator mode.
The PLL is only available to the primary oscillator when
the FOSC<3:0> Configuration bits are programmed for
HSPLL mode (= 0110).

FIGURE 2-6: PLL BLOCK DIAGRAM

(HS MODE)
HS Oscillator Enable
PLL Enable
(from Configuration Register 1H)

OSC2
Phase
HS Mode FIN Comparator
OSC1 Crystal FOUT
Osc

Loop
Filter

4 VCO
SYSCLK
MUX

 2010 Microchip Technology Inc. DS41303G-page 35

PIC18F2XK20/4XK20
2.7 Effects of Power-Managed Modes 2.8 Power-up Delays
on the Various Clock Sources Power-up delays are controlled by two timers, so that
For more information about the modes discussed in this no external Reset circuitry is required for most applica-
section see Section 3.0 “Power-Managed Modes”. A tions. The de lays ensure t hat the d evice i s k ept i n
quick reference list is also available in Table 3-1. Reset until the device power supply is stable under nor-
mal circumstances and the primary clock is operating
When PRI_IDLE mode is selected, the designated pri-
and s table. Fo r ad ditional information o n p ower-up
mary oscillator continues to run w ithout int erruption.
delays, see Section 4.5 “Device Reset Timers”.
For a ll other p ower-managed modes, t he oscillator
using the OSC1 pi n i s disabled. Th e O SC1 pin (an d The first tim er is the Power-up Timer (PWRT), w hich
OSC2 pin, if used by the oscillator) will stop oscillating. provides a f ixed de lay on pow er-up (parameter 3 3,
Table 26-10). It i s en abled by c learing (= 0) th e
In se condary clock mo des (SEC_RUN a nd
PWRTEN Configuration bit.
SEC_IDLE), th e T imer1 oscillator is ope rating an d
providing the device clock. The Timer1 oscillator may The s econd tim er i s t he O scillator S tart-up T imer
also run in al l po wer-managed mo des if required to (OST), i ntended to ke ep the ch ip in Res et un til th e
clock Timer1 or Timer3. crystal oscillator is stable (LP, XT and HS modes). The
OST d oes th is by co unting 10 24 o scillator c ycles
In internal o scillator m odes (INT OSC_RUN a nd
before allowing the oscillator to clock the device.
INTOSC_IDLE), t he internal oscillator b lock p rovides
the device clock source. The 31 kHz LFINTOSC output When the H SPLL O scillator m ode i s selected, th e
can be used directly to provide the clock and may be device is kept in Reset for an additional 2 ms, following
enabled to support various special features, regardless the H S mode OST delay, so the PLL can lock to th e
of th e power-managed m ode (s ee Section 23.2 incoming clock frequency.
“Watchdog Timer (WDT)”, Section 2.10 “Two- There is a del ay of in terval TCSD (pa rameter 38,
Speed Clock Start-up Mode” and Section 2.11 “Fail- Table 26-10), fol lowing POR, w hile th e c ontroller
Safe Clock Monitor” fo r m ore in formation on W DT, becomes ready to execute instructions. This delay runs
Fail-Safe Clock Monitor and Two-Speed Start-up). The concurrently w ith any oth er del ays. Th is m ay be the
HFINTOSC output at 16 MHz may be used directly to only delay that occurs when any of the EC, RC or INTIO
clock the device or may be divided down by the post- modes are used as the primary clock source.
scaler. The HFINTOSC output is disabled if the clock is
When the HFINTOSC is selected as the primary clock,
provided directly from the LFINTOSC output.
the ma in s ystem cl ock ca n be delayed un til th e
If the Slee p m ode is se lected, al l c lock sou rces a re HFINTOSC is st able. This is us er sel ectable by the
stopped. Si nce all th e transistor s witching currents HFOFST bit o f the CONFIG3H Configuration register.
have been stopped, Sleep mode achieves the lowest When the HFOFST bit is cleared the main system clock
current c onsumption of the de vice (only l eakage is de layed u ntil t he H FINTOSC is sta ble. W hen t he
currents). HFOFST bit is set the main system clock starts imme-
Enabling any on- chip fe ature tha t w ill operate d uring diately. In either case the IOFS bit of the OSCCON reg-
Sleep will increase the current consumed during Sleep. ister can be read to determine whether the HFINTOSC
The LFINTOSC is required to support WDT operation. is operating and stable.
The T imer1 o scillator m ay be operating to s upport a
real-time clock. Other features may be operating that
do not require a device clock source (i.e., SSP s lave,
PSP, INTn pins and others). Peripherals that may add
significant cu rrent consumption are li sted in
Section 26.8 “DC Characteristics”.

TABLE 2-2: OSC1 AND OSC2 PIN STATES IN SLEEP MODE

OSC Mode OSC1 Pin OSC2 Pin
RC, INTOSC Floating, external resistor should pull high At logic low (clock/4 output)
RCIO Floating, external resistor should pull high Configured as PORTA, bit 6
INTOSCIO Configured as PORTA, bit 7 Configured as PORTA, bit 6
ECIO Floating, pulled by external clock Configured as PORTA, bit 6
EC Floating, pulled by external clock At logic low (clock/4 output)
LP, XT, HS and HSPLL Feedback inverter disabled at quiescent Feedback inverter disabled at quiescent
voltage level voltage level
Note: See Table 4-2 in Section 4.0 “Reset” for time-outs due to Sleep and MCLR Reset.

DS41303G-page 36  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
2.9 Clock Switching 2.9.3 CLOCK SWITCH TIMING
The s ystem cl ock s ource c an b e sw itched b etween When sw itching bet ween one os cillator and ano ther,
external and internal clock sources via software using the new oscillator may not be op erating w hich saves
the S ystem C lock S elect (SCS<1:0>) b its of the power (s ee Fi gure 2-7). If th is is th e c ase, the re is a
OSCCON register. delay after the SCS<1:0> bits of the OSCCON register
are modified before the frequency change takes place.
PIC18F2XK20/4XK20 devices contain circuitry to pre- The OSTS and IOFS bits of the OSCCON register will
vent c lock “glitches” when s witching b etween clock reflect the current ac tive s tatus of th e ex ternal an d
sources. A short pause in the device clock occurs dur- HFINTOSC o scillators. The t iming of a frequency
ing the clock switch. The length of this pause is the sum selection is as follows:
of two cycles of the old clock source and three to four
cycles of the new clock source. This formula assumes 1. SCS<1:0> bits of the OSCCON register are mod-
that the new clock source is stable. ified.
2. The old clock continues to operate until the new
Clock t ransitions a re discussed in gre ater de tail i n
clock is ready.
Section 3.1.2 “Entering Power-Managed Modes”.
3. Clock switch circuitry waits for two consecutive
2.9.1 SYSTEM CLOCK SELECT rising edges of the old clock after the new clock
(SCS<1:0>) BITS ready signal goes true.
The Sys tem Clock Sele ct (SC S<1:0>) bi ts o f the 4. The system clock is held low starting at the next
OSCCON register select the system clock source that falling edge of the old clock.
is used for the CPU and peripherals. 5. Clock switch circuitry waits for an additional two
rising edges of the new clock.
• When SCS<1:0> = 00, the system clock source is
determined by configuration of the FOSC<2:0> 6. On the next falling edge of the new clock the low
bits in the CONFIG1H Configuration register. hold on t he system c lock i s released a nd new
clock is switched in as the system clock.
• When SCS<1:0> = 10, the system clock source is
chosen by the internal oscillator frequency 7. Clock switch is complete.
selected by the INTSRC bit of the OSCTUNE See Figure 2-1 for more details.
register and the IRCF<2:0> bits of the OSCCON If the HFINTOSC is the source of both the old and new
register. frequency, th ere is no st art-up d elay b efore th e n ew
• When SCS<1:0> = 01, the system clock source is frequency is active. This is because the ol d and new
the 32.768 kHz secondary oscillator shared with frequencies are der ived fro m t he H FINTOSC vi a th e
Timer1. postscaler and multiplexer.
After a Reset, th e SC S<1:0> bits o f the OSCCON Start-up de lay sp ecifications are located in
register are always cleared. Section 26.0 “Electrical Characteristics”, under AC
Note: Any automa tic clock sw itch, whi ch may Specifications (Oscillator Module).
occur from Two-Speed Start-up or Fail-Safe
Clock Mon itor, does not upd ate the
SCS<1:0> bi ts of the O SCCON register.
The user can monitor the T1RUN bit of the
T1CON register and the IOFS and O STS
bits of the OSCCON register to d etermine
the current system clock source.

2.9.2 OSCILLATOR START-UP TIME-OUT

STATUS (OSTS) BIT
The O scillator Start-up Time-out Status (O STS) bit of
the OSCCON register in dicates w hether the sy stem
clock is run ning from the ex ternal cl ock source, a s
defined b y t he F OSC<3:0> bi ts in t he C ONFIG1H
Configuration re gister, o r fro m the in ternal clock
source. In particular, when the primary oscillator is the
source of th e p rimary cl ock, O STS indicates th at th e
Oscillator Start-up Timer ( OST) h as timed ou t for LP,
XT or HS modes.

 2010 Microchip Technology Inc. DS41303G-page 37

PIC18F2XK20/4XK20
2.10 Two-Speed Clock Start-up Mode 2.10.2 TWO-SPEED START-UP
SEQUENCE
Two-Speed S tart-up m ode pro vides a dditional po wer
savings b y m inimizing th e la tency bet ween ext ernal 1. Wake-up from Power-on Reset or Sleep.
oscillator start-up and code execution. In app lications 2. Instructions b egin e xecuting by the int ernal
that make heavy use of the Sleep mode, Two-Speed oscillator at the frequency set in the IRCF<2:0>
Start-up w ill rem ove the external os cillator s tart-up bits of the OSCCON register.
time fro m the tim e spent aw ake and c an red uce th e 3. OST e nabled to count 1 024 ex ternal cl ock
overall power consumption of the device. cycles.
This mode a llows th e app lication to w ake-up fr om 4. OST timed out. External clock is ready.
Sleep, perform a few instructions using the HFINTOSC 5. OSTS is set.
as t he cl ock sou rce and g o ba ck to S leep w ithout 6. Clock switch finishes according to FIGURE 2-7:
waiting for the primary oscillator to become stable. “Clock Switch Timing”
Note: Executing a SLEEP ins truction w ill abo rt
the oscillator start-up time and w ill cause 2.10.3 CHECKING TWO-SPEED CLOCK
the OS TS bi t of the OSCCON register t o STATUS
remain clear. Checking t he s tate of t he OS TS b it of the OSCCON
When the Oscillator module is configured for LP, XT or register will c onfirm if th e m icrocontroller is running
HS mode s, th e Oscilla tor S tart-up Timer (OS T) is from the ex ternal cl ock so urce, as defined by t he
enabled (see Section 2.4.1 “Oscillator Start-up Timer FOSC<2:0> bits in CONFIG1H Configuration register,
(OST)”). The OST will suspend program execution until or the internal oscillator. OSTS = 0 when the external
1024 osc illations ar e co unted. T wo-Speed S tart-up oscillator is not ready, which indicates that the system
mode mi nimizes the delay i n code e xecution b y is running from the internal oscillator.
operating from the in ternal oscill ator as t he OST is
counting. When the OST count reaches 1024 and the
OSTS bit of the O SCCON regis ter i s set, program
execution switches to the external oscillator.

2.10.1 TWO-SPEED START-UP MODE

CONFIGURATION
Two-Speed Start-up mode is enabled w hen all of the
following settings are configured as noted:
• Two-Speed Start-up mode is enabled by setting
the IESO of the CONFIG1H Configuration register
is set. Fail-Safe mode (FCMEM = 1) also enables
two-speed by default.
• SCS<1:0> (of the OSCCON register) = 00.
• FOSC<2:0> bits of the CONFIG1H Configuration
register are configured for LP, XT or HS mode.
Two-Speed Start-up mode becomes active after:
• Power-on Reset (POR) and, if enabled, after
Power-up Timer (PWRT) has expired, or
• Wake-up from Sleep.
If th e ext ernal clock oscillator is co nfigured to be
anything ot her t han LP, XT or HS m ode, t hen T wo-
Speed S tart-up is d isabled. This is be cause t he
external clock o scillator does n ot re quire a ny
stabilization time after POR or an exit from Sleep.

DS41303G-page 38  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 2-7: CLOCK SWITCH TIMING

High Speed Low Speed

Old Clock
Start-up Time(1) Clock Sync Running

New Clock

New Clk Ready

IRCF <2:0> Select Old Select New

System Clock

Low Speed High Speed

Old Clock
Start-up Time(1) Clock Sync Running

New Clock

New Clk Ready

IRCF <2:0> Select Old Select New

System Clock

Note 1: Start-up time includes TOST (1024 TOSC) for external clocks, plus TPLL (approx. 2 ms) for HSPLL mode.

 2010 Microchip Technology Inc. DS41303G-page 39

PIC18F2XK20/4XK20
2.11 Fail-Safe Clock Monitor 2.11.3 FAIL-SAFE CONDITION CLEARING
The Fail-Safe Clock Monitor (FSCM) allows the device The Fail-Safe condition is cleared by either one of the
to continue operating should the external oscillator fail. following:
The FSCM can detect oscillator failure any time after • Any R eset
the Oscillator Start-up Timer (OST) h as ex pired. Th e • By toggling the SCS1 bit of the OSCCON register
FSCM is enabled by s etting th e F CMEN bit in th e
CONFIG1H C onfiguration register. The FSC M i s Both of th ese co nditions re start the OST. Whi le th e
applicable to all external oscillator modes (LP, XT, HS, OST is running, the device continues to operate from
EC, RC and RCIO). the IN TOSC s elected in OS CCON. Wh en th e O ST
times o ut, th e Fa il-Safe con dition is cl eared an d th e
device automatically switches over to the external clock
FIGURE 2-8: FSCM BLOCK DIAGRAM
source. The Fai l-Safe co ndition nee d not be cl eared
Clock Monitor before the OSCFIF flag is cleared.
Latch
External
S Q
2.11.4 RESET OR WAKE-UP FROM SLEEP
Clock
The FSC M is designed to detect an os cillator fa ilure
after the Oscillator Start-up Timer (OST) has expired.
LFINTOSC The OST is used after waking up from Sleep and after
÷ 64 R Q any type of Reset. The OST is not used with the EC or
Oscillator
RC C lock m odes so tha t th e F SCM w ill be active a s
31 kHz 488 Hz soon as t he R eset o r w ake-up has completed. W hen
(~32 s) (~2 ms)
the FSCM is enabled, the Two-Speed Start-up is also
enabled. Therefore, the device will always be executing
Sample Clock Clock code while the OST is operating.
Failure
Detected Note: Due to the wide range of oscillator start-up
times, the Fail-Safe circuit is not ac tive
during oscillator st art-up (i.e., af ter ex iting
2.11.1 FAIL-SAFE DETECTION Reset or Sleep). Af ter an appropriate
The FS CM m odule dete cts a fai led os cillator b y amount of time, the user should check the
comparing the external oscillator to the FSCM sample OSTS bit of the OSCCON register to verify
clock. The s ample cl ock i s g enerated by di viding th e the oscillator start-up and that the sys tem
LFINTOSC by 64. See Figure 2-8. Ins ide the fai l clock sw itchover has succ essfully
detector block is a latc h. The ex ternal c lock s ets the completed.
latch on each fal ling ed ge o f the external cl ock. Th e
sample clock clears the latch on each rising edge of the
sample clock. A failure is detected when an entire half-
cycle of the sample clock elapses before the primary
clock goes low.

2.11.2 FAIL-SAFE OPERATION

When the external clock fails, the FSCM switches the
device clock to an internal clock source and sets the bit
flag OSCFIF of the PIR2 register. The OSCFIF flag will
generate an int errupt if the OSCFIE bit of th e PIE2
register is also set. The device firmware can then take
steps to mi tigate the problems that may arise from a
failed cl ock. T he s ystem c lock w ill co ntinue t o be
sourced from the internal clock source until the device
firmware s uccessfully re starts the e xternal os cillator
and switches back to external operation. An automatic
transition back to the failed clock source will not occur.
The in ternal cl ock so urce ch osen by the FSC M is
determined by the IRCF<2:0> b its of th e OSC CON
register. Thi s al lows the internal os cillator to be
configured before a failure occurs.

DS41303G-page 40  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 2-9: FSCM TIMING DIAGRAM

Sample Clock

System Oscillator
Clock Failure
Output

Clock Monitor Output

(Q)
Failure
Detected
OSCFIF

Test Test Test

Note: The system clock is normally at a much higher frequency than the sample clock. The relative frequencies in
this example have been chosen for clarity.

TABLE 2-3: SUMMARY OF REGISTERS ASSOCIATED WITH CLOCK SOURCES

Value on
Value on
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 all other
POR, BOR
Resets(1)

CONFIG1H IESO FCMEN — — FOSC3 FOSC2 FOSC1 FOSC0 — —

INTCON GIE/GIEH P EIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000x
OSCCON IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 0011 q000 0011 q000
OSCTUNE INTSRC PLLEN TUN5 TUN4 TUN3 TUN2 TUN1 TUN0 0000 0000 000u uuuu
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 0000 0000 0000 0000
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 0000 0000 0000 0000
IPR2 OSCFIP — — — — — — — 1111 1111 1111 1111
Legend: x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by oscillators.
Note 1: Other (non Power-up) Resets include MCLR Reset and Watchdog Timer Reset during normal operation.

 2010 Microchip Technology Inc. DS41303G-page 41

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 42  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
3.0 POWER-MANAGED MODES 3.1.1 CLOCK SOURCES
PIC18F2XK20/4XK20 dev ices of fer a to tal of s even The SCS<1:0> bits allow the selection of one of three
operating modes fo r m ore e fficient po wer manage- clock sources for power-managed modes. They are:
ment. The se mo des pro vide a v ariety of op tions for • the primary clock, as defined by the FOSC<3:0>
selective p ower conservation in ap plications w here Configuration bits
resources ma y be lim ited (i.e ., battery-powered • the secondary clock (the Timer1 oscillator)
devices). • the internal oscillator block
There are three categories of power-managed modes:
3.1.2 ENTERING POWER-MANAGED
• Run modes
MODES
• Idle modes
• Sleep mode Switching from one power-managed mode to another
begins by lo ading the O SCCON re gister. Th e
These categories define w hich portions of the device SCS<1:0> bits select the clock source and determine
are clocked and sometimes, what speed. The Run and which Run or Idle mode is to be used. Changing these
Idle modes m ay us e a ny of the three av ailable cl ock bits ca uses a n im mediate sw itch to th e ne w cl ock
sources (pr imary, s econdary or i nternal os cillator source, assuming that it is run ning. The switch ma y
block); the Sleep mode does not use a clock source. also be s ubject t o cl ock t ransition d elays. T hese are
The pow er-managed modes include several pow er- discussed in Section 3.1.3 “Clock Transitions and
saving features offered on previous PIC® microcontroller Status Indicators” and subsequent sections.
devices. One is the clock switching feature which allows Entry to the po wer-managed Idle or S leep mo des is
the controller to use the Timer1 oscillator in place of the triggered by the execution of a SLEEP instruction. The
primary oscillator. Also inc luded is the S leep mode, actual mode that results depends on the status of the
offered by al l PIC ® microcontroller d evices, w here all IDLEN bit of the OSCCON register.
device clocks are stopped.
Depending on the c urrent mod e and the m ode being
switched to, a change to a power-managed mode does
3.1 Selecting Power-Managed Modes not always require s etting all of the se bi ts. M any
Selecting a pow er-managed mode r equires two transitions may be done by changing the oscillator select
decisions: bits, or changing the IDLEN bit, prior to issuing a SLEEP
instruction. If the ID LEN bit is al ready c onfigured
• Whether or not the CPU is to be clocked
correctly, it may only be necessary to perform a SLEEP
• The selection of a clock source instruction to switch to the desired mode.
The IDLEN bit of the OSCCON register controls CPU
clocking, w hile t he S CS<1:0> b its of the OS CCON
register select the clock source. The individual modes,
bit settings, c lock sources a nd affected m odules a re
summarized in Table 3-1.

TABLE 3-1: POWER-MANAGED MODES

OSCCON Bits Module Clocking
Mode Available Clock and Oscillator Source
IDLEN(1) SCS<1:0> CPU Peripherals
Sleep 0 N/A Off Off None – All clocks are disabled
PRI_RUN N/A 00 Clocked Clocked Primary – LP, XT, HS, HSPLL, RC, EC and
Internal Oscillator Block(2).
This is the normal full power execution mode.
SEC_RUN N/A 01 Clocked Clocked Secondary – Timer1 Oscillator
RC_RUN N/A 1x Clocked Clocked Internal Oscillator Block(2)
PRI_IDLE 1 00 Off Clocked Primary – LP, XT, HS, HSPLL, RC, EC
SEC_IDLE 1 01 Off Clocked Secondary – Timer1 Oscillator
RC_IDLE 1 1x Off Clocked Internal Oscillator Block(2)
Note 1: IDLEN reflects its value when the SLEEP instruction is executed.
2: Includes HFINTOSC and HFINTOSC postscaler, as well as the LFINTOSC source.

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PIC18F2XK20/4XK20
3.1.3 CLOCK TRANSITIONS AND 3.2 Run Modes
STATUS INDICATORS
In the Run m odes, c locks to bot h the co re an d
The length of the transition between clock sources is peripherals are ac tive. Th e difference bet ween these
the sum of: modes is the clock source.
• Start-up time of the new clock
3.2.1 PRI_RUN MODE
• Two and one half cycles of the old clock source
• Two and one half cycles of the new clock The PRI_RUN mode is the normal, full power execution
mode o f th e microcontroller. Th is i s also the default
Three flag bits indicate the current clock source and its mode upon a device R eset, unless Two-Speed Start-
status. They are: up is en abled (se e Section 2.10 “Two-Speed Clock
• OSTS (of the OSCCON register) Start-up Mode” for details). In this mode, the OSTS bit
• IOFS (of the OSCCON register) is set. The IOFS bit will be set if the HFINTOSC is the
• T1RUN (of the T1CON register) primary clock source and the oscillator is stable (see
Section 2.2 “Oscillator Control”).
In general, only one of these bits will be set while in a
given power-managed mode. Table 3-2 shows the rela- 3.2.2 SEC_RUN MODE
tionship of the fla gs to the active ma in sy stem cl ock
The SEC_RUN mo de i s t he mode compatible to th e
source.
“clock s witching” f eature offered i n o ther PIC 18
devices. I n thi s m ode, th e C PU and pe ripherals a re
TABLE 3-2: SYSTEM CLOCK INDICATORS clocked from the Timer1 oscillator. This gives users the
OSTS IOFS T1RUN Main System Clock Source option o f l ower p ower consumption w hile s till u sing a
high accuracy clock source.
1 0 0 Primary Oscillator
SEC_RUN mo de i s en tered b y s etting t he S CS<1:0>
0 1 0 HFINTOSC
bits to ‘01’. When SEC_RUN mode is active all of the
0 0 1 Secondary Oscillator following are true:
1 1 0 HFINTOSC as primary clock • The main clock source is switched to the Timer1
LFINTOSC or oscillator
0 0 0
HFINTOSC is not yet stable • Primary oscillator is shut down
. • T1RUN bit of the T1CON register is set
Note 1: Executing a SLEEP in struction do es not • OSTS bit is cleared.
necessarily pl ace th e d evice i nto Sleep Note: The T imer1 osc illator sh ould al ready be
mode. It a cts as the t rigger to place the running prior to entering SEC_RUN mode.
controller in to eit her the Sleep mode or If t he T1 OSCEN b it is not set when th e
one of the Idle modes, depending on the SCS<1:0> bits a re s et t o ‘ 01’, en try to
setting of the IDLEN bit. SEC_RUN mo de will n ot o ccur until
T1OSCEN bit is set and Timer1 oscillator
3.1.4 MULTIPLE FUNCTIONS OF THE is ready.
SLEEP COMMAND
On transitions from SEC_RUN mode to PRI_RUN, the
The po wer-managed mode tha t is i nvoked w ith the peripherals and CPU continue to be clocked from the
SLEEP instruction is determined by the s etting of the Timer1 o scillator w hile th e primary clock i s started.
IDLEN bit o f the OSCCON regi ster at th e tim e th e When the primary clock becomes ready, a clock switch
instruction is executed. All c locks sto p an d mi nimum back to th e pri mary c lock oc curs (s ee Fi gure 2-7).
power is consumed when SLEEP is executed with the When th e clock swi tch is co mplete, th e T1RUN bit i s
IDLEN bit cleared. The system clock continues to sup- cleared, the O STS bit is set and the primary clock is
ply a clock to the peripherals but is disconnected from providing the main system clock. The Timer1 oscillator
the CPU when SLEEP is executed with the IDLEN bit continues to run as long as the T1OSCEN bit is set.
set.

DS41303G-page 44  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
3.2.3 RC_RUN MODE 3.3 Sleep Mode
In R C_RUN mode, th e C PU a nd p eripherals are The Power-Managed Sleep mode in the PIC18F2XK20/
clocked from the internal oscillator block using one of 4XK20 devi ces is id entical t o the lega cy Sle ep mod e
the selections from the HFINTOSC multiplexer. In this offered in all oth er PIC® mi crocontroller devi ces. It is
mode, t he primary osc illator i s shut down. R C_RUN entered by clearing the IDLEN bit (the default state on
mode provides the best power conservation of all the device R eset) and execu ting the SLEEP i nstruction.
Run m odes w hen the LFINTOSC is the m ain cl ock This shuts down the selected oscillator (Figure 3-1). All
source. It works well for user applications which are not clock source Status bits are cleared.
highly timing se nsitive or do no t require hig h-speed
clocks at all times. Entering the Sleep mode from any other mode does not
require a clock switch. This is because no cl ocks are
If the pri mary clock s ource is the in ternal oscillator needed once th e controller h as e ntered Sleep. If th e
block (either LFINTOSC or HFINTOSC), there are no WDT is selected, the LFINTOSC source will continue to
distinguishable d ifferences b etween PRI_RUN a nd operate. If the Timer1 oscillator is enabled, it w ill also
RC_RUN m odes during e xecution. Ho wever, a c lock continue to run.
switch de lay w ill oc cur du ring ent ry to and exi t fro m
RC_RUN mode. Therefore, if the primary clock source When a wake event occurs in Sleep mode (by interrupt,
is the inte rnal os cillator bl ock, th e us e of R C_RUN Reset or WDT time-out), the device will not be clocked
mode is not recommended. See 2.9.3 “Clock Switch until the cl ock s ource s elected b y th e SC S<1:0> bits
Timing” for details about clock switching. becomes ready (see Figure 3-2), or i t w ill be clocked
from the internal oscillator block if either the Two-Speed
RC_RUN mo de i s e ntered b y s etting the SCS1 b it to Start-up or the Fai l-Safe C lock Mo nitor are ena bled
‘1’. The SCS0 bit can be either ‘0’ or ‘1’ but should be (see Section 23.0 “Special Features of the CPU”). In
‘0’ to ma intain so ftware co mpatibility w ith futu re either case, the OSTS bit is set when the primary clock
devices. When t he cl ock s ource i s swi tched f rom t he is providing the device clocks. The IDLEN and SCS bits
primary oscillator to the HFINTOSC multiplexer, the pri- are not affected by the wake-up.
mary os cillator is sh ut do wn an d the OST S bit i s
cleared. The IRCF bits may be modified at any time to
3.4 Idle Modes
immediately change the clock speed.
On transitions from RC_RUN mode to PRI_RUN mode, The Id le m odes al low th e c ontroller’s C PU to b e
the dev ice co ntinues to be c locked from the int ernal selectively shut down while the peripherals continue to
oscillator block w hile the pri mary oscillator is st arted. operate. Selecting a particular Idle mode allows users
When the pri mary o scillator b ecomes ready, a cl ock to further manage power consumption.
switch t o t he primary c lock oc curs. Wh en the clock If the IDLEN bit is set to a ‘1’ when a SLEEP instruction is
switch is complete, the IOFS bit is cleared, the OSTS executed, the peripherals will be clocked from the clock
bit is set and the primary oscillator is providing the main source selected by the SCS<1:0> bits; however, the CPU
system clock. The HFINTOSC will continue to run if any will not be clocked. The clock source Status bits are not
of the conditions noted in Section 2.5.2 “HFINTOSC” affected. Setting IDLEN and executing a SLEEP instruc-
are met. The LFINTOSC source will continue to run if tion provides a quick method of switching from a given
any of the co nditions noted in Section 2.5.3 “LFIN- Run mode to its corresponding Idle mode.
TOSC” are met.
If the WDT is selected, the LFINTOSC source will con-
tinue to operate. If the Timer1 oscillator is enabled, it
will also continue to run.
Since the C PU is not executing instructions, the only
exits from any of the Idle modes are by interrupt, WDT
time-out, or a Reset. When a wake event occurs, CPU
execution is d elayed by an i nterval of T CSD
(parameter 38, Table 26-10) while it becomes ready to
execute code. When the CPU begins executing code,
it resumes with the same clock source for the current
Idle mode. For example, when waking from RC_IDLE
mode, the in ternal oscillator block w ill clock the CPU
and peripherals (in other words, RC_RUN mode). The
IDLEN and SCS bits are not affected by the wake-up.
While in an y Idle mode or t he S leep mod e, a WDT
time-out will result in a WDT wake-up to the Run mode
currently specified by the SCS<1:0> bits.

 2010 Microchip Technology Inc. DS41303G-page 45

PIC18F2XK20/4XK20
FIGURE 3-1: TRANSITION TIMING FOR ENTRY TO SLEEP MODE
Q1 Q2 Q3 Q4 Q1

OSC1

CPU
Clock
Peripheral
Clock

Sleep

Program
Counter PC PC + 2

FIGURE 3-2: TRANSITION TIMING FOR WAKE FROM SLEEP (HSPLL)

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

OSC1
TOST(1) TPLL(1)
PLL Clock
Output

CPU Clock
Peripheral
Clock
Program PC PC + 2 PC + 4 PC + 6
Counter
Wake Event OSTS bit set
Note1: TOST = 1024 TOSC; TPLL = 2 ms (approx). These intervals are not shown to scale.

DS41303G-page 46  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
3.4.1 PRI_IDLE MODE 3.4.2 SEC_IDLE MODE
This mo de is un ique am ong the th ree lo w-power Idle In SEC_IDLE mo de, the CPU is disabled but the
modes, in that it d oes not disable the primary device peripherals continue to be cl ocked from the Timer1
clock. For timing sensitive applications, this allows for oscillator. This mode is entered from SEC_RUN by set-
the fastest resumption of device operation with its more ting the IDLEN bit and executing a SLEEP instruction. If
accurate primary clock source, since the clock source the device is in another Run mode, set the IDLEN bit
does not have to “warm-up” or transition from another first, then se t the SCS<1:0 > bits to ‘ 01’ a nd execute
oscillator. SLEEP. When th e clock so urce i s swi tched t o t he
PRI_IDLE mo de is ent ered from PR I_RUN m ode by Timer1 os cillator, the pr imary os cillator is shut down,
setting the IDLEN bit and executing a SLEEP instruc- the OSTS bit is cleared and the T1RUN bit is set.
tion. If the device is in another Run mode, set IDLEN When a wake event occurs, the peripherals continue to
first, then cle ar th e SC S bits and exe cute SLEEP. be clocked from the Timer1 oscillator. After an interval
Although the CPU is disabled, the peripherals continue of TCSD following the wake event, the CPU begins exe-
to be clocked from the primary clock source specified cuting code being clocked by the Timer1 oscillator. The
by th e FO SC<3:0> C onfiguration b its. Th e O STS b it IDLEN and SCS bits are not affected by the wake-up;
remains set (see Figure 3.3). the Timer1 oscillator continues to run (see Figure 3-4).
When a wake event occurs, the CPU is clocked from the Note: The T imer1 osc illator sh ould al ready be
primary clock so urce. A delay of in terval T CSD is running prior to entering SEC_IDLE mode.
required between the w ake even t and w hen cod e If th e T1 OSCEN b it is not set wh en th e
execution starts. T his is re quired t o allow th e CPU t o SLEEP instruction is ex ecuted, th e m ain
become ready to execute instructions. After the wake- system clock will continue to operate in the
up, the OSTS bit remains set. The IDLEN and SCS bits previously sel ected mode and the co rre-
are not affected by the wake-up (see Figure 3-4). sponding IDLE mode will be entered (i.e.,
PRI_IDLE or RC_IDLE).

FIGURE 3-3: TRANSITION TIMING FOR ENTRY TO IDLE MODE

Q1 Q2 Q3 Q4 Q1

OSC1

CPU Clock

Peripheral
Clock

Program PC PC + 2
Counter

FIGURE 3-4: TRANSITION TIMING FOR WAKE FROM IDLE TO RUN MODE

Q1 Q2 Q3 Q4

OSC1

TCSD
CPU Clock

Peripheral
Clock

Program PC
Counter

Wake Event

 2010 Microchip Technology Inc. DS41303G-page 47

PIC18F2XK20/4XK20
3.4.3 RC_IDLE MODE 3.5.1 EXIT BY INTERRUPT
In RC_IDLE mode, the CPU is disabled but the periph- Any o f the av ailable i nterrupt so urces can ca use th e
erals continue to be clocked from the internal oscillator device to exit from an Idle mode or the Sleep mode to
block from t he H FINTOSC multiplexer output. Thi s a Run mode. To enable this functionality, an interrupt
mode allows for controllable power conservation during source must be enabled by setting its enable bit in one
Idle periods. of the INTCON or PIE registers. The PEIE bIt must also
From RC_RUN, t his mo de i s entered b y setting th e be set If the desired interrupt enable bit is in a PIE reg-
IDLEN b it an d ex ecuting a SLEEP i nstruction. If th e ister. The ex it s equence i s in itiated w hen the co rre-
device is in another Run mode, first set IDLEN, then set sponding interrupt flag bit is set.
the S CS1 b it an d e xecute SLEEP. It is recommended The in struction im mediately fo llowing the SLEEP
that SCS0 al so be cl eared, alt hough its v alue i s instruction is executed on all exits by interrupt from Idle
ignored, to m aintain software compatibility with future or Sleep modes. Code execution then branches to the
devices. The H FINTOSC multiplexer may be used to interrupt vector if the GIE/GIEH bit of the INTCON reg-
select a higher clock frequency by modifying the IRCF ister is set, otherwise code execution continues without
bits before executing the SLEEP instruction. When the branching (see Section 9.0 “Interrupts”).
clock source is switched to the HFINTOSC multiplexer, A fixed delay of interval TCSD following the wake event
the primary oscillator is shut down and the OSTS bit is is required when leaving Sleep and Idle modes. This
cleared. delay is required for the CPU to prepare for execution.
If the IRCF bits are set to a ny non-zero value, or th e Instruction execution r esumes on t he first c lock c ycle
INTSRC bit is set, the H FINTOSC output is e nabled. following this delay.
The IOFS bit becomes set, after the HFINTOSC output
becomes s table, a fter an inte rval of T IOBST 3.5.2 EXIT BY WDT TIME-OUT
(parameter 39, Table 26-10). Clocks to the peripherals A WDT time-out will cause different actions depending
continue while the HFINTOSC source stabilizes. If the on which power-managed mode the device is in when
IRCF b its w ere prev iously a t a n on-zero va lue, or the time-out occurs.
INTSRC was set before the SLEEP instruction was exe-
cuted and the HFINTOSC source was already stable, If the device is not executing code (all Idle modes and
the I OFS bi t wil l re main set. If the IRCF b its an d Sleep mode), the time-out will result in an exit from the
INTSRC are all clear, the HFINTOSC output will not be power-managed m ode (s ee Section 3.2 “Run
enabled, the IOFS bit will remain clear and there will be Modes” and Section 3.3 “Sleep Mode”). If the device
no indication of the current clock source. is ex ecuting co de ( all R un mo des), the t ime-out w ill
result in a WD T Reset (see Section 23.2 “Watchdog
When a wake event occurs, the peripherals continue to Timer (WDT)”).
be c locked from t he HFINTOSC mul tiplexer output.
After a de lay of T CSD fol lowing th e w ake eve nt, the The WDT timer and postscaler are cleared by any one
CPU beg ins ex ecuting cod e bei ng clocked by the of the following:
HFINTOSC multiplexer. The IDLEN and SCS bits are • executing a SLEEP instruction
not af fected by the w ake-up. The LFINTOSC s ource • executing a CLRWDT instruction
will continue to run if either the WDT or th e Fail-Safe • the loss of the currently selected clock source
Clock Monitor is enabled. when the Fail-Safe Clock Monitor is enabled
• modifying the IRCF bits in the OSCCON register
3.5 Exiting Idle and Sleep Modes when the internal oscillator block is the device
An exit from Sleep mode or an y of the Idle modes is clock source
triggered by any one of the following:
3.5.3 EXIT BY RESET
• an interrupt
Exiting Sleep an d Id le mo des by R eset causes c ode
• a R eset
execution to r estart a t ad dress 0. See Section 4.0
• a watchdog time-out “Reset” for more details.
This section di scusses the triggers that c ause ex its The ex it de lay tim e fro m R eset to the s tart o f code
from power-managed modes. The clocking subsystem execution de pends o n b oth th e c lock s ources b efore
actions are discussed in each of the power-managed and a fter the wake-up and the ty pe o f os cillator. Ex it
modes ( see Section 3.2 “Run Modes”, Section 3.3 delays are summarized in Table 3-3.
“Sleep Mode” and Section 3.4 “Idle Modes”).

DS41303G-page 48  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
3.5.4 EXIT WITHOUT AN OSCILLATOR In t hese instances, the primary c lock s ource e ither
START-UP DELAY does not require an oscillator start-up delay since it is
already running (PR I_IDLE), or norm ally does not
Certain e xits from p ower-managed modes d o n ot
require an oscillator start-up delay (RC, EC, INTOSC,
invoke the OST at all. There are two cases:
and INT OSCIO mod es). However, a fix ed delay of
• PRI_IDLE mode, where the primary clock source interval TCSD following the wake event is still required
is not stopped and when leaving Sleep and Idle modes to allow the CPU
• the primary clock source is not any of the LP, XT, to prepare for execution. Instruction execution resumes
HS or HSPLL modes. on the first clock cycle following this delay.

TABLE 3-3: EXIT DELAY ON WAKE-UP BY RESET FROM SLEEP MODE OR ANY IDLE MODE
(BY CLOCK SOURCES)
Clock Source Clock Source Clock Ready Status
Exit Delay
before Wake-up after Wake-up Bit (OSCCON)
LP, XT, HS
Primary Device Clock HSPLL OSTS
TCSD(1)
(PRI_IDLE mode) EC, RC
HFINTOSC(2) IOFS
LP, XT, HS TOST(3)
HSPLL TOST + tPLL(3) OSTS
T1OSC or LFINTOSC(1)
EC, RC TCSD(1)
HFINTOSC(1) TIOBST(4) IOFS
LP, XT, HS TOST(4)
HSPLL TOST + tPLL(3) OSTS
HFINTOSC(2)
EC, RC TCSD(1)
HFINTOSC(1) None IOFS
LP, XT, HS TOST(3)
None HSPLL TOST + tPLL(3) OSTS
(Sleep mode) EC, RC TCSD(1)
HFINTOSC(1) TIOBST(4) IOFS
Note 1: TCSD (parameter 38) is a required delay when waking from Sleep and all Idle modes and runs concurrently
with any other required delays (see Section 3.4 “Idle Modes”). On Reset, HFINTOSC defaults to 1 MHz.
2: Includes both the HFINTOSC 16 MHz source and postscaler derived frequencies.
3: TOST is the Oscillator Start-up Timer (parameter 32). tPLL is the PLL Lock-out Timer (parameter F12).
4: Execution continues during the HFINTOSC stabilization period, TIOBST (parameter 39).

 2010 Microchip Technology Inc. DS41303G-page 49

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 50  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
4.0 RESET A simplified block diagram of the On-Chip Reset Circuit
is shown in Figure 4-1.
The PIC18F2XK20/4XK20 devi ces d ifferentiate
between various kinds of Reset: 4.1 RCON Register
a) Power-on Reset (POR)
Device R eset ev ents a re tra cked through the RCON
b) MCLR Reset during normal operation
register (Register 4-1). The lower five bits of the regis-
c) MCLR Reset during power-managed modes ter indicate that a specific Reset event has occurred. In
d) Watchdog Timer (WDT) Reset (during most cases, these bits can only be cleared by the event
execution) and must be set by the application after the event. The
e) Programmable Brown-out Reset (BOR) state of these flag bits, taken together, can be read to
f) RESET Instruction indicate the typ e of Reset tha t jus t oc curred. Thi s i s
described in more detail in Section 4.6 “Reset State
g) Stack Full Reset
of Registers”.
h) Stack Underflow Reset
The R CON r egister al so ha s c ontrol bi ts f or s etting
This sec tion di scusses R esets ge nerated by M CLR, interrupt priority (I PEN) an d s oftware control o f th e
POR and BOR and covers the operation of the various BOR (SBO REN). Interrupt p riority i s d iscussed in
start-up timers. S tack R eset events a re covered i n Section 9.0 “Interrupts”. B OR is co vered i n
Section 5.1.2.4 “Stack Full and Underflow Resets”. Section 4.4 “Brown-out Reset (BOR)”.
WDT Resets are covered in Section 23.2 “Watchdog
Timer (WDT)”.

FIGURE 4-1: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT

RESET
Instruction

Stack Stack Full/Underflow Reset

Pointer

External Reset

MCLRE
MCLR
( )_IDLE
Sleep

WDT
Time-out

VDD POR
Detect
VDD
Brown-out
Reset
BOREN S

OST/PWRT
OST(2) 1024 Cycles
Chip_Reset
10-bit Ripple Counter R Q
OSC1

32 s
PWRT(2) 65.5 ms
LFINTOSC 11-bit Ripple Counter

Enable PWRT

Enable OST(1)

Note 1: See Table 4-2 for time-out situations.

2: PWRT and OST counters are reset by POR and BOR. See Sections 4.3 and 4.4.

 2010 Microchip Technology Inc. DS41303G-page 51

PIC18F2XK20/4XK20

REGISTER 4-1: RCON: RESET CONTROL REGISTER

R/W-0 R/W-1 U-0 R/W-1 R-1 R-1 R/W-0 R/W-0
IPEN SBOREN (1)
— RI TO PD POR (2)
BOR
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 IPEN: Interrupt Priority Enable bit

1 = Enable priority levels on interrupts
0 = Disable priority levels on interrupts (PIC16CXXX Compatibility mode)
bit 6 SBOREN: BOR Software Enable bit(1)
If BOREN<1:0> = 01:
1 = BOR is enabled
0 = BOR is disabled
If BOREN<1:0> = 00, 10 or 11:
Bit is disabled and read as ‘0’.
bit 5 Unimplemented: Read as ‘0’
bit 4 RI: RESET Instruction Flag bit
1 = The RESET instruction was not executed (set by firmware or Power-on Reset)
0 = The RESET instruction was executed causing a dev ice Reset (must be se t in firmware after a
code-executed Reset occurs)
bit 3 TO: Watchdog Time-out Flag bit
1 = Set by power-up, CLRWDT instruction or SLEEP instruction
0 = A WDT time-out occurred
bit 2 PD: Power-down Detection Flag bit
1 = Set by power-up or by the CLRWDT instruction
0 = Set by execution of the SLEEP instruction
bit 1 POR: Power-on Reset Status bit(2)
1 = No Power-on Reset occurred
0 = A Power-on Reset occurred (must be set in software after a Power-on Reset occurs)
bit 0 BOR: Brown-out Reset Status bit(3)
1 = A Brown-out Reset has not occurred (set by firmware only)
0 = A Brown-out Reset occurred (must be set by firmware after a POR or Brown-out Reset occurs)

Note 1: When CONFIG2L[2:1] = 01, then the SBOREN Reset state is ‘1’; otherwise, it is ‘0’.
2: The actual Reset value of POR is determined by the type of device Reset. See the notes following this
register and Section 4.6 “Reset State of Registers” for additional information.
3: See Table 4-3.

Note 1: Brown-out Reset is indicated when BOR is ‘0’ and POR is ‘1’ (assuming that both POR and BOR were set
to ‘1’ by firmware immediately after POR).
2: It is recommended that the POR bit be set after a Power-on Reset has been detected so that subsequent
Power-on Resets may be detected.

DS41303G-page 52  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
4.2 Master Clear (MCLR) FIGURE 4-2: EXTERNAL POWER-ON
RESET CIRCUIT (FOR
The M CLR pin p rovides a me thod fo r t riggering an
SLOW VDD POWER-UP)
external Reset of the device. A Reset is generated by
holding the pin low. These devices have a noise filter in
the MCLR Reset path which detects and ignores small VDD VDD
pulses.
PIC® MCU
The MCLR pin is not driven low by any internal Resets, D R
including the WDT. R1
MCLR
In PIC18F2XK20/4XK20 devices, the MCLR input can
be disabled with the MCLRE C onfiguration bit. When C
MCLR is disabled, the pin becomes a digital input. See
Section 10.6 “PORTE, TRISE and LATE Registers”
for more information.
Note 1: External Power-on Res et c ircuit is r equired
only i f t he V DD power -up slope is too slow.
4.3 Power-on Reset (POR) The diode D helps disc harge t he c apacitor
quickly when VDD powers down.
A Power-on R eset pu lse i s generated on-chip
whenever V DD ri ses above a c ertain threshold. This 2: 15 k < R < 40 k is recommended to make
sure that the voltage drop across R does not
allows the device to start in th e initialized state when
violate the device’s electrical specification.
VDD is adequate for operation.
3: R1  1 k  wil l limit any c urrent fl owing into
To take advantage of th e POR circuitry, tie the MCLR MCLR from external capacitor C, in the event
pin through a resistor to V DD. This will eliminate exter- of M CLR/VPP pi n brea kdown, due t o
nal R C co mponents usually needed to cre ate a Electrostatic Dischar ge (ES D) or E lectrical
Power-on Reset delay. A minimum rise rate for VDD is Overstress (EOS).
specified (parameter D004). For a s low rise time, see
Figure 4-2.
When the device starts normal operation (i.e., exits the
Reset condition), dev ice op erating p arameters (vo lt-
age, freq uency, tem perature, etc.) mu st be met to
ensure pro per opera tion. If the se conditions are not
met, the device must be held in Reset until the operat-
ing conditions are met.
POR events are captured by the POR bit of the RCON
register. The st ate of the bi t is set to ‘ 0’ w henever a
POR oc curs; it does not change for any oth er R eset
event. POR is not reset to ‘1’ by any hardware event.
To capture multiple events, the user must manually set
the bit to ‘1’ by software following any POR.

 2010 Microchip Technology Inc. DS41303G-page 53

PIC18F2XK20/4XK20
4.4 Brown-out Reset (BOR) 4.4.2 SOFTWARE ENABLED BOR
PIC18F2XK20/4XK20 devices implement a BO R circuit When BOREN<1:0> = 01, the BOR can be enabled or
that provides the user with a number of configuration and disabled by the user in software. This is done with the
power-saving o ptions. Th e BO R i s c ontrolled by th e SBOREN co ntrol bi t of t he R CON register. S etting
BORV<1:0> a nd BO REN<1:0> bits of th e CONFIG2L SBOREN enables the BOR to fun ction as previously
Configuration re gister. There ar e a to tal of fo ur BO R described. C learing S BOREN disables th e BO R
configurations which are summarized in Table 4-1. entirely. The SBOREN bit operates only in this mode;
otherwise it is read as ‘0’.
The BO R th reshold is s et by the BOR V<1:0> bit s. If
BOR is enabled (any values of BOREN<1:0>, except Placing the BOR under software control g ives the user
‘00’), any drop of V DD below V BOR (parameter D005) the additional flexibility of tailoring the application to it s
for gre ater th an TBOR (p arameter 35) w ill reset th e environment without having to reprogram the device to
device. A Reset may or may not occur if VDD falls below change BOR config uration. It also allow s the user to
VBOR for l ess th an TBOR. Th e ch ip w ill r emain in tailor devi ce pow er con sumption in sof tware by
Brown-out Reset until VDD rises above VBOR. eliminating the increm ental c urrent that the BOR
consumes. While the BOR current is typically very small,
If the Power-up Timer is enabled, it will be invoked after it may have some impact in low-power applications.
VDD ris es a bove V BOR; it t hen w ill k eep t he c hip in
Reset for an add itional tim e del ay, T PWRT Note: Even when BOR is under software control,
(parameter 33). If VDD dr ops b elow V BOR wh ile the the BOR Reset voltage level is still set by
Power-up Timer is running, the chip will go back into a the BO RV<1:0> C onfiguration bi ts. It
Brown-out R eset and the Po wer-up Timer w ill be cannot be changed by software.
initialized. Once VDD rises above VBOR, the Power-up
Timer will execute the additional time delay. 4.4.3 DISABLING BOR IN SLEEP MODE
BOR an d the Pow er-on T imer (PWRT) a re When BOREN<1 :0> = 10, th e BO R re mains und er
independently co nfigured. Ena bling BO R Reset doe s hardware co ntrol an d op erates as p reviously
not automatically enable the PWRT. described. Whe never the dev ice enters Sleep m ode,
however, the BOR is automatically disabled. When the
The BOR circuit has an output that feeds into the POR
device returns to any other operating mo de, BO R is
circuit and rearms the POR within the operating range
automatically re-enabled.
of the BOR . T his early r earming of the POR en sures
that the device will remain in Reset in the event that VDD This mode allows for ap plications to recover from
falls below the operating range of the BOR circuitry. brown-out s ituations, w hile ac tively ex ecuting c ode,
when the device requires BOR protection the most. At
4.4.1 DETECTING BOR the same time, it saves additional power in Sleep mode
When BOR is enabled, the BOR bit always resets to ‘0’ by eliminating the small incremental BOR current.
on an y BOR or PO R ev ent. This makes it d ifficult to
4.4.4 MINIMUM BOR ENABLE TIME
determine if a BOR event has occurred just by reading
the state of BOR alone. A more reliable method is to Enabling t he B OR a lso en ables the Fixe d V oltage
simultaneously check the state of both POR and BOR. Reference (FVR) when no other peripheral requiring the
This assumes that the POR and BOR bits are reset to FVR is active. The BOR becomes active only after the
‘1’ b y so ftware i mmediately a fter any POR event. I f FVR stabi lizes. Therefore, t o ensure B OR p rotection,
BOR is ‘0’ while POR is ‘1’, it can be reliably assumed the FV R set tling t ime must be con sidered when
that a BOR event has occurred. enabling th e BOR in softw are or when th e BOR is
automatically en abled after w aking fr om S leep. If th e
BOR is disa bled, in softw are or by r eentering Sleep
before the FVR stabilizes, the BOR circuit will not sense
a B OR con dition. The FV RST bi t of the C VRCON2
register can be used to determine FVR stability.

TABLE 4-1: BOR CONFIGURATIONS

BOR Configuration Status of
SBOREN BOR Operation
BOREN1 BOREN0 (RCON<6>)
0 0 Unavailable BOR disabled; must be enabled by reprogramming the Configuration bits.
0 1 Available BOR enabled by software; operation controlled by SBOREN.
1 0 Unavailable BOR enabled by hardware in Run and Idle modes, disabled during
Sleep mode.
1 1 Unavailable BOR enabled by hardware; must be disabled by reprogramming the Configuration bits.

DS41303G-page 54  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
4.5 Device Reset Timers The OST time-out is invoked only for XT, LP, HS and
HSPLL modes and only on Power-on Reset, or on exit
PIC18F2XK20/4XK20 dev ices inc orporate thre e from all power-managed modes that stop the external
separate on -chip timers tha t he lp regu late th e oscillator.
Power-on Reset process. Th eir main func tion is to
ensure tha t the de vice clock is stable bef ore c ode is 4.5.3 PLL LOCK TIME-OUT
executed. These timers are:
With th e PLL ena bled in it s PLL m ode, the tim e-out
• Power-up Timer (PWRT) sequence fo llowing a Pow er-on R eset i s s lightly
• Oscillator Start-up Timer (OST) different from other oscillator modes. A separate timer
• PLL Lock Time-out is used to provide a fixed time-out that is sufficient for
the PLL to loc k to the main oscillator frequency. This
4.5.1 POWER-UP TIMER (PWRT) PLL lock time-out (TPLL) is typically 2 m s and follows
the oscillator start-up time-out.
The Po wer-up T imer (P WRT) of
PIC18F2XK20/4XK20 devices is an 1 1-bit counter
4.5.4 TIME-OUT SEQUENCE
which uses the LFINTOSC source as the clock input.
This yields an approximate time inter val of On power-up, the time-out sequence is as follows:
2048 x 32 s = 65.6 ms. While the PWRT is counting, 1. After the POR pulse has cleared, PWRT time-out
the device is held in Reset. is invoked (if enabled).
The power-up time delay depends on the LFINTOSC 2. Then, the OST is activated.
clock and will vary from chip-to-chip due to temperature The t otal ti me-out w ill v ary b ased on oscillator
and p rocess v ariation. Se e D C p arameter 33 for configuration and the status of th e PWRT. Figure 4-3,
details. Figure 4-4, F igure 4-5, Figure 4-6 and Fi gure 4-7 al l
The PW RT i s enabled b y c learing th e PW RTEN depict ti me-out s equences on po wer-up, w ith th e
Configuration bit. Power-up Timer e nabled a nd the device o perating i n
HS Os cillator m ode. Fig ures 4-3 th rough 4-6 a lso
4.5.2 OSCILLATOR START-UP TIMER apply to de vices o perating i n XT or L P mo des. F or
(OST) devices in RC mode and with the PWRT disabled, on
The Os cillator Start-up Timer (O ST) provides a 102 4 the other hand, there will be no time-out at all.
oscillator cy cle (fro m O SC1 i nput) de lay af ter th e Since the time-outs occur from the POR pulse, if MCLR
PWRT delay is over (parameter 33). This ensures that is kept low long enough, all time-outs will expire, after
the c rystal os cillator o r res onator has st arted an d which, bri nging M CLR h igh w ill all ow pro gram
stabilized. execution to begin immediately (F igure 4-5). T his i s
useful for testing purposes or to synchronize more than
one PIC18FXXK20 device operating in parallel.

TABLE 4-2: TIME-OUT IN VARIOUS SITUATIONS

Oscillator Power-up(2) and Brown-out Exit from
Configuration PWRTEN = 0 PWRTEN = 1 Power-Managed Mode

HSPLL 66 ms(1) + 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2) 1024 TOSC + 2 ms(2)
HS, XT, LP 66 ms(1) + 1024 TOSC 1024 TOSC 1024 TOSC
EC, ECIO 66 ms(1) — —
RC, RCIO 66 ms(1) — —
INTIO1, INTIO2 66 ms (1)
— —
Note 1: 66 ms (65.5 ms) is the nominal Power-up Timer (PWRT) delay.
2: 2 ms is the nominal time required for the PLL to lock.

 2010 Microchip Technology Inc. DS41303G-page 55

PIC18F2XK20/4XK20
FIGURE 4-3: TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO VDD, VDD RISE < TPWRT)

VDD

MCLR

INTERNAL POR

TPWRT

PWRT TIME-OUT
TOST

OST TIME-OUT

INTERNAL RESET

FIGURE 4-4: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 1

VDD

MCLR

INTERNAL POR
TPWRT

PWRT TIME-OUT
TOST

OST TIME-OUT

INTERNAL RESET

FIGURE 4-5: TIME-OUT SEQUENCE ON POWER-UP (MCLR NOT TIED TO VDD): CASE 2

VDD

MCLR

INTERNAL POR
TPWRT

PWRT TIME-OUT
TOST

OST TIME-OUT

INTERNAL RESET

DS41303G-page 56  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 4-6: SLOW RISE TIME (MCLR TIED TO VDD, VDD RISE > TPWRT)
5V
VDD 0V

MCLR

INTERNAL POR

TPWRT

PWRT TIME-OUT
TOST

OST TIME-OUT

INTERNAL RESET

FIGURE 4-7: TIME-OUT SEQUENCE ON POR W/PLL ENABLED (MCLR TIED TO VDD)

VDD

MCLR

INTERNAL POR
TPWRT

PWRT TIME-OUT
TOST

OST TIME-OUT TPLL

PLL TIME-OUT

INTERNAL RESET

Note: TOST = 1024 clock cycles.

TPLL  2 ms max. First three stages of the PWRT timer.

 2010 Microchip Technology Inc. DS41303G-page 57

PIC18F2XK20/4XK20
4.6 Reset State of Registers Table 4-4 de scribes the R eset st ates fo r all of th e
Special Function Registers. These are categorized by
Some registers are unaffected by a Reset. Their status Power-on and Brow n-out R esets, Ma ster C lear an d
is unknown o n PO R and un changed by a ll other WDT Resets and WDT wake-ups.
Resets. All other registers are forced to a “Reset state”
depending on the type of Reset that occurred.
Most re gisters a re n ot a ffected by a W DT w ake-up,
since t his is vi ewed as th e re sumption of no rmal
operation. Status bits from the RCON register, RI, TO,
PD, PO R and BOR, a re s et or cleared d ifferently i n
different R eset s ituations, as i ndicated in T able 4-3.
These bi ts a re us ed by s oftware to determine th e
nature of the Reset.

TABLE 4-3: STATUS BITS, THEIR SIGNIFICANCE AND THE INITIALIZATION CONDITION
FOR RCON REGISTER
Program RCON Register STKPTR Register
Condition
Counter SBOREN RI TO PD POR BOR STKFUL STKUNF
Power-on Reset 0000h 1 1 1 1 0 0 0 0
RESET Instruction 0000h u(2) 0 u u u u u u
Brown-out Reset 0000h u(2)
1 1 1 u 0 u u
MCLR during Power-Managed 0000h u(2) u 1 u u u u u
Run Modes
MCLR during Power-Managed 0000h u(2) u 1 0 u u u u
Idle Modes and Sleep Mode
WDT Time-out during Full Power 0000h u(2) u 0 u u u u u
or Power-Managed Run Mode
MCLR during Full Power 0000h u(2) u u u u u u u
Execution
Stack Full Reset (STVREN = 1) 0000h u(2) u u u u u 1 u
Stack Underflow Reset 0000h u(2) u u u u u u 1
(STVREN = 1)
Stack Underflow Error (not an 0000h u(2) u u u u u u 1
actual Reset, STVREN = 0)
WDT Time-out during PC + 2 u(2) u 0 0 u u u u
Power-Managed Idle or Sleep
Modes
Interrupt Exit from PC + 2(1) u(2) u u 0 u u u u
Power-Managed Modes
Legend: u = unchanged
Note 1: When the wake-up is due to an interrupt and the GIEH or GIEL bits are set, the PC is loaded with the
interrupt vector (008h or 0018h).
2: Reset state is ‘1’ for SBOREN and unchanged for all other Resets when software BOR is enabled
(BOREN<1:0> Configuration bits = 01). Otherwise, the Reset state is ‘0’.

DS41303G-page 58  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS

MCLR Resets,
Power-on Reset, WDT Reset, Wake-up via WDT
Register Applicable Devices
Brown-out Reset RESET Instruction, or Interrupt
Stack Resets

TOSU PIC18F2XK20 PIC18F4XK20 ---0 0000 ---0 0000 ---0 uuuu(3)

TOSH PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu(3)
TOSL PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu(3)
STKPTR PIC18F2XK20 PIC18F4XK20 00-0 0000 uu-0 0000 uu-u uuuu(3)
PCLATU PIC18F2XK20 PIC18F4XK20 ---0 0000 ---0 0000 ---u uuuu
PCLATH PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
PCL PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 PC + 2(2)
TBLPTRU PIC18F2XK20 PIC18F4XK20 --00 0000 --00 0000 --uu uuuu
TBLPTRH PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TBLPTRL PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TABLAT PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
PRODH PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
PRODL PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
INTCON PIC18F2XK20 PIC18F4XK20 0000 000x 0000 000u uuuu uuuu(1)
INTCON2 PIC18F2XK20 PIC18F4XK20 1111 -1-1 1111 -1-1 uuuu -u-u(1)
INTCON3 PIC18F2XK20 PIC18F4XK20 11-0 0-00 11-0 0-00 uu-u u-uu(1)
INDF0 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTINC0 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTDEC0 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PREINC0 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PLUSW0 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
FSR0H PIC18F2XK20 PIC18F4XK20 ---- 0000 ---- 0000 ---- uuuu
FSR0L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
WREG PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
INDF1 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTINC1 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTDEC1 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PREINC1 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PLUSW1 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector
(0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with
the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack.
4: See Table 4-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When not enabled as
PORTA pins, they are disabled and read ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.

 2010 Microchip Technology Inc. DS41303G-page 59

PIC18F2XK20/4XK20
TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
MCLR Resets,
Power-on Reset, WDT Reset, Wake-up via WDT
Register Applicable Devices
Brown-out Reset RESET Instruction, or Interrupt
Stack Resets
FSR1H PIC18F2XK20 PIC18F4XK20 ---- 0000 ---- 0000 ---- uuuu
FSR1L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
BSR PIC18F2XK20 PIC18F4XK20 ---- 0000 ---- 0000 ---- uuuu
INDF2 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTINC2 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
POSTDEC2 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PREINC2 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
PLUSW2 PIC18F2XK20 PIC18F4XK20 N/A N/A N/A
FSR2H PIC18F2XK20 PIC18F4XK20 ---- 0000 ---- 0000 ---- uuuu
FSR2L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
STATUS PIC18F2XK20 PIC18F4XK20 ---x xxxx ---u uuuu ---u uuuu
TMR0H PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TMR0L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
T0CON PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
OSCCON PIC18F2XK20 PIC18F4XK20 0011 qq00 0011 qq00 uuuu uuuu
HLVDCON PIC18F2XK20 PIC18F4XK20 0-00 0101 0-00 0101 u-uu uuuu
WDTCON PIC18F2XK20 PIC18F4XK20 ---- ---0 ---- ---0 ---- ---u
RCON (4)
PIC18F2XK20 PIC18F4XK20 0q-1 11q0 0u-q qquu uu-u qquu
TMR1H PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
TMR1L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
T1CON PIC18F2XK20 PIC18F4XK20 0000 0000 u0uu uuuu uuuu uuuu
TMR2 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
PR2 PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 1111 1111
T2CON PIC18F2XK20 PIC18F4XK20 -000 0000 -000 0000 -uuu uuuu
SSPBUF PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
SSPADD PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
SSPSTAT PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
SSPCON1 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
SSPCON2 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector
(0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with
the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack.
4: See Table 4-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When not enabled as
PORTA pins, they are disabled and read ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.

DS41303G-page 60  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
MCLR Resets,
Power-on Reset, WDT Reset, Wake-up via WDT
Register Applicable Devices
Brown-out Reset RESET Instruction, or Interrupt
Stack Resets
ADRESH PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
ADRESL PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
ADCON0 PIC18F2XK20 PIC18F4XK20 --00 0000 --00 0000 --uu uuuu
ADCON1 PIC18F2XK20 PIC18F4XK20 --00 0qqq --00 0qqq --uu uuuu
ADCON2 PIC18F2XK20 PIC18F4XK20 0-00 0000 0-00 0000 u-uu uuuu
CCPR1H PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
CCPR1L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu

CCP1CON PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu

CCPR2H PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
CCPR2L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
CCP2CON PIC18F2XK20 PIC18F4XK20 --00 0000 --00 0000 --uu uuuu
PSTRCON PIC18F2XK20 PIC18F4XK20 ---0 0001 ---0 0001 ---u uuuu
BAUDCON PIC18F2XK20 PIC18F4XK20 0100 0-00 0100 0-00 uuuu u-uu
PWM1CON PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu

ECCP1AS PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu

CVRCON PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
CVRCON2 PIC18F2XK20 PIC18F4XK20 00-- ---- 00-- ---- uu-- ----
TMR3H PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
TMR3L PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
T3CON PIC18F2XK20 PIC18F4XK20 0000 0000 uuuu uuuu uuuu uuuu
SPBRGH PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
SPBRG PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
RCREG PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TXREG PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TXSTA PIC18F2XK20 PIC18F4XK20 0000 0010 0000 0010 uuuu uuuu
RCSTA PIC18F2XK20 PIC18F4XK20 0000 000x 0000 000x uuuu uuuu
EEADR PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
EEADRH PIC18F26K20 PIC18F46K20 ---- --00 ---- --00 ---- --uu
EEDATA PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
EECON2 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 0000 0000
EECON1 PIC18F2XK20 PIC18F4XK20 xx-0 x000 uu-0 u000 uu-0 u000
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector
(0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with
the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack.
4: See Table 4-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When not enabled as
PORTA pins, they are disabled and read ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.

 2010 Microchip Technology Inc. DS41303G-page 61

PIC18F2XK20/4XK20
TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
MCLR Resets,
Power-on Reset, WDT Reset, Wake-up via WDT
Register Applicable Devices
Brown-out Reset RESET Instruction, or Interrupt
Stack Resets
IPR2 PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
PIR2 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu(1)
PIE2 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu

PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu

IPR1
PIC18F2XK20 PIC18F4XK20 -111 1111 -111 1111 -uuu uuuu

PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu(1)

PIR1
PIC18F2XK20 PIC18F4XK20 -000 0000 -000 0000 -uuu uuuu(1)

PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu

PIE1
PIC18F2XK20 PIC18F4XK20 -000 0000 -000 0000 -uuu uuuu
OSCTUNE PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
TRISE PIC18F2XK20 PIC18F4XK20 ---- -111 ---- -111 ---- -uuu
TRISD PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
TRISC PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
TRISB PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
TRISA (5)
PIC18F2XK20 PIC18F4XK20 1111 1111 (5)
1111 1111 (5)
uuuu uuuu(5)
LATE PIC18F2XK20 PIC18F4XK20 ---- -xxx ---- -uuu ---- -uuu
LATD PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
LATC PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
LATB PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
LATA(5) PIC18F2XK20 PIC18F4XK20 xxxx xxxx(5) uuuu uuuu(5) uuuu uuuu(5)

PIC18F2XK20 PIC18F4XK20 ---- x000 ---- u000 ---- uuuu

PORTE
PIC18F2XK20 PIC18F4XK20 ---- x--- ---- u--- ---- u---
PORTD PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
PORTC PIC18F2XK20 PIC18F4XK20 xxxx xxxx uuuu uuuu uuuu uuuu
PORTB PIC18F2XK20 PIC18F4XK20 xxx0 0000 uuu0 0000 uuuu uuuu
PORTA (5)
PIC18F2XK20 PIC18F4XK20 xx0x 0000 (5)
uu0u 0000 (5)
uuuu uuuu(5)
ANSELH(6) PIC18F2XK20 PIC18F4XK20 ---1 1111 ---1 1111 ---u uuuu
ANSEL PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
IOCB PIC18F2XK20 PIC18F4XK20 0000 ---- 0000 ---- uuuu ----
WPUB PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
CM1CON0 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
CM2CON0 PIC18F2XK20 PIC18F4XK20 0000 0000 0000 0000 uuuu uuuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector
(0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with
the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack.
4: See Table 4-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When not enabled as
PORTA pins, they are disabled and read ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.

DS41303G-page 62  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 4-4: INITIALIZATION CONDITIONS FOR ALL REGISTERS (CONTINUED)
MCLR Resets,
Power-on Reset, WDT Reset, Wake-up via WDT
Register Applicable Devices
Brown-out Reset RESET Instruction, or Interrupt
Stack Resets
CM2CON1 PIC18F2XK20 PIC18F4XK20 0000 ---- 0000 ---- uuuu ----
SLRCON PIC18F2XK20 PIC18F4XK20 ---1 1111 ---1 1111 ---u uuuu
SSPMSK PIC18F2XK20 PIC18F4XK20 1111 1111 1111 1111 uuuu uuuu
Legend: u = unchanged, x = unknown, - = unimplemented bit, read as ‘0’, q = value depends on condition.
Shaded cells indicate conditions do not apply for the designated device.
Note 1: One or more bits in the INTCONx or PIRx registers will be affected (to cause wake-up).
2: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the PC is loaded with the interrupt vector
(0008h or 0018h).
3: When the wake-up is due to an interrupt and the GIEL or GIEH bit is set, the TOSU, TOSH and TOSL are updated with
the current value of the PC. The STKPTR is modified to point to the next location in the hardware stack.
4: See Table 4-3 for Reset value for specific condition.
5: Bits 6 and 7 of PORTA, LATA and TRISA are enabled, depending on the oscillator mode selected. When not enabled as
PORTA pins, they are disabled and read ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.

 2010 Microchip Technology Inc. DS41303G-page 63

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 64  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.0 MEMORY ORGANIZATION 5.1 Program Memory Organization
There are three types of m emory in PIC18 Enhanced PIC18 m icrocontrollers i mplement a 2 1-bit pro gram
microcontroller devices: counter, which is ca pable of addressing a 2-M byte
program memory space. Accessing a location between
• Program Memory
the upp er bou ndary of the phy sically im plemented
• Data RAM memory and the 2-Mbyte address will return all ‘0’s (a
• Data EEPROM NOP instruction).
As Harvard architecture devices, the data and program This family of devices contain the following:
memories use separate busses; this allows for concur-
• PIC18F23K20, PIC18F43K20: 8 Kbytes of Flash
rent ac cess of th e tw o m emory spaces. Th e da ta
Memory, up to 4,096 single-word instructions
EEPROM, for practical purposes, can be regarded as
a peripheral device, since it is addressed and accessed • PIC18F24K20, PIC18F44K20: 16 Kbytes of Flash
through a set of control registers. Memory, up to 8,192 single-word instructions
• PIC18F25K20, PIC18F45K20: 32 Kbytes of Flash
Additional detailed information on the operation of the
Memory, up to 16,384 single-word instructions
Flash program m emory i s provided i n Section 6.0
“Flash Program Memory”. Dat a EEP ROM i s • PIC18F26K20, PIC18F46K20: 64 Kbytes of Flash
discussed s eparately i n Section 7.0 “Data EEPROM Memory, up to 37,768 single-word instructions
Memory”. PIC18 devices have two interrupt vectors. The Reset
vector ad dress is a t 000 0h a nd th e in terrupt v ector
addresses are at 0008h and 0018h.
The p rogram memory m ap for P IC18F2XK20/4XK20
devices is shown in Figure 5-1. Memory block details
are shown in Figure 23-2.

FIGURE 5-1: PROGRAM MEMORY MAP AND STACK FOR PIC18F2XK20/4XK20 DEVICES
PC<20:0>
CALL,RCALL,RETURN 21
RETFIE,RETLW
Stack Level 1




Stack Level 31

Reset Vector 0000h

High Priority Interrupt Vector 0008h

Low Priority Interrupt Vector 0018h

On-Chip
Program Memory
1FFFh On-Chip
Program Memory
2000h
3FFFh On-Chip
PIC18F23K20/ Program Memory
4000h
43K20
User Memory Space

PIC18F24K20/ On-Chip
Program Memory
44K20
7FFFh
8000h

PIC18F25K20/
45K20

FFFFh
10000h
Read ‘0’ Read ‘0’ Read ‘0’
PIC18F26K20/
46K20

Read ‘0’
1FFFFFh
200000h

 2010 Microchip Technology Inc. DS41303G-page 65

PIC18F2XK20/4XK20
5.1.1 PROGRAM COUNTER The stack operates as a 31-word by 21-bit RAM and a
5-bit Stack P ointer, STKPTR. The stac k spac e is not
The Program Counter (PC) specifies the address of the
part of either program or data space. The Stack Pointer
instruction to fetch for execution. The PC is 21 bits wide
is readable and writable and the address on the top of
and is contained in three separate 8-bit registers. The
the stack is readable and writable through the Top-of-
low byte, known as the PCL register, is both readable
Stack (TOS) Special File Registers. Data can also be
and writable. The high byte, or PCH register, contains
pushed t o, o r pop ped from the st ack, u sing th ese
the PC<15:8> bits; it is not directly readable or writable.
registers.
Updates to the PCH register are performed through the
PCLATH register. The upper byte is called PCU. This A CALL type instruction causes a push onto the stack;
register contains the P C<20:16> bit s; i t is als o n ot the Stack Pointer is first incremented and the location
directly rea dable o r writable. Updates to the PC U pointed to b y th e S tack Poi nter is writte n wi th th e
register are performed through the PCLATU register. contents of the PC (already pointing to the instruction
following the CALL). A RETURN type instruction causes
The contents of PCLATH and PCLATU are transferred
a pop f rom th e s tack; th e contents of the l ocation
to the prog ram co unter by any op eration tha t w rites
pointed to by th e STKPTR are tran sferred to the PC
PCL. Si milarly, the u pper two bytes o f t he program
and then the Stack Pointer is decremented.
counter are transferred to PCLATH and PCLATU by an
operation that reads PCL. This is useful for computed The S tack Po inter is ini tialized to ‘ 00000’ a fter a ll
offsets t o t he PC (s ee Section 5.1.4.1 “Computed Resets. There is no RAM associated with the location
GOTO”). corresponding to a Stack Pointer value of ‘00000’; this
is only a Reset value. Status bits indicate if the stack is
The PC addresses bytes in the pro gram memory. To
full or has overflowed or has underflowed.
prevent the PC f rom be coming misaligned w ith w ord
instructions, the Least Significant bit of PCL is fixed to
5.1.2.1 Top-of-Stack Access
a v alue o f ‘ 0’. Th e PC in crements by 2 to add ress
sequential instructions in the program memory. Only the top of the return address stack (TOS) is readable
and writable. A set of three registers, TOSU:TOSH:TOSL,
The CALL, RCALL, GOTO a nd program br anch
hold the contents of the st ack location pointed to by the
instructions w rite to the program counter directly. For
STKPTR regist er (Fig ure 5-2). This allows users to
these in structions, the c ontents o f PC LATH an d
implement a sof tware stack if necessary. After a CALL,
PCLATU are not transferred to the program counter.
RCALL or inte rrupt, t he softw are can read the pu shed
value by reading the TOSU:TOSH:TOSL registers. These
5.1.2 RETURN ADDRESS STACK
values can be placed on a user defined software stack. At
The return address stack allows any combination of up return t ime, t he sof tware can ret urn t hese value s to
to 31 program calls and interrupts to occur. The PC is TOSU:TOSH:TOSL and do a return.
pushed ont o th e s tack w hen a CALL or RCALL
The user must disable the global interrupt enable bits
instruction is executed or an interrupt is Acknowledged.
while accessing the stack to prevent inadvertent stack
The PC value is pulled of f the st ack on a RETURN,
corruption.
RETLW or a RETFIE instruction. PCLATU and PCLATH
are no t af fected by an y o f th e RETURN or CALL
instructions.

FIGURE 5-2: RETURN ADDRESS STACK AND ASSOCIATED REGISTERS

Return Address Stack <20:0>

11111
11110
Top-of-Stack Registers 11101 Stack Pointer

TOSU TOSH TOSL STKPTR<4:0>

00h 1Ah 34h 00010
00011
Top-of-Stack 001A34h 00010
000D58h 00001
00000

DS41303G-page 66  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.1.2.2 Return Stack Pointer (STKPTR) When the st ack ha s be en po pped en ough tim es to
unload the stack, the next pop will return a value of zero
The STKPTR register (Register 5-1) contains the Stack
to the PC a nd sets the STKUNF bit, whi le the Stack
Pointer v alue, the STKFUL (s tack ful l) Status b it an d
Pointer remains at z ero. The STKUNF bit will remain
the STKUNF (stack underflow) Status bits. The value of
set until cleared by software or until a POR occurs.
the S tack Po inter c an b e 0 th rough 31 . Th e S tack
Pointer increments before values are pushed onto the Note: Returning a value of zero to the PC on an
stack and decrements after values are popped off the underflow ha s the effect of vec toring the
stack. On Reset, the Stack Pointer value will be zero. program t o th e R eset vector, w here th e
The user may read and write the Stack Pointer value. stack conditions can b e v erified an d
This feature ca n be u sed by a R eal-Time O perating appropriate actions can be taken. This is
System (RTOS) for return stack maintenance. not the same as a Reset, as the contents
After the PC is pushed onto the stack 31 times (without of the SFRs are not affected.
popping an y values off th e stack), t he STKFUL bi t i s
set. The S TKFUL bi t is cl eared b y so ftware or by a 5.1.2.3 PUSH and POP Instructions
POR. Since t he Top-of-Stack is re adable and w ritable, th e
The action that takes place when the stack becomes ability to push values onto the stack and pull values off
full depends on the state of the STVREN (Stack Over- the stack without disturbing normal program execution
flow R eset Ena ble) C onfiguration bi t. (R efer to is a de sirable feature. T he PIC18 instruction se t
Section 23.1 “Configuration Bits” for a description of includes tw o instructions, PUSH and POP, t hat permit
the dev ice C onfiguration bits.) If STVR EN is s et the T OS to be m anipulated u nder s oftware control.
(default), the 31 st push will pu sh the (PC + 2) v alue TOSU, TOSH and TOSL can be modified to place data
onto th e st ack, se t the STKFUL bit and res et the or a return address on the stack.
device. The STKFUL bit will remain set and the Stack The PUSH instruction places the current PC value onto
Pointer will be set to zero. the stack. This increments the Stack Pointer and loads
If STVREN is cleared, the STKFUL bit will be set on the the current PC value onto the stack.
31st push and the Stack Pointer will increment to 31. The POP instruction discards the current TOS by decre-
Any additional pushes will not overwrite the 31st push menting the Stack Pointer. The previous value pushed
and STKPTR will remain at 31. onto the stack then becomes the TOS value.

REGISTER 5-1: STKPTR: STACK POINTER REGISTER

R/C-0 R /C-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
STKFUL(1) STKUNF(1) — SP4 SP3 SP2 SP1 SP0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented C = Clearable only bit
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 STKFUL: Stack Full Flag bit(1)

1 = Stack became full or overflowed
0 = Stack has not become full or overflowed
bit 6 STKUNF: Stack Underflow Flag bit(1)
1 = Stack underflow occurred
0 = Stack underflow did not occur
bit 5 Unimplemented: Read as ‘0’
bit 4-0 SP<4:0>: Stack Pointer Location bits

Note 1: Bit 7 and bit 6 are cleared by user software or by a POR.

 2010 Microchip Technology Inc. DS41303G-page 67

PIC18F2XK20/4XK20
5.1.2.4 Stack Full and Underflow Resets 5.1.4 LOOK-UP TABLES IN PROGRAM
Device Resets on stack overflow and stack underflow MEMORY
conditions are en abled by se tting the STVR EN bi t in There may be programming situations that require the
Configuration Register 4L. When STVREN is set, a full creation of dat a st ructures, or lo ok-up t ables, in
or underflow w ill set the appropriate STKFU L or program memory. F or P IC18 de vices, l ook-up ta bles
STKUNF bit a nd t hen cau se a de vice R eset. Whe n can be implemented in two ways:
STVREN is cleared, a full or underflow condition will set
• Computed GOTO
the appropriate STKFUL or STKUNF bit but not cause
a dev ice R eset. The STKFU L or ST KUNF bi ts a re • Table Reads
cleared by the user software or a Power-on Reset.
5.1.4.1 Computed GOTO
5.1.3 FAST REGISTER STACK A computed GOTO is accomplished by adding an offset
A fast register stack is provided for the Status, WREG to the p rogram counter. An e xample is sh own i n
and BSR registers, to provide a “fast return” option for Example 5-2.
interrupts. The stack for each register is only one level A loo k-up t able ca n be form ed with an ADDWF PCL
deep and is neither readable nor writable. It is loaded instruction and a group of RETLW nn instructions. The
with t he c urrent value of t he c orresponding r egister W register is loaded with an offset into the table before
when the processor vectors for an interrupt. All inter- executing a call to that table. The first instruction of the
rupt sources will push values into the stack registers. called routine is the ADDWF PCL instruction. The next
The values in the registers are then loaded back into instruction executed w ill be one of the RETLW nn
their as sociated re gisters i f th e RETFIE, FAST instructions that retu rns th e v alue ‘ nn’ t o th e c alling
instruction is used to return from the interrupt. function.
If both low and high priority interrupts are enabled, the The of fset va lue (in WREG) s pecifies the num ber of
stack registers cannot be u sed reliably to return from bytes that the prog ram counter sh ould adv ance and
low priority interrupts. If a high priority interrupt occurs should be multiples of 2 (LSb = 0).
while servicing a low priority interrupt, the stack register In thi s m ethod, o nly on e da ta by te may be sto red i n
values s tored by t he l ow pr iority interrupt w ill be each instruction loc ation and roo m on the retu rn
overwritten. In th ese cases, users must save the key address stack is required.
registers by software during a low priority interrupt.
If interrupt priority is not used, all interrupts may use the EXAMPLE 5-2: COMPUTED GOTO USING
fast register stack fo r ret urns f rom in terrupt. If n o AN OFFSET VALUE
interrupts are used, the fast register stack can be used MOVF OFFSET, W
to restore the Status, WREG and BSR registers at the CALL TABLE
end of a subroutine call. To use the fast register stack ORG nn00h
for a subroutine call, a CALL label, FAST instruction TABLE ADDWF PCL
must be executed to save the Status, WREG and BSR RETLW nnh
registers to the fas t re gister st ack. A RETURN, FAST RETLW nnh
instruction is then executed to restore these registers RETLW nnh
from the fast register stack. .
.
Example 5-1 shows a source code example that uses .
the fas t regi ster st ack during a su broutine ca ll an d
return.
5.1.4.2 Table Reads and Table Writes
EXAMPLE 5-1: FAST REGISTER STACK A better m ethod of storing d ata in pro gram memory
CODE EXAMPLE allows two bytes of data to be stored in each instruction
CALL SUB1, FAST ;STATUS, WREG, BSR location.
;SAVED IN FAST REGISTER Look-up table data may be stored two bytes per p ro-
;STACK gram word by using table reads and writes. The Table
 Pointer ( TBLPTR) r egister s pecifies the b yte ad dress

and the Table Lat ch (T ABLAT) regi ster con tains the
SUB1 
data that is read from or w ritten to program memory.
 Data is trans ferred to or from prog ram me mory on e
RETURN, FAST ;RESTORE VALUES SAVED byte at a time.
;IN FAST REGISTER STACK Table re ad an d t able w rite o perations are di scussed
further in Section 6.1 “Table Reads and Table
Writes”.

DS41303G-page 68  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.2 PIC18 Instruction Cycle 5.2.2 INSTRUCTION FLOW/PIPELINING
An “Instruction C ycle” co nsists of four Q cy cles: Q1
5.2.1 CLOCKING SCHEME through Q4 . The in struction fetch and ex ecute are
The m icrocontroller clock input, w hether f rom an pipelined in such a ma nner that a fetc h t akes one
internal or external source, is internally divided by four instruction cy cle, w hile the decode and e xecute t ake
to gen erate fou r non -overlapping qua drature c locks another in struction cycle. H owever, du e to th e
(Q1, Q2, Q3 and Q4). Internally, the program counter is pipelining, each instruction effectively executes in one
incremented on ev ery Q1; the instruction is fet ched cycle. If an instruction causes the program counter to
from t he p rogram me mory a nd l atched in to th e change (e .g., GOTO), t hen tw o c ycles are required to
instruction regi ster duri ng Q 4. Th e in struction is complete the instruction (Example 5-3).
decoded and executed during the following Q1 through A fetc h cy cle be gins w ith the Program C ounter (PC )
Q4. The cl ocks an d in struction ex ecution f low a re incrementing in Q1.
shown in Figure 5-3.
In the execution cycle, the fetched instruction is latched
into the Instruction R egister ( IR) in cy cle Q 1. This
instruction is the n d ecoded an d ex ecuted d uring th e
Q2, Q3 and Q4 cycles. Data memory is read during Q2
(operand rea d) and written during Q4 (destination
write).

FIGURE 5-3: CLOCK/INSTRUCTION CYCLE

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
Q1
Q2 Internal
Q3 Phase
Clock
Q4
PC PC PC + 2 PC + 4
OSC2/CLKOUT
(RC mode)
Execute INST (PC – 2)
Fetch INST (PC) Execute INST (PC)
Fetch INST (PC + 2) Execute INST (PC + 2)
Fetch INST (PC + 4)

EXAMPLE 5-3: INSTRUCTION PIPELINE FLOW

TCY0 TCY1 TCY2 TCY3 TCY4 TCY5

1. MOVLW 55h Fetch 1 Execute 1
2. MOVWF PORTB Fetch 2 Execute 2
3. BRA SUB_1 Fetch 3 Execute 3
4. BSF PORTA, BIT3 (Forced NOP) Fetch 4 Flush (NOP)
5. Instruction @ address SUB_1 Fetch SUB_1 Execute SUB_1

All instructions are single cycle, except for any program branches. These take two cycles since the fetch instruction
is “flushed” from the pipeline while the new instruction is being fetched and then executed.

 2010 Microchip Technology Inc. DS41303G-page 69

PIC18F2XK20/4XK20
5.2.3 INSTRUCTIONS IN PROGRAM The CALL and GOTO ins tructions hav e the abs olute
MEMORY program memory address embedded into the
instruction. Since instructions are always stored on word
The program m emory is a ddressed in by tes.
boundaries, the da ta cont ained in the i nstruction i s a
Instructions are stored as either two bytes or four bytes
word address. The word address is written to PC<20:1>,
in program memory. The Least Significant Byte of a n
which accesses the des ired b yte a ddress in program
instruction word is always stored in a program memory
memory. Instructio n #2 in Figure 5-4 sh ows how the
location with an even address (LSb = 0). To maintain
instruction GOTO 0006h i s enc oded in the program
alignment with in struction b oundaries, the PC
memory. Program branch instructions, which encode a
increments in steps of 2 and the LSb will always read
relative address offset, operate in the same manner. The
‘0’ (see Section 5.1.1 “Program Counter”).
offset value stored in a branch instruction represents the
Figure 5-4 shows an example of how instruction words number of single-word instructions that the PC w ill be
are stored in the program memory. offset by . Section 24.0 “Instruction Set Summary”
provides further details of the instruction set.

FIGURE 5-4: INSTRUCTIONS IN PROGRAM MEMORY

Word Address
LSB = 1 LSB = 0 
Program Memory 000000h
Byte Locations  000002h
000004h
000006h
Instruction 1: MOVLW 055h 0Fh 55h 000008h
Instruction 2: GOTO 0006h EFh 03h 00000Ah
F0h 00h 00000Ch
Instruction 3: MOVFF 123h, 456h C1h 23h 00000Eh
F4h 56h 000010h
000012h
000014h

5.2.4 TWO-WORD INSTRUCTIONS and used by the instruction sequence. If the first word
is sk ipped fo r some reason an d the se cond w ord is
The standard PIC18 instruction set has four two-word
executed by itself, a NOP is executed instead. This is
instructions: CALL, MOVFF, GOTO a nd LSFR. In al l
necessary f or ca ses wh en t he two-word i nstruction is
cases, the second word of th e instruction always has
preceded by a conditional instruction that changes the
‘1111’ as its four Most Significant bits; the other 12 bits
PC. Example 5-4 shows how this works.
are literal data, usually a data memory address.
The us e of ‘1111’ in the 4 MSbs of an instruction Note: See Section 5.6 “PIC18 Instruction
specifies a sp ecial form of NOP. If th e ins truction i s Execution and the Extended Instruc-
executed in proper sequence – i mmediately after the tion Set” for information on tw o-word
first w ord – the d ata in the s econd w ord is accessed instructions in the extended instruction set.

EXAMPLE 5-4: TWO-WORD INSTRUCTIONS

CASE 1:
Object Code Source Code
0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?
1100 0001 0010 0011 MOVFF REG1, REG2 ; No, skip this word
1111 0100 0101 0110 ; Execute this word as a NOP
0010 0100 0000 0000 ADDWF REG3 ; continue code
CASE 2:
Object Code Source Code
0110 0110 0000 0000 TSTFSZ REG1 ; is RAM location 0?
1100 0001 0010 0011 MOVFF REG1, REG2 ; Yes, execute this word
1111 0100 0101 0110 ; 2nd word of instruction
0010 0100 0000 0000 ADDWF REG3 ; continue code

DS41303G-page 70  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.3 Data Memory Organization 5.3.1 BANK SELECT REGISTER (BSR)
Large area s o f da ta m emory req uire an ef ficient
Note: The o peration of s ome a spects o f da ta
addressing sc heme to m ake rap id a ccess to an y
memory a re c hanged when the PI C18
address po ssible. I deally, this means that an en tire
extended in struction set i s en abled. See
address does not need to be provided for each read or
Section 5.5 “Data Memory and the
write operation. For PIC 18 d evices, th is i s accom-
Extended Instruction Set” f or more
plished with a RAM banking scheme. This divides the
information.
memory space into 16 contiguous banks of 256 bytes.
The data memory in PIC18 devices is implemented as Depending o n th e i nstruction, each location can b e
static R AM. Each register in the dat a memory has a addressed directly by its full 12-bit address, or an 8-bit
12-bit address, al lowing up to 409 6 by tes of da ta low-order address and a 4-bit Bank Pointer.
memory. The memory space is divided into as many as Most instructions in the PIC18 instruction set make use
16 banks t hat co ntain 2 56 by tes ea ch. Fi gures 5 -5 of the Bank Pointer, known as the Bank Select Register
through 5-7 show the data memory organization for the (BSR). This SFR holds the 4 Most Significant bits of a
PIC18F2XK20/4XK20 devices. location’s ad dress; the ins truction it self includes the
The data memory contains Special Function Registers 8 Least Significant bits. Only the four lower bits of the
(SFRs) and G eneral Pu rpose Registers (G PRs). Th e BSR are implemented (BSR<3:0>). The upper four bits
SFRs are used for control and status of the controller are unu sed; th ey w ill al ways rea d ‘ 0’ and ca nnot be
and peripheral functions, while GPRs are used for data written to. The BSR can be loaded directly by using the
storage and sc ratchpad op erations i n th e u ser’s MOVLB instruction.
application. Any read of an unimplemented location will The va lue of th e BSR ind icates th e ban k i n dat a
read as ‘0’s. memory; the 8 bits in the instruction show the location
The in struction set and a rchitecture all ow op erations in the bank and can be thought of as an offset from the
across all ba nks. Th e e ntire da ta m emory ma y b e bank’s l ower b oundary. Th e rel ationship b etween th e
accessed by Direct, Ind irect o r Indexed Add ressing BSR’s value and the b ank division in data memory is
modes. Addressing modes are discussed later in thi s shown in Figures 5-5 through 5-7.
subsection. Since up to 16 registers may share the same low-order
To e nsure t hat c ommonly us ed r egisters (SFRs a nd address, the user must always be careful to ensure that
select GPRs) can be accessed in a single cycle, PIC18 the proper bank is selected before performing a dat a
devices implement an Access Bank. This is a 256-byte read or write. For example, writing w hat sh ould be
memory space that provides fast access to SFRs and program data to an 8-bit address of F9h while the BSR
the lower portion of GPR Bank 0 without using the Bank is 0Fh will end up resetting the program counter.
Select Register (BSR). Section 5.3.2 “Access Bank” While any bank can be selected, only those banks that
provides a detailed description of the Access RAM. are a ctually implemented c an be re ad or written t o.
Writes to unimplemented ba nks are ign ored, w hile
reads from unimplemented banks will return ‘0’s. Even
so, the STATUS register will still be affected as if th e
operation was successful. The data memory maps in
Figures 5 -5 th rough 5-7 in dicate w hich b anks a re
implemented.
In the co re PIC1 8 in struction se t, on ly the MOVFF
instruction full y s pecifies the 1 2-bit add ress of th e
source and target registers. This instruction ignores the
BSR completely when it executes. All other instructions
include only the low-order address as an operand and
must use either the BSR or the Access Bank to locate
their target registers.

 2010 Microchip Technology Inc. DS41303G-page 71

PIC18F2XK20/4XK20
FIGURE 5-5: DATA MEMORY MAP FOR PIC18F23K20/43K20 DEVICES

When ‘a’ = 0:
BSR<3:0> Data Memory Map
The BSR is ignored an d the
00h 000h Access Bank is used.
= 0000 Access RAM 05Fh
Bank 0 The first 96 bytes are
GPR 060h
FFh 0FFh general purpose RAM
00h 100h (from Bank 0).
= 0001
Bank 1 GPR The second 1 60 b ytes ar e
FFh 1FFh Special Fu nction R egisters
= 0010 00h 200h (from Bank 15).
Bank 2
FFh 2FFh When ‘a’ = 1:
= 0011 00h 300h
Bank 3 The BSR specifies the Bank
used by the instruction.
FFh 3FFh
00h 400h
= 0100 Bank 4
FFh 4FFh
= 0101 00h 500h
Bank 5
FFh 5FFh
= 0110 00h 600h
Bank 6
Access Bank
FFh 6FFh
= 0111 00h 700h 00h
Bank 7 Access RAM Low
5Fh
FFh 7FFh Access RAM High 60h
= 1000 00h 800h (SFRs)
Bank 8 FFh

FFh 8FFh
= 1001 00h Unused 900h
Bank 9 Read 00h
FFh 9FFh
00h A00h
= 1010
Bank 10
FFh AFFh
= 1011 00h B00h
Bank 11
FFh BFFh
= 1100 00h C00h
Bank 12

FFh CFFh
= 1101 D00h
Bank 13 00h

FFh DFFh
00h E00h
= 1110
Bank 14
FFh EFFh
00h Unused F00h
= 1111 F5Fh
Bank 15
SFR F60h
FFh FFFh

DS41303G-page 72  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 5-6: DATA MEMORY MAP FOR PIC18F24K20/44K20 DEVICES

When ‘a’ = 0:
BSR<3:0> Data Memory Map
The BSR is ignored an d the
00h 000h Access Bank is used.
= 0000 Access RAM 05Fh
Bank 0 The first 96 bytes are
GPR 060h
FFh 0FFh general purpose RAM
00h 100h (from Bank 0).
= 0001
Bank 1 GPR The second 1 60 b ytes ar e
FFh 1FFh Special Fu nction R egisters
= 0010 00h 200h (from Bank 15).
Bank 2 GPR
FFh 2FFh When ‘a’ = 1:
= 0011 00h 300h
Bank 3 The BSR specifies the Bank
used by the instruction.
FFh 3FFh
00h 400h
= 0100 Bank 4
FFh 4FFh
= 0101 00h 500h
Bank 5
FFh 5FFh
= 0110 00h 600h
Bank 6
Access Bank
FFh 6FFh
= 0111 00h 700h 00h
Bank 7 Access RAM Low
5Fh
FFh 7FFh Access RAM High 60h
= 1000 00h 800h (SFRs)
Bank 8 FFh

FFh 8FFh
= 1001 00h Unused 900h
Bank 9 Read 00h
FFh 9FFh
00h A00h
= 1010
Bank 10
FFh AFFh
= 1011 00h B00h
Bank 11
FFh BFFh
= 1100 00h C00h
Bank 12

FFh CFFh
= 1101 D00h
Bank 13 00h

FFh DFFh
00h E00h
= 1110
Bank 14
FFh EFFh
00h Unused F00h
= 1111 F5Fh
Bank 15
SFR F60h
FFh FFFh

 2010 Microchip Technology Inc. DS41303G-page 73

PIC18F2XK20/4XK20
FIGURE 5-7: DATA MEMORY MAP FOR PIC18F25K20/45K20 DEVICES

When ‘a’ = 0:
BSR<3:0> Data Memory Map
The BSR is ignored an d the
00h 000h Access Bank is used.
= 0000 Access RAM 05Fh
Bank 0 The first 96 bytes are
GPR 060h
FFh 0FFh general purpose RAM
00h 100h (from Bank 0).
= 0001
Bank 1 GPR The second 1 60 b ytes ar e
FFh 1FFh Special Fu nction R egisters
= 0010 00h 200h (from Bank 15).
Bank 2 GPR
FFh 2FFh When ‘a’ = 1:
= 0011 00h 300h
Bank 3 The BSR specifies the Bank
GPR
used by the instruction.
FFh 3FFh
00h 400h
= 0100 Bank 4 GPR
FFh 4FFh
= 0101 00h 500h
Bank 5 GPR
FFh 5FFh
= 0110 00h 600h
Bank 6
Access Bank
FFh 6FFh
= 0111 00h 700h 00h
Bank 7 Access RAM Low
5Fh
FFh 7FFh Access RAM High 60h
= 1000 00h 800h (SFRs)
Bank 8 FFh

FFh 8FFh
= 1001 00h 900h
Bank 9
FFh 9FFh
00h Unused A00h
= 1010
Bank 10 Read 00h
FFh AFFh
= 1011 00h B00h
Bank 11
FFh BFFh
= 1100 00h C00h
Bank 12

FFh CFFh
= 1101 D00h
Bank 13 00h

FFh DFFh
00h E00h
= 1110
Bank 14
FFh EFFh
00h Unused F00h
= 1111 F5Fh
Bank 15
SFR F60h
FFh FFFh

DS41303G-page 74  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 5-8: DATA MEMORY MAP FOR PIC18F26K20/46K20 DEVICES

When ‘a’ = 0:
BSR<3:0> Data Memory Map
The BSR is ignored an d the
00h 000h Access Bank is used.
= 0000 Access RAM 05Fh
Bank 0 The first 96 bytes are
GPR 060h
FFh 0FFh general purpose RAM
00h 100h (from Bank 0).
= 0001
Bank 1 GPR The second 1 60 b ytes ar e
FFh 1FFh Special Fu nction R egisters
= 0010 00h 200h (from Bank 15).
Bank 2 GPR
FFh 2FFh When ‘a’ = 1:
= 0011 00h 300h
Bank 3 The BSR specifies the Bank
GPR
used by the instruction.
FFh 3FFh
00h 400h
= 0100 Bank 4 GPR
FFh 4FFh
= 0101 00h 500h
Bank 5 GPR
FFh 5FFh
= 0110 00h 600h
Bank 6 GPR
Access Bank
FFh 6FFh
= 0111 00h 700h 00h
Bank 7 GPR Access RAM Low
5Fh
FFh 7FFh Access RAM High 60h
= 1000 00h 800h (SFRs)
Bank 8 FFh
GPR
FFh 8FFh
= 1001 00h 900h
Bank 9 GPR
FFh 9FFh
00h A00h
= 1010
Bank 10 GPR
FFh AFFh
= 1011 00h B00h
Bank 11 GPR
FFh BFFh
= 1100 00h C00h
Bank 12 GPR
FFh CFFh
= 1101 D00h
Bank 13 00h GPR
FFh DFFh
00h E00h
= 1110
Bank 14 GPR
FFh EFFh
00h GPR F00h
= 1111 F5Fh
Bank 15
SFR F60h
FFh FFFh

 2010 Microchip Technology Inc. DS41303G-page 75

PIC18F2XK20/4XK20
FIGURE 5-9: USE OF THE BANK SELECT REGISTER (DIRECT ADDRESSING)

BSR(1) Data Memory From Opcode(2)

7 0 000h 00h 7 0
0 0 0 0 0 0 1 1 Bank 0 1 1 1 1 1 1 1 1
FFh
100h 00h
Bank 1
Bank Select(2) 200h FFh
00h
Bank 2
300h FFh
00h

Bank 3
through
Bank 13

FFh
E00h
00h
Bank 14
F00h FFh
00h
Bank 15
FFFh FFh

Note 1: The Access RAM bit of the instruction can be used to force an override of the selected bank (BSR<3:0>) to
the registers of the Access Bank.
2: The MOVFF instruction embeds the entire 12-bit address in the instruction.

DS41303G-page 76  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.3.2 ACCESS BANK 5.3.3 GENERAL PURPOSE REGISTER
While the us e of the BSR w ith an em bedded 8-b it FILE
address a llows users to ad dress th e e ntire range of PIC18 devices may have banked memory in the G PR
data memory, it also means that the user must always area. This is data RAM, which is available for use by all
ensure th at th e co rrect ban k i s s elected. O therwise, instructions. G PRs st art at the bottom of B ank 0
data may be read from or written to the wrong location. (address 000h) and grow upwards towards the bottom of
This can be disastrous if a GPR is the intended target the SFR area. GPR s are not initialized by a P ower-on
of an op eration, b ut a n SF R is w ritten to i nstead. Reset and are unchanged on all other Resets.
Verifying an d/or ch anging the BSR for ea ch read or
write to data memory can become very inefficient. 5.3.4 SPECIAL FUNCTION REGISTERS
To streamline access for the most commonly used data The Special Fun ction Registers (SFR s) are re gisters
memory locations, the data memory is configured with used by the CPU and peripheral modules for controlling
an Access Bank , w hich all ows us ers to access a the desired operation of the device. These registers are
mapped block of me mory w ithout sp ecifying a BSR. implemented as s tatic RAM. SFR s s tart at the to p of
The Access Bank consists of the first 96 bytes of mem- data memory (FFFh) and extend downward to occupy
ory (00h-5Fh) in Bank 0 and the last 160 bytes of mem- the t op portion of Bank 1 5 (F 60h to FFF h). A list of
ory (60h-FFh) in Block 15. The lower half is known as these registers is given in Table 5-1 and Table 5-2.
the “Ac cess RAM” an d is co mposed of GPRs. Thi s The SFRs c an b e classified i nto t wo sets: th ose
upper hal f is al so w here the dev ice’s SFR s a re associated w ith the “c ore” de vice functionality (ALU ,
mapped. These two areas are mapped contiguously in Resets a nd in terrupts) a nd those related to th e
the Ac cess Ba nk and ca n b e a ddressed in a l inear peripheral functions. The Reset and interrupt registers
fashion by an 8-bit address (Figures 5-5 through 5-7). are des cribed in their res pective c hapters, w hile th e
The A ccess B ank is used by core P IC18 instructions ALU’s ST ATUS re gister is de scribed later i n this
that include the Access RAM bit (the ‘a’ parameter in section. R egisters rela ted to the ope ration o f a
the instruction). When ‘a’ is equal to ‘1’, the instruction peripheral feature are described in the chapter for that
uses the BSR a nd th e 8 -bit a ddress i ncluded in th e peripheral.
opcode for the da ta memory address. When ‘a’ is ‘ 0’, The SF Rs a re ty pically d istributed am ong th e
however, th e in struction i s f orced t o us e t he A ccess peripherals whose functions they control. Unused SFR
Bank add ress m ap; the cu rrent va lue of th e BSR i s locations are unimplemented and read as ‘0’s.
ignored entirely.
Using this “forced” addressing allows the instruction to
operate o n a da ta address i n a s ingle cycle, w ithout
updating the BSR first. For 8-bit addresses of 60h and
above, this means that users can evaluate and operate
on SFRs more efficiently. The Access RAM below 60h
is a good place for data values that the user might need
to ac cess ra pidly, s uch a s immediate c omputational
results or co mmon pr ogram variables. Access RAM
also allows for f aster and more code efficient context
saving and switching of variables.
The ma pping of the Access Bank is slightly different
when the extended instruction set is enabled (XINST
Configuration bit = 1). This is discussed in more detail
in Section 5.5.3 “Mapping the Access Bank in
Indexed Literal Offset Mode”.

 2010 Microchip Technology Inc. DS41303G-page 77

PIC18F2XK20/4XK20
TABLE 5-1: SPECIAL FUNCTION REGISTER MAP FOR PIC18F2XK20/4XK20 DEVICES
Address Name Address Name Address Name Address Name
FFFh TOSU FD7h TMR0H FAFh SPBRG F87h —(2)
FFEh TOSH FD6h TMR0L FAEh RCREG F86h —(2)
FFDh TOSL FD5h T0CON FADh TXREG F85h —(2)
FFCh STKPTR FD4h —(2) FACh TXSTA F84h PORTE
FFBh PCLATU FD3h OSCCON FABh RCSTA F83h PORTD(3)
FFAh PCLATH FD2h HLVDCON FAAh EEADRH(4) F82h PORTC
FF9h PCL FD1h WDTCON FA9h EEADR F81h PORTB
FF8h TBLPTRU FD0h RCON FA8h EEDATA F80h PORTA
FF7h TBLPTRH FCFh TMR1H FA7h EECON2(1) F7Fh ANSELH
FF6h TBLPTRL FCEh TMR1L FA6h EECON1 F7Eh ANSEL
FF5h TABLAT FCDh T1CON FA5h —(2) F7Dh IOCB
FF4h PRODH FCCh TMR2 FA4h —(2) F7Ch WPUB
FF3h PRODL FCBh PR2 FA3h —(2) F7Bh CM1CON0
FF2h INTCON FCAh T2CON FA2h IPR2 F7Ah CM2CON0
FF1h INTCON2 FC9h SSPBUF FA1h PIR2 F79h CM2CON1
FF0h INTCON3 FC8h SSPADD FA0h PIE2 F78h SLRCON
FEFh INDF0(1) F C7h SSPSTAT F9Fh IPR1 F77h SSPMSK
FEEh POSTINC0 (1)
FC6h SSPCON1 F9Eh PIR1 F76h —(2)
FEDh POSTDEC0(1) FC5h SSPCON2 F9Dh PIE1 F75h —(2)
FECh PREINC0(1) FC4h ADRESH F9Ch —(2) F74h —(2)
FEBh PLUSW0(1) FC3h ADRESL F9Bh OSCTUNE F73h —(2)
FEAh FSR0H FC2h ADCON0 F9Ah —(2) F72h —(2)
FE9h FSR0L FC1h ADCON1 F99h —(2) F71h —(2)
FE8h WREG FC0h ADCON2 F98h —(2) F70h —(2)
FE7h INDF1(1) FBFh CCPR1H F97h —(2) F6Fh —(2)
FE6h POSTINC1(1) FBEh CCPR1L F96h TRISE(3) F6Eh —(2)
FE5h POSTDEC1(1) FBDh CCP1CON F95h TRISD(3) F6Dh —(2)
FE4h PREINC1(1) FBCh CCPR2H F94h TRISC F6Ch —(2)
FE3h PLUSW1(1) FBBh CCPR2L F93h TRISB F6Bh —(2)
FE2h FSR1H FBAh CCP2CON F92h TRISA F6Ah —(2)
FE1h FSR1L FB9h PSTRCON F91h — (2)
F69h —(2)
FE0h BSR FB8h BAUDCON F90h —(2) F68h —(2)
FDFh INDF2(1) F B7h PWM1CON F8Fh —(2) F67h —(2)
FDEh POSTINC2(1) FB6h ECCP1AS F8Eh —(2) F66h —(2)
FDDh POSTDEC2 (1)
FB5h CVRCON F8Dh LATE (3)
F65 h —(2)
FDCh PREINC2(1) FB4h CVRCON2 F8Ch LATD(3) F64 h —(2)
FDBh PLUSW2(1) FB3h TMR3H F8Bh LATC F63h —(2)
FDAh FSR2H FB2h TMR3L F8Ah LATB F62h —(2)
FD9h FSR2L FB1h T3CON F89h LATA F61h —(2)
FD8h STATUS FB0h SPBRGH F88h —(2) F60h —(2)
Note 1: This is not a physical register.
2: Unimplemented registers are read as ‘0’.
3: This register is not available on PIC18F2XK20 devices.
4: This register is only implemented in the PIC18F46K20 and PIC18F26K20 devices.

DS41303G-page 78  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

TABLE 5-2: REGISTER FILE SUMMARY (PIC18F2XK20/4XK20)

Value on Details
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
POR, BOR on page:

TOSU — — — Top-of-Stack Upper Byte (TOS<20:16>) ---0 0000 59, 66

TOSH Top-of-Stack, High Byte (TOS<15:8>) 0000 0000 59, 66
TOSL Top-of-Stack, Low Byte (TOS<7:0>) 0000 0000 59, 66
STKPTR STKFUL STKUNF — SP4 SP3 SP2 SP1 SP0 00-0 0000 59, 67
PCLATU — — — Holding Register for PC<20:16> ---0 0000 59, 66
PCLATH Holding Register for PC<15:8> 0000 0000 59, 66
PCL PC, Low Byte (PC<7:0>) 0000 0000 59, 66
TBLPTRU — — bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) --00 0000 59, 92
TBLPTRH Program Memory Table Pointer, High Byte (TBLPTR<15:8>) 0000 0000 59, 92
TBLPTRL Program Memory Table Pointer, Low Byte (TBLPTR<7:0>) 0000 0000 59, 92
TABLAT Program Memory Table Latch 0000 0000 59, 92
PRODH Product Register, High Byte xxxx xxxx 59, 105
PRODL Product Register, Low Byte xxxx xxxx 59, 105
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 59, 109
INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP 1111 -1-1 59, 110
INTCON3 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF 11-0 0-00 59, 111
INDF0 Uses contents of FSR0 to address data memory – value of FSR0 not changed (not a physical register) N/A 59, 84
POSTINC0 Uses contents of FSR0 to address data memory – value of FSR0 post-incremented (not a physical register) N/A 59, 84
POSTDEC0 Uses contents of FSR0 to address data memory – value of FSR0 post-decremented (not a physical register) N/A 59, 84
PREINC0 Uses contents of FSR0 to address data memory – value of FSR0 pre-incremented (not a physical register) N/A 59, 84
PLUSW0 Uses contents of FSR0 to address data memory – value of FSR0 offset by W (not a physical register) – N/A 59, 84
FSR0H — — — — Indirect Data Memory Address Pointer 0, High Byte ---- 0000 59, 84
FSR0L Indirect Data Memory Address Pointer 0, Low Byte xxxx xxxx 59, 84
WREG Working Register xxxx xxxx 59
INDF1 Uses contents of FSR1 to address data memory – value of FSR1 not changed (not a physical register) N/A 59, 84
POSTINC1 Uses contents of FSR1 to address data memory – value of FSR1 post-incremented (not a physical register) N/A 59, 84
POSTDEC1 Uses contents of FSR1 to address data memory – value of FSR1 post-decremented (not a physical register) N/A 59, 84
PREINC1 Uses contents of FSR1 to address data memory – value of FSR1 pre-incremented (not a physical register) N/A 59, 84
PLUSW1 Uses contents of FSR1 to address data memory – value of FSR1 offset by W (not a physical register) – value of N/A 59, 84
FSR1H — — — — Indirect Data Memory Address Pointer 1, High Byte ---- 0000 60, 84
FSR1L Indirect Data Memory Address Pointer 1, Low Byte xxxx xxxx 60, 84
BSR — — — — Bank Select Register ---- 0000 60, 71
INDF2 Uses contents of FSR2 to address data memory – value of FSR2 not changed (not a physical register) N/A 60, 84
POSTINC2 Uses contents of FSR2 to address data memory – value of FSR2 post-incremented (not a physical register) N/A 60, 84
POSTDEC2 Uses contents of FSR2 to address data memory – value of FSR2 post-decremented (not a physical register) N/A 60, 84
PREINC2 Uses contents of FSR2 to address data memory – value of FSR2 pre-incremented (not a physical register) N/A 60, 84
PLUSW2 Uses contents of FSR2 to address data memory – value of FSR2 offset by W (not a physical register) – value of N/A 60, 84
FSR2H — — — — Indirect Data Memory Address Pointer 2, High Byte ---- 0000 60, 84
FSR2L Indirect Data Memory Address Pointer 2, Low Byte xxxx xxxx 60, 84
STATUS — — — N OV Z DC C ---x xxxx 60, 82
Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise it is disabled and reads as ‘0’. See
Section 4.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as ‘-’.
3: The PLLEN bit is only available in specific oscillator configuration; otherwise it is disabled and reads as ‘0’. See Section 2.6.2 “PLL in
HFINTOSC Modes”.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0). Otherwise, RE3 reads as ‘0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.
7: This register is only implemented in the PIC18F46K20 and PIC18F26K20 devices.

 2010 Microchip Technology Inc. DS41303G-page 79

PIC18F2XK20/4XK20
TABLE 5-2: REGISTER FILE SUMMARY (PIC18F2XK20/4XK20) (CONTINUED)
Value on Details
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
POR, BOR on page:

TMR0H Timer0 Register, High Byte 0000 0000 60, 157

TMR0L Timer0 Register, Low Byte xxxx xxxx 60, 157
T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 1111 1111 60, 155
OSCCON IDLEN IRCF2 IRCF1 IRCF0 OSTS IOFS SCS1 SCS0 0011 qq00 29, 60
HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 0-00 0101 60, 293
WDTCON — — — — — — — SWDTEN --- ---0 60, 309
RCON IPEN SBOREN(1) — RI TO PD POR BOR 0q-1 11q0 51, 58,
118
TMR1H Timer1 Register, High Byte xxxx xxxx 60, 165
TMR1L Timer1 Register, Low Bytes xxxx xxxx 60, 165
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 0000 0000 60, 159
TMR2 Timer2 Register 0000 0000 60, 168
PR2 Timer2 Period Register 1111 1111 60, 168
T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 -000 0000 60, 167
SSPBUF SSP Receive Buffer/Transmit Register xxxx xxxx 60, 201,
202
SSPADD SSP Address Register in I2C™ Slave Mode. SSP Baud Rate Reload Register in I2C Master Mode. 0000 0000 60, 202
SSPSTAT SMP CKE D/A P S R/W UA BF 0000 0000 60, 194,
204
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 60, 195,
205
SSPCON2 GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN 0000 0000 60, 206
ADRESH A/D Result Register, High Byte xxxx xxxx 61, 277
ADRESL A/D Result Register, Low Byte xxxx xxxx 61, 277
ADCON0 — — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON --00 0000 61, 271
ADCON1 — — VCFG1 VCFG0 — — — — --00 ---- 59, 272
ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 0-00 0000 61, 273
CCPR1H Capture/Compare/PWM Register 1, High Byte xxxx xxxx 61, 144
CCPR1L Capture/Compare/PWM Register 1, Low Byte xxxx xxxx 61, 144
CCP1CON P1 M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 0000 0000 61, 173
CCPR2H Capture/Compare/PWM Register 2, High Byte xxxx xxxx 61, 144
CCPR2L Capture/Compare/PWM Register 2, Low Byte xxxx xxxx 61, 144
CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 --00 0000 61, 143
PSTRCON — — — STRSYNC STRD STRC STRB STRA ---0 0001 61, 187
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 0100 0-00 61, 248
PWM1CON PRSEN PDC6 PDC5 PDC4 PDC3 PDC2 PDC1 PDC0 0000 0000 61, 186
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1 PSSBD0 0000 0000 61, 183
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 0000 0000 61, 291
CVRCON2 FVREN FVRST — — — — — — 00-- ---- 61, 292
TMR3H Timer3 Register, High Byte xxxx xxxx 61, 172
TMR3L Timer3 Register, Low Byte xxxx xxxx 61, 172
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 0000 0000 61, 169
Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise it is disabled and reads as ‘0’. See
Section 4.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as ‘-’.
3: The PLLEN bit is only available in specific oscillator configuration; otherwise it is disabled and reads as ‘0’. See Section 2.6.2 “PLL in
HFINTOSC Modes”.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0). Otherwise, RE3 reads as ‘0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.
7: This register is only implemented in the PIC18F46K20 and PIC18F26K20 devices.

DS41303G-page 80  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 5-2: REGISTER FILE SUMMARY (PIC18F2XK20/4XK20) (CONTINUED)
Value on Details
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
POR, BOR on page:

SPBRGH EUSART Baud Rate Generator Register, High Byte 0000 0000 61, 241
SPBRG EUSART Baud Rate Generator Register, Low Byte 0000 0000 61, 241
RCREG EUSART Receive Register 0000 0000 61, 238
TXREG EUSART Transmit Register 0000 0000 61, 237
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 0000 0010 61, 246
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 0000 000x 61, 247
EEADR EEADR7 EEADR6 EEADR5 EEADR4 EEADR3 EEADR2 EEADR1 EEADR0 0000 0000 61, 90, 99
EEADRH(7) — — — — — — EEADR9 EEADR8 ---- --00 61, 90, 99
EEDATA EEPROM Data Register 0000 0000 61, 90, 99
EECON2 EEPROM Control Register 2 (not a physical register) 0000 0000 61, 90, 99
EECON1 EEPGD CFGS — FREE WRERR WREN WR RD xx-0 x000 61, 91, 99
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 1111 1111 62, 117
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 0000 0000 62, 113
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 0000 0000 62, 115
IPR1 PSPIP(2) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 62, 116
PIR1 PSPIF(2) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 62, 112
PIE1 PSPIE(2) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 62, 114
OSCTUNE INTSRC PLLEN(3) TUN5 TUN4 TUN3 TUN2 TUN1 TUN0 0q00 0000 33, 62
TRISE(2) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 0000 -111 62, 134
TRISD(2) PORTD Data Direction Control Register 1111 1111 62, 130
TRISC PORTC Data Direction Control Register 1111 1111 62, 127
TRISB PORTB Data Direction Control Register 1111 1111 62, 124
TRISA TRISA7(5) TRISA6(5) Data Direction Control Register for PORTA 1111 1111 62, 121
LATE(2) — — — — — PORTE Data Latch Register ---- -xxx 62, 133
(Read and Write to Data Latch)
LATD(2) PORTD Data Latch Register (Read and Write to Data Latch) xxxx xxxx 62, 130
LATC PORTC Data Latch Register (Read and Write to Data Latch) xxxx xxxx 62, 127
LATB PORTB Data Latch Register (Read and Write to Data Latch) xxxx xxxx 62, 124
LATA LATA7(5) LATA6(5) PORTA Data Latch Register (Read and Write to Data Latch) xxxx xxxx 62, 121
PORTE — — — — RE3(4) RE2(2) RE1(2) RE0(2) ---- x000 62, 133
PORTD(2) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 xxxx xxxx 62, 130
PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 xxxx xxxx 62, 127
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 xxx0 0000 62, 124
PORTA RA7(5) RA6(5) RA5 RA4 RA3 RA2 RA1 RA0 xx0x 0000 62, 121
ANSELH(6) — — — ANS12 ANS11 ANS10 ANS9 ANS8 ---1 1111 62, 137
ANSEL ANS7(2) ANS6(2) ANS5(2) ANS4 ANS3 ANS2 ANS1 ANS0 1111 1111 62, 136
IOCB IOCB7 IOCB6 IOCB5 IOCB4 — — — — 0000 ---- 62, 124
WPUB WPUB7 WPUB6 WPUB5 WPUB4 WPUB3 WPUB2 WPUB1 WPUB0 1111 1111 62, 124
CM1CON0 C1ON C1OUT C1OE C1POL C1SP C1R C1CH1 C1CH0 0000 0000 62, 284
CM2CON0 C2ON C2OUT C2OE C2POL C2SP C2R C2CH1 C2CH0 0000 0000 62, 285
CM2CON1 MC1OUT MC2OUT C1RSEL C2RSEL — — — — 0000 ---- 63, 287
SLRCON — — — SLRE(2) SLRD(2) SLRC SLRB SLRA ---1 1111 63, 138
SSPMSK MSK7 MSK6 MSK5 MSK4 MSK3 MSK2 MSK1 MSK0 1111 1111 63, 213
Legend: x = unknown, u = unchanged, — = unimplemented, q = value depends on condition
Note 1: The SBOREN bit is only available when the BOREN<1:0> Configuration bits = 01; otherwise it is disabled and reads as ‘0’. See
Section 4.4 “Brown-out Reset (BOR)”.
2: These registers and/or bits are not implemented on 28-pin devices and are read as ‘0’. Reset values are shown for 40/44-pin devices;
individual unimplemented bits should be interpreted as ‘-’.
3: The PLLEN bit is only available in specific oscillator configuration; otherwise it is disabled and reads as ‘0’. See Section 2.6.2 “PLL in
HFINTOSC Modes”.
4: The RE3 bit is only available when Master Clear Reset is disabled (MCLRE Configuration bit = 0). Otherwise, RE3 reads as ‘0’. This bit is
read-only.
5: RA6/RA7 and their associated latch and direction bits are individually configured as port pins based on various primary oscillator modes.
When disabled, these bits read as ‘0’.
6: All bits of the ANSELH register initialize to ‘0’ if the PBADEN bit of CONFIG3H is ‘0’.
7: This register is only implemented in the PIC18F46K20 and PIC18F26K20 devices.

 2010 Microchip Technology Inc. DS41303G-page 81

PIC18F2XK20/4XK20
5.3.5 STATUS REGISTER It is recommended that only BCF, BSF, SWAPF, MOVFF
and MOVWF instructions are used to alter the STATUS
The STATUS register, shown in Register 5-2, contains
register, because these instructions do not affect the Z,
the arithmetic status of the ALU. As with any other SFR,
C, DC, OV or N bits in the STATUS register.
it can be the operand for any instruction.
For other instructions that do not affect Status bits, see
If the STATUS register is the destination for an instruc-
the ins truction s et s ummaries in T able 24-2 an d
tion that affects the Z, DC, C, OV or N bits, the results
Table 24-3.
of the instruction are not written; instead, the STATUS
register is u pdated according to th e ins truction p er- Note: The C and DC bits operate as the borrow
formed. Therefore, the result of an instruction with the and di git borrow bits, res pectively, in
STATUS re gister as it s d estination may b e d ifferent subtraction.
than intended. As an example, CLRF STATUS will set
the Z bit and le ave the rem aining S tatus bit s
unchanged (‘000u u1uu’).

REGISTER 5-2: STATUS: STATUS REGISTER

U-0 U-0 U-0 R/W-x R/W-x R/W-x R/W-x R/W-x
— — — N OV Z DC (1)
C(1)
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4 N: Negative bit
This bit is used for signed arithmetic (two’s complement). It indicates whether the result was negative
(ALU MSB = 1).
1 = Result was negative
0 = Result was positive
bit 3 OV: Overflow bit
This bit is used for signed arithmetic (two’s complement). It indicates an overflow of the 7-bit magni-
tude which causes the sign bit (bit 7 of the result) to change state.
1 = Overflow occurred for signed arithmetic (in this arithmetic operation)
0 = No overflow occurred
bit 2 Z: Zero bit
1 = The result of an arithmetic or logic operation is zero
0 = The result of an arithmetic or logic operation is not zero
bit 1 DC: Digit Carry/Borrow bit (ADDWF, ADDLW,SUBLW,SUBWF instructions)(1)
1 = A carry-out from the 4th low-order bit of the result occurred
0 = No carry-out from the 4th low-order bit of the result
bit 0 C: Carry/Borrow bit (ADDWF, ADDLW, SUBLW, SUBWF instructions)(1)
1 = A carry-out from the Most Significant bit of the result occurred
0 = No carry-out from the Most Significant bit of the result occurred

Note 1: For Borrow, the polarity is reversed. A subtraction is executed by adding the two’s complement of the
second operand. For rotate (RRF, RLF) instructions, this bit is loaded with either the high-order or low-order
bit of the source register.

DS41303G-page 82  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
5.4 Data Addressing Modes The Access RAM bit ‘a’ determines how the address is
interpreted. Wh en ‘a ’ is ‘1’, th e co ntents of the BSR
Note: The execution of so me instructions in the (Section 5.3.1 “Bank Select Register (BSR)”) a re
core P IC18 i nstruction set are c hanged used with the address to determine the complete 12-bit
when the PIC18 extended instruction set is address of the register. When ‘a’ is ‘0’, the address is
enabled. See Section 5.5 “Data Memory interpreted a s being a register i n t he Access Bank.
and the Extended Instruction Set” for Addressing tha t uses the Acc ess R AM is sometimes
more information. also known as Direct Forced Addressing mode.
While the program memory can be ad dressed in only A few instructions, such as MOVFF, include the entire
one way – through the program counter – information 12-bit ad dress (either s ource or de stination) in the ir
in the data memory space can be addressed in several opcodes. In these cases, the BSR is ignored entirely.
ways. Fo r mo st ins tructions, t he a ddressing m ode i s The destination of the operation’s results is determined
fixed. O ther instructions may use up to three modes, by the destination bit ‘d’. When ‘d’ is ‘1’, the results are
depending on which operands are used and whether or stored back in the source register, overwriting its origi-
not the extended instruction set is enabled. nal contents. When ‘d’ is ‘0’, the results are stored in
The addressing modes are: the W reg ister. Instructions with out the ‘d ’ a rgument
have a destination that is implicit in the instruction; their
• Inherent
destination is either the target register being operated
• Literal on or the W register.
• Direct
• Indirect 5.4.3 INDIRECT ADDRESSING
An additional addressing mode, Indexed Literal Offset, Indirect addressing allows the user to access a location
is a vailable w hen the ext ended i nstruction s et i s in d ata m emory w ithout giving a f ixed address in th e
enabled (XINST Configuration bit = 1). Its operation is instruction. This is done by using File Select Registers
discussed in greater detail in Section 5.5.1 “Indexed (FSRs) as pointers to the locations which are to be read
Addressing with Literal Offset”. or w ritten. Since the FSRs are themselves located in
RAM as Special F ile R egisters, th ey ca n al so be
5.4.1 INHERENT AND LITERAL directly manipulated un der pro gram co ntrol. Thi s
ADDRESSING makes FSR s ve ry useful in im plementing dat a s truc-
tures, such as tables and arrays in data memory.
Many PIC18 control instructions do not need any argu-
ment at all; they either perform an operation that glob- The re gisters fo r in direct add ressing are a lso
ally affects the device or they operate implicitly on one implemented with Indirect File Operands (INDFs) that
register. Th is a ddressing m ode i s known as Inh erent permit automatic manipulation of the pointer value with
Addressing. Examples include SLEEP, RESET and DAW. auto-incrementing, au to-decrementing o r of fsetting
with another value. This allows for efficient code, using
Other instructions work in a similar way but require an
loops, such as the example of clearing an entire RAM
additional explicit argument in th e opc ode. Th is i s
bank in Example 5-5.
known as Li teral Add ressing mo de b ecause the y
require some literal value as an argument. Examples
include ADDLW and MOVLW, which respectively, add or EXAMPLE 5-5: HOW TO CLEAR RAM
move a literal value to the W register. Other examples (BANK 1) USING
include CALL an d GOTO, w hich i nclude a 20-bit INDIRECT ADDRESSING
program memory address. LFSR FSR0, 100h ;
NEXT CLRF POSTINC0 ; Clear INDF
5.4.2 DIRECT ADDRESSING ; register then
; inc pointer
Direct ad dressing sp ecifies all or part of the so urce BTFSS FSR0H, 1 ; All done with
and/or destination address of the operation within the ; Bank1?
opcode it self. The o ptions a re specified by th e BRA NEXT ; NO, clear next
arguments accompanying the instruction. CONTINUE ; YES, continue
In the core PIC18 instruction set, bit-oriented and byte-
oriented ins tructions us e s ome v ersion of d irect
addressing by default. All of these instructions include
some 8 -bit literal add ress a s t heir Lea st Sign ificant
Byte. This address specifies either a register address in
one of the banks of data RAM (Section 5.3.3 “General
Purpose Register File”) or a loc ation in the Access
Bank ( Section 5.3.2 “Access Bank”) as the da ta
source for the instruction.

 2010 Microchip Technology Inc. DS41303G-page 83

PIC18F2XK20/4XK20
5.4.3.1 FSR Registers and the INDF 5.4.3.2 FSR Registers and POSTINC,
Operand POSTDEC, PREINC and PLUSW
At the core of indirect addressing are three sets of reg- In addition to the INDF operand, each FSR register pair
isters: FSR0, FSR1 and FSR2. Each represents a pair also has four additional indirect operands. Like INDF,
of 8-bit registers, FSRnH and FSRnL. Each FSR pair these a re “virtual” re gisters which cannot b e d irectly
holds a 12-bit value, therefore the four upper bits of the read o r written. Ac cessing thes e re gisters ac tually
FSRnH register are not used. The 12-bit FSR value can accesses the loc ation to w hich th e as sociated FSR
address the entire range of the data memory in a linear register pair points, and also performs a specific action
fashion. The FSR register pairs, then, serve as pointers on the FSR value. They are:
to data memory locations. • POSTDEC: accesses the location to which the
Indirect addressing is ac complished w ith a s et of FSR points, then automatically decrements the
Indirect File Operands, INDF0 through INDF2. These FSR by 1 afterwards
can be tho ught o f a s “virtual” re gisters: they a re • POSTINC: accesses the location to which the
mapped in th e SFR sp ace but are no t phy sically FSR points, then automatically increments the
implemented. R eading or w riting to a particular IN DF FSR by 1 afterwards
register actually a ccesses it s co rresponding FSR • PREINC: automatically increments the FSR by 1,
register pair. A read from IN DF1, for ex ample, reads then uses the location to which the FSR points in
the da ta at th e add ress in dicated by FSR1H:FSR1L. the operation
Instructions that u se the IN DF registers as o perands
• PLUSW: adds the signed value of the W register
actually use the contents of their corresponding FSR as
(range of -127 to 128) to that of the FSR and uses
a pointer to the instruction’s target. The INDF operand
the location to which the result points in the
is just a convenient way of using the pointer.
operation.
Because indirect addressing uses a full 12-bit address,
In thi s c ontext, ac cessing an IN DF reg ister u ses th e
data RAM banking is not necessary. Thus, the current
value in the associated FSR register without changing
contents of the BSR and the Access RAM bit have no
it. S imilarly, accessing a PLUSW r egister g ives t he
effect on determining the target address.
FSR value an offset by that in the W register; however,
neither W no r the FSR is act ually changed in th e
operation. Ac cessing th e o ther vi rtual re gisters
changes the value of the FSR register.

FIGURE 5-10: INDIRECT ADDRESSING

000h
Using an instruction with one of the ADDWF, INDF1, 1 Bank 0
indirect addressing registers as the 100h
operand.... Bank 1
200h
Bank 2
300h
...uses the 12-bit address stored in FSR1H:FSR1L
the F SR p air assoc iated wit h that
7 0 7 0
register.... Bank 3
x x x x 1 1 1 0 1 1 0 0 1 1 0 0 through
Bank 13

...to det ermine t he data mem ory

location to be used in that operation.
In this case, the FSR1 pair contains E00h
ECCh. T his means the cont ents of Bank 14
location ECCh will be added to that F00h
of the W register and stored back in Bank 15
ECCh. FFFh
Data Memory

DS41303G-page 84  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
Operations on the F SRs w ith PO STDEC, PO STINC 5.5.1 INDEXED ADDRESSING WITH
and PREINC affect the entire register pair; that is, roll- LITERAL OFFSET
overs of the FSRnL register from FFh to 00h carry over
Enabling the PIC18 extended instruction set changes
to the FSR nH register. O n the oth er h and, res ults of
the b ehavior o f i ndirect ad dressing us ing t he FSR2
these operations do not change the value of any flags
register p air w ithin Access R AM. U nder the prop er
in the STATUS register (e.g., Z, N, OV, etc.).
conditions, instructions that use the Access Bank – that
The PLUSW register can be used to implement a form is, mo st bit-oriented and by te-oriented i nstructions –
of i ndexed ad dressing i n t he data m emory spac e. B y can invoke a f orm of in dexed ad dressing u sing an
manipulating the v alue i n the W regi ster, us ers ca n offset sp ecified in the instruction. This special
reach ad dresses tha t are fix ed of fsets from po inter addressing mode is known as Indexed Addressing with
addresses. In so me applications, this can be used to Literal Offset, or Indexed Literal Offset mode.
implement s ome powerful pro gram control s tructure,
When using the extended ins truction se t, thi s
such as software stacks, inside of data memory.
addressing mode requires the following:
5.4.3.3 Operations by FSRs on FSRs • The use of the Access Bank is forced (‘a’ = 0) and
Indirect addressing operations that target other FSRs • The file address argument is less than or equal to
or virtual r egisters r epresent s pecial cases. For 5Fh.
example, using a n F SR to po int to on e of the virtual Under t hese conditions, t he f ile a ddress o f t he
registers will not result in successful operations. As a instruction is not i nterpreted as the l ower byte of an
specific case, as sume that FSR 0H:FSR0L c ontains address (used with the BSR in direct addressing), or as
FE7h, the address o f IN DF1. Atte mpts t o rea d th e an 8-bit address in the Access Bank. Instead, the value
value of the IN DF1 u sing INDF0 as a n o perand w ill is interpreted as an offset value to an Address Pointer,
return 00h. Attempts to write to INDF1 using INDF0 as specified by F SR2. Th e of fset an d the co ntents of
the operand will result in a NOP. FSR2 are ad ded to ob tain the t arget add ress of th e
On the other hand, using the virtual registers to write to operation.
an FSR pair may not occur as planned. In these cases,
the value will be written to the FSR pair but without any 5.5.2 INSTRUCTIONS AFFECTED BY
incrementing or decrementing. Thus, w riting t o e ither INDEXED LITERAL OFFSET MODE
the INDF2 or POSTDEC2 register will write the same Any of the core PIC18 instructions that can use direct
value to the FSR2H:FSR2L. addressing a re p otentially affected by th e Indexed
Since the FSRs are physical registers mapped in the Literal O ffset Ad dressing mo de. Thi s i ncludes al l
SFR space, they can be manipulated through all direct byte-oriented and bit-oriented instructions, or a lmost
operations. U sers sh ould pro ceed c autiously w hen one-half of the s tandard PIC 18 instruction se t.
working on these reg isters, p articularly if thei r cod e Instructions that only use Inherent or Literal Addressing
uses indirect addressing. modes are unaffected.
Similarly, operations by indirect addressing are generally Additionally, byte-oriented and bit-oriented instructions
permitted on all other SFRs. Users should exercise the are no t af fected if they do no t us e th e Ac cess Ban k
appropriate caution that they do not inadvertently change (Access RAM bit is ‘1’), or include a file address of 60h
settings that might affect the operation of the device. or abo ve. Ins tructions m eeting the se cri teria w ill
continue to ex ecute as be fore. A co mparison of t he
5.5 Data Memory and the Extended different pos sible addressing mo des w hen the
extended ins truction s et is enabled is s hown in
Instruction Set Figure 5-11.
Enabling th e PIC18 extended in struction s et (XINST Those who desire to u se byte-oriented or bit-oriented
Configuration bi t = 1) s ignificantly changes ce rtain instructions in the Indexed Literal Offset mode should
aspects of da ta m emory and it s add ressing. Specifi- note the changes to assembler syntax for this mode.
cally, the use of the Access Bank for many of the core This is des cribed in mo re de tail in Section 24.2.1
PIC18 instructions is different; this is due to th e intro- “Extended Instruction Syntax”.
duction of a new addressing mode for the data memory
space.
What does not change is just as important. The size of
the data m emory s pace is un changed, as w ell as it s
linear ad dressing. Th e SFR m ap remains th e s ame.
Core PIC18 instructions can still operate in both Direct
and Ind irect Add ressing m ode; inherent and li teral
instructions d o no t cha nge at al l. In direct addressing
with FSR0 and FSR1 also remain unchanged.

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PIC18F2XK20/4XK20
FIGURE 5-11: COMPARING ADDRESSING OPTIONS FOR BIT-ORIENTED AND
BYTE-ORIENTED INSTRUCTIONS (EXTENDED INSTRUCTION SET ENABLED)

EXAMPLE INSTRUCTION: ADDWF, f, d, a (Opcode: 0010 01da ffff ffff)

000h
When ‘a’ = 0 and f  60h:
060h
The ins truction ex ecutes in
Direct Forced mode. ‘f’ is inter- Bank 0

preted as a location in the 100h

Access R AM be tween 0 60h 00h
Bank 1
and 0FFh. This is the same as through 60h
locations F60h to FFFh Bank 14
Valid range
(Bank 15) of data memory. for ‘f’
Locations bel ow 60 h are not FFh
F00h Access RAM
available in th is ad dressing
Bank 15
mode.
F60h
SFRs
FFFh
Data Memory

When ‘a’ = 0 and f5Fh: 000h

The instruction ex ecutes in
Indexed Literal Offset mode. ‘f’ 060h
Bank 0
is interpreted as an offset to the
100h
address value in FSR 2. The 001001da ffffffff
two are ad ded toge ther to Bank 1
obtain the address of the target through
Bank 14
register for the instruction. The
address ca n be an ywhere in FSR2H FSR2L
the data memory space.
F00h
Note that in thi s mo de, the Bank 15
correct syntax is now: F60h
ADDWF [k], d SFRs
where ‘k’ is the same as ‘f’. FFFh
Data Memory

BSR
When ‘a’ = 1 (all values of f): 000h 00000000

The ins truction ex ecutes in

060h
Direct mo de (also kn own as
Bank 0
Direct Long mode). ‘f’ is inter- 100h
preted as a location in one of
the 1 6 b anks of th e d ata Bank 1 001001da ffffffff
memory s pace. Th e bank is through
Bank 14
designated by the Bank Select
Register ( BSR). Th e ad dress
can be in any implemented F00h
bank in the da ta memory Bank 15
space. F60h
SFRs
FFFh
Data Memory

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 PIC18F2XK20/4XK20
5.5.3 MAPPING THE ACCESS BANK IN Remapping of the Access Bank applies only to opera-
INDEXED LITERAL OFFSET MODE tions using the Indexed Literal Offset mode. Operations
that use the BSR (Access RAM bit is ‘1’) will continue
The u se of Ind exed Literal O ffset Add ressing m ode
to use direct addressing as before.
effectively changes how the first 96 locations of Access
RAM (00h to 5Fh) are mapped. Rather than containing
just the contents of the bottom section of Bank 0, this 5.6 PIC18 Instruction Execution and
mode maps the contents from a user defined “window” the Extended Instruction Set
that c an be l ocated an ywhere i n th e d ata me mory
Enabling the ex tended instruction s et a dds eight
space. The value of FSR2 establishes the lower bound-
additional com mands to the ex isting PIC 18 ins truction
ary of the addresses mapped into the window, while the
set. The se ins tructions are ex ecuted as desc ribed in
upper bou ndary is def ined by FSR 2 pl us 95 (5F h).
Section 24.2 “Extended Instruction Set”.
Addresses in the Access RAM above 5Fh are mapped
as pre viously des cribed (se e Section 5.3.2 “Access
Bank”). An example of Access Bank remapping in this
addressing mode is shown in Figure 5-12.

FIGURE 5-12: REMAPPING THE ACCESS BANK WITH INDEXED LITERAL OFFSET
ADDRESSING
Example Situation:
ADDWF f, d, a 000h
FSR2H:FSR2L = 120h
Bank 0
Locations i n t he region
from t he F SR2 point er 100h
(120h) t o t he point er plus Bank 1
120h
05Fh (17Fh) a re m apped Window
17Fh 00h
to t he bot tom of the
Bank 1
Access RAM (000h-05Fh). 200h Bank 1 “Window”
Special F ile Regist ers at 5Fh
60h
F60h t hrough F FFh are
mapped t o 60h t hrough Bank 2
FFh, as usual. SFRs
through
Bank 0 addre sses below Bank 14
5Fh can still be addressed FFh
by using the BSR. Access Bank
F00h
Bank 15
F60h
SFRs
FFFh
Data Memory

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PIC18F2XK20/4XK20
NOTES:

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 PIC18F2XK20/4XK20
6.0 FLASH PROGRAM MEMORY A value written to program memory does not need to be
a valid in struction. Ex ecuting a pr ogram memory
The Flash program memory is readable, writable and location t hat f orms an i nvalid instruction r esults in a
erasable during normal operation over the entire V DD NOP.
range.
A read from program memory is executed one byte at 6.1 Table Reads and Table Writes
a time. A w rite to prog ram me mory is ex ecuted on
blocks of 64, 32 or 16 bytes at a time, depending on the In order to read and w rite program memory, there are
specific device (See Table 6-1). Prog ram m emory i s two operations that all ow the processor to m ove bytes
erased in blocks of 64 bytes at a time. The difference between the program memory space and the data RAM:
between the write and erase block sizes requires from • Table Read (TBLRD)
1 to 4 block writes to res tore the contents of a si ngle • Table Write (TBLWT)
block erase. A b ulk erase operation cannot be issued
The program memory space is 16 bits wide, while the
from user code.
data RAM space is 8 bits wide. Table reads and table
writes move data between these two memory spaces
TABLE 6-1: WRITE/ERASE BLOCK SIZES through an 8-bit register (TABLAT).
Write Block Erase Block The t able rea d o peration re trieves o ne b yte of dat a
Device
Size (bytes) Size (bytes) directly f rom pr ogram memory and p laces i t i nto th e
PIC18F43K20, 16 64 TABLAT register. Figure 6-1 shows the operation of a
PIC18F23K20 table read.
PIC18F24K20, 32 64 The table write operation stores one byte of data from the
PIC18F25K20, TABLAT register into a w rite block holding register. The
PIC18F44K20, procedure to write the contents of t he holding registers
PIC18F45K20 into program memory is detailed in Section 6.5 “Writing
PIC18F26K20, 64 64 to Flash Program Memory”. Fi gure 6-2 shows th e
PIC18F46K20 operation of a table write with program memory and data
RAM.
Writing or eras ing pro gram me mory w ill c ease
Table operations work with byte entities. Tables contain-
instruction fetches until the operation is complete. The
ing data, rather than program instruction s, are not
program memory cannot be accessed during the write
required to be word aligned. Therefore, a table can start
or erase, therefore, code cannot execute. An int ernal
and e nd at any by te address. If a t able w rite is being
programming timer terminates program memory writes
used to w rite executable code into pr ogram memory,
and erases.
program instructions will need to be word aligned.

FIGURE 6-1: TABLE READ OPERATION

Instruction: TBLRD*

Program Memory
Table Pointer(1)
Table Latch (8-bit)
TBLPTRU TBLPTRH TBLPTRL
TABLAT

Program Memory
(TBLPTR)

Note 1: Table Pointer register points to a byte in program memory.

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PIC18F2XK20/4XK20
FIGURE 6-2: TABLE WRITE OPERATION

Instruction: TBLWT*

Program Memory Holding Registers

Table Pointer(1) Table Latch (8-bit)

TBLPTRU TBLPTRH TBLPTRL TABLAT

Program Memory
(TBLPTR<MSBs>)

Note 1: During table writes the Table Pointer does not point directly to Program Memory. The LSBs of TBLPRTL
actually point to an address within the write block holding registers. The MSBs of the Table Pointer deter-
mine where the write block will eventually be written. The process for writing the holding registers to the
program memory array is discussed in Section 6.5 “Writing to Flash Program Memory”.

6.2 Control Registers The FREE bit allows the program memory erase oper-
ation. When FREE is set, an erase operation is initiated
Several control registers are us ed in co njunction with on the next WR command. When FREE is clear, only
the TBLRD and TBLWT instructions. These include the: writes are enabled.
• EECON1 register The WREN bit, when set, will allow a write operation.
• EECON2 register The WREN bit is clear on power-up.
• TABLAT register The WRERR bit is set by hardware when the WR bit is
• TBLPTR registers set and cleared when the internal programming timer
expires and the write operation is complete.
6.2.1 EECON1 AND EECON2 REGISTERS
Note: During normal op eration, the WRERR i s
The EECON1 re gister (Re gister 6-1) is t he control read as ‘1’. This can indicate that a write
register for memory accesses. The EECON2 register is operation was prematurely terminated by
not a ph ysical register; it is us ed ex clusively in th e a R eset, or a w rite ope ration w as
memory w rite and e rase sequences. R eading attempted improperly.
EECON2 will read all ‘0’s.
The EEPGD control bit determines if the access will be The WR control bit initiates write operations. The WR
a prog ram or d ata EEPRO M m emory ac cess. Whe n bit cannot be cleared, only set, by firmware. Then WR
EEPGD is c lear, any subsequent op erations wil l bit is cleared by hardware at the completion of the write
operate on the data EEPROM memory. When EEPGD operation.
is set, any subsequent operations will operate on the Note: The EEIF in terrupt fl ag bi t of the PIR 2
program memory. register is set when the write is complete.
The CFGS control bit determines if the access will be The EEIF fl ag s tays se t unt il c leared b y
to the Configuration/Calibration registers or to program firmware.
memory/data EEPROM m emory. When CFGS is s et,
subsequent ope rations w ill operate o n C onfiguration
registers reg ardless of EEPGD (s ee Section 23.0
“Special Features of the CPU”). When CFGS is clear,
memory selection access is determined by EEPGD.

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 PIC18F2XK20/4XK20

REGISTER 6-1: EECON1: DATA EEPROM CONTROL 1 REGISTER

R/W-x R/W-x U-0 R/W -0 R/W-x R/W-0 R/S-0 R/S-0
EEPGD CFGS — FREE WRERR WREN WR RD
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit
S = Bit can be set by software, but not cleared U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit

1 = Access Flash program memory
0 = Access data EEPROM memory
bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit
1 = Access Configuration registers
0 = Access Flash program or data EEPROM memory
bit 5 Unimplemented: Read as ‘0’
bit 4 FREE: Flash Row (Block) Erase Enable bit
1 = Erase the program memory block addressed by TBLPTR on the next WR command
(cleared by completion of erase operation)
0 = Perform write-only
bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit(1)
1 = A write operation is prematurely terminated (any Reset during self-timed programming in normal
operation, or an improper write attempt)
0 = The write operation completed
bit 2 WREN: Flash Program/Data EEPROM Write Enable bit
1 = Allows write cycles to Flash program/data EEPROM
0 = Inhibits write cycles to Flash program/data EEPROM
bit 1 WR: Write Control bit
1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle.
(The operation is self-timed and the bit is cleared by hardware once write is complete.
The WR bit can only be set (not cleared) by software.)
0 = Write cycle to the EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared by hardware. The RD bit can only
be set (not cleared) by software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)
0 = Does not initiate an EEPROM read

Note 1: When a WRERR occurs, the EEPGD and CFGS bits are not cleared. This allows tracing of the
error condition.

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PIC18F2XK20/4XK20
6.2.2 TABLAT – TABLE LATCH REGISTER When a TBLRD is executed, all 22 bits of the TBLPTR
determine w hich b yte is r ead f rom pr ogram m emory
The Table Latch (TABLAT) is an 8-bit register mapped
directly into the TABLAT register.
into the SFR space. The Table Latch register is used to
hold 8-bit data during data transfers between program When a TBLWT is executed the byte in the TABLAT reg-
memory and data RAM. ister is written, not to Flash memory but, to a holding
register in preparation for a program memory write. The
6.2.3 TBLPTR – TABLE POINTER holding registers constitute a w rite block which varies
REGISTER depending on the device (See Table 6-1).The 3, 4, or 5
LSbs of the TBLPTRL register determine which specific
The Table Pointer (TBLPTR) register addresses a byte
address within the holding register block is written to.
within the program memory. The TBLPTR is comprised
The MS Bs of t he Table P ointer h ave n o eff ect du ring
of t hree S FR registers: T able Pointer U pper Byte,
TBLWT operations.
Table Poi nter High Byte and Table Poin ter Lo w By te
(TBLPTRU:TBLPTRH:TBLPTRL). The se thre e re gis- When a p rogram memory write is executed the entire
ters join to f orm a 22 -bit w ide po inter. T he lo w-order holding register block is written to the Flash memory at
21 bits allow the device to a ddress up to 2 Mbytes of the address determined by the MSbs of the TBLPTR.
program memory space. The 22nd bit allows access to The 3, 4, or 5 LSBs are ignored during Flash memory
the device ID, the user ID and the Configuration bits. writes. Fo r m ore de tail, see Section 6.5 “Writing to
Flash Program Memory”.
The Table Poi nter regi ster, TBL PTR, is us ed by th e
TBLRD and TBLWT instructions. These instructions can When an e rase o f pro gram m emory is ex ecuted, th e
update the TBLPTR in one of four ways based on the 16 MSbs o ft he Table Po inter register
table op eration. Th ese o perations are sh own i n (TBLPTR<21:6>) point to the 64-byte block that will be
Table 6-2. These operations on the TBLPTR affect only erased. The Least Significant bits (TBLPTR<5:0>) are
the low-order 21 bits. ignored.
Figure 6-3 de scribes t he re levant bo undaries of
6.2.4 TABLE POINTER BOUNDARIES TBLPTR based on Flash program memory operations.
TBLPTR is used in rea ds, writes and erases of the
Flash program memory.

TABLE 6-2: TABLE POINTER OPERATIONS WITH TBLRD AND TBLWT INSTRUCTIONS
Example Operation on Table Pointer
TBLRD*
TBLPTR is not modified
TBLWT*
TBLRD*+
TBLPTR is incremented after the read/write
TBLWT*+
TBLRD*-
TBLPTR is decremented after the read/write
TBLWT*-
TBLRD+*
TBLPTR is incremented before the read/write
TBLWT+*

FIGURE 6-3: TABLE POINTER BOUNDARIES BASED ON OPERATION

21 TBLPTRU 16 15 TBLPTRH 8 7 TBLPTRL 0

TABLE ERASE/WRITE TABLE WRITE

TBLPTR<21:n+1>(1) TBLPTR<n:0>(1)

TABLE READ – TBLPTR<21:0>

Note 1: n = 3, 4, 5, or 6 for block sizes of 8, 16, 32 or 64 bytes, respectively.

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 PIC18F2XK20/4XK20
6.3 Reading the Flash Program The internal program memory is typically organized by
Memory words. The Least Significant bit of the address selects
between the high and low bytes of the word. Figure 6-4
The TBLRD in struction ret rieves da ta from pro gram shows t he i nterface b etween th e in ternal pr ogram
memory and places it into data RAM. Table reads from memory and the TABLAT.
program memory are performed one byte at a time.
TBLPTR p oints to a byte a ddress i n p rogram space.
Executing TBLRD pl aces the by te pointed to in to
TABLAT. In a ddition, T BLPTR c an b e m odified
automatically for the next table read operation.

FIGURE 6-4: READS FROM FLASH PROGRAM MEMORY

Program Memory

(Even Byte Address) (Odd Byte Address)

TBLPTR = xxxxx1 TBLPTR = xxxxx0

Instruction Register TABLAT

FETCH TBLRD
(IR) Read Register

EXAMPLE 6-1: READING A FLASH PROGRAM MEMORY WORD

MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base
MOVWF TBLPTRU ; address of the word
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
READ_WORD
TBLRD*+ ; read into TABLAT and increment
MOVF TABLAT, W ; get data
MOVWF WORD_EVEN
TBLRD*+ ; read into TABLAT and increment
MOVFW TABLAT, W ; get data
MOVF WORD_ODD

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PIC18F2XK20/4XK20
6.4 Erasing Flash Program Memory 6.4.1 FLASH PROGRAM MEMORY
ERASE SEQUENCE
The minimum erase block is 32 words or 64 bytes. Only
through the use of an external programmer, or through The sequence of events for erasing a block of internal
ICSP™ control, can larger blocks of program memory program memory is:
be bulk erased. Word erase in t he Flash array is not 1. Load T able Poi nter reg ister with address of
supported. block being erased.
When initiating an erase sequence from the Microcon- 2. Set the EECON1 register for the erase operation:
troller itself, a block of 64 bytes of program memory is • set EEPGD bit to point to program memory;
erased. Th e Mo st Si gnificant 16 bi ts of the • clear the CFGS bit to access program memory;
TBLPTR<21:6> p oint t o t he block b eing erased. Th e
• set WREN bit to enable writes;
TBLPTR<5:0> bits are ignored.
• set FREE bit to enable the erase.
The EECON1 register commands the erase operation.
3. Disable interrupts.
The EEPGD bit must be set to point to the Flash pro-
gram memory. Th e WR EN bit mu st be set to en able 4. Write 55h to EECON2.
write operations. The FREE bit is set to select an erase 5. Write 0AAh to EECON2.
operation. 6. Set the WR bit. This will begin the block erase
The w rite in itiate s equence fo r EEC ON2, sh own a s cycle.
steps 4 thro ugh 6 in Section 6.4.1 “Flash Program 7. The C PU w ill st all for duration of th e erase
Memory Erase Sequence”, is used to guard against (about 2 ms using internal timer).
accidental w rites. Thi s is so metimes referred to as a 8. Re-enable interrupts.
long write.
A long write is necessary for erasing the internal Flash.
Instruction ex ecution is ha lted d uring t he long w rite
cycle. The long write is terminated by the internal pro-
gramming timer.

EXAMPLE 6-2: ERASING A FLASH PROGRAM MEMORY BLOCK

MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
ERASE_BLOCK
BSF EECON1, EEPGD ; point to Flash program memory
BCF EECON1, CFGS ; access Flash program memory
BSF EECON1, WREN ; enable write to memory
BSF EECON1, FREE ; enable block Erase operation
BCF INTCON, GIE ; disable interrupts
Required MOVLW 55h
Sequence MOVWF EECON2 ; write 55h
MOVLW 0AAh
MOVWF EECON2 ; write 0AAh
BSF EECON1, WR ; start erase (CPU stall)
BSF INTCON, GIE ; re-enable interrupts

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 PIC18F2XK20/4XK20
6.5 Writing to Flash Program Memory The long write is necessary for programming the inter-
nal Flash. Instruction execution is halted during a long
The p rogramming block s ize is 1 6, 3 2 o r 64 by tes, write c ycle. The l ong w rite w ill be te rminated b y th e
depending on the device (See Table 6-1). Word or byte internal programming timer.
programming is not supported.
The EEPRO M on-c hip tim er c ontrols the write time.
Table w rites a re us ed i nternally to loa d the hol ding The write/erase voltages are generated by an on-c hip
registers needed to program the Flash memory. There charge pump, rated to operate over the voltage range
are only as many holding registers as there are bytes of the device.
in a write block (See Table 6-1).
Note: The default value of the holding registers on
Since the Table Latch (TABLAT) is only a s ingle byte,
device Resets and after write operations is
the TBLWT instruction may need to be executed 16, 32
FFh. A w rite of FF h t o a ho lding register
or 64 ti mes, depending on the de vice, fo r e ach p ro-
does not modify that byte. This means that
gramming ope ration. All of the t able w rite operations
individual bytes of program memory may be
will essentially be short writes because only the holding
modified, provided that the change does not
registers are written. After all the holding registers have
attempt to change any bit from a ‘0’ to a ‘1’.
been written, the programming operation of that block
of memory is started by configuring the EECON1 reg- When mod ifying in dividual bytes, it is not
ister for a prog ram memory write and performing the necessary to lo ad al l holding re gisters
long write sequence. before executing a long write operation.

FIGURE 6-5: TABLE WRITES TO FLASH PROGRAM MEMORY

TABLAT
Write Register

8 8 8 8

TBLPTR = xxxx00 TBLPTR = xxxx01 TBLPTR = xxxx02 TBLPTR = xxxxYY(1)

Holding Register Holding Register Holding Register Holding Register

Program Memory

Note 1: YY = x7, xF, or 1F for 8, 16 or 32 byte write blocks, respectively.

6.5.1 FLASH PROGRAM MEMORY WRITE 8. Disable interrupts.

SEQUENCE 9. Write 55h to EECON2.
The sequence o f e vents fo r p rogramming an internal 10. Write 0AAh to EECON2.
program memory location should be: 11. Set the WR bit. This will begin the write cycle.
1. Read 64 bytes into RAM. 12. The CPU will stall for duration of the write (about
2 ms using internal timer).
2. Update data values in RAM as necessary.
3. Load Table Pointer register with address being 13. Re-enable interrupts.
erased. 14. Repeat steps 6 to 13 for each block until all 64
4. Execute the block erase procedure. bytes are written.
5. Load Table Pointer register with address of first 15. Verify the memory (table read).
byte being written. This procedure will require about 6 ms to update each
6. Write the 16, 32 or 64 byte block into the holding write block of memory. An example of the required code
registers with auto-increment. is given in Example 6-3.
7. Set the EECON1 register for the write operation: Note: Before s etting the WR bit , the T able
• set EEPGD bit to point to program memory; Pointer add ress nee ds to be w ithin the
• clear the CFGS bit to access program memory; intended address range of the bytes in the
• set WREN to enable byte writes. holding registers.

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PIC18F2XK20/4XK20
EXAMPLE 6-3: WRITING TO FLASH PROGRAM MEMORY
MOVLW D'64’ ; number of bytes in erase block
MOVWF COUNTER
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
MOVLW CODE_ADDR_UPPER ; Load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
READ_BLOCK
TBLRD*+ ; read into TABLAT, and inc
MOVF TABLAT, W ; get data
MOVWF POSTINC0 ; store data
DECFSZ COUNTER ; done?
BRA READ_BLOCK ; repeat
MODIFY_WORD
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
MOVLW NEW_DATA_LOW ; update buffer word
MOVWF POSTINC0
MOVLW NEW_DATA_HIGH
MOVWF INDF0
ERASE_BLOCK
MOVLW CODE_ADDR_UPPER ; load TBLPTR with the base
MOVWF TBLPTRU ; address of the memory block
MOVLW CODE_ADDR_HIGH
MOVWF TBLPTRH
MOVLW CODE_ADDR_LOW
MOVWF TBLPTRL
BSF EECON1, EEPGD ; point to Flash program memory
BCF EECON1, CFGS ; access Flash program memory
BSF EECON1, WREN ; enable write to memory
BSF EECON1, FREE ; enable Erase operation
BCF INTCON, GIE ; disable interrupts
MOVLW 55h
Required MOVWF EECON2 ; write 55h
Sequence MOVLW 0AAh
MOVWF EECON2 ; write 0AAh
BSF EECON1, WR ; start erase (CPU stall)
BSF INTCON, GIE ; re-enable interrupts
TBLRD*- ; dummy read decrement
MOVLW BUFFER_ADDR_HIGH ; point to buffer
MOVWF FSR0H
MOVLW BUFFER_ADDR_LOW
MOVWF FSR0L
WRITE_BUFFER_BACK
MOVLW BlockSize ; number of bytes in holding register
MOVWF COUNTER
MOVLW D’64’/BlockSize ; number of write blocks in 64 bytes
MOVWF COUNTER2
WRITE_BYTE_TO_HREGS
MOVF POSTINC0, W ; get low byte of buffer data
MOVWF TABLAT ; present data to table latch
TBLWT+* ; write data, perform a short write
; to internal TBLWT holding register.

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 PIC18F2XK20/4XK20
EXAMPLE 6-3: WRITING TO FLASH PROGRAM MEMORY (CONTINUED)
DECFSZ COUNTER ; loop until holding registers are full
BRA WRITE_WORD_TO_HREGS
PROGRAM_MEMORY
BSF EECON1, EEPGD ; point to Flash program memory
BCF EECON1, CFGS ; access Flash program memory
BSF EECON1, WREN ; enable write to memory
BCF INTCON, GIE ; disable interrupts
MOVLW 55h
Required MOVWF EECON2 ; write 55h
Sequence MOVLW 0AAh
MOVWF EECON2 ; write 0AAh
BSF EECON1, WR ; start program (CPU stall)
DCFSZ COUNTER2 ; repeat for remaining write blocks
BRA WRITE_BYTE_TO_HREGS ;
BSF INTCON, GIE ; re-enable interrupts
BCF EECON1, WREN ; disable write to memory

6.5.2 WRITE VERIFY 6.5.4 PROTECTION AGAINST

Depending o n th e a pplication, good p rogramming SPURIOUS WRITES
practice m ay di ctate tha t th e v alue written t o th e To prot ect against spu rious w rites to Flash pro gram
memory should be v erified against the original value. memory, the w rite ini tiate sequence must als o be
This s hould b e used in a pplications w here excessive followed. See Section 23.0 “Special Features of the
writes can stress bits near the specification limit. CPU” for more detail.

6.5.3 UNEXPECTED TERMINATION OF 6.6 Flash Program Operation During

WRITE OPERATION
Code Protection
If a write is terminated by an unplanned event, such as
loss of power or an une xpected R eset, the me mory See Section 23.3 “Program Verification and Code
location ju st p rogrammed sh ould be ver ified an d Protection” for details on c ode p rotection of Fl ash
reprogrammed if n eeded. If the w rite ope ration i s program memory.
interrupted by a MCLR Reset or a WDT Time-out Reset
during n ormal op eration, t he WRERR b it w ill be s et
which the user can check to decide whether a rew rite
of the location(s) is needed.

TABLE 6-3: REGISTERS ASSOCIATED WITH PROGRAM FLASH MEMORY

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values on
page
TBLPTRU — — bit 21 Program Memory Table Pointer Upper Byte (TBLPTR<20:16>) 59
TBPLTRH Program Memory Table Pointer High Byte (TBLPTR<15:8>) 59
TBLPTRL Program Memory Table Pointer Low Byte (TBLPTR<7:0>) 59
TABLAT Program Memory Table Latch 59
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
EECON2 EEPROM Control Register 2 (not a physical register) 61
EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 61
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.

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PIC18F2XK20/4XK20
NOTES:

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 PIC18F2XK20/4XK20
7.0 DATA EEPROM MEMORY The EECON1 register (Register 7-1) is the control reg-
ister for data and program memory access. Control bit
The data EEPROM is a nonvolatile memory array, sep- EEPGD determines if the access will be to program or
arate from the data RAM and program memory, which data EEPROM memory. When the EEPGD bit is clear,
is used for long-term storage of program data. It is not operations wil l ac cess the da ta EEPROM m emory.
directly mapped i n either the re gister fi le or program When the EEPGD b it is s et, program m emory i s
memory space but is indirectly addressed through the accessed.
Special Function Reg isters (SF Rs). The EEPROM i s
Control bit, CFGS, determines if the access will be to
readable and writable during normal operation over the
the Configuration registers or to program memory/data
entire VDD range.
EEPROM memory. Whe n the CFGS b it is s et,
Four SFR s are u sed to re ad an d w rite to th e da ta subsequent operations access Configuration registers.
EEPROM as well as the program memory. They are: When the CFGS b it is c lear, t he EEPGD bit s elects
• EECON1 either program Flash or data EEPROM memory.
• EECON2 The WREN bit, when set, will allow a write operation.
• EEDATA On power-up, the WREN bit is clear.
• EEADR The WRERR bit is set by hardware when the WR bit is
• EEADRH set and cleared when the internal programming timer
expires and the write operation is complete.
The data EEPROM allows byte read and write. When
interfacing t o th e da ta m emory bl ock, E EDATA ho lds Note: During norm al op eration, the WR ERR
the 8-bit data for read/write and the EEADR:EEADRH may read a s ‘ 1’. This can indicate that a
register pair hold the address of the EEPROM location write o peration w as prematurely t ermi-
being accessed. nated by a Reset, or a write operation was
The EEPROM data memory is rated for high erase/write attempted improperly.
cycle endurance. A by te write automatically erases the The WR control bit ini tiates write ope rations. The bit
location and w rites the new dat a (er ase-before-write). can be set but not cleared by software. It is cleared only
The w rite time is controlled by an on-chip time r; it w ill by hardware at the completion of the write operation.
vary with voltage and temperature as well as from chip-
to-chip. Please refer to parameter D122 (Table 26.10 in Note: The EEIF in terrupt fl ag bi t of the PIR 2
Section 26.0 “Electrical Characteristics”) for e xact register is set when the write is complete.
limits. It must be cleared by software.

Control bi ts, RD and WR , star t read an d er ase/write

7.1 EEADR and EEADRH Registers
operations, respectively. These bits are set by firmware
The EEAD R reg ister is us ed to add ress th e da ta and c leared by ha rdware at the completion of th e
EEPROM for read and write op erations. Th e 8-b it operation.
range of the register can address a me mory range of The RD bit cannot be se t when acc essing program
256 bytes (00h to FFh). The EEADRH register expands memory (EEPGD = 1). Program memory is read using
the ran ge to 1024 by tes by ad ding an additional tw o table read instructions. See Section 6.1 “Table Reads
address bits. and Table Writes” regarding table reads.

7.2 EECON1 and EECON2 Registers The EEC ON2 regi ster is not a physical regi ster. It i s
used e xclusively in t he memory w rite a nd erase
Access to th e data EEPROM i s controlled b y two sequences. Reading EECON2 will read all ‘0’s.
registers: EECON1 and EECON2. These are the same
registers which control access to the program memory
and are used in a s imilar manner fo r the da ta
EEPROM.

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PIC18F2XK20/4XK20

REGISTER 7-1: EECON1: DATA EEPROM CONTROL 1 REGISTER

R/W-x R/W-x U-0 R/W -0 R/W-x R/W-0 R/S-0 R/S-0
EEPGD CFGS — FREE WRERR WREN WR RD
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit
S = Bit can be set by software, but not cleared U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 EEPGD: Flash Program or Data EEPROM Memory Select bit

1 = Access Flash program memory
0 = Access data EEPROM memory
bit 6 CFGS: Flash Program/Data EEPROM or Configuration Select bit
1 = Access Configuration registers
0 = Access Flash program or data EEPROM memory
bit 5 Unimplemented: Read as ‘0’
bit 4 FREE: Flash Row (Block) Erase Enable bit
1 = Erase the program memory block addressed by TBLPTR on the next WR command
(cleared by completion of erase operation)
0 = Perform write-only
bit 3 WRERR: Flash Program/Data EEPROM Error Flag bit(1)
1 = A write operation is prematurely terminated (any Reset during self-timed programming in normal
operation, or an improper write attempt)
0 = The write operation completed
bit 2 WREN: Flash Program/Data EEPROM Write Enable bit
1 = Allows write cycles to Flash program/data EEPROM
0 = Inhibits write cycles to Flash program/data EEPROM
bit 1 WR: Write Control bit
1 = Initiates a data EEPROM erase/write cycle or a program memory erase cycle or write cycle.
(The operation is self-timed and the bit is cleared by hardware once write is complete.
The WR bit can only be set (not cleared) by software.)
0 = Write cycle to the EEPROM is complete
bit 0 RD: Read Control bit
1 = Initiates an EEPROM read (Read takes one cycle. RD is cleared by hardware. The RD bit can only
be set (not cleared) by software. RD bit cannot be set when EEPGD = 1 or CFGS = 1.)
0 = Does not initiate an EEPROM read

Note 1: When a WRERR occurs, the EEPGD and CFGS bits are not cleared. This allows tracing of the
error condition.

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 PIC18F2XK20/4XK20
7.3 Reading the Data EEPROM Additionally, the WREN bit in EECON1 must be set to
Memory enable w rites. Th is mechanism pre vents accidental
writes to d ata EEPROM du e to une xpected c ode
To read a da ta me mory lo cation, the us er must w rite execution (i.e ., run away pro grams). Th e WR EN b it
the address to the EEADR reg ister, clear the EEPGD should be kept clear at all times, except when updating
control bit of the EECON1 register and then set control the EEPROM . Th e WREN b it i s not cleared b y
bit, RD. The data is available on the very next instruc- hardware.
tion cycle; therefore, the EEDATA register can be read
After a write sequence ha s b een ini tiated, EEC ON1,
by the next instruction. EEDATA will hold this value until
EEADR and EEDATA cannot be modified. The WR bit
another re ad op eration, or un til it is w ritten to by th e
will be inhibited from being set unless the WREN bit is
user (during a write operation).
set. Both WR and WREN cannot be set with the same
The basic process is shown in Example 7-1. instruction.
At the completion of the write cy cle, the WR bit is
7.4 Writing to the Data EEPROM cleared by hardware and the EEPROM Interrupt Flag
Memory bit, EEIF, is s et. Th e u ser m ay ei ther en able this
interrupt o r poll thi s bi t. EEIF m ust be c leared b y
To write an EEPROM data location, the address must
software.
first be written to the EEADR register and the data writ-
ten to the EED ATA reg ister. T he s equence i n
Example 7-2 must be followed to initiate the write cycle. 7.5 Write Verify
The write will not begin if this sequence is not exactly Depending o n th e a pplication, good p rogramming
followed (w rite 55h to EEC ON2, w rite 0 AAh to practice m ay di ctate that th e v alue written t o th e
EECON2, then set WR bit) for each byte. It is strongly memory should be v erified against the original value.
recommended that interrupts b e di sabled du ring thi s This should be used in ap plications where excessive
code segment. writes can stress bits near the specification limit.

EXAMPLE 7-1: DATA EEPROM READ

MOVLW DATA_EE_ADDR ;
MOVWF EEADR ; Data Memory Address to read
BCF EECON1, EEPGD ; Point to DATA memory
BCF EECON1, CFGS ; Access EEPROM
BSF EECON1, RD ; EEPROM Read
MOVF EEDATA, W ; W = EEDATA

EXAMPLE 7-2: DATA EEPROM WRITE

MOVLW DATA_EE_ADDR_LOW ;
MOVWF EEADR ; Data Memory Address to write
MOVLW DATA_EE_ADDR_HI ;
MOVWF EEADRH ;
MOVLW DATA_EE_DATA ;
MOVWF EEDATA ; Data Memory Value to write
BCF EECON1, EEPGD ; Point to DATA memory
BCF EECON1, CFGS ; Access EEPROM
BSF EECON1, WREN ; Enable writes
BCF INTCON, GIE ; Disable Interrupts
MOVLW 55h ;
Required MOVWF EECON2 ; Write 55h
Sequence MOVLW 0AAh ;
MOVWF EECON2 ; Write 0AAh
BSF EECON1, WR ; Set WR bit to begin write
BSF INTCON, GIE ; Enable Interrupts

; User code execution

BCF EECON1, WREN ; Disable writes on write complete (EEIF set)

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PIC18F2XK20/4XK20
7.6 Operation During Code-Protect The write initiate sequence and the WREN bit together
help prev ent an ac cidental w rite du ring bro wn-out,
Data EEPROM memory has its own code-protect bits power glitch or software malfunction.
in C onfiguration W ords. Ex ternal read an d w rite
operations are disabled if code protection is enabled.
7.8 Using the Data EEPROM
The microcontroller itself can both read and write to the
internal data EEPROM, regardless of the state of the The d ata EE PROM is a high-endurance, byte
code-protect C onfiguration b it. R efer to Section 23.0 addressable a rray that has bee n optimiz ed for the
“Special Features of the CPU” fo r add itional storage of frequently ch anging information (e.g.,
information. program variables or other data that are updated often).
When variables in one section change frequently, while
variables in another section do not change, it is possible
7.7 Protection Against Spurious Write
to ex ceed the tot al n umber of w rite cycl es to the
There are c onditions when t he user may n ot w ant t o EEPROM (s pecification D 124) withou t exceeding the
write to the data EEPROM memory. To protect against total number of write cycles to a singlebyte (specification
spurious EEPROM write s, v arious mechanisms hav e D120). If this is the case, then an array refresh must be
been im plemented. On po wer-up, t he WREN bi t i s performed. For this reas on, va riables that c hange
cleared. In addition, writes to the EEPROM are blocked infrequently (su ch as con stants, IDs, calibration, etc.)
during the Pow er-up T imer per iod (TPWRT, should be stored in Flash program memory.
parameter 33). A s imple data EEPRO M refre sh routine i s s hown in
Example 7-3.
Note: If da ta EEPRO M is onl y us ed to s tore
constants and/or data that changes rarely,
an array refresh is likely not required. See
specification.

EXAMPLE 7-3: DATA EEPROM REFRESH ROUTINE

CLRF EEADR ; Start at address 0
BCF EECON1, CFGS ; Set for memory
BCF EECON1, EEPGD ; Set for Data EEPROM
BCF INTCON, GIE ; Disable interrupts
BSF EECON1, WREN ; Enable writes
Loop ; Loop to refresh array
BSF EECON1, RD ; Read current address
MOVLW 55h ;
MOVWF EECON2 ; Write 55h
MOVLW 0AAh ;
MOVWF EECON2 ; Write 0AAh
BSF EECON1, WR ; Set WR bit to begin write
BTFSC EECON1, WR ; Wait for write to complete
BRA $-2
INCFSZ EEADR, F ; Increment address
BRA LOOP ; Not zero, do it again

BCF EECON1, WREN ; Disable writes

BSF INTCON, GIE ; Enable interrupts

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 PIC18F2XK20/4XK20
TABLE 7-1: REGISTERS ASSOCIATED WITH DATA EEPROM MEMORY
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
EEADR EEADR7 EEADR6 EEADR5 EEADR4 EEADR3 EEADR2 EEADR1 EEADR0 61
EEADRH(1) — — — — — — EEADR9 EEADR8 61
EEDATA EEPROM Data Register 61
EECON2 EEPROM Control Register 2 (not a physical register) 61
EECON1 EEPGD CFGS — FREE WRERR WREN WR RD 61
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during Flash/EEPROM access.
Note 1: PIC18F26K20/PIC18F46K20 only.

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PIC18F2XK20/4XK20
NOTES:

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 PIC18F2XK20/4XK20
8.0 8 x 8 HARDWARE MULTIPLIER EXAMPLE 8-1: 8 x 8 UNSIGNED
MULTIPLY ROUTINE
8.1 Introduction MOVF ARG1, W ;
MULWF ARG2 ; ARG1 * ARG2 ->
All PIC18 devices include an 8 x 8 hardware multiplier ; PRODH:PRODL
as part of the ALU. The multiplier performs an unsigned
operation and yields a 16-bit result that is stored in the
product register pair, PRODH:PRODL. The multiplier’s EXAMPLE 8-2: 8 x 8 SIGNED MULTIPLY
operation doe s n ot af fect any fla gs in the ST ATUS ROUTINE
register.
MOVF ARG1, W
Making multiplication a hardware operation allows it to MULWF ARG2 ; ARG1 * ARG2 ->
be completed in a single instruction cycle. This has the ; PRODH:PRODL
advantages of hig her c omputational th roughput an d BTFSC ARG2, SB ; Test Sign Bit
reduced c ode s ize f or m ultiplication al gorithms a nd SUBWF PRODH, F ; PRODH = PRODH
allows the PIC18 devices to be used in many applica- ; - ARG1
MOVF ARG2, W
tions previously reserved for digital signal processors.
BTFSC ARG1, SB ; Test Sign Bit
A c omparison of v arious ha rdware an d s oftware
SUBWF PRODH, F ; PRODH = PRODH
multiply operations, along with the savings in memory ; - ARG2
and execution time, is shown in Table 8-1.

8.2 Operation
Example 8-1 shows the instruction sequence for an 8 x 8
unsigned multiplication. Only one instruction is required
when o ne of the arguments i s a lready lo aded i n th e
WREG register.
Example 8-2 shows the sequence to do an 8 x 8 signed
multiplication. To account for the sign bits of the argu-
ments, each argument’s Most Significant bit (MSb) is
tested and the appropriate subtractions are done.

TABLE 8-1: PERFORMANCE COMPARISON FOR VARIOUS MULTIPLY OPERATIONS

Program Time
Cycles
Routine Multiply Method Memory
(Max) @ 40 MHz @ 10 MHz @ 4 MHz
(Words)
Without hardware multiply 13 69 6.9 s 27.6 s 69 s
8 x 8 unsigned
Hardware multiply 1 1 100 ns 400 ns 1 s
Without hardware multiply 33 91 9.1 s 36.4 s 91 s
8 x 8 signed
Hardware multiply 6 6 600 ns 2.4 s 6 s
Without hardware multiply 21 242 24.2 s 96.8 s 242 s
16 x 16 unsigned
Hardware multiply 28 28 2.8 s 11.2 s 28 s
Without hardware multiply 52 254 25.4 s 102.6 s 254 s
16 x 16 signed
Hardware multiply 35 40 4.0 s 16.0 s 40 s

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PIC18F2XK20/4XK20
Example 8-3 s hows t he sequence t o d o a 1 6 x 1 6 EQUATION 8-2: 16 x 16 SIGNED
unsigned m ultiplication. Equ ation 8-1 sh ows the MULTIPLICATION
algorithm that is used. The 32-bit result is stored in four ALGORITHM
registers (RES<3:0>). RES3:RES0 = ARG1H:ARG1L  ARG2H:ARG2L
= (ARG1H  ARG2H  216) +
EQUATION 8-1: 16 x 16 UNSIGNED (ARG1H  ARG2L  28) +
MULTIPLICATION (ARG1L  ARG2H  28) +
(ARG1L  ARG2L) +
ALGORITHM
(-1  ARG2H<7>  ARG1H:ARG1L  216) +
RES3:RES0 = ARG1H:ARG1L  ARG2H:ARG2L
(-1  ARG1H<7>  ARG2H:ARG2L  216)
= (ARG1H  ARG2H  216) +
(ARG1H  ARG2L  28) +
(ARG1L  ARG2H  28) + EXAMPLE 8-4: 16 x 16 SIGNED
(ARG1L  ARG2L) MULTIPLY ROUTINE
MOVF ARG1L, W
EXAMPLE 8-3: 16 x 16 UNSIGNED MULWF ARG2L ; ARG1L * ARG2L ->
MULTIPLY ROUTINE ; PRODH:PRODL
MOVFF PRODH, RES1 ;
MOVF ARG1L, W
MOVFF PRODL, RES0 ;
MULWF ARG2L ; ARG1L * ARG2L->
;
; PRODH:PRODL
MOVF ARG1H, W
MOVFF PRODH, RES1 ;
MULWF ARG2H ; ARG1H * ARG2H ->
MOVFF PRODL, RES0 ;
; PRODH:PRODL
;
MOVFF PRODH, RES3 ;
MOVF ARG1H, W
MOVFF PRODL, RES2 ;
MULWF ARG2H ; ARG1H * ARG2H->
;
; PRODH:PRODL
MOVF ARG1L, W
MOVFF PRODH, RES3 ;
MULWF ARG2H ; ARG1L * ARG2H ->
MOVFF PRODL, RES2 ;
; PRODH:PRODL
;
MOVF PRODL, W ;
MOVF ARG1L, W
ADDWF RES1, F ; Add cross
MULWF ARG2H ; ARG1L * ARG2H->
MOVF PRODH, W ; products
; PRODH:PRODL
ADDWFC RES2, F ;
MOVF PRODL, W ;
CLRF WREG ;
ADDWF RES1, F ; Add cross
ADDWFC RES3, F ;
MOVF PRODH, W ; products
;
ADDWFC RES2, F ;
MOVF ARG1H, W ;
CLRF WREG ;
MULWF ARG2L ; ARG1H * ARG2L ->
ADDWFC RES3, F ;
; PRODH:PRODL
;
MOVF PRODL, W ;
MOVF ARG1H, W ;
ADDWF RES1, F ; Add cross
MULWF ARG2L ; ARG1H * ARG2L->
MOVF PRODH, W ; products
; PRODH:PRODL
ADDWFC RES2, F ;
MOVF PRODL, W ;
CLRF WREG ;
ADDWF RES1, F ; Add cross
ADDWFC RES3, F ;
MOVF PRODH, W ; products
;
ADDWFC RES2, F ;
BTFSS ARG2H, 7 ; ARG2H:ARG2L neg?
CLRF WREG ;
BRA SIGN_ARG1 ; no, check ARG1
ADDWFC RES3, F ;
MOVF ARG1L, W ;
SUBWF RES2 ;
Example 8-4 s hows t he sequence t o d o a 1 6 x 1 6 MOVF ARG1H, W ;
signed multiply. Equ ation 8-2 s hows the al gorithm SUBWFB RES3
used. The 32 -bit res ult is sto red in four registers ;
(RES<3:0>). To account for the sign bits of the arg u- SIGN_ARG1
ments, the MSb for ea ch argument pair is tested and BTFSS ARG1H, 7 ; ARG1H:ARG1L neg?
BRA CONT_CODE ; no, done
the appropriate subtractions are done.
MOVF ARG2L, W ;
SUBWF RES2 ;
MOVF ARG2H, W ;
SUBWFB RES3
;
CONT_CODE
:

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 PIC18F2XK20/4XK20
9.0 INTERRUPTS 9.2 Interrupt Priority
The PIC 18F2XK20/4XK20 dev ices hav e m ultiple The interrupt priority feature is enabled by setting the
interrupt sources and an i nterrupt priority feature that IPEN bit of the RCON register. When interrupt priority
allows m ost in terrupt s ources to b e as signed a hig h is ena bled the GIE and PEIE global in terrupt en able
priority lev el or a l ow pri ority l evel. T he h igh pri ority bits of Compatibility mo de are repl aced by the GIEH
interrupt vector is at 0008h and the low priority interrupt high priority, an d G IEL lo w p riority, gl obal in terrupt
vector is at 00 18h. A high prio rity inte rrupt eve nt w ill enables. When set, the GIEH bit of the INTCON regis-
interrupt a low priority interrupt that may be in progress. ter ena bles a ll i nterrupts th at h ave the ir as sociated
IPRx register or INTCONx register priority bit set (high
There ar e t en registers w hich a re used to control
priority). When clear, the GIEH bit disables all interrupt
interrupt operation. These registers are:
sources including those selected as low priority. When
• RCON clear, the GIEL bit of the INTCON register disables only
• INTCON the int errupts th at hav e the ir as sociated priority bit
• INTCON2 cleared (low priority). When set, the GIEL bit enables
• INTCON3 the low priority sources when the GIEH bit is also set.
• PIR1, PIR2 When th e i nterrupt fl ag, e nable bit a nd appropriate
• PIE1, PIE2 global interrupt enable bit are all set, the interrupt will
vector immediately to address 0008h for high priority,
• IPR1, IPR2
or 001 8h for l ow pri ority, d epending on l evel of th e
It is recommended that the Microchip header files sup- interrupting s ource’s prio rity bi t. Ind ividual i nterrupts
plied w ith M PLAB® ID E be u sed f or the symbolic b it can be disabled through their corresponding interrupt
names in t hese registers. T his a llows the a ssembler/ enable bits.
compiler to automatically take care of the placement of
these bits within the specified register. 9.3 Interrupt Response
In general, interrupt sources have three bits to control
When an interrupt is responded to, the global interrupt
their operation. They are:
enable bit is cleared to di sable further interrupts. The
• Flag bit to indicate that an interrupt event GIE bit is the global interrupt enable when the IPEN bit
occurred is cleared. When the IPEN bit is set, enabling interrupt
• Enable bit that allows program execution to priority l evels, the GIEH bi t is th e hig h pri ority gl obal
branch to the interrupt vector address when the interrupt en able an d the GIEL bit is the low pri ority
flag bit is set global interrupt enable. High priority interrupt sources
• Priority bit to select high priority or low priority can interrupt a l ow p riority in terrupt. Low priority
interrupts a re n ot processed w hile hi gh priority
9.1 Mid-Range Compatibility interrupts are in progress.
The return address is pu shed onto the stack and the
When the IPEN bit is cleared (default state), the interrupt PC is loaded with the interrupt vector address (0008h
priority feature is disabled and interrupts are compatible or 0018h). Once in th e Interrupt Service Routine, the
with PIC ® microcontroller mid-range devic es. In source(s) of the interrupt can be determined by polling
Compatibility mode, the interrupt priority bits of the IPRx the int errupt flag bits in th e INTCO Nx and PIRx
registers have no ef fect. The P EIE bit of the IN TCON registers. Th e int errupt fla g bit s m ust be c leared b y
register is the global interrupt enable for the peripherals. software b efore re -enabling in terrupts to av oid
The PEIE bit disables only the peripheral interrupt repeating the same interrupt.
sources and ena bles the peripheral in terrupt so urces
when the GIE bit is also set. The GIE bit of the INTCON The “return f rom in terrupt” instruction, RETFIE, e xits
register is the global in terrupt enable which enables all the interrupt routine and sets the GIE bit (GIEH or GIEL
non-peripheral interrupt s ources and dis ables all if priority levels are used), which re-enables interrupts.
interrupt sources, including the peripherals. All interrupts For external interrupt events, such as the INT pins or
branch to address 0008h in Compatibility mode. the PO RTB in terrupt-on-change, the in terrupt l atency
will be thre e to four instruction cycles. The exact
latency i s t he sa me f or one-cycle o r t wo-cycle
instructions. I ndividual in terrupt fl ag bi ts ar e set,
regardless of the status of their corresponding enable
bits or the global interrupt enable bit.
Note: Do not use the MOVFF instruction to modify
any of the interrupt control registers while
any in terrupt is enabled. D oing so ma y
cause erratic microcontroller behavior.

 2010 Microchip Technology Inc. DS41303G-page 107

PIC18F2XK20/4XK20
FIGURE 9-1: PIC18 INTERRUPT LOGIC

Wake-up if in
Idle or Sleep modes
TMR0IF
TMR0IE
TMR0IP
RBIF (1)
RBIE
RBIP
INT0IF
INT0IE
Interrupt to CPU
INT1IF Vector to Location
INT1IE
INT1IP 0008h
SSPIF
SSPIE INT2IF
SSPIP INT2IE
INT2IP
ADIF GIEH/GIE
ADIE
ADIP IPEN

RCIF IPEN
RCIE
RCIP GIEL/PEIE
IPEN
Additional Peripheral Interrupts
High Priority Interrupt Generation

Low Priority Interrupt Generation

SSPIF
SSPIE
SSPIP
Interrupt to CPU
TMR0IF Vector to Location
TMR0IE 0018h
ADIF TMR0IP
ADIE
ADIP RBIF
(1)
RBIE
RCIF RBIP GIEH/GIE
RCIE GIEL/PEIE
RCIP
INT1IF
INT1IE
INT1IP
Additional Peripheral Interrupts
INT2IF
INT2IE
INT2IP

Note 1: The RBIF interrupt also requires the individual pin IOCB enables.

DS41303G-page 108  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
9.4 INTCON Registers Note: Interrupt flag bits are set when an interrupt
The IN TCON registers are read able and writable condition occurs, regardless of the state of
registers, w hich contain va rious en able, pri ority an d its corresponding enable bit or t he global
flag bits. enable bi t. U ser sof tware should ensure
the appropriate interrupt flag bits are clear
prior to enabling an interrupt. This feature
allows for software polling.

REGISTER 9-1: INTCON: INTERRUPT CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-x
GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 GIE/GIEH: Global Interrupt Enable bit

When IPEN = 0:
1 = Enables all unmasked interrupts
0 = Disables all interrupts including peripherals
When IPEN = 1:
1 = Enables all high priority interrupts
0 = Disables all interrupts including low priority.
bit 6 PEIE/GIEL: Peripheral Interrupt Enable bit
When IPEN = 0:
1 = Enables all unmasked peripheral interrupts
0 = Disables all peripheral interrupts
When IPEN = 1:
1 = Enables all low priority interrupts
0 = Disables all low priority interrupts
bit 5 TMR0IE: TMR0 Overflow Interrupt Enable bit
1 = Enables the TMR0 overflow interrupt
0 = Disables the TMR0 overflow interrupt
bit 4 INT0IE: INT0 External Interrupt Enable bit
1 = Enables the INT0 external interrupt
0 = Disables the INT0 external interrupt
bit 3 RBIE: RB Port Change Interrupt Enable bit(2)
1 = Enables the RB port change interrupt
0 = Disables the RB port change interrupt
bit 2 TMR0IF: TMR0 Overflow Interrupt Flag bit
1 = TMR0 register has overflowed (must be cleared by software)
0 = TMR0 register did not overflow
bit 1 INT0IF: INT0 External Interrupt Flag bit
1 = The INT0 external interrupt occurred (must be cleared by software)
0 = The INT0 external interrupt did not occur
bit 0 RBIF: RB Port Change Interrupt Flag bit(1)
1 = At least one of the RB<7:4> pins changed state (must be cleared by software)
0 = None of the RB<7:4> pins have changed state

Note 1: A mismatch condition will continue to set the RBIF bit. Reading PORTB will end the
mismatch condition and allow the bit to be cleared.
2: RB port change interrupts also require the individual pin IOCB enables.

 2010 Microchip Technology Inc. DS41303G-page 109

PIC18F2XK20/4XK20

REGISTER 9-2: INTCON2: INTERRUPT CONTROL 2 REGISTER

R/W-1 R/W-1 R/W-1 R/W-1 U-0 R/W-1 U-0 R/W-1
RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 RBPU: PORTB Pull-up Enable bit

1 = All PORTB pull-ups are disabled
0 = PORTB pull-ups are enabled provided that the pin is an input and the corresponding WPUB bit is
set.
bit 6 INTEDG0: External Interrupt 0 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 5 INTEDG1: External Interrupt 1 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 4 INTEDG2: External Interrupt 2 Edge Select bit
1 = Interrupt on rising edge
0 = Interrupt on falling edge
bit 3 Unimplemented: Read as ‘0’
bit 2 TMR0IP: TMR0 Overflow Interrupt Priority bit
1 = High priority
0 = Low priority
bit 1 Unimplemented: Read as ‘0’
bit 0 RBIP: RB Port Change Interrupt Priority bit
1 = High priority
0 = Low priority

Note: Interrupt flag bits are set when an interrupt

condition occurs, regardless of the state of
its corresponding enable bit or th e global
enable b it. U ser s oftware sh ould en sure
the appropriate interrupt flag bits are clear
prior to enabling an interrupt. This feature
allows for software polling.

DS41303G-page 110  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 9-3: INTCON3: INTERRUPT CONTROL 3 REGISTER

R/W-1 R/W-1 U-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0
INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 INT2IP: INT2 External Interrupt Priority bit

1 = High priority
0 = Low priority
bit 6 INT1IP: INT1 External Interrupt Priority bit
1 = High priority
0 = Low priority
bit 5 Unimplemented: Read as ‘0’
bit 4 INT2IE: INT2 External Interrupt Enable bit
1 = Enables the INT2 external interrupt
0 = Disables the INT2 external interrupt
bit 3 INT1IE: INT1 External Interrupt Enable bit
1 = Enables the INT1 external interrupt
0 = Disables the INT1 external interrupt
bit 2 Unimplemented: Read as ‘0’
bit 1 INT2IF: INT2 External Interrupt Flag bit
1 = The INT2 external interrupt occurred (must be cleared by software)
0 = The INT2 external interrupt did not occur
bit 0 INT1IF: INT1 External Interrupt Flag bit
1 = The INT1 external interrupt occurred (must be cleared by software)
0 = The INT1 external interrupt did not occur

Note: Interrupt flag bits are set when an interrupt

condition occurs, regardless of the state of
its corresponding enable bit or th e global
enable b it. U ser s oftware sh ould en sure
the appropriate interrupt flag bits are clear
prior to enabling an interrupt. This feature
allows for software polling.

 2010 Microchip Technology Inc. DS41303G-page 111

PIC18F2XK20/4XK20
9.5 PIR Registers Note 1: Interrupt flag bits are set when an interrupt
The PIR registers contain the individual flag bits for the condition occurs, regardless of the state of
peripheral interrupts. Due to the n umber of p eripheral its corresponding enable bit or the Global
interrupt so urces, the re a re t wo Pe ripheral In terrupt Interrupt En able bi t, G IE of t he IN TCON
Request Flag registers (PIR1 and PIR2). register.
2: User software should ensure the appropri-
ate in terrupt f lag bi ts ar e cl eared p rior to
enabling an in terrupt and a fter se rvicing
that interrupt.

REGISTER 9-4: PIR1: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 1

R/W-0 R/W-0 R-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0
PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 PSPIF: Parallel Slave Port Read/Write Interrupt Flag bit(1)

1 = A read or a write operation has taken place (must be cleared by software)
0 = No read or write has occurred
bit 6 ADIF: A/D Converter Interrupt Flag bit
1 = An A/D conversion completed (must be cleared by software)
0 = The A/D conversion is not complete or has not been started
bit 5 RCIF: EUSART Receive Interrupt Flag bit
1 = The EUSART receive buffer, RCREG, is full (cleared when RCREG is read)
0 = The EUSART receive buffer is empty
bit 4 TXIF: EUSART Transmit Interrupt Flag bit
1 = The EUSART transmit buffer, TXREG, is empty (cleared when TXREG is written)
0 = The EUSART transmit buffer is full
bit 3 SSPIF: Master Synchronous Serial Port Interrupt Flag bit
1 = The transmission/reception is complete (must be cleared by software)
0 = Waiting to transmit/receive
bit 2 CCP1IF: CCP1 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared by software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared by software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused in this mode
bit 1 TMR2IF: TMR2 to PR2 Match Interrupt Flag bit
1 = TMR2 to PR2 match occurred (must be cleared by software)
0 = No TMR2 to PR2 match occurred
bit 0 TMR1IF: TMR1 Overflow Interrupt Flag bit
1 = TMR1 register overflowed (must be cleared by software)
0 = TMR1 register did not overflow

Note 1: The PSPIF bit is unimplemented on 28-pin devices and will read as ‘0’.

DS41303G-page 112  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 9-5: PIR2: PERIPHERAL INTERRUPT REQUEST (FLAG) REGISTER 2

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 OSCFIF: Oscillator Fail Interrupt Flag bit

1 = Device oscillator failed, clock input has changed to HFINTOSC (must be cleared by software)
0 = Device clock operating
bit 6 C1IF: Comparator C1 Interrupt Flag bit
1 = Comparator C1 output has changed (must be cleared by software)
0 = Comparator C1 output has not changed
bit 5 C2IF: Comparator C2 Interrupt Flag bit
1 = Comparator C2 output has changed (must be cleared by software)
0 = Comparator C2 output has not changed
bit 4 EEIF: Data EEPROM/Flash Write Operation Interrupt Flag bit
1 = The write operation is complete (must be cleared by software)
0 = The write operation is not complete or has not been started
bit 3 BCLIF: Bus Collision Interrupt Flag bit
1 = A bus collision occurred (must be cleared by software)
0 = No bus collision occurred
bit 2 HLVDIF: Low-Voltage Detect Interrupt Flag bit
1 = A low-voltage condition occurred (direction determined by the VDIRMAG bit of the
HLVDCON register)
0 = A low-voltage condition has not occurred
bit 1 TMR3IF: TMR3 Overflow Interrupt Flag bit
1 = TMR3 register overflowed (must be cleared by software)
0 = TMR3 register did not overflow
bit 0 CCP2IF: CCP2 Interrupt Flag bit
Capture mode:
1 = A TMR1 register capture occurred (must be cleared by software)
0 = No TMR1 register capture occurred
Compare mode:
1 = A TMR1 register compare match occurred (must be cleared by software)
0 = No TMR1 register compare match occurred
PWM mode:
Unused in this mode.

 2010 Microchip Technology Inc. DS41303G-page 113

PIC18F2XK20/4XK20
9.6 PIE Registers
The PIE registers contain the in dividual enable bits for
the peripheral interrupt s. Due to the number of periph-
eral interrupt sources, there are two Peripheral Interrupt
Enable registers (PIE1 and PIE2). When IPEN = 0, the
PEIE bit must be se t to enable any of thes e peripheral
interrupts.
REGISTER 9-6: PIE1: PERIPHERAL INTERRUPT ENABLE (FLAG) REGISTER 1
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 PSPIE: Parallel Slave Port Read/Write Interrupt Enable bit(1)

1 = Enables the PSP read/write interrupt
0 = Disables the PSP read/write interrupt
bit 6 ADIE: A/D Converter Interrupt Enable bit
1 = Enables the A/D interrupt
0 = Disables the A/D interrupt
bit 5 RCIE: EUSART Receive Interrupt Enable bit
1 = Enables the EUSART receive interrupt
0 = Disables the EUSART receive interrupt
bit 4 TXIE: EUSART Transmit Interrupt Enable bit
1 = Enables the EUSART transmit interrupt
0 = Disables the EUSART transmit interrupt
bit 3 SSPIE: Master Synchronous Serial Port Interrupt Enable bit
1 = Enables the MSSP interrupt
0 = Disables the MSSP interrupt
bit 2 CCP1IE: CCP1 Interrupt Enable bit
1 = Enables the CCP1 interrupt
0 = Disables the CCP1 interrupt
bit 1 TMR2IE: TMR2 to PR2 Match Interrupt Enable bit
1 = Enables the TMR2 to PR2 match interrupt
0 = Disables the TMR2 to PR2 match interrupt
bit 0 TMR1IE: TMR1 Overflow Interrupt Enable bit
1 = Enables the TMR1 overflow interrupt
0 = Disables the TMR1 overflow interrupt

Note 1: The PSPIE bit is unimplemented on 28-pin devices and will read as ‘0’.

DS41303G-page 114  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 9-7: PIE2: PERIPHERAL INTERRUPT ENABLE (FLAG) REGISTER 2

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 OSCFIE: Oscillator Fail Interrupt Enable bit

1 = Enabled
0 =D isabled
bit 6 C1IE: Comparator C1 Interrupt Enable bit
1 = Enabled
0 = Disabled
bit 5 C2IE: Comparator C2 Interrupt Enable bit
1 = Enabled
0 = Disabled
bit 4 EEIE: Data EEPROM/Flash Write Operation Interrupt Enable bit
1 = Enabled
0 =D isabled
bit 3 BCLIE: Bus Collision Interrupt Enable bit
1 = Enabled
0 =D isabled
bit 2 HLVDIE: Low-Voltage Detect Interrupt Enable bit
1 = Enabled
0 =D isabled
bit 1 TMR3IE: TMR3 Overflow Interrupt Enable bit
1 = Enabled
0 =D isabled
bit 0 CCP2IE: CCP2 Interrupt Enable bit
1 = Enabled
0 =D isabled

 2010 Microchip Technology Inc. DS41303G-page 115

PIC18F2XK20/4XK20
9.7 IPR Registers
The IPR registers contain the individual priority bits for the
peripheral inte rrupts. D ue t o the n umber of per ipheral
interrupt s ources, there are two Per ipheral Interrupt
Priority registers (IPR1 and IPR2). Using the priority bits
requires that the Interrupt P riority E nable (I PEN) bit be
set.
REGISTER 9-8: IPR1: PERIPHERAL INTERRUPT PRIORITY REGISTER 1
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 PSPIP: Parallel Slave Port Read/Write Interrupt Priority bit(1)

1 = High priority
0 = Low priority
bit 6 ADIP: A/D Converter Interrupt Priority bit
1 = High priority
0 = Low priority
bit 5 RCIP: EUSART Receive Interrupt Priority bit
1 = High priority
0 = Low priority
bit 4 TXIP: EUSART Transmit Interrupt Priority bit
1 = High priority
0 = Low priority
bit 3 SSPIP: Master Synchronous Serial Port Interrupt Priority bit
1 = High priority
0 = Low priority
bit 2 CCP1IP: CCP1 Interrupt Priority bit
1 = High priority
0 = Low priority
bit 1 TMR2IP: TMR2 to PR2 Match Interrupt Priority bit
1 = High priority
0 = Low priority
bit 0 TMR1IP: TMR1 Overflow Interrupt Priority bit
1 = High priority
0 = Low priority

Note 1: The PSPIF bit is unimplemented on 28-pin devices and will read as ‘0’.

DS41303G-page 116  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 9-9: IPR2: PERIPHERAL INTERRUPT PRIORITY REGISTER 2

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 OSCFIP: Oscillator Fail Interrupt Priority bit

1 = High priority
0 = Low priority
bit 6 C1IP: Comparator C1 Interrupt Priority bit
1 = High priority
0 = Low priority
bit 5 C2IP: Comparator C2 Interrupt Priority bit
1 = High priority
0 = Low priority
bit 4 EEIP: Data EEPROM/Flash Write Operation Interrupt Priority bit
1 = High priority
0 = Low priority
bit 3 BCLIP: Bus Collision Interrupt Priority bit
1 = High priority
0 = Low priority
bit 2 HLVDIP: Low-Voltage Detect Interrupt Priority bit
1 = High priority
0 = Low priority
bit 1 TMR3IP: TMR3 Overflow Interrupt Priority bit
1 = High priority
0 = Low priority
bit 0 CCP2IP: CCP2 Interrupt Priority bit
1 = High priority
0 = Low priority

 2010 Microchip Technology Inc. DS41303G-page 117

PIC18F2XK20/4XK20
9.8 RCON Register
The RCON register contains flag bits which are used to
determine the cause of the last Reset or wake-up from
Idle or Sleep modes. RCON also contains the IPEN bit
which enables interrupt priorities.
The operation of the SBOREN bit and the Reset flag
bits is discussed in more detail in Section 4.1 “RCON
Register”.
REGISTER 9-10: RCON: RESET CONTROL REGISTER
R/W-0 R/W-1 U-0 R/W-1 R-1 R-1 R/W-0 R/W-0
IPEN SBOREN (1)
— RI TO PD POR (1)
BOR
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 IPEN: Interrupt Priority Enable bit

1 = Enable priority levels on interrupts
0 = Disable priority levels on interrupts (Mid-Range Compatibility mode)
bit 6 SBOREN: Software BOR Enable bit(1)
For details of bit operation, see Register 4-1.
bit 5 Unimplemented: Read as ‘0’
bit 4 RI: RESET Instruction Flag bit
For details of bit operation, see Register 4-1.
bit 3 TO: Watchdog Time-out Flag bit
For details of bit operation, see Register 4-1.
bit 2 PD: Power-down Detection Flag bit
For details of bit operation, see Register 4-1
bit 1 POR: Power-on Reset Status bit
For details of bit operation, see Register 4-1.
bit 0 BOR: Brown-out Reset Status bit
For details of bit operation, see Register 4-1.

Note 1: Actual Reset values are determined by device configuration and the nature of the device Reset.
See Register 4-1 for additional information.

DS41303G-page 118  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
9.9 INTn Pin Interrupts 9.10 TMR0 Interrupt
External i nterrupts on the R B0/INT0, R B1/INT1 an d In 8-bit mode (which is the default), an overflow in the
RB2/INT2 pins are edge-triggered. If the corresponding TMR0 register (FFh  00h) will set flag bit, TMR0IF. In
INTEDGx bit in the INTCON2 register is set (= 1), the 16-bit mode, an overflow in the TMR0H:TMR0L regis-
interrupt is triggered by a rising edge; if the bit is clear, ter pair (FFFFh 0000h) will set TMR0IF. The interrupt
the tri gger is on the fal ling ed ge. When a va lid edg e can be enabled/disabled by setting/clearing enable bit,
appears on the R Bx/INTx pin, the corresponding flag TMR0IE of the INTCO N re gister. I nterrupt priority f or
bit, INTxF, i s set. Th is in terrupt c an be di sabled b y Timer0 i s determined b y the v alue c ontained in th e
clearing the corresponding enable bit, INTxE. Flag bit, interrupt priority bit, TMR0IP of the INTCON2 register.
INTxF, mu st be cleared by software in the In terrupt See Section 12.0 “Timer0 Module” for further details
Service Routine before re-enabling the interrupt. on the Timer0 module.
All external interrupts (INT0, INT1 and INT2) can wake-
up the processor from Idle or Sleep modes if bit INTxE 9.11 PORTB Interrupt-on-Change
was set prior to going into those modes. If the Global
An input change on PORTB<7:4> sets flag bit, RBIF of
Interrupt E nable bit, G IE, is s et, the pro cessor wil l
the IN TCON register. The i nterrupt c an be enabled/
branch to the interrupt vector following wake-up.
disabled b y s etting/clearing ena ble bi t, R BIE of th e
Interrupt priority for INT1 and INT2 is determined by the INTCON r egister. P ins mu st al so be in dividually
value contained in the interrupt priority bits, INT1IP and enabled w ith t he IOCB re gister. In terrupt priority f or
INT2IP of the INTCON3 register. There is no priority bit PORTB interrupt-on-change is determined by the value
associated with INT0. It is always a high priority inter- contained in the interrupt prio rity bit, RBIP of the
rupt source. INTCON2 register.

9.12 Context Saving During Interrupts

During inte rrupts, the r eturn PC add ress i s s aved o n
the stack. Additionally, the WREG, STATUS and BSR
registers a re saved on t he fast return stack. I f a f ast
return fro m interrupt i s not us ed (s ee Section 5.1.3
“Fast Register Stack”), the user may need to save the
WREG, ST ATUS a nd BSR re gisters o n en try to th e
Interrupt Serv ice R outine. D epending on the user’s
application, other registers may also need to be saved.
Example 9-1 saves and restores the WREG, STATUS
and BSR registers during an Interrupt Service Routine.

EXAMPLE 9-1: SAVING STATUS, WREG AND BSR REGISTERS IN RAM

MOVWF W_TEMP ; W_TEMP is in virtual bank
MOVFF STATUS, STATUS_TEMP ; STATUS_TEMP located anywhere
MOVFF BSR, BSR_TEMP ; BSR_TMEP located anywhere
;
; USER ISR CODE
;
MOVFF BSR_TEMP, BSR ; Restore BSR
MOVF W_TEMP, W ; Restore WREG
MOVFF STATUS_TEMP, STATUS ; Restore STATUS

 2010 Microchip Technology Inc. DS41303G-page 119

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 120  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
10.0 I/O PORTS Reading the PORTA regi ster read s the status of the
pins, whereas writing to it, will write to the PORT latch.
Depending on the de vice s elected and fea tures
The Data Latch (LATA) register is also memory mapped.
enabled, there are up to five ports available. Some pins
Read-modify-write operations on the LATA register read
of the I/O por ts are mu ltiplexed with an alte rnate
and write the latched output value for PORTA.
function from the peripheral features on the device. In
general, when a peripheral is enabled, that pin may not The R A4 pin is mu ltiplexed w ith the T imer0 mo dule
be used as a general purpose I/O pin. clock in put and on e o f th e c omparator ou tputs to
become t he R A4/T0CKI/C1OUT pin. P ins RA6 a nd
Each port has three registers for it s operation. These
RA7 are multiplexed with the main oscillator pins; they
registers are:
are enabled as oscillator or I/O pins by the selection of
• TRIS register (data direction register) the main o scillator i n t he Configuration register ( see
• PORT register (reads the levels on the pins of the Section 23.1 “Configuration Bits” for details). When
device) they are not used as port pins, RA6 and RA7 and their
• LAT register (output latch) associated TRIS and LAT bits are read as ‘0’.
The Data Latch (LAT register) is useful for read-modify- The ot her P ORTA pins ar e mu ltiplexed w ith a nalog
write op erations o n th e va lue tha t the I/O pi ns a re inputs, t he a nalog VREF+ and VREF- i nputs, and the
driving. comparator voltage reference output. The operation of
pins RA<3:0> and RA5 as analog is selected by setting
A simplified m odel o f a g eneric I/O port, w ithout th e
the ANS<4:0> bits in t he ANSEL register which is the
interfaces to other peripherals, is shown in Figure 10-1.
default setting after a Power-on Reset.

FIGURE 10-1: GENERIC I/O PORT Pins RA0 through RA5 may also be used as comparator
inputs or outputs by setting th e appropriate bits in th e
OPERATION
CM1CON0 and CM2CON0 registers.

RD LAT Note: On a Power-on Reset, RA5 and RA<3:0>

are configured as analog inputs and read
Data as ‘0’. RA4 is configured as a digital input.
Bus D Q
WR LAT I/O pin(1)
The RA4/T0CKI/C1OUT pin is a Schmitt Trigger input.
or Port
CK
All o ther P ORTA pi ns h ave T TL in put l evels a nd f ull
CMOS output drivers.
Data Latch
The TRISA register controls the drivers of the PORTA
D Q pins, even when they are being used as analog inputs.
The user should ensure the bits in the TRISA register
WR TRIS
CK are maintained set when using them as analog inputs.
TRIS Latch Input
Buffer EXAMPLE 10-1: INITIALIZING PORTA
RD TRIS CLRF PORTA ; Initialize PORTA by
; clearing output
; data latches
Q D
CLRF LATA ; Alternate method
; to clear output
ENEN ; data latches
RD Port MOVLW E0h ; Configure I/O
MOVWF ANSEL ; for digital inputs
MOVLW 0CFh ; Value used to
Note 1: I/O pins have diode protection to VDD and VSS.
; initialize data
; direction
MOVWF TRISA ; Set RA<3:0> as inputs
10.1 PORTA, TRISA and LATA ; RA<5:4> as outputs
Registers
PORTA i s an 8-b it w ide, bidirectional po rt. Th e
corresponding data direction register is TRISA. Setting
a TRISA bit (= 1) will make the corresponding PORTA
pin an input (i.e., disable the output driver). Clearing a
TRISA bi t (= 0) will m ake th e c orresponding PO RTA
pin an output (i.e., enable the output driver and put the
contents of the output latch on the selected pin).

 2010 Microchip Technology Inc. DS41303G-page 121

PIC18F2XK20/4XK20

TABLE 10-1: PORTA I/O SUMMARY

TRIS I/O
Pin Function I/O Description
Setting Type
RA0/AN0/C12IN0- RA0 0 O DIG LATA<0> data output; not affected by analog input.
1 I TTL PORTA<0> data input; disabled when analog input enabled.
AN0 1 I ANA ADC input channel 0. Default input configuration on POR; does not
affect digital output.
C12IN0- 1 I ANA Comparators C1 and C2 inverting input, channel 0. Analog select is
shared with ADC.
RA1/AN1/C12IN1- RA1 0 O DIG LATA<1> data output; not affected by analog input.
1 I TTL PORTA<1> data input; disabled when analog input enabled.
AN1 1 I ANA ADC input channel 1. Default input configuration on POR; does not
affect digital output.
C12IN1- 1 I ANA Comparators C1 and C2 inverting input, channel 1. Analog select is
shared with ADC.
RA2/AN2/C2IN+ RA2 0 O DIG LATA<2> data output; not affected by analog input. Disabled when
VREF-/CVREF CVREF output enabled.
1 I TTL PORTA<2> data input. Disabled when analog functions enabled;
disabled when CVREF output enabled.
AN2 1 I ANA ADC input channel 2. Default input configuration on POR; not affected
by analog output.
C2IN+ 1 I ANA Comparator C2 non-inverting input. Analog selection is shared with
ADC.
VREF- 1 I ANA ADC and comparator voltage reference low input.
CVREF x O ANA Comparator voltage reference output. Enabling this feature disables
digital I/O.
RA3/AN3/C1IN+/ RA3 0 O DIG LATA<3> data output; not affected by analog input.
VREF+ 1 I TTL PORTA<3> data input; disabled when analog input enabled.
AN3 1 I ANA A/D input channel 3. Default input configuration on POR.
C1IN+ 1 I ANA Comparator C1 non-inverting input. Analog selection is shared with
ADC.
VREF+ 1 I ANA ADC and comparator voltage reference high input.
RA4/T0CKI/C1OUT RA4 0 O DIG LATA<4> data output.
1 I ST PORTA<4> data input; default configuration on POR.
T0CKI 1 I ST Timer0 clock input.
C1OUT 0 O DIG Comparator 1 output; takes priority over port data.
RA5/AN4/SS/ RA5 0 O DIG LATA<5> data output; not affected by analog input.
HLVDIN/C2OUT 1 I TTL PORTA<5> data input; disabled when analog input enabled.
AN4 1 I ANA A/D input channel 4. Default configuration on POR.
SS 1 I TTL Slave select input for SSP (MSSP module).
HLVDIN 1 I ANA Low-Voltage Detect external trip point input.
C2OUT 0 O DIG Comparator 2 output; takes priority over port data.
OSC2/CLKOUT/ RA6 0 O DIG LATA<6> data output. Enabled in RCIO, INTIO2 and ECIO modes only.
RA6 1 I TTL PORTA<6> data input. Enabled in RCIO, INTIO2 and ECIO modes
only.
OSC2 x O ANA Main oscillator feedback output connection (XT, HS and LP modes).
CLKOUT x O DIG System cycle clock output (FOSC/4) in RC, INTIO1 and EC Oscillator
modes.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

DS41303G-page 122  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 10-1: PORTA I/O SUMMARY (CONTINUED)
TRIS I/O
Pin Function I/O Description
Setting Type
OSC1/CLKIN/RA7 RA7 0 O DIG LATA<7> data output. Disabled in external oscillator modes.
1 I TTL PORTA<7> data input. Disabled in external oscillator modes.
OSC1 x I ANA Main oscillator input connection.
CLKIN x I ANA Main clock input connection.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).

TABLE 10-2: SUMMARY OF REGISTERS ASSOCIATED WITH PORTA

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 62
LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 62
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 62
ANSEL ANS7(2) ANS6(2) ANS5(2) ANS4 ANS3 ANS2 ANS1 ANS0 62
SLRCON — — — SLRE(2) SLRD(2) SLRC SLRB SLRA 63
CM1CON0 C1ON C1OUT C1OE C1POL C1SP C1R C1CH1 C1CH0 62
CM2CON0 C2ON C2OUT C2OE C2POL C2SP C2R C2CH1 C2CH0 62
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTA.
Note 1: RA<7:6> and their associated latch and data direction bits are enabled as I/O pins based on oscillator
configuration; otherwise, they are read as ‘0’.
2: Not implemented on PIC18F2XK20 devices.

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PIC18F2XK20/4XK20
10.2 PORTB, TRISB and LATB 10.3.2 INTERRUPT-ON-CHANGE
Registers Four o f the PO RTB p ins (R B<7:4>) a re i ndividually
configurable as interrupt-on-change pins. C ontrol bits
PORTB is an 8-b it wide, bidirectional port. The corre-
in the IOCB register enable (when set) or disable (when
sponding da ta dire ction register is TRISB. Setting a
clear) the interrupt function for each pin.
TRISB bit (= 1) w ill m ake t he c orresponding PO RTB
pin an input (i.e., disable the output driver). Clearing a When set, the RBIE bit of the INTCON register enables
TRISB bit (= 0) w ill m ake t he c orresponding PO RTB interrupts on all pins which also have their correspond-
pin an output (i.e., enable the output driver and put the ing IOCB bit set. When clear, the RBIE bit disables all
contents of the output latch on the selected pin). interrupt-on-changes.
The D ata Latch reg ister (LA TB) is also me mory Only pins configured as inputs can cause this interrupt
mapped. R ead-modify-write o perations o n t he LATB to occur (i.e., any RB<7:4> pin configured as an output
register read a nd w rite th e lat ched ou tput va lue for is excluded from the interrupt-on-change comparison).
PORTB. For ena bled in terrupt-on-change pins, th e va lues a re
compared with the old value latched on the last read of
EXAMPLE 10-2: INITIALIZING PORTB PORTB. T he ‘ mismatch’ outputs of t he la st r ead ar e
CLRF PORTB ; Initialize PORTB by OR’d together to set the PORTB Change Interrupt flag
; clearing output bit (RBIF) in the INTCON register.
; data latches
This i nterrupt c an wa ke th e device from the Sleep
CLRF LATB ; Alternate method
; to clear output mode, o r an y o f th e Id le modes. Th e u ser, i n th e
; data latches Interrupt Service Routine, can clear the interrupt in the
CLRF ANSELH ; Set RB<4:0> as following manner:
; digital I/O pins a) Any r ead o r w rite of PORTB to c lear t he mis-
;(required if config bit
match condition ( except w hen P ORTB i s t he
; PBADEN is set)
source or destination of a MOVFF instruction).
MOVLW 0CFh ; Value used to
; initialize data b) Clear the flag bit, RBIF.
; direction A mismatch condition will continue to set the RBIF flag bit.
MOVWF TRISB ; Set RB<3:0> as inputs
Reading or w riting P ORTB will e nd the mis match
; RB<5:4> as outputs
condition and allow the RBIF bit to be cleared. The latch
; RB<7:6> as inputs
holding the last read value is not affected by a MCLR nor
Brown-out R eset. Afte r ei ther o ne of th ese R esets, th e
10.3 Additional PORTB Pin Functions RBIF flag will continue to be set if a mismatch is present.
PORTB pins R B<7:4> h ave an i nterrupt-on-change Note: If a change on th e I/O p in should occur
option. All PORTB pins have a weak pull-up option. An when the read operation is being executed
alternate CCP2 peripheral option is available on RB3. (start of the Q2 cycle), t hen the RBIF
interrupt flag may not get set. Furthermore,
10.3.1 WEAK PULL-UPS since a read or write on a port affects all bits
Each of the PORTB pins has an individually controlled of that port, care must be taken when using
weak internal pull-up. When set, each bit of the WPUB multiple pins in Interrupt-on-change mode.
register enables the corresponding pin pull-up. When Changes on one pin may not be seen while
cleared, the RBPU bit of the INTCON2 register enables servicing changes on another pin.
pull-ups on all pins which also have their corresponding The i nterrupt-on-change fea ture is rec ommended f or
WPUB bit se t. Whe n se t, the RBPU bit disables al l wake-up on k ey depression operation and operations
weak pull-ups. The weak pull-up is automatically turned where PORTB is only used for the interrupt-on-change
off w hen t he p ort pin is co nfigured as a n output. T he feature. Polling of P ORTB is not recommended while
pull-ups are disabled on a Power-on Reset. using the interrupt-on-change feature.
Note: On a Power-o n R eset, R B<4:0> are 10.3.3 ALTERNATE CCP2 OPTION
configured as analog inputs by default and
read as ‘0’; R B<7:5> are configured as RB3 can be configured as the alternate peripheral pin
digital inputs. for the CCP2 module by clearing the CCP2MX Config-
uration bit of C ONFIG3H. The d efault state of th e
When the PBADEN Configuration bit is set CCP2MX Configuration bit is ‘1’ which selects RC1 as
to ‘1 ’, R B<4:0> w ill al ternatively b e the CCP2 peripheral pin.
configured as digital inputs on POR.

DS41303G-page 124  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

TABLE 10-3: PORTB I/O SUMMARY

TRIS I/O
Pin Function I/O Description
Setting Type
RB0/INT0/FLT0/ RB0 0 O DIG LATB<0> data output; not affected by analog input.
AN12
1 I TTL PORTB<0> data input; Programmable weak pull-up. Disabled when
analog input enabled.(1)
INT0 1 I ST External interrupt 0 input.
FLT0 1 I ST Enhanced PWM Fault input (ECCP1 module); enabled by software.
AN12 1 I ANA A/D input channel 12.(1)
RB1/INT1/AN10/ RB1 0 O DIG LATB<1> data output; not affected by analog input.
C12IN3-/P1C
1 I TTL PORTB<1> data input; Programmable weak pull-up. Disabled when
analog input enabled.(1)
INT1 1 I ST External Interrupt 1 input.
AN10 1 I ANA ADC input channel 10.(1)
C12IN3- 1 I ANA Comparators C1 and C2 inverting input, channel 3. Analog select is
shared with ADC.
P1C 0 O DIG ECCP PWM output (28-pin devices only).
RB2/INT2/AN8/ RB2 0 O DIG LATB<2> data output; not affected by analog input.
P1B 1 I TTL PORTB<2> data input; Programmable weak pull-up. Disabled when
analog input enabled.(1)
INT2 1 I ST External interrupt 2 input.
AN8 1 I ANA ADC input channel 8.(1)
P1B 0 O DIG ECCP PWM output (28-pin devices only).
RB3/AN9/C12IN2-/ RB3 0 O DIG LATB<3> data output; not affected by analog input.
CCP2
1 I TTL PORTB<3> data input; Programmable weak pull-up. Disabled when
analog input enabled.(1)
AN9 1 I ANA ADC input channel 9.(1)
C12IN2- 1 I ANA Comparators C1 and C2 inverting input, channel 2. Analog select is
shared with ADC.
CCP2(2) 0 O DIG CCP2 compare and PWM output.
1 I ST CCP2 capture input
RB4/KBI0/AN11/ RB4 0 O DIG LATB<4> data output; not affected by analog input.
P1D
1 I TTL PORTB<4> data input; Programmable weak pull-up. Disabled when
analog input enabled.(1)
KBI0 1 I TTL Interrupt-on-pin change.
AN11 1 I ANA ADC input channel 11.(1)
P1D 0 O DIG ECCP PWM output (28-pin devices only).
RB5/KBI1/PGM RB5 0 O DIG LATB<5> data output.
1 I TTL PORTB<5> data input; Programmable weak pull-up.
KBI1 1 I TTL Interrupt-on-pin change.
PGM x I ST Single-Supply Programming mode entry (ICSP™). Enabled by LVP
Configuration bit; all other pin functions disabled.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: Configuration on POR is determined by the PBADEN Configuration bit. Pins are configured as analog inputs by default
when PBADEN is set and digital inputs when PBADEN is cleared.
2: Alternate assignment for CCP2 when the CCP2MX Configuration bit is ‘0’. Default assignment is RC1.
3: All other pin functions are disabled when ICSP or ICD are enabled.

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PIC18F2XK20/4XK20
TABLE 10-3: PORTB I/O SUMMARY (CONTINUED)
TRIS I/O
Pin Function I/O Description
Setting Type
RB6/KBI2/PGC RB6 0 O DIG LATB<6> data output.
1 I TTL PORTB<6> data input; Programmable weak pull-up.
KBI2 1 I TTL Interrupt-on-pin change.
PGC x I ST Serial execution (ICSP) clock input for ICSP and ICD operation.(3)
RB7/KBI3/PGD RB7 0 O DIG LATB<7> data output.
1 I TTL PORTB<7> data input; Programmable weak pull-up.
KBI3 1 I TTL Interrupt-on-pin change.
PGD x O DIG Serial execution data output for ICSP and ICD operation.(3)
x I ST Serial execution data input for ICSP and ICD operation.(3)
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: Configuration on POR is determined by the PBADEN Configuration bit. Pins are configured as analog inputs by default
when PBADEN is set and digital inputs when PBADEN is cleared.
2: Alternate assignment for CCP2 when the CCP2MX Configuration bit is ‘0’. Default assignment is RC1.
3: All other pin functions are disabled when ICSP or ICD are enabled.

TABLE 10-4: SUMMARY OF REGISTERS ASSOCIATED WITH PORTB

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 62
LATB PORTB Data Latch Register (Read and Write to Data Latch) 62
TRISB PORTB Data Direction Control Register 62
WPUB WPUB7 WPUB6 WPUB5 WPUB4 WPUB3 WPUB2 WPUB1 WPUB0 62
IOCB IOCB7 IOCB6 IOCB5 IOCB4 — — — — 62
SLRCON — — — SLRE(1) SLRD(1) SLRC SLRB SLRA 63
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
INTCON2 RBPU INTEDG0 INTEDG1 INTEDG2 — TMR0IP — RBIP 59
INTCON3 INT2IP INT1IP — INT2IE INT1IE — INT2IF INT1IF 59
ANSELH — — — ANS12 ANS11 ANS10 ANS9 ANS8 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTB.
Note 1: Not implemented on PIC18F2XK20 devices.

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 PIC18F2XK20/4XK20
10.4 PORTC, TRISC and LATC EXAMPLE 10-3: INITIALIZING PORTC
Registers CLRF PORTC ; Initialize PORTC by
; clearing output
PORTC is an 8-bit wide, bidirectional port. The corre- ; data latches
sponding d ata di rection reg ister i s T RISC. Sett ing a CLRF LATC ; Alternate method
TRISC b it ( = 1) w ill make the corresponding PO RTC ; to clear output
pin an input (i.e., disable the output driver). Clearing a ; data latches
TRISC b it ( = 0) w ill make the corresponding PO RTC MOVLW 0CFh ; Value used to
pin an output (i.e., enable the output driver and put the ; initialize data
; direction
contents of the output latch on the selected pin).
MOVWF TRISC ; Set RC<3:0> as inputs
The Data Latc h regi ster (LATC) is als o me mory ; RC<5:4> as outputs
mapped. R ead-modify-write op erations on the LA TC ; RC<7:6> as inputs
register read a nd w rite th e lat ched ou tput va lue for
PORTC.
PORTC is multiplexed with several peripheral functions
(Table 10-5). The pins have Schmitt Trigger input buf-
fers. RC1 is the de fault configuration for the CCP2
peripheral pin. The CCP2 function can be relocated to
the RB3 pin by clearing the CCP2MX bit of Configura-
tion Word C ONFIG3H. T he default st ate of th e
CCP2MX Configuration bit is ‘1’.
When e nabling peripheral f unctions, c are s hould b e
taken in defining TRIS bits for each PORTC pin. The
EUSART and MSSP peripherals override the TRIS bit
to make a pin an output or an input, depending on the
peripheral con figuration. Refer to the co rresponding
peripheral section for additional information.
Note: On a Power-on Reset, these pins are con-
figured as digital inputs.

The c ontents o f the TR ISC re gister a re a ffected b y

peripheral ov errides. Reading TR ISC alw ays returns
the current contents, even though a peripheral device
may be overriding one or more of the pins.

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PIC18F2XK20/4XK20
TABLE 10-5: PORTC I/O SUMMARY
TRIS I/O
Pin Function I/O Description
Setting Type
RC0/T1OSO/ RC0 0 O DIG LATC<0> data output.
T13CKI 1 I ST PORTC<0> data input.
T1OSO x O ANA Timer1 oscillator output; enabled when Timer1 oscillator enabled.
Disables digital I/O.
T13CKI 1 I ST Timer1/Timer3 counter input.
RC1/T1OSI/CCP2 RC1 0 O DIG LATC<1> data output.
1 I ST PORTC<1> data input.
T1OSI x I ANA Timer1 oscillator input; enabled when Timer1 oscillator enabled.
Disables digital I/O.
CCP2(1) 0 O DIG CCP2 compare and PWM output; takes priority over port data.
1 I ST CCP2 capture input.
RC2/CCP1/P1A RC2 0 O DIG LATC<2> data output.
1 I ST PORTC<2> data input.
CCP1 0 O DIG ECCP1 compare or PWM output; takes priority over port data.
1 I ST ECCP1 capture input.
P1A 0 O DIG ECCP1 Enhanced PWM output, channel A. May be configured for
tri-state during Enhanced PWM shutdown events. Takes priority over
port data.
RC3/SCK/SCL RC3 0 O DIG LATC<3> data output.
1 I ST PORTC<3> data input.
SCK 0 O DIG SPI clock output (MSSP module); takes priority over port data.
1 I ST SPI clock input (MSSP module).
SCL 0 O DIG I2C™ clock output (MSSP module); takes priority over port data.
1 I I C/SMB I2C clock input (MSSP module); input type depends on module setting.
2

RC4/SDI/SDA RC4 0 O DIG LATC<4> data output.

1 I ST PORTC<4> data input.
SDI 1 I ST SPI data input (MSSP module).
SDA 1 O DIG I2C data output (MSSP module); takes priority over port data.
1 I I2C/SMB I2C data input (MSSP module); input type depends on module setting.
RC5/SDO RC5 0 O DIG LATC<5> data output.
1 I ST PORTC<5> data input.
SDO 0 O DIG SPI data output (MSSP module); takes priority over port data.
RC6/TX/CK RC6 0 O DIG LATC<6> data output.
1 I ST PORTC<6> data input.
TX 1 O DIG Asynchronous serial transmit data output (USART module); takes
priority over port data. User must configure as output.
CK 1 O DIG Synchronous serial clock output (USART module); takes priority over
port data.
1 I ST Synchronous serial clock input (USART module).
RC7/RX/DT RC7 0 O DIG LATC<7> data output.
1 I ST PORTC<7> data input.
RX 1 I ST Asynchronous serial receive data input (USART module).
DT 1 O DIG Synchronous serial data output (USART module); takes priority over
port data.
1 I ST Synchronous serial data input (USART module). User must configure
as an input.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
I2C/SMB = I2C/SMBus input buffer; x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: Default assignment for CCP2 when the CCP2MX Configuration bit is set. Alternate assignment is RB3.

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 PIC18F2XK20/4XK20
TABLE 10-6: SUMMARY OF REGISTERS ASSOCIATED WITH PORTC
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTC RC7 RC6 RC5 RC4 RC3 RC2 RC1 RC0 62
LATC PORTC Data Latch Register (Read and Write to Data Latch) 62
TRISC PORTC Data Direction Control Register 62
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 60
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 61
CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 61
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1 PSSBD0 61
SLRCON — — — SLRE(1) SLRD(1) SLRC SLRB SLRA 63
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTC.
Note 1: Not implemented on PIC18F2XK20 devices.

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PIC18F2XK20/4XK20
10.5 PORTD, TRISD and LATD PORTD can also be configured as an 8-bit wide micro-
Registers processor port (Parallel Slave Port) by setting control
bit, PSPM ODE (TRISE< 4>). I n th is m ode, t he i nput
Note: PORTD is onl y av ailable on 40/44-pin buffers are TT L. Se e Section 10.9 “Parallel Slave
devices. Port” f or ad ditional i nformation on t he P arallel S lave
Port (PSP).
PORTD is an 8-bit wide, bidirectional port. The corre-
sponding d ata di rection reg ister i s T RISD. Sett ing a Note: When the enhanced PWM mode is used
TRISD b it ( = 1) w ill make the corresponding PO RTD with either dual or quad outputs, the PSP
pin an input (i.e., disable the output driver). Clearing a functions o f POR TD are au tomatically
TRISD b it ( = 0) w ill make the corresponding PO RTD disabled.
pin an output (i.e., enable the output driver and put the
contents of the output latch on the selected pin). EXAMPLE 10-4: INITIALIZING PORTD
The Data Latc h regi ster (LATD) is als o me mory CLRF PORTD ; Initialize PORTD by
mapped. R ead-modify-write op erations on the LA TD ; clearing output
register read a nd w rite th e lat ched ou tput va lue for ; data latches
PORTD. CLRF LATD ; Alternate method
; to clear output
All pins on PORTD are implemented with Schmitt Trig- ; data latches
ger input buffers. Each pin is individually configurable MOVLW 0CFh ; Value used to
as an input or output. ; initialize data
; direction
Three of the PORTD pins are multiplexed with outputs MOVWF TRISD ; Set RD<3:0> as inputs
P1B, P1C and P1D of the enhanced CCP module. The ; RD<5:4> as outputs
operation of the se ad ditional PWM out put pi ns is ; RD<7:6> as inputs
covered in gre ater detail in Section 16.0 “Enhanced
Capture/Compare/PWM (ECCP) Module”.
Note: On a Pow er-on Reset, thes e pi ns are
configured as digital inputs.

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 PIC18F2XK20/4XK20
TABLE 10-7: PORTD I/O SUMMARY
TRIS I/O
Pin Function I/O Description
Setting Type
RD0/PSP0 RD0 0 O DIG LATD<0> data output.
1 I ST PORTD<0> data input.
PSP0 x O DIG PSP read data output (LATD<0>); takes priority over port data.
x I TTL PSP write data input.
RD1/PSP1 RD1 0 O DIG LATD<1> data output.
1 I ST PORTD<1> data input.
PSP1 x O DIG PSP read data output (LATD<1>); takes priority over port data.
x I TTL PSP write data input.
RD2/PSP2 RD2 0 O DIG LATD<2> data output.
1 I ST PORTD<2> data input.
PSP2 x O DIG PSP read data output (LATD<2>); takes priority over port data.
x I TTL PSP write data input.
RD3/PSP3 RD3 0 O DIG LATD<3> data output.
1 I ST PORTD<3> data input.
PSP3 x O DIG PSP read data output (LATD<3>); takes priority over port data.
x I TTL PSP write data input.
RD4/PSP4 RD4 0 O DIG LATD<4> data output.
1 I ST PORTD<4> data input.
PSP4 x O DIG PSP read data output (LATD<4>); takes priority over port data.
x I TTL PSP write data input.
RD5/PSP5/P1B RD5 0 O DIG LATD<5> data output.
1 I ST PORTD<5> data input.
PSP5 x O DIG PSP read data output (LATD<5>); takes priority over port data.
x I TTL PSP write data input.
P1B 0 O DIG ECCP1 Enhanced PWM output, channel B; takes priority over port and
PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
RD6/PSP6/P1C RD6 0 O DIG LATD<6> data output.
1 I ST PORTD<6> data input.
PSP6 x O DIG PSP read data output (LATD<6>); takes priority over port data.
x I TTL PSP write data input.
P1C 0 O DIG ECCP1 Enhanced PWM output, channel C; takes priority over port and
PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
RD7/PSP7/P1D RD7 0 O DIG LATD<7> data output.
1 I ST PORTD<7> data input.
PSP7 x O DIG PSP read data output (LATD<7>); takes priority over port data.
x I TTL PSP write data input.
P1D 0 O DIG ECCP1 Enhanced PWM output, channel D; takes priority over port and
PSP data. May be configured for tri-state during Enhanced PWM
shutdown events.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; x = Don’t care
(TRIS bit does not affect port direction or is overridden for this option).

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PIC18F2XK20/4XK20
TABLE 10-8: SUMMARY OF REGISTERS ASSOCIATED WITH PORTD
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTD(1) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 62
LATD(1) PORTD Data Latch Register (Read and Write to Data Latch) 62
TRISD(1) PORTD Data Direction Control Register 62
TRISE(1) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 62
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 61
SLRCON — — — SLRE(1) SLRD(1) SLRC SLRB SLRA 63
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTD.
Note 1: Not implemented on PIC18F2XK20 devices.

DS41303G-page 132  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
10.6 PORTE, TRISE and LATE The fou rth pin of POR TE (MC LR/VPP/RE3) is an inpu t
Registers only pin. It s oper ation is controlled by the MC LRE
Configuration bit. When select ed as a port pin
Depending o n th e p articular PIC18F2XK20/4XK20 (MCLRE = 0), it functi ons as a digit al input only pin; as
device selected, PO RTE is im plemented in tw o such, it does not have TRIS or LAT bits associated with its
different ways. operation. Otherwise, it functions as the device’s Master
Clear input. In either configuration, RE3 also functions as
10.6.1 PORTE IN PIC18F4XK20 DEVICES the programming voltage input during programming.
For PIC18F4XK20 devices, PORTE is a 4-bit wide port. Note: On a Power-on Reset, RE3 is enabled as
Three pins (RE0/RD/AN5, RE1/WR/AN6 and RE2/CS/ a d igital input onl y if M aster C lear
AN7) are individually configurable as inputs or outputs. functionality is disabled.
These pins have Schmitt Trigger input buffers. When
selected as an analog input, these pins will read as ‘0’s.
EXAMPLE 10-5: INITIALIZING PORTE
The co rresponding da ta d irection reg ister is TR ISE. CLRF PORTE ; Initialize PORTE by
Setting a TRISE bit (= 1) will make the corresponding ; clearing output
PORTE p in an in put ( i.e., d isable t he o utput dr iver). ; data latches
Clearing a TRISE bit (= 0) will make the corresponding CLRF LATE ; Alternate method
PORTE pin an output (i.e., enable the output driver and ; to clear output
put the contents of the output latch on the selected pin). ; data latches
MOVLW 1Fh ; Configure analog pins
TRISE controls the direction of the RE pins, even when ANDWF ANSEL,w ; for digital only
they are b eing used as analog inputs. The user must MOVLW 05h ; Value used to
make sure to keep the pins configured as inputs when ; initialize data
using them as analog inputs. ; direction
MOVWF TRISE ; Set RE<0> as input
Note: On a Power-o n R eset, R E<2:0> are ; RE<1> as output
configured as analog inputs. ; RE<2> as input
The upper four bits of the TR ISE register also control
the operation of the Parallel Slave Port. Their operation 10.6.2 PORTE IN PIC18F2XK20 DEVICES
is explained in Register 10-1. For PIC 18F2XK20 devices, PO RTE is onl y available
The D ata Latch reg ister (LA TE) is also me mory when M aster C lear f unctionality is di sabled
mapped. R ead-modify-write o perations o n t he LATE (MCLR = 0). In t hese ca ses, P ORTE is a si ngle b it,
register, rea d an d w rite the latched ou tput va lue for input only port comprised of RE3 only. The pin operates
PORTE. as previously described.

 2010 Microchip Technology Inc. DS41303G-page 133

PIC18F2XK20/4XK20

REGISTER 10-1: TRISE: PORTE/PSP CONTROL REGISTER (PIC18F4XK20 DEVICES ONLY)

R-0 R-0 R/W-0 R/W-0 U-0 R/W-1 R/W-1 R/W-1
IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 IBF: Input Buffer Full Status bit

1 = A word has been received and waiting to be read by the CPU
0 = No word has been received
bit 6 OBF: Output Buffer Full Status bit
1 = The output buffer still holds a previously written word
0 = The output buffer has been read
bit 5 IBOV: Input Buffer Overflow Detect bit (in Microprocessor mode)
1 = A write occurred when a previously input word has not been read (must be cleared by software)
0 = No overflow occurred
bit 4 PSPMODE: Parallel Slave Port Mode Select bit
1 = Parallel Slave Port mode
0 = General purpose I/O mode
bit 3 Unimplemented: Read as ‘0’
bit 2 TRISE2: RE2 Direction Control bit
1 = Input
0 = Output
bit 1 TRISE1: RE1 Direction Control bit
1 = Input
0 = Output
bit 0 TRISE0: RE0 Direction Control bit
1 = Input
0 = Output

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 PIC18F2XK20/4XK20
TABLE 10-9: PORTE I/O SUMMARY
TRIS I/O
Pin Function I/O Description
Setting Type

RE0/RD/AN5 RE0 0 O DIG LATE<0> data output; not affected by analog input.
1 I ST PORTE<0> data input; disabled when analog input enabled.
RD 1 I TTL PSP read enable input (PSP enabled).
AN5 1 I ANA A/D input channel 5; default input configuration on POR.
RE1/WR/AN6 RE1 0 O DIG LATE<1> data output; not affected by analog input.
1 I ST PORTE<1> data input; disabled when analog input enabled.
WR 1 I TTL PSP write enable input (PSP enabled).
AN6 1 I ANA A/D input channel 6; default input configuration on POR.
RE2/CS/AN7 RE2 0 O DIG LATE<2> data output; not affected by analog input.
1 I ST PORTE<2> data input; disabled when analog input enabled.
CS 1 I TTL PSP write enable input (PSP enabled).
AN7 1 I ANA A/D input channel 7; default input configuration on POR.
MCLR/VPP/ MCLR — I ST External Master Clear input; enabled when MCLRE Configuration bit is
RE3(1,2) set.
VPP — I ANA High-voltage detection; used for ICSP™ mode entry detection. Always
available, regardless of pin mode.
RE3 —(2) I ST PORTE<3> data input; enabled when MCLRE Configuration bit is
clear.
Legend: DIG = Digital level output; TTL = TTL input buffer; ST = Schmitt Trigger input buffer; ANA = Analog level input/output;
x = Don’t care (TRIS bit does not affect port direction or is overridden for this option).
Note 1: RE3 is available on both PIC18F2XK20 and PIC18F4XK20 devices. All other PORTE pins are only implemented on
PIC18F4XK20 devices.
2: RE3 does not have a corresponding TRIS bit to control data direction.

TABLE 10-10: SUMMARY OF REGISTERS ASSOCIATED WITH PORTE

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTE — — — — RE3(1,2) RE2 RE1 RE0 62
LATE(2) — — — — — LATE Data Output Register 62
TRISE(3) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 62
SLRCON — — — SLRE(3) SLRD(3) SLRC SLRB SLRA 63
ANSEL ANS7(3) ANS6 (3)
ANS5 (3)
ANS4 ANS3 ANS2 ANS1 ANS0 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTE.
Note 1: Implemented only when Master Clear functionality is disabled (MCLRE Configuration bit = 0).
2: RE3 is the only PORTE bit implemented on both PIC18F2XK20 and PIC18F4XK20 devices. All other bits
are implemented only when PORTE is implemented (i.e., PIC18F4XK20 devices).
3: Unimplemented on PIC18F2XK20 devices.

 2010 Microchip Technology Inc. DS41303G-page 135

PIC18F2XK20/4XK20
10.7 Port Analog Control buffer and cause all reads of that pin to return ‘0’ while
allowing analog fu nctions of that pi n to op erate
Some port pins are multiplexed with analog functions correctly.
such as the Analog-to-Digital Converter and compara-
tors. Whe n th ese I/ O pins a re t o b e us ed as an alog The st ate of the AN Sx bit s ha s no affect o n dig ital
inputs it is necessary to disable the digital input buffer output fu nctions. A pi n w ith th e as sociated TR ISx b it
to avoid excessive current caused by improper biasing clear and AN Sx b it s et w ill st ill ope rate as a dig ital
of the digital input. Individual control of the digital input output but the in put mo de w ill be analog. This ca n
buffers on pi ns w hich sh are an alog f unctions is p ro- cause unexpected b ehavior w hen performing rea d-
vided by the ANSEL and ANSELH registers. Setting an modify-write operations on the affected port.
ANSx bit high will disable the associated digital input

REGISTER 10-2: ANSEL: ANALOG SELECT REGISTER 1

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
ANS7(1) ANS6(1) ANS5(1) ANS4 ANS3 ANS2 ANS1 ANS0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 ANS7: RE2 Analog Select Control bit(1)

1 = Digital input buffer of RE2 is disabled
0 = Digital input buffer of RE2 is enabled
bit 6 ANS6: RE1 Analog Select Control bit(1)
1 = Digital input buffer of RE1 is disabled
0 = Digital input buffer of RE1 is enabled
bit 5 ANS5: RE0 Analog Select Control bit(1)
1 = Digital input buffer of RE0 is disabled
0 = Digital input buffer of RE0 is enabled
bit 4 ANS4: RA5 Analog Select Control bit
1 = Digital input buffer of RA5 is disabled
0 = Digital input buffer of RA5 is enabled
bit 3 ANS3: RA3 Analog Select Control bit
1 = Digital input buffer of RA3 is disabled
0 = Digital input buffer of RA3 is enabled
bit 2 ANS2: RA2 Analog Select Control bit
1 = Digital input buffer of RA2 is disabled
0 = Digital input buffer of RA2 is enabled
bit 1 ANS1: RA1 Analog Select Control bit
1 = Digital input buffer of RA1 is disabled
0 = Digital input buffer of RA1 is enabled
bit 0 ANS0: RA0 Analog Select Control bit
1 = Digital input buffer of RA0 is disabled
0 = Digital input buffer of RA0 is enabled

Note 1: These bits are not implemented on PIC18F2XK20 devices.

DS41303G-page 136  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 10-3: ANSELH: ANALOG SELECT REGISTER 2

U-0 U-0 U-0 R/W-1(1) R/W-1(1) R/W-1(1) R/W-1(1) R/W-1(1)
— — — ANS12 ANS11 ANS10 ANS9 ANS8
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4 ANS12: RB0 Analog Select Control bit
1 = Digital input buffer of RB0 is disabled
0 = Digital input buffer of RB0 is enabled
bit 3 ANS11: RB4 Analog Select Control bit
1 = Digital input buffer of RB4 is disabled
0 = Digital input buffer of RB4 is enabled
bit 2 ANS10: RB1 Analog Select Control bit
1 = Digital input buffer of RB1 is disabled
0 = Digital input buffer of RB1 is enabled
bit 1 ANS9: RB3 Analog Select Control bit
1 = Digital input buffer of RB3 is disabled
0 = Digital input buffer of RB3 is enabled
bit 0 ANS8: RB2 Analog Select Control bit
1 = Digital input buffer of RB2 is disabled
0 = Digital input buffer of RB2 is enabled

Note 1: Default state is determined by the PBADEN bit of CONFIG3H. The default state is ‘0’ When
PBADEN = ‘0’.

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PIC18F2XK20/4XK20
10.8 Port Slew Rate Control
The output slew rate of each port is programmable to
select either the s tandard transition rate or a red uced
transition rate of 0.1 ti mes t he standard to minimize
EMI. The re duced tra nsition time is th e d efault slew
rate for all ports.
REGISTER 10-4: SLRCON: SLEW RATE CONTROL REGISTER
U-0 U-0 U-0 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
— — — SLRE(1) SLRD(1) SLRC SLRB SLRA
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4 SLRE: PORTE Slew Rate Control bit(1)
1 = All outputs on PORTE slew at a limited rate
0 = All outputs on PORTE slew at the standard rate
bit 3 SLRD: PORTD Slew Rate Control bit(1)
1 = All outputs on PORTD slew at a limited rate
0 = All outputs on PORTD slew at the standard rate
bit 2 SLRC: PORTC Slew Rate Control bit
1 = All outputs on PORTC slew at a limited rate
0 = All outputs on PORTC slew at the standard rate
bit 1 SLRB: PORTB Slew Rate Control bit
1 = All outputs on PORTB slew at a limited rate
0 = All outputs on PORTB slew at the standard rate
bit 0 SLRA: PORTA Slew Rate Control bit
1 = All outputs on PORTA slew at a limited rate(2)
0 = All outputs on PORTA slew at the standard rate

Note 1: These bits are not implemented on PIC18F2XK20 devices.

2: The slew rate of RA6 defaults to standard rate when the pin is used as CLKOUT.

DS41303G-page 138  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
10.9 Parallel Slave Port The ti ming for t he control s ignals in W rite an d R ead
modes is sh own in Figure 10-3 and Figure 10-4,
Note: The Parallel Slave Port is only available on respectively.
PIC18F4XK20 devices.
In addition to its function as a general I/O port, PORTD FIGURE 10-2: PORTD AND PORTE
can also operate as an 8-bit wide Parallel Slave Port BLOCK DIAGRAM
(PSP) o r microprocessor po rt. PSP ope ration is (PARALLEL SLAVE PORT)
controlled by th e 4 u pper bi ts o f the TR ISE reg ister
(Register 10-1). Se tting c ontrol b it, PSPM ODE One bit of PORTD

(TRISE<4>), en ables PSP op eration as lon g a s th e

Data Bus
enhanced CCP module is not operating in dual output D Q
or quad output PWM mode. In Slave mode, the port is
RDx pin
asynchronously readable and writable by the external WR LATD
or CK
world. WR PORTD
Data Latch TTL
The P SP ca n di rectly interface to an 8- bit
Q D
microprocessor data bus. The external microprocessor
can r ead or w rite th e P ORTD lat ch a s an 8 -bit la tch.
RD PORTD ENEN
Setting the control bit, PSPMODE, enables the PORTE
I/O pins to become control inputs for the microprocessor
port. When set, port pin RE0 is the RD input, RE1 is the
WR input and RE2 is the CS (Chip Select) input. For this
RD LATD
functionality, the corresponding data direction bits of the
TRISE r egister ( TRISE<2:0>) must be conf igured as
inputs (set) and the ANSEL<7:5> bits must be cleared. Set Interrupt Flag
PSPIF (PIR1<7>)
A write to the PSP occurs when both the CS and WR
lines are first detected low and ends when either are
detected high. The PSPIF and IBF flag bits are both set PORTE Pins
when the write ends.
Read
A read from the PSP occurs when both the CS and RD TTL RD
lines are first detected low. The data in PORTD is read Chip Select
out and the OBF bit is clear. If the user writes new data TTL CS
to PORTD to set OBF, the data is immediately read out;
however, the OBF bit is not set. Write
TTL WR
When either the CS or RD lines are detected high, the
PORTD pins return to the input state and the PSPIF bit
is set. User applications should wait for PSPIF to be set Note: I/O pins have diode protection to VDD and VSS.
before servicing the PSP; when this happens, the IBF
and OBF bits can be polled and the appropriate action
taken.

 2010 Microchip Technology Inc. DS41303G-page 139

PIC18F2XK20/4XK20
FIGURE 10-3: PARALLEL SLAVE PORT WRITE WAVEFORMS
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

CS

WR

RD

PORTD<7:0>

IBF

OBF

PSPIF

FIGURE 10-4: PARALLEL SLAVE PORT READ WAVEFORMS

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

CS

WR

RD

PORTD<7:0>

IBF

OBF

PSPIF

DS41303G-page 140  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 10-11: REGISTERS ASSOCIATED WITH PARALLEL SLAVE PORT
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
PORTD(1) RD7 RD6 RD5 RD4 RD3 RD2 RD1 RD0 62
LATD(1) PORTD Data Latch Register (Read and Write to Data Latch) 62
TRISD(1) PORTD Data Direction Control Register 62
PORTE — — — — RE3 RE2(1) RE1(1) RE0(1) 62
LATE(1) — — — — — LATE Data Output bits 62
TRISE(1) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 62
SLRCON — — — SLRE(1) SLRD(1) SLRC SLRB SLRA 63
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF (1)
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
ANSEL ANS7(1) ANS6(1) ANS5(1) ANS4 ANS3 ANS2 ANS1 ANS0 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Parallel Slave Port.
Note 1: Unimplemented on PIC18F2XK20 devices.

 2010 Microchip Technology Inc. DS41303G-page 141

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 142  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
11.0 CAPTURE/COMPARE/PWM The Capture and Compare operations described in this
chapter ap ply to b oth s tandard and enhanced C CP
(CCP) MODULES
modules.
PIC18F2XK20/4XK20 dev ices hav e tw o C CP
Note: Throughout th is s ection and Section 16.0
Capture/Compare/PWM) mo dules. Each mo dule
“Enhanced Capture/Compare/PWM (ECCP)
contains a 16-bit register which can operate as a 16-bit
Module”, ref erences to th e re gister a nd bi t
Capture register, a 16-bit Compare register or a PWM
names fo r C CP m odules a re r eferred t o
Master/Slave Duty Cycle register.
generically by the use of ‘x’ or ‘y’ in place of the
CCP1 is implemented as an enhanced CCP module with specific mo dule n umber. T hus, “ CCPxCON”
standard C apture and C ompare mod es an d en hanced might refe r to th e c ontrol re gister fo r CCP1 ,
PWM modes. The ECCP implementation is discussed in CCP2 o r E CCP1. “CCPxCON” i s u sed
Section 16.0 “Enhanced Capture/Compare/PWM throughout th ese se ctions to refe r to th e
(ECCP) Module”. CCP2 is implemented as a standard module control register, regardless of whether
CCP module without the enhanced features. the CCP mo dule is a stan dard or en hanced
implementation.

REGISTER 11-1: CCP2CON: STANDARD CAPTURE/COMPARE/PWM CONTROL REGISTER

U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 Unimplemented: Read as ‘0’

bit 5-4 DC2B<1:0>: PWM Duty Cycle bit 1 and bit 0 for CCP2 Module
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs (bit 1 and bit 0) of the 10-bit PWM duty cycle. The eight MSbs
(DC2B<9:2>) of the duty cycle are found in CCPR2L.
bit 3-0 CCP2M<3:0>: CCP2 Mode Select bits
0000 = Capture/Compare/PWM disabled (resets CCP2 module)
0001 = Reserved
0010 = Compare mode, toggle output on match (CCP2IF bit is set)
0011 = Reserved
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode: initialize CCP2 pin low; on compare match, force CCP2 pin high
(CCP2IF bit is set)
1001 = Compare mode: initialize CCP2 pin high; on compare match, force CCP2 pin low
(CCP2IF bit is set)
1010 = Compare mode: generate software interrupt on compare match (CCP2IF bit is set,
CCP2 pin reflects I/O state)
1011 = Compare mode: trigger special event, reset timer, start A/D conversion on
CCP2 match (CCP2IF bit is set)
11xx =PWM mode

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PIC18F2XK20/4XK20
11.1 CCP Module Configuration The as signment of a par ticular t imer to a mo dule i s
determined b y th e T imer-to-CCP en able bi ts in t he
Each Capture/Compare/PWM mo dule is associated T3CON re gister (R egister 15-1). Bo th mo dules c an b e
with a con trol register (generically, C CPxCON) and a active at the same time and can share the same timer
data register (C CPRx). The da ta reg ister, in turn, is resource if they are configured to operate in the same
comprised of tw o 8-bi t registers: C CPRxL (low by te) mode (C apture/Compare or PWM ). The in teractions
and C CPRxH (h igh byt e). All regi sters a re bo th between the two modules are summarized in Figure 11-1
readable and writable. and Figure 11-2. I n A synchronous C ounter mode, t he
capture operation will not work reliably.
11.1.1 CCP MODULES AND TIMER
RESOURCES 11.1.2 CCP2 PIN ASSIGNMENT
The CCP modules utilize Timers 1, 2 or 3, de pending The pin assignment for CCP2 (Capture input, Compare
on the mode selected. Timer1 and Timer3 are available and PWM output) can change, based on device config-
to modules in C apture or Compare modes, w hile uration. The CCP2MX Configuration bit determines the
Timer2 is available for modules in PWM mode. pin w ith w hich CCP2 i s multiplexed. B y de fault, i t is
assigned to RC1 (CCP2MX = 1). If the Configuration bit
TABLE 11-1: CCP MODE – TIMER is cleared, CCP2 is multiplexed with RB3.
RESOURCE Changing the pin as signment of C CP2 doe s n ot
CCP/ECCP Mode Timer Resource automatically change any requirements for configuring
the port pin. U sers m ust always ve rify that the
Capture Timer1 or Timer3 appropriate TRIS re gister is co nfigured c orrectly f or
Compare Timer1 or Timer3 CCP2 operation, regardless of where it is located.
PWM Timer2

TABLE 11-2: INTERACTIONS BETWEEN CCP1 AND CCP2 FOR TIMER RESOURCES
CCP1 Mode CCP2 Mode Interaction
Capture Capture Each module can use TMR1 or TMR3 as the time base. The time base can be different
for each CCP.
Capture Compare CCP2 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Automatic A/D conversions on trigger event
can also be done. Operation of CCP1 could be affected if it is using the same timer as a
time base.
Compare Capture CCP1 can be configured for the Special Event Trigger to reset TMR1 or TMR3
(depending upon which time base is used). Operation of CCP2 could be affected if it is
using the same timer as a time base.
Compare Compare Either module can be configured for the Special Event Trigger to reset the time base.
Automatic A/D conversions on CCP2 trigger event can be done. Conflicts may occur if
both modules are using the same time base.
Capture PWM None
Compare PWM None
PWM (1) Capture None
PWM(1) Compare None
PWM (1)
PWM Both PWMs will have the same frequency and update rate (TMR2 interrupt).
Note 1: Includes standard and enhanced PWM operation.

DS41303G-page 144  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
11.2 Capture Mode EXAMPLE 11-1: CHANGING BETWEEN
CAPTURE PRESCALERS
In Capture m ode, the CCPRx H:CCPRxL re gister pair
(CCP2 SHOWN)
captures the 16-b it v alue of th e TM R1 or TM R3
registers when an event occurs on the corresponding CLRF CCP2CON ; Turn CCP module off
CCPx pin. An event is defined as one of the following: MOVLW NEW_CAPT_PS ; Load WREG with the
; new prescaler mode
• every falling edge ; value and CCP ON
• every rising edge MOVWF CCP2CON ; Load CCP2CON with
• every 4th rising edge ; this value

• every 16th rising edge

The ev ent is sel ected by the m ode sele ct bit s,
CCPxM<3:0> of the CCPxCON register. When a cap-
ture is made, t he interrupt r equest flag bit, C CPxIF, is
set; it must be cleared by sof tware. If another capture
occurs before the v alue in register CCPRx is read, the
old captured v alue is overw ritten by the new captured
value.

11.2.1 CCP PIN CONFIGURATION

In Capture mode, the appropriate CCPx pin should be
configured as an input by s etting th e co rresponding
TRIS direction bit.
Note: If the CCPx pin is configured as an output,
a w rite t o t he p ort ca n c ause a c apture
condition.

11.2.2 TIMER1/TIMER3 MODE SELECTION

The timers that are to be used with the capture feature
(Timer1 and/or Timer3) must be running in Timer mode
or Synchronized Counter mode. In Asynchronous Coun-
ter mode, the capture operation may not work. The timer
to be used w ith e ach C CP m odule i s s elected in the
T3CON r egister (se e Section 11.1.1 “CCP Modules
and Timer Resources”).

11.2.3 SOFTWARE INTERRUPT

When th e Capture mode i s changed, a f alse capture
interrupt may be generated. The user should keep the
CCPxIE interrupt enable bit clear to avoid false inter-
rupts. The inte rrupt fla g bit , C CPxIF, sh ould al so be
cleared following any such change in operating mode.

11.2.4 CCP PRESCALER

There are four prescaler settings in Capture mode; they
are specified as part of the operating mode selected by
the m ode select b its (CCPx M<3:0>). W henever th e
CCP module is turned off or Capture mode is disabled,
the prescaler counter is cleared. This means that any
Reset will clear the prescaler counter.
Switching from one capture prescaler to another may
generate an interrupt. Also, the prescaler counter will
not be cleared; therefore, the first capture may be from
a non -zero pre scaler. Ex ample 11-1 sho ws th e
recommended method for switching between capture
prescalers. Thi s ex ample also cl ears the pr escaler
counter and will not generate the “false” interrupt.

 2010 Microchip Technology Inc. DS41303G-page 145

PIC18F2XK20/4XK20
FIGURE 11-1: CAPTURE MODE OPERATION BLOCK DIAGRAM

TMR3H TMR3L
Set CCP1IF
T3CCP2 TMR3
CCP1 pin Enable
Prescaler and CCPR1H CCPR1L
 1, 4, 16 Edge Detect
TMR1
T3CCP2 Enable

CCP1CON<3:0> 4 TMR1H TMR1L

Set CCP2IF
4
Q1:Q4
4
CCP2CON<3:0>
T3CCP1 TMR3H TMR3L
T3CCP2
TMR3
Enable
CCP2 pin
Prescaler and CCPR2H CCPR2L
 1, 4, 16 Edge Detect
TMR1
Enable
T3CCP2
TMR1H TMR1L
T3CCP1

DS41303G-page 146  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
11.3 Compare Mode 11.3.2 TIMER1/TIMER3 MODE SELECTION
In Compare mode, the 16-bit CCPRx register value is Timer1 and/or Timer3 must be running in Timer mode
constantly compared against either the TMR1 or TMR3 or Synchronized Counter mode if the C CP module is
register pair value. When a match occurs, the CCPx pin using the compare feature. In As ynchronous Counter
can be: mode, the compare operation will not work reliably.

• driven high 11.3.3 SOFTWARE INTERRUPT MODE

• driven low
When the Generate Software Interrupt mode is chosen
• toggled (high-to-low or low-to-high) (CCPxM<3:0> = 1010), the corresponding CCPx pin is
• remain unchanged (that is, reflects the state of the not affected. Only the CCPxIF interrupt flag is affected.
I/O latch)
The action on the pin is based on the value of the mode 11.3.4 SPECIAL EVENT TRIGGER
select bits (CCPxM<3:0>). At the same time, the inter- Both CCP modules are equipped with a Special Event
rupt flag bit, CCPxIF, is set. Trigger. This is an internal hardware signal generated
in Compare mode to trigger actions by other modules.
11.3.1 CCP PIN CONFIGURATION The Special Event Trigger is enabled by selecting
The user must configure the CCPx pin as an output by the C ompare S pecial Ev ent T rigger m ode
clearing the appropriate TRIS bit. (CCPxM<3:0> = 1011).
For either CCP module, the Special Event Trigger resets
Note: Clearing the CCPxCON register will force
the tim er register p air for whichever tim er resource is
the CCPx compare output latch (depend-
currently assigned as the module’s t ime base. This
ing on device configuration) to the default
allows the CCPRx registers to serve as a programmable
low le vel. Th is is not t he PO RTB or
period register for either timer.
PORTC I/O data latch.
The Special Event Trigger for CCP2 can also start an
A/D conversion. In order to do this, the A/D converter
must already be enabled.

FIGURE 11-2: COMPARE MODE OPERATION BLOCK DIAGRAM

Special Event Trigger

Set CCP1IF (Timer1/Timer3 Reset)
CCPR1H CCPR1L
CCP1 pin

Compare Output S Q
Comparator
Match Logic
R
TRIS
4 Output Enable

CCP1CON<3:0>

0 TMR1H TMR1L 0

1 TMR3H TMR3L 1 Special Event Trigger

(Timer1/Timer3 Reset, A/D Trigger)
T3CCP1
T3CCP2
Set CCP2IF CCP2 pin

Compare Output S Q
Comparator
Match Logic
R
TRIS
4 Output Enable
CCPR2H CCPR2L
CCP2CON<3:0>

 2010 Microchip Technology Inc. DS41303G-page 147

PIC18F2XK20/4XK20
TABLE 11-3: REGISTERS ASSOCIATED WITH CAPTURE, COMPARE, TIMER1 AND TIMER3
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
RCON IPEN SBOREN — RI TO PD POR BOR 58
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
TRISB PORTB Data Direction Control Register 62
TRISC PORTC Data Direction Control Register 62
TMR1L Timer1 Register, Low Byte 60
TMR1H Timer1 Register, High Byte 60
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
TMR3H Timer3 Register, High Byte 61
TMR3L Timer3 Register, Low Byte 61
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 61
CCPR1L Capture/Compare/PWM Register 1, Low Byte 61
CCPR1H Capture/Compare/PWM Register 1, High Byte 61
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 61
CCPR2L Capture/Compare/PWM Register 2, Low Byte 61
CCPR2H Capture/Compare/PWM Register 2, High Byte 61
CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by Capture/Compare, Timer1 or Timer3.
Note 1: Not impemented on PIC18F2XK20 devices.

DS41303G-page 148  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
11.4 PWM Mode The PWM outp ut (Figure 11-4) has a tim e bas e
(period) and a time that the output stays high (duty
The P WM mo de ge nerates a P ulse-Width Mo dulated cycle).
signal on th e C CP2 p in fo r th e C CP mo dule a nd th e
P1A through P1D pins for the ECCP module. Hereafter
FIGURE 11-4: CCP PWM OUTPUT
the modulated output pin will be referred to as the CCPx
pin. T he d uty cycle, p eriod and resolution a re Period
determined by the following registers:
• PR2 Pulse Width
TMR2 = PR2
• T2CON
TMR2 = CCPRxL:DCxB<1:0>
• CCPRxL
• CCPxCON TMR2 = 0

In Puls e-Width Mo dulation (PW M) m ode, the C CP

module produces up to a 10-bit resolution PWM output
on th e C CPx pi n. Since the CCPx p in is m ultiplexed
with the PORT data latch, the TRIS for that pin must be
cleared to enable the CCPx pin output driver.
Note: Clearing the C CPxCON re gister w ill
relinquish CCPx control of the CCPx pin.
Figure 11.1.1 s hows a simplified bl ock dia gram of
PWM operation.
Figure 11-4 s hows a typical w aveform o f the PW M
signal.
For a step-by-step procedure on how to set up the CCP
module f or P WM op eration, se e Section 11.4.7
“Setup for PWM Operation”.

FIGURE 11-3: SIMPLIFIED PWM BLOCK

DIAGRAM
DCxB<1:0>
Duty Cycle Registers

CCPRxL

CCPRxH(2) (Slave)
CCPx

Comparator R Q

(1) S
TMR2
TRIS

Comparator
Clear Timer2,
toggle CCPx pin and
latch duty cycle
PR2

Note 1: The 8-bit timer TMR2 register is concatenated

with the 2-bit internal system clock (FOSC), or
2 bits of the prescaler, to create the 10-bit time
base.
2: In PWM mode, CCPRxH is a read-only register.

 2010 Microchip Technology Inc. DS41303G-page 149

PIC18F2XK20/4XK20
11.4.1 PWM PERIOD 11.4.2 PWM DUTY CYCLE
The PWM pe riod is specified by the PR 2 register of The PWM du ty cycle is s pecified by w riting a 1 0-bit
Timer2. The PWM period can be calculated using the value to multiple re gisters: C CPRxL reg ister an d
formula of Equation 11-1. DCxB<1:0> bit s of the C CPxCON reg ister. Th e
CCPRxL contains the eight MSbs and the DCxB<1:0>
EQUATION 11-1: PWM PERIOD bits of the C CPxCON re gister co ntain the tw o LSbs.
CCPRxL and D CxB<1:0> bit s of the C CPxCON
PWM Period =   PR2  + 1   4  T OSC  register can be written to at any time. The duty cycle
(TMR2 Prescale Value) value is not latched into CCPRxH until after the period
completes (i.e ., a ma tch between PR2 a nd TM R2
Note: TOSC = 1/FOSC. registers occurs). While using the PWM, the CCPRxH
register is read-only.
When TMR2 is equal to PR2, the following three events Equation 11-2 is used to ca lculate the PWM pulse
occur on the next increment cycle: width.
• TMR2 is cleared Equation 11-3 is used to calculate the PWM duty cycle
• The CCPx pin is set. (Exception: If the PWM duty ratio.
cycle = 0%, the pin will not be set.)
• The PWM duty cycle is latched from CCPRxL into EQUATION 11-2: PULSE WIDTH
CCPRxH.
Pulse Width =  CCPRxL:DCxB<1:0>  
Note: The Timer2 post scaler ( see Section 14.1
T OSC  (TMR2 Prescale Value)
“Timer2 Operation”) is not used in t he
determination of the PWM frequency.

EQUATION 11-3: DUTY CYCLE RATIO

 CCPRxL:DCxB<1:0> 
Duty Cycle Ratio = -----------------------------------------------------------
4  PR2 + 1 

The CCPR xH re gister a nd a 2 -bit internal lat ch a re

used to double buffer the PWM duty cycle. This double
buffering is essential for glitchless PWM operation.
The 8 -bit timer TMR 2 regis ter i s conc atenated w ith
either the 2-bit internal system clock (FOSC), or 2 bits of
the prescaler, to create the 10-bit time base. The system
clock is used if the Timer2 prescaler is set to 1:1.
When the 10-bit time base matches the CCPR xH and
2-bit latch, th en the C CPx pi n is cl eared (see
Figure 11-3).

DS41303G-page 150  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
11.4.3 PWM RESOLUTION EQUATION 11-4: PWM RESOLUTION
The resolution determines the number of available duty
cycles for a given period. For example, a 10-bit resolution log  4  PR2 + 1  
Resolution = ------------------------------------------ bits
will result in 1024 discrete duty cycles, whereas an 8-bit log  2 
resolution will result in 256 discrete duty cycles.
The maximum PWM resolution is 10 bits when PR2 is
255. T he res olution i s a fu nction of th e PR 2 reg ister Note: If the pulse width value is greater than the
value as shown by Equation 11-4. period th e a ssigned PWM pi n(s) w ill
remain unchanged.

TABLE 11-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz

PWM Frequency 2.44 kHz 9.77 kHz 39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz
Timer rescaler 1, P , 6) ( 4 1 16 4 1 1 1 1
PR2 Value FFh FFh FFh 3Fh 1Fh 17h
Maximum Resolution (bits) 10 10 10 8 7 6.58

TABLE 11-5: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 20 MHz)

PWM Frequency 1.22 kHz 4.88 kHz 19.53 kHz 78.12 kHz 156.3 kHz 208.3 kHz
Timer Prescale (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0xFF 0xFF 0xFF 0x3F 0x1F 0x17
Maximum Resolution (bits) 10 10 10 8 7 6.6

TABLE 11-6: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 8 MHz)

PWM Frequency 1.22 kHz 4.90 kHz 19.61 kHz 76.92 kHz 153.85 kHz 200.0 kHz
Timer Prescale (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0x65 0x65 0x65 0x19 0x0C 0x09
Maximum Resolution (bits) 8 8 8 6 5 5

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PIC18F2XK20/4XK20
11.4.4 OPERATION IN POWER-MANAGED 11.4.7 SETUP FOR PWM OPERATION
MODES The following steps should be taken when configuring
In Sle ep mode, the TM R2 register will no t in crement the CCP module for PWM operation:
and the state of the module will not change. If the CCPx 1. Disable the PWM pin (CCPx) output drivers by
pin is driving a value, it will continue to drive that value. setting the associated TRIS bit.
When the device wakes up, TMR2 will continue from its
2. For the ECCP module only: Select the desired
previous state.
PWM outputs (P1A through P1D) by setting the
In PRI_IDLE mode, the primary clock will continue to appropriate steering bi ts of the P STRCON
clock the C CP m odule w ithout ch ange. In a ll oth er register.
power-managed modes, the selected power-managed 3. Set the PWM period by loading the PR2 register.
mode c lock w ill clock Timer2. Ot her power-managed
4. Configure the CCP module for the PWM mode
mode cl ocks will m ost li kely b e dif ferent th an th e
by lo ading th e C CPxCON regi ster w ith th e
primary clock frequency.
appropriate values.
11.4.5 CHANGES IN SYSTEM CLOCK 5. Set the PWM duty cycle by loading the CCPRxL
FREQUENCY register and CCPx bits of the CCPxCON register.
6. Configure and start Timer2:
The PWM frequency is derived from the system clock
frequency. Any changes in the system clock frequency • Clear the TMR2IF interrupt flag bit of the
will re sult in ch anges to the PWM freq uency. Se e PIR1 register.
Section 2.0 “Oscillator Module (With Fail-Safe • Set the Timer2 prescale value by loading the
Clock Monitor)” for additional details. T2CKPS bits of the T2CON register.
• Enable Timer2 by setting the TMR2ON bit of
11.4.6 EFFECTS OF RESET the T2CON register.
Any Re set will forc e a ll port s to Inp ut m ode an d th e 7. Enable PWM output after a new PWM cycle has
CCP registers to their Reset states. started:
• Wait until Timer2 overflows (TMR2IF bit of
the PIR1 register is set).
• Enable the CCPx pin output driver by
clearing the associated TRIS bit.

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 PIC18F2XK20/4XK20
TABLE 11-7: REGISTERS ASSOCIATED WITH PWM AND TIMER2
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
RCON IPEN SBOREN — RI TO PD POR BOR 58
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
TRISB PORTB Data Direction Control Register 62
TRISC PORTC Data Direction Control Register 62
TMR2 Timer2 Register 60
PR2 Timer2 Period Register 60
T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 60
CCPR1L Capture/Compare/PWM Register 1, Low Byte 61
CCPR1H Capture/Compare/PWM Register 1, High Byte 61
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 61
CCPR2L Capture/Compare/PWM Register 2, Low Byte 61
CCPR2H Capture/Compare/PWM Register 2, High Byte 61
CCP2CON — — DC2B1 DC2B0 CCP2M3 CCP2M2 CCP2M1 CCP2M0 61
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1 PSSBD0 61
PWM1CON PRSEN PDC6 PDC5 PDC4 PDC3 PDC2 PDC PDC0 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PWM or Timer2.
Note 1: Not implemented on PIC18F2XK20 devices.

 2010 Microchip Technology Inc. DS41303G-page 153

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 154  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
12.0 TIMER0 MODULE The T0C ON reg ister (R egister 12-1) controls al l
aspects of the mo dule’s op eration, including the
The T imer0 mo dule in corporates the fol lowing fe a- prescale selection. It is both readable and writable.
tures:
A simplified block diagram of the Timer0 module in 8-bit
• Software selectable operation as a timer or coun- mode is show n in Figure 12-1. Figure 12-2 show s a
ter in both 8-bit or 16-bit modes simplified block diagram of the Timer0 module in 16-bit
• Readable and writable registers mode.
• Dedicated 8-bit, software programmable
prescaler
• Selectable clock source (internal or external)
• Edge select for external clock
• Interrupt-on-overflow
REGISTER 12-1: T0CON: TIMER0 CONTROL REGISTER
R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 TMR0ON: Timer0 On/Off Control bit

1 = Enables Timer0
0 = Stops Timer0
bit 6 T08BIT: Timer0 8-bit/16-bit Control bit
1 = Timer0 is configured as an 8-bit timer/counter
0 = Timer0 is configured as a 16-bit timer/counter
bit 5 T0CS: Timer0 Clock Source Select bit
1 = Transition on T0CKI pin
0 = Internal instruction cycle clock (CLKOUT)
bit 4 T0SE: Timer0 Source Edge Select bit
1 = Increment on high-to-low transition on T0CKI pin
0 = Increment on low-to-high transition on T0CKI pin
bit 3 PSA: Timer0 Prescaler Assignment bit
1 = TImer0 prescaler is NOT assigned. Timer0 clock input bypasses prescaler.
0 = Timer0 prescaler is assigned. Timer0 clock input comes from prescaler output.
bit 2-0 T0PS<2:0>: Timer0 Prescaler Select bits
111 = 1:256 prescale value
110 = 1:128 prescale value
101 = 1:64 prescale value
100 = 1:32 prescale value
011 = 1:16 prescale value
010 = 1:8 prescale value
001 = 1:4 prescale value
000 = 1:2 prescale value

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PIC18F2XK20/4XK20
12.1 Timer0 Operation 12.2 Timer0 Reads and Writes in
Timer0 can operate as either a timer or a counter; the
16-Bit Mode
mode is se lected w ith the T 0CS bi t of th e T0 CON TMR0H is not the actual high byte of Timer0 in 16-bit
register. In T imer mo de (T0 CS = 0), th e module mode; it is actually a buffered version of the real high
increments on every clock by default unless a different byte of Timer0 w hich i s n either directly readable n or
prescaler va lue is se lected (see Section 12.3 writable (refer to Figure 12-2). TMR0H is updated with
“Prescaler”). Timer0 incrementing is inhibited for two the contents of the high byte of Timer0 during a read of
instruction cycles following a TMR0 register write. The TMR0L. This provides the ability to read all 16 bits of
user can work around this by adjusting the value written Timer0 without the need to v erify that the read of the
to the TMR0 register to compensate for the anticipated high and low b yte w ere val id. Inv alid re ads c ould
missing increments. otherwise occur due to a rollover between successive
The Counter mode is selected by setting the T0CS bit reads of the high and low byte.
(= 1). In this mode, Timer0 increments either on every Similarly, a w rite to the high byte of Timer0 must also
rising or falling edge of pin RA4/T0CKI. The increment- take place through the TMR0H Buffer register. Writing
ing e dge is de termined b y t he T imer0 So urce Edg e to TMR0H does not directly affect Timer0. Instead, the
Select bit, T0SE of the T0CON register; clearing this bit high byte of T imer0 i s upd ated w ith the co ntents of
selects th e ris ing ed ge. Restrictions on the ext ernal TMR0H when a write occurs to TMR0L. This allows all
clock input are discussed below. 16 bits of Timer0 to be updated at once.
An external clock source can be used to drive Timer0;
however, it mu st me et ce rtain requirements ( see
Table 26-11) to ensure that the external clock can be
synchronized w ith th e i nternal ph ase c lock (TOSC).
There i s a d elay between s ynchronization and th e
onset of incrementing the timer/counter.

FIGURE 12-1: TIMER0 BLOCK DIAGRAM (8-BIT MODE)

FOSC/4 0
0
Sync with Set
1 Internal TMR0L TMR0IF
T0CKI pin Programmable 1 Clocks on Overflow
Prescaler
T0SE (2 TCY Delay)
T0CS 8
3
T0PS<2:0>
8
PSA Internal Data Bus

Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.

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 PIC18F2XK20/4XK20
FIGURE 12-2: TIMER0 BLOCK DIAGRAM (16-BIT MODE)

FOSC/4 0
0
Sync with Set
Internal TMR0
1 TMR0L High Byte TMR0IF
T0CKI pin Programmable 1 Clocks on Overflow
Prescaler 8
T0SE (2 TCY Delay)
T0CS 3 Read TMR0L
T0PS<2:0>
Write TMR0L
PSA
8
8
TMR0H

8
8
Internal Data Bus

Note: Upon Reset, Timer0 is enabled in 8-bit mode with clock input from T0CKI max. prescale.

12.3 Prescaler 12.3.1 SWITCHING PRESCALER

ASSIGNMENT
An 8-bit counter is available as a prescaler for the Timer0
module. The prescaler is not directly readable or writable; The pre scaler as signment is fu lly un der s oftware
its v alue i s se t by t he P SA and T 0PS<2:0> b its of t he control and can be changed “on-the-fly” during program
T0CON re gister w hich d etermine the pr escaler execution.
assignment and prescale ratio.
Clearing the PSA bi t assigns th e prescaler to th e 12.4 Timer0 Interrupt
Timer0 m odule. When t he prescaler i s assigned, The TMR0 interrupt is generated when the TMR0 reg-
prescale va lues from 1:2 through 1:2 56 in integer ister overflows from FFh to 00h in 8-bit mode, or from
power-of-2 increments are selectable. FFFFh to 0000h in 16-bit mode. This overflow sets the
When assigned to the Timer0 module, all instructions TMR0IF flag bit. The interrupt can be masked by clear-
writing to the TMR0 register (e.g., CLRF TMR0, MOVWF ing the TM R0IE bit of the IN TCON register. Befo re
TMR0, BSF TMR0, etc.) clear the prescaler count. re-enabling the in terrupt, the TM R0IF bi t m ust b e
cleared by software in the Interrupt Service Routine.
Note: Writing to T MR0 w hen the prescaler i s
assigned to Timer0 will clear the prescaler Since Timer0 is shut down in Sleep mode, the TMR0
count b ut will no t c hange the pr escaler interrupt cannot awaken the processor from Sleep.
assignment.

TABLE 12-1: REGISTERS ASSOCIATED WITH TIMER0

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
TMR0L Timer0 Register, Low Byte 60
TMR0H Timer0 Register, High Byte 60
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
T0CON TMR0ON T08BIT T0CS T0SE PSA T0PS2 T0PS1 T0PS0 60
TRISA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 62
Legend: Shaded cells are not used by Timer0.
Note 1: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.

 2010 Microchip Technology Inc. DS41303G-page 157

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 158  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
13.0 TIMER1 MODULE A s implified bl ock d iagram of th e T imer1 mo dule i s
shown in Figure 13-1. A block diagram of the module’s
The T imer1 timer/counter mo dule inc orporates the operation in Read/Write mode is shown in Figure 13-2.
following features:
The module incorporates its own low-power oscillator
• Software selectable operation as a 16-bit timer or to provide an add itional cl ocking op tion. The Timer1
counter oscillator can also be used as a low-power clock source
• Readable and writable 8-bit registers (TMR1H for the microcontroller in power-managed operation.
and TMR1L) Timer1 can also be used to provide R eal-Time C lock
• Selectable internal or external clock source and (RTC) functionality to applications with only a minimal
Timer1 oscillator options addition of external components and code overhead.
• Interrupt-on-overflow Timer1 is controlled through th e T1C ON Control
• Reset on CCP Special Event Trigger register (Register 13-1). It al so co ntains th e T imer1
• Device clock status flag (T1RUN) Oscillator En able b it (T 1OSCEN). T imer1 ca n b e
enabled or disabled by setting or cl earing control bit,
TMR1ON of the T1CON register.

REGISTER 13-1: T1CON: TIMER1 CONTROL REGISTER

R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 RD16: 16-bit Read/Write Mode Enable bit

1 = Enables register read/write of TImer1 in one 16-bit operation
0 = Enables register read/write of Timer1 in two 8-bit operations
bit 6 T1RUN: Timer1 System Clock Status bit
1 = Main system clock is derived from Timer1 oscillator
0 = Main system clock is derived from another source
bit 5-4 T1CKPS<1:0>: Timer1 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 3 T1OSCEN: Timer1 Oscillator Enable bit
1 = Timer1 oscillator is enabled
0 = Timer1 oscillator is shut off
The oscillator inverter and feedback resistor are turned off to eliminate power drain.
bit 2 T1SYNC: Timer1 External Clock Input Synchronization Select bit
When TMR1CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR1CS = 0:
This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.
bit 1 TMR1CS: Timer1 Clock Source Select bit
1 = External clock from pin RC0/T1OSO/T13CKI (on the rising edge)
0 = Internal clock (FOSC/4)
bit 0 TMR1ON: Timer1 On bit
1 = Enables Timer1
0 = Stops Timer1

 2010 Microchip Technology Inc. DS41303G-page 159

PIC18F2XK20/4XK20
13.1 Timer1 Operation instruction cycle (FOSC/4). When the bit is set, Timer1
increments on ev ery ris ing e dge of e ither th e Timer1
Timer1 can operate in one of the following modes: external clock input or the Timer1 oscillator, if enabled.
• Timer When the Timer1 oscillator is ena bled, the dig ital
• Synchronous Counter circuitry a ssociated w ith th e R C1/T1OSI an d
• Asynchronous Counter RC0/T1OSO/T13CKI pins is disabled. This means the
values o f T RISC<1:0> a re i gnored a nd t he p ins ar e
The operating mode is determined by the clock select
read as ‘0’.
bit, TMR1CS of the T1CON register. When TMR1CS is
cleared ( = 0), T imer1 inc rements o n ev ery int ernal

FIGURE 13-1: TIMER1 BLOCK DIAGRAM

Timer1 Oscillator Timer1 Clock Input
On/Off 1

T1OSO/T13CKI 1
Prescaler Synchronize
FOSC/4 1, 2, 4, 8 Detect
0
Internal
Clock 0
T1OSI 2
Sleep Input
T1OSCEN(1) TMR1CS Timer1
On/Off
T1CKPS<1:0>
T1SYNC
TMR1ON

TMR1 Set
Clear TMR1 TMR1L TMR1IF
High Byte
(CCP Special Event Trigger) on Overflow

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

FIGURE 13-2: TIMER1 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)

Timer1 Oscillator Timer1 Clock Input
1
T1OSO/T13CKI 1
Prescaler Synchronize
FOSC/4 1, 2, 4, 8 Detect
0
Internal
Clock 0
T1OSI 2
Sleep Input
T1OSCEN(1) TMR1CS Timer1
T1CKPS<1:0> On/Off
T1SYNC
TMR1ON

TMR1 Set
Clear TMR1 TMR1L TMR1IF
High Byte
(CCP Special Event Trigger) on Overflow
8

Read TMR1L
Write TMR1L
8
8
TMR1H

8
8
Internal Data Bus

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

DS41303G-page 160  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
13.2 Clock Source Selection 13.2.3 READING AND WRITING TIMER1 IN
ASYNCHRONOUS COUNTER
The TM R1CS bi t of the T1CON register is u sed to
MODE
select the clock source. When TMR1CS = 0, the clock
source is FOSC/4. When TMR1CS = 1, the clock source Reading TMR1H or TMR1L while the timer is running
is supplied externally. from an external asynchronous clock will ensure a valid
read (t aken c are o f in h ardware). Ho wever, the us er
13.2.1 INTERNAL CLOCK SOURCE should keep in mind that reading the 16-bit timer in two
When the i nternal c lock source is selected, the 8-bit values i tself, p oses c ertain p roblems, s ince the
TMR1H:TMR1L register pair will increment on multiples timer may overflow between the reads.
of TCY as determined by the Timer1 prescaler. For writes, it is recommended that the user simply stop
the tim er and write the desired values. A write
13.2.2 EXTERNAL CLOCK SOURCE contention may occur by writing to the timer registers,
When the external clock source is selected, the Timer1 while the register is incrementing. This may produce an
module may work as a timer or a counter. unpredictable value i n th e TM R1H:TTMR1L reg ister
pair.
When cou nting, T imer1 is incremented on the rising
edge of the external clock input T1CKI. In addition, the
Counter mod e clock can be s ynchronized to the
13.3 Timer1 Prescaler
microcontroller system clock or run asynchronously. Timer1 has four presc aler options allowing 1, 2, 4 or 8
If an ex ternal cl ock os cillator i s n eeded (a nd th e divisions of the cl ock input. The T1C KPS bit s of the
microcontroller is using the INTOSC without CLKOUT), T1CON register control the prescale counter . The
Timer1 can use the LP oscillator as a clock source. prescale c ounter is not direc tly readabl e or w ritable;
however, the prescaler counter is cleared upon a write to
Note: In C ounter mode, a fall ing ed ge must be TMR1H or TMR1L.
registered by the cou nter prior to th e fir st
incrementing rising edge af ter one or more
13.4 Timer1 Operation in
of the following conditions (see Figure 13-3):
Asynchronous Counter Mode
• Timer1 is enabled after POR or BOR
Reset If control bit T1SYNC of the T1CON register is set, the
• A write to TMR1H or TMR1L external clock inp ut is not synchronized. The timer
continues to incre ment asy nchronous to the int ernal
• Timer1 is disabled (TMR1ON = 0)
phase clock s. The timer will continue to run during
when T1CKI is high then Timer1 is
Sleep and can gener ate an interr upt on overflow ,
enabled (TMR1ON = 1) when T1CKI
which w ill w ake-up t he processor . H owever, special
is low.
precautions in sof tware are needed to r ead/write the
timer ( see Section 13.2.3 “Reading and Writing
Timer1 in Asynchronous Counter Mode”).
Note 1: When switching from s ynchronous to
asynchronous operation, it is possible to
skip an increment. When switching from
asynchronous to synchronous operation,
it is po ssible t o p roduce an additional
increment.

FIGURE 13-3: TIMER1 INCREMENTING EDGE

T1CKI = 1
when TMR1
Enabled

T1CKI = 0
when TMR1
Enabled

Note 1: Arrows indicate counter increments.

2: In Counter mode, a falling edge must be registered by the counter prior to the first incrementing rising edge of
the clock.

 2010 Microchip Technology Inc. DS41303G-page 161

PIC18F2XK20/4XK20
13.5 Timer1 16-Bit Read/Write Mode TABLE 13-1: CAPACITOR SELECTION FOR
THE TIMER OSCILLATOR
Timer1 can be configured for 16-bit reads and w rites
(see Fig ure 13-2). Whe n th e RD16 c ontrol bi t of th e Osc Type Freq C1 C2
T1CON re gister is se t, th e ad dress for TM R1H i s LP 32 kHz 27 pF (1)
27 pF(1)
mapped to a buffer register for the high byte of Timer1.
A read from TMR1L will load the contents of the high Note 1: Microchip suggests these values only as a
byte of T imer1 in to th e Timer1 hig h by te buf fer. Thi s starting point in va lidating the os cillator
provides the user with the ability to accurately read all circuit.
16 bi ts of T imer1 w ithout t he ne ed t o de termine 2: Higher capacitance increases the stability
whether a read of the high byte, followed by a read of of th e o scillator bu t a lso i ncreases th e
the low byte, has become invalid due to a ro llover or start-up time.
carry between reads.
3: Since each resonator/crystal has its own
Writing to TM R1H does not d irectly affect T imer1. characteristics, the us er s hould consult
Instead, the hi gh by te of T imer1 is up dated w ith the the res onator/crystal m anufacturer for
contents o f T MR1H when a write oc curs to T MR1L. appropriate values of external
This allows all 16 bits of Timer1 to be updated at once. components.
The h igh by te of T imer1 i s n ot d irectly re adable or 4: Capacitor values are for design guidance
writable in thi s mode. All reads and w rites must take only.
place through t he T imer1 H igh B yte Buffer register.
Writes to TM R1H do not clear the T imer1 pre scaler. 13.6.1 USING TIMER1 AS A
The prescaler is only cleared on writes to TMR1L. CLOCK SOURCE
The T imer1 os cillator is al so available a s a cl ock
13.6 Timer1 Oscillator source in power-managed modes. By setting the clock
An on-chip cryst al oscillator circuit is incorporated select bits, SCS<1:0> of the OSCCON register, to ‘01’,
between pin s T1OSI (input) and T1OSO ( amplifier the device switches to SEC_RUN mode; both the CPU
output). It is enab led by se tting the T imer1 Os cillator and peripherals are clocked from the Timer1 oscillator.
Enable bit, T1O SCEN of the T1C ON regis ter. The If the IDLEN bit of the OSCCON register is cleared and
oscillator is a low-power circuit rated for 32 kHz crystals. a SLEEP i nstruction i s executed, th e d evice e nters
It will continue to run during all power-managed modes. SEC_IDLE mo de. Additional details are av ailable in
The c ircuit for a typ ical LP os cillator is show n in Section 3.0 “Power-Managed Modes”.
Figure 13-4. Table 13-1 sh ows the capacitor sele ction Whenever t he Timer1 os cillator i s p roviding t he c lock
for the Timer1 oscillator. source, the Timer1 system clock status flag, T1RUN of
The user must provide a software time delay to ensure the T1CON register, is set. This can be used to deter-
proper start-up of the Timer1 oscillator. mine the controller’s current clocking mode. It can also
indicate which clock source is currently being used by
FIGURE 13-4: EXTERNAL the Fai l-Safe Clo ck Monitor. If the C lock M onitor i s
enabled and the Timer1 oscillator fails while providing
COMPONENTS FOR THE
the c lock, p olling the T1 RUN b it will i ndicate whether
TIMER1 LP OSCILLATOR
the clock is being provided by the Timer1 oscillator or
C1 another source.
PIC® MCU
27 pF
T1OSI

XTAL
32.768 kHz

T1OSO
C2
27 pF

Note: See t he Not es wit h Table 13-1 f or addit ional

information about capacitor selection.

DS41303G-page 162  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
13.6.2 LOW-POWER TIMER1 OPTION 13.7 Timer1 Interrupt
The Timer1 oscillator can operate at two distinct levels The TM R1 register p air (T MR1H:TMR1L) i ncrements
of power consumption based on device configuration. from 00 00h to FFF Fh an d roll s ov er to 0000h. Th e
When the LPT1OSC C onfiguration bi t of th e Timer1 interrupt, if enabled, is generated on overflow,
CONFIG3H register is set, the Timer1 oscillator oper- which is latched in the TMR1IF interrupt flag bit of the
ates in a low-power mode. When LPT1OSC is not set, PIR1 register. This interrupt can be enabled or disabled
Timer1 operates at a higher power level. Power con- by setting or clearing the TMR1IE Interrupt Enable bit
sumption for a p articular mode is relatively constant, of the PIE1 register.
regardless of the device’s operating mode. The default
Timer1 configuration is the higher power mode.
13.8 Resetting Timer1 Using the CCP
As th e l ow-power T imer1 m ode te nds t o b e m ore Special Event Trigger
sensitive t o i nterference, hi gh no ise en vironments ma y
cause some oscillator instability. The low-power option is, If either of the CCP modules is configured to use Timer1
therefore, b est suited fo r l ow no ise ap plications w here and generate a Special Event Trigger in Compare mode
power conservation is an important design consideration. (CCP1M<3:0> or CCP2M<3:0> = 1011), this signal will
reset Timer1. The trigger from C CP2 will also start an
13.6.3 TIMER1 OSCILLATOR LAYOUT A/D conversion if the A /D module is enabled (see
CONSIDERATIONS Section 11.3.4 “Special Event Trigger” for m ore
information).
The T imer1 o scillator c ircuit dra ws v ery li ttle po wer
during operation. Due to the low-power nature of the The module must be configured as either a timer or a
oscillator, it m ay also be s ensitive to rap idly changing synchronous counter to take advantage of this feature.
signals in close proximity. When used this way, the CCPRH:CCPRL register pair
effectively becomes a period register for Timer1.
The oscillator circuit, shown in Figure 13-4, should be
located as c lose as p ossible to t he m icrocontroller. If Timer1 i s ru nning i n As ynchronous C ounter m ode,
There should be no circuits passing within the oscillator this Reset operation may not work.
circuit boundaries other than VSS or VDD. In th e e vent that a write to T imer1 c oincides wi th a
If a high-speed circuit must be located near the oscilla- special Ev ent T rigger, the write op eration w ill take
tor (such as the CCP1 pin in Output Compare or PWM precedence.
mode, or the primary oscillator using the OSC2 pin), a Note: The Special Event Triggers from the CCP2
grounded gua rd rin g aro und the oscillator ci rcuit, a s module will no t set th e TMR1 IF in terrupt
shown in Figure 13-5, may be helpful when used on a flag bit of the PIR1 register.
single-sided PCB or in addition to a ground plane.

FIGURE 13-5: OSCILLATOR CIRCUIT

WITH GROUNDED
GUARD RING
VDD

VSS

OSC1

OSC2

RC0

RC1

RC2

Note: Not drawn to scale.

 2010 Microchip Technology Inc. DS41303G-page 163

PIC18F2XK20/4XK20
13.9 Using Timer1 as a Real-Time Clock Since t he r egister p air i s 1 6 bits w ide, a 3 2.768 kHz
clock source will take 2 seconds to count up to over-
Adding an external LP oscillator to Timer1 (such as the flow. To force the overflow at the required one-second
one de scribed in Section 13.6 “Timer1 Oscillator” intervals, it is nec essary to preload it; the simplest
above) gives users the option to include RTC function- method is to set the MSb of TMR1H with a BSF instruc-
ality to their applications. This is accomplished with an tion. Note that the TMR1L register is never preloaded
inexpensive watch crystal to provide an accurate time or al tered; doing so m ay i ntroduce cumulative e rror
base and several lines of application code to calculate over many cycles.
the time. When operating in Sleep mode and using a
battery or su percapacitor as a p ower so urce, i t c an For this method to be accurate, Timer1 must operate in
completely el iminate t he n eed for a s eparate R TC Asynchronous mode and the Timer1 overflow interrupt
device and battery backup. must be e nabled (PIE1< 0> = 1), as sh own i n t he
routine, RTCinit. The Timer1 oscillator must also be
The application co de rou tine, RTCisr, sho wn in enabled and running at all times.
Example 13-1, demonstrates a s imple m ethod to
increment a c ounter at on e-second intervals using an
Interrupt Serv ice R outine. Inc rementing the TM R1
register pair to overflow triggers the interrupt and calls
the routine, which increments the seconds counter by
one; additional counters fo r m inutes and h ours a re
incremented on overflows of th e les s s ignificant
counters.

EXAMPLE 13-1: IMPLEMENTING A REAL-TIME CLOCK USING A TIMER1 INTERRUPT SERVICE

RTCinit
MOVLW 80h ; Preload TMR1 register pair
MOVWF TMR1H ; for 1 second overflow
CLRF TMR1L
MOVLW b’00001111’ ; Configure for external clock,
MOVWF T1CON ; Asynchronous operation, external oscillator
CLRF secs ; Initialize timekeeping registers
CLRF mins ;
MOVLW .12
MOVWF hours
BSF PIE1, TMR1IE ; Enable Timer1 interrupt
RETURN
RTCisr
BSF TMR1H, 7 ; Preload for 1 sec overflow
BCF PIR1, TMR1IF ; Clear interrupt flag
INCF secs, F ; Increment seconds
MOVLW .59 ; 60 seconds elapsed?
CPFSGT secs
RETURN ; No, done
CLRF secs ; Clear seconds
INCF mins, F ; Increment minutes
MOVLW .59 ; 60 minutes elapsed?
CPFSGT mins
RETURN ; No, done
CLRF mins ; clear minutes
INCF hours, F ; Increment hours
MOVLW .23 ; 24 hours elapsed?
CPFSGT hours
RETURN ; No, done
CLRF hours ; Reset hours
RETURN ; Done

DS41303G-page 164  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 13-2: REGISTERS ASSOCIATED WITH TIMER1 AS A TIMER/COUNTER
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
TMR1L Timer1 Register, Low Byte 60
TMR1H Timer1 Register, High Byte 60
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
Legend: Shaded cells are not used by the Timer1 module.
Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear.

 2010 Microchip Technology Inc. DS41303G-page 165

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 166  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
14.0 TIMER2 MODULE 14.1 Timer2 Operation
The T imer2 m odule tim er i ncorporates t he following In normal operation, TMR2 is incremented from 00h on
features: each clock (FOSC/4). A 4-b it counter/prescaler on the
clock i nput gi ves direct in put, divide-by-4 and
• 8-bit timer and period registers (TMR2 and PR2,
divide-by-16 p rescale o ptions; th ese ar e s elected b y
respectively)
the prescaler control bits, T2CKPS<1:0> of the T2CON
• Readable and writable (both registers) register. The value of TMR2 is compared to that of the
• Software programmable prescaler (1:1, 1:4 and period regi ster, PR 2, on ea ch clock cycle. When the
1:16) two values match, the comparator generates a m atch
• Software programmable postscaler (1:1 through signal as the timer output. This signal also resets the
1:16) value of TMR2 to 00h on the next cycle and drives the
• Interrupt on TMR2-to-PR2 match output counter/postscaler (see Section 14.2 “Timer2
• Optional use as the shift clock for the MSSP Interrupt”).
module The TMR2 and PR2 registers are both directly readable
The module is controlled through the T2CON register and w ritable. The TM R2 reg ister i s c leared on an y
(Register 14-1), w hich en ables or di sables t he timer device Reset, w hereas the PR 2 register ini tializes to
and c onfigures the pre scaler and pos tscaler. Timer2 FFh. Both the pre scaler and postscaler co unters are
can be shut off by clearing control bit, TMR2ON of the cleared on the following events:
T2CON register, to minimize power consumption. • a write to the TMR2 register
A simplified block diagram of the module is shown in • a write to the T2CON register
Figure 14-1. • any device Reset (Power-on Reset, MCLR Reset,
Watchdog Timer Reset or Brown-out Reset)
TMR2 is not cleared when T2CON is written.

REGISTER 14-1: T2CON: TIMER2 CONTROL REGISTER

U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6-3 T2OUTPS<3:0>: Timer2 Output Postscale Select bits
0000 = 1:1 Postscale
0001 = 1:2 Postscale
•
•
•
1111 = 1:16 Postscale
bit 2 TMR2ON: Timer2 On bit
1 = Timer2 is on
0 = Timer2 is off
bit 1-0 T2CKPS<1:0>: Timer2 Clock Prescale Select bits
00 = Prescaler is 1
01 = Prescaler is 4
1x = Prescaler is 16

 2010 Microchip Technology Inc. DS41303G-page 167

PIC18F2XK20/4XK20
14.2 Timer2 Interrupt 14.3 Timer2 Output
Timer2 can also generate an optional device interrupt. The unscaled output of TMR2 is available primarily to
The Timer2 output si gnal (TM R2-to-PR2 ma tch) pro- the CCP modules, where it is used as a time base for
vides the input for the 4-bit output counter/postscaler. operations in PWM mode.
This counter generates the TMR2 match interrupt flag Timer2 can be optionally used as the shift clock source
which is latched in TMR2IF of the PIR 1 register. The for the M SSP m odule ope rating in SPI m ode. Add i-
interrupt is enabled by setting the TMR2 Match Inter- tional information is provided in Section 17.0 “Master
rupt Enable bit, TMR2IE of the PIE1 register. Synchronous Serial Port (MSSP) Module”.
A range of 16 postscale options (from 1:1 through 1:16
inclusive) can be selected w ith the postscaler control
bits, T2OUTPS<3:0> of the T2CON register.

FIGURE 14-1: TIMER2 BLOCK DIAGRAM

4 1:1 to 1:16
T2OUTPS<3:0> Set TMR2IF
Postscaler
2
T2CKPS<1:0> TMR2 Output
(to PWM or MSSP)
TMR2/PR2
Reset Match
1:1, 1:4, 1:16
FOSC/4 TMR2 Comparator PR2
Prescaler
8 8
8
Internal Data Bus

TABLE 14-1: REGISTERS ASSOCIATED WITH TIMER2 AS A TIMER/COUNTER

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP (1)
ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
TMR2 Timer2 Register 60
T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 60
PR2 Timer2 Period Register 60
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer2 module.
Note 1: These bits are unimplemented on 28-pin devices; always maintain these bits clear.

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 PIC18F2XK20/4XK20
15.0 TIMER3 MODULE A s implified bl ock d iagram of th e T imer3 mo dule i s
shown in Figure 15-1. A block diagram of the module’s
The T imer3 mo dule tim er/counter incorporates these operation in Read/Write mode is shown in Figure 15-2.
features:
The Timer3 module is controlled through the T3CON
• Software selectable operation as a 16-bit timer or register (Register 15-1). It also selects the clock source
counter options fo r t he CCP m odules (see Section 11.1.1
• Readable and writable 8-bit registers (TMR3H “CCP Modules and Timer Resources” for more
and TMR3L) information).
• Selectable clock source (internal or external) with
device clock or Timer1 oscillator internal options
• Interrupt-on-overflow
• Module Reset on CCP Special Event Trigger

REGISTER 15-1: T3CON: TIMER3 CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 RD16: 16-bit Read/Write Mode Enable bit

1 = Enables register read/write of Timer3 in one 16-bit operation
0 = Enables register read/write of Timer3 in two 8-bit operations
bit 6,3 T3CCP<2:1>: Timer3 and Timer1 to CCPx Enable bits
1x = Timer3 is the capture/compare clock source for CCP1 and CP2
01 = Timer3 is the capture/compare clock source for CCP2 and
Timer1 is the capture/compare clock source for CCP1
00 = Timer1 is the capture/compare clock source for CCP1 and CP2
bit 5-4 T3CKPS<1:0>: Timer3 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 2 T3SYNC: Timer3 External Clock Input Synchronization Control bit
(Not usable if the device clock comes from Timer1/Timer3.)
When TMR3CS = 1:
1 = Do not synchronize external clock input
0 = Synchronize external clock input
When TMR3CS = 0:
This bit is ignored. Timer3 uses the internal clock when TMR3CS = 0.
bit 1 TMR3CS: Timer3 Clock Source Select bit
1 = External clock input from Timer1 oscillator or T13CKI (on the rising edge after the first
falling edge)
0 = Internal clock (FOSC/4)
bit 0 TMR3ON: Timer3 On bit
1 = Enables Timer3
0 = Stops Timer3

 2010 Microchip Technology Inc. DS41303G-page 169

PIC18F2XK20/4XK20
15.1 Timer3 Operation The operating mode is determined by the clock select
bit, TMR3CS of the T3CON register. When TMR3CS is
Timer3 can operate in one of three modes: cleared ( = 0), T imer3 inc rements o n ev ery int ernal
• Timer instruction cycle (FOSC/4). When the bit is set, Timer3
• Synchronous Counter increments on every rising edge of the Timer1 external
clock input or the Timer1 oscillator, if enabled.
• Asynchronous Counter
As with Timer1, the digital circuitry associated with the
RC1/T1OSI and RC0/T1OSO/T13CKI pins is disabled
when the Timer1 oscillator is enabled. This means the
values o f T RISC<1:0> a re i gnored a nd t he p ins ar e
read as ‘0’.

FIGURE 15-1: TIMER3 BLOCK DIAGRAM

Timer1 Oscillator Timer1 Clock Input
1
T1OSO/T13CKI 1
Prescaler Synchronize
FOSC/4 1, 2, 4, 8 Detect 0
Internal
Clock 0
T1OSI 2
Sleep Input
T1OSCEN(1) TMR3CS Timer3
On/Off
T3CKPS<1:0>
T3SYNC
TMR3ON

CCP1/CCP2 Special Event Trigger Clear TMR3 TMR3 Set

CCP1/CCP2 Select from T3CON<6,3> TMR3L High Byte TMR3IF
on Overflow

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

DS41303G-page 170  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 15-2: TIMER3 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)
Timer1 Oscillator Timer1 Clock Input
1
T13CKI/T1OSO 1
Prescaler Synchronize
FOSC/4 1, 2, 4, 8 Detect 0
Internal
Clock 0
T1OSI 2
Sleep Input
T1OSCEN(1) TMR3CS Timer3
T3CKPS<1:0> On/Off
T3SYNC
TMR3ON

CCP1/CCP2 Special Event Trigger Clear TMR3 TMR3 Set

CCP1/CCP2 Select from T3CON<6,3> TMR3L High Byte TMR3IF
on Overflow
8

Read TMR1L
Write TMR1L
8
8
TMR3H

8
8
Internal Data Bus

Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.

15.2 Timer3 16-Bit Read/Write Mode 15.3 Using the Timer1 Oscillator as the
Timer3 can be configured for 16-bit reads and w rites
Timer3 Clock Source
(see Fig ure 15-2). Whe n th e RD16 c ontrol bi t of th e The Timer1 internal oscillator may be used as the clock
T3CON re gister is se t, th e ad dress for TM R3H i s source for Timer3. The Timer1 oscillator is enabled by
mapped to a buffer register for the high byte of Timer3. setting the T1OSCEN bit of the T1CON register. To use
A read from TMR3L will load the contents of the high it as the Timer3 c lock s ource, the TMR3CS bit m ust
byte of Timer3 into the Timer3 High Byte Buffer regis- also be set. As pre viously noted, this also configures
ter. This provides the user with the ability to accurately Timer3 to i ncrement on e very ri sing e dge of th e
read all 16 bits of Timer1 without having to determine oscillator source.
whether a read of the high byte, followed by a read of
The T imer1 oscillator is des cribed in Section 13.0
the low by te, has become invalid due to a roll over
“Timer1 Module”.
between reads.
A write to the high byte of Timer3 must also take place 15.4 Timer3 Interrupt
through th e TM R3H Buf fer reg ister. The Timer3 hig h
byte is updated with t he contents of TM R3H w hen a The TM R3 register p air (T MR3H:TMR3L) i ncrements
write occurs to TMR3L. This allows a u ser to w rite all from 000 0h to FFFF h and ov erflows to 00 00h. The
16 bits to both the high and low bytes of Timer3 at once. Timer3 interrupt, if enabled, is g enerated on overflow
The h igh by te of T imer3 i s n ot d irectly re adable or and is latched in interrupt flag bit, TMR3IF of the PIR2
writable in thi s mode. All reads and w rites must take register. This interrupt can be enabled or disabled by
place through the Timer3 High Byte Buffer register. setting or c learing the T imer3 In terrupt Enab le bi t,
TMR3IE of the PIE2 register.
Writes to TM R3H do not clear the T imer3 pre scaler.
The prescaler is only cleared on writes to TMR3L.

 2010 Microchip Technology Inc. DS41303G-page 171

PIC18F2XK20/4XK20
15.5 Resetting Timer3 Using the CCP
Special Event Trigger
If eit her of t he C CP m odules is co nfigured to us e
Timer3 an d to ge nerate a S pecial Ev ent Trigger
in Compare mode (CCP1M<3:0> o r C CP2M<3:0> =
1011), this signal will reset Timer3. It will also start an
A/D conversion if th e A/D module is e nabled (se e
Section 11.3.4 “Special Event Trigger” for m ore
information).
The m odule m ust be con figured as either a ti mer or
synchronous counter to take advantage of this feature.
When used th is wa y, th e CCPR2 H:CCPR2L re gister
pair effectively becomes a period register for Timer3.
If Timer3 i s ru nning in As ynchronous C ounter m ode,
the Reset operation may not work.
In th e e vent that a write to T imer3 c oincides with a
Special Event Trigger from a CCP module, the write will
take precedence.
Note: The Special Event Triggers from the CCP2
module wi ll not s et th e TMR3IF interrupt
flag bit of the PIR2 register.

TABLE 15-1: REGISTERS ASSOCIATED WITH TIMER3 AS A TIMER/COUNTER

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
TMR3L Timer3 Register, Low Byte 61
TMR3H Timer3 Register, High Byte 61
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Timer3 module.

DS41303G-page 172  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.0 ENHANCED The en hanced fe atures are d iscussed i n d etail i n
Section 16.4 “PWM (Enhanced Mode)”. C apture,
CAPTURE/COMPARE/PWM
Compare an d si ngle-output PWM fu nctions of the
(ECCP) MODULE ECCP mo dule are the same as described fo r the
CCP1 is implemented as a standard CCP module with standard CCP module.
enhanced PWM capabilities. These include: The control register for th e enhanced CCP module is
• Provision for 2 or 4 output channels shown in Register 16-1. It differs from the C CP2CON
• Output steering register in t hat the two M ost Sig nificant bit s a re
implemented to control PWM functionality.
• Programmable polarity
• Programmable dead-band control
• Automatic shutdown and restart.

REGISTER 16-1: CCP1CON: ENHANCED CAPTURE/COMPARE/PWM CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 P1M<1:0>: Enhanced PWM Output Configuration bits

If CCP1M<3:2> = 00, 01, 10:
xx = P1A assigned as Capture/Compare input/output; P1B, P1C, P1D assigned as port pins
If CCP1M<3:2> = 11:
00 = Single output: P1A, P1B, P1C and P1D controlled by steering (See Section 16.4.7 “Pulse Steering
Mode”).
01 = Full-bridge output forward: P1D modulated; P1A active; P1B, P1C inactive
10 = Half-bridge output: P1A, P1B modulated with dead-band control; P1C, P1D assigned as port pins
11 = Full-bridge output reverse: P1B modulated; P1C active; P1A, P1D inactive
bit 5-4 DC1B<1:0>: PWM Duty Cycle bit 1 and bit 0
Capture mode:
Unused.
Compare mode:
Unused.
PWM mode:
These bits are the two LSbs of the 10-bit PWM duty cycle. The eight MSbs of the duty cycle are found in
CCPR1L.
bit 3-0 CCP1M<3:0>: Enhanced CCP Mode Select bits
0000 = Capture/Compare/PWM off (resets ECCP module)
0001 = Reserved
0010 = Compare mode, toggle output on match
0011 = Reserved
0100 = Capture mode, every falling edge
0101 = Capture mode, every rising edge
0110 = Capture mode, every 4th rising edge
0111 = Capture mode, every 16th rising edge
1000 = Compare mode, initialize CCP1 pin low, set output on compare match (set CCP1IF)
1001 = Compare mode, initialize CCP1 pin high, clear output on compare match (set CCP1IF)
1010 = Compare mode, generate software interrupt only, CCP1 pin reverts to I/O state
1011 = Compare mode, trigger special event (ECCP resets TMR1 or TMR3, sets CC1IF bit)
1100 = PWM mode; P1A, P1C active-high; P1B, P1D active-high
1101 = PWM mode; P1A, P1C active-high; P1B, P1D active-low
1110 = PWM mode; P1A, P1C active-low; P1B, P1D active-high
1111 = PWM mode; P1A, P1C active-low; P1B, P1D active-low

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PIC18F2XK20/4XK20
In addition to the expanded range of modes available 16.3 Standard PWM Mode
through the C CP1CON reg ister an d EC CP1AS
register, the ECCP module has two additional registers When co nfigured i n Si ngle O utput mo de, th e EC CP
associated w ith Enhan ced PWM operation and module fun ctions i dentically to th e s tandard C CP
auto-shutdown features. They are: module in PW M m ode, as de scribed i n Section 11.4
“PWM Mode”. This is also sometimes referred to as
• PWM1CON (Dead-band delay)
“Single CCP” mode, as in Table 16-1.
• PSTRCON (output steering)

16.1 ECCP Outputs and Configuration

The enhanced CCP module may have up to four PWM
outputs, dep ending on the sel ected ope rating m ode.
These out puts, de signated P1A through P1 D, are
multiplexed with I/O pins on PO RTC and PORTD (for
PIC18F4XK20 devices) or PORTB (for PIC18F2XK20
devices). Th e o utputs th at are active depend on th e
CCP ope rating m ode selected. The pi n ass ignments
are summarized in Table 16-1.
To configure the I/O pins as PWM outputs, the proper
PWM mode must be selected by setting the P1M<1:0>
and C CP1M<3:0> bit s. T he a ppropriate TR ISC an d
TRISD direction bits for the port pins must also be set
as outputs.

16.1.1 ECCP MODULES AND TIMER

RESOURCES
Like the standard CCP modules, the ECCP module can
utilize T imers 1, 2 or 3, depending on the mode
selected. Timer1 and Timer3 are available for modules
in C apture or C ompare mo des, w hile T imer2 is
available fo r m odules in PWM m ode. In teractions
between the standard and enhanced CCP modules are
identical to those described for standard CCP modules.
Additional d etails on tim er r esources are prov ided i n
Section 11.1.1 “CCP Modules and Timer
Resources”.

16.2 Capture and Compare Modes

Except for the operation of the S pecial Event Trigger
discussed below, the Capture and Compare modes of
the ECCP module are identical in op eration to that of
CCP2. T hese a re di scussed in de tail in Section 11.2
“Capture Mode” a nd Section 11.3 “Compare
Mode”. N o changes are requ ired when mo ving
between 28-pin and 40/44-pin devices.

16.2.1 SPECIAL EVENT TRIGGER

The Special Event Trigger output of ECCP1 resets the
TMR1 or TMR3 register pair, depending on which timer
resource is currently selected. This allows the CCPR1
register to effectively be a 16-bit programmable period
register for Timer1 or Timer3.

DS41303G-page 174  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4 PWM (Enhanced Mode) The PWM outputs are multiplexed with I/O pins and are
designated P1A, P1B, P1C and P1D. The polarity of the
The Enhanced PWM Mode can generate a PWM signal PWM pins is configurable and is selected by setting the
on up to four dif ferent output pins w ith up to 10-bits of CCP1M bits in the CCP1CON register appropriately.
resolution. It can do this through four different PWM
output modes: Table 16-1 s hows the p in as signments for e ach
Enhanced PWM mode.
• Single PWM
Figure 16-1 s hows an example of a simplified bloc k
• Half-Bridge PWM
diagram of the Enhanced PWM module.
• Full-Bridge PWM, Forward mode
• Full-Bridge PWM, Reverse mode Note: To prevent th e generation o f a n
incomplete w aveform w hen the PWM i s
To select an Enhanced PWM mode, the P1M bits of the first enabled, the ECCP module waits until
CCP1CON register must be set appropriately. the star t of a new PWM pe riod be fore
Note: The PWM Enhanced mode is available on generating a PWM signal.
the En hanced C apture/Compare/PWM
module (CCP1) only.

FIGURE 16-1: EXAMPLE SIMPLIFIED BLOCK DIAGRAM OF THE ENHANCED PWM MODE
DC1B<1:0> P1M<1:0> CCP1M<3:0>
Duty Cycle Registers
2 4
CCPR1L
CCP1/P1A CCP1/P1A
TRIS

CCPR1H (Slave)
P1B P1B

Output TRIS
Comparator R Q
Controller
P1C P1C
TMR2 (1)
S TRIS

P1D P1D
Comparator
Clear Timer2, TRIS
toggle PWM pin and
latch duty cycle
PR2 PWM1CON

Note 1: The 8-bit timer TMR2 register is concatenated with the 2-bit internal Q clock, or 2 bits of the prescaler to create the 10-bit
time base.

Note 1: The TRIS register value for each PWM output must be configured appropriately.
2: Clearing the CCPxCON register will relinquish ECCP control of all PWM output pins.
3: Any pin not used by an Enhanced PWM mode is available for alternate pin functions.

TABLE 16-1: EXAMPLE PIN ASSIGNMENTS FOR VARIOUS PWM ENHANCED MODES
ECCP Mode P1M<1:0> CCP1/P1A P1B P1C P1D
Single 00 Yes(1) Yes (1)
Yes (1)
Yes(1)
Half-Bridge 10 Yes Yes No No
Full-Bridge, Forward 01 Yes Yes Yes Yes
Full-Bridge, Reverse 11 Yes Yes Yes Yes
Note 1: Outputs are enabled by pulse steering in Single mode. See Register 16-4.

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PIC18F2XK20/4XK20
FIGURE 16-2: EXAMPLE PWM (ENHANCED MODE) OUTPUT RELATIONSHIPS (ACTIVE-HIGH
STATE)
Pulse PR2+1
P1M<1:0> Signal 0
Width
Period

00 (Single Output) P1A Modulated

Delay(1) Delay(1)
P1A Modulated

10 (Half-Bridge) P1B Modulated

P1A Active

(Full-Bridge, P1B Inactive

01 Forward)
P1C Inactive

P1D Modulated

P1A Inactive

(Full-Bridge, P1B Modulated

11
Reverse)
P1C Active

P1D Inactive

Relationships:
• Period = 4 * TOSC * (PR2 + 1) * (TMR2 Prescale Value)
• Pulse Width = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value)
• Delay = 4 * TOSC * (PWM1CON<6:0>)
Note 1: Dead-band d elay i s p rogrammed us ing th e P WM1CON re gister ( Section 16.4.6 “Programmable Dead-Band Delay
mode”).

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 PIC18F2XK20/4XK20
FIGURE 16-3: EXAMPLE ENHANCED PWM OUTPUT RELATIONSHIPS (ACTIVE-LOW STATE)

Pulse PR2+1
P1M<1:0> Signal 0
Width
Period

00 (Single Output) P1A Modulated

P1A Modulated
Delay(1) Delay(1)
10 (Half-Bridge) P1B Modulated

P1A Active

(Full-Bridge, P1B Inactive

01 Forward)
P1C Inactive

P1D Modulated

P1A Inactive

(Full-Bridge, P1B Modulated

11
Reverse)
P1C Active

P1D Inactive

Relationships:
• Period = 4 * TOSC * (PR2 + 1) * (TMR2 Prescale Value)
• Pulse Width = TOSC * (CCPR1L<7:0>:CCP1CON<5:4>) * (TMR2 Prescale Value)
• Delay = 4 * TOSC * (PWM1CON<6:0>)
Note 1: Dead-band delay is p rogrammed u sing th e P WM1CON re gister ( Section 16.4.6 “Programmable Dead-Band Delay
mode”).

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PIC18F2XK20/4XK20
16.4.1 HALF-BRIDGE MODE Since th e P 1A an d P1B o utputs are mu ltiplexed w ith
the PORT data latches, the associated TRIS bits must
In Half-Bridge mode, two pins are used as outputs to
be cleared to configure P1A and P1B as outputs.
drive push-pull loads. The PWM output signal is output
on the CCPx/P1A pin, while the complementary PWM
output si gnal i s ou tput on t he P 1B pi n (se e FIGURE 16-4: EXAMPLE OF
Figure 16-5). This mo de can be us ed for H alf-Bridge HALF-BRIDGE PWM
applications, as shown in Figure 16-5, or for Full-Bridge OUTPUT
applications, w here four po wer s witches a re b eing Period Period
modulated with two PWM signals.
Pulse Width
In Half-Bridge mode, the programmable dead-band delay
can be used to preven t shoot -through curr ent in P1A(2)
Half-Bridge power devices. The value of t he PDC<6:0> td
bits of t he P WM1CON r egister se ts th e numbe r o f td
instruction cycles before the output is driven active. If the P1B(2)
value is gr eater than t he duty cycle, the corr esponding
output r emains inacti ve dur ing the e ntire cycle. S ee (1) (1) (1)
Section 16.4.6 “Programmable Dead-Band Delay
mode” for more det ails of the d ead-band de lay td = Dead-Band Delay
operations. Note 1: At this time, the TMR2 register is equal to the
PR2 register.
2: Output signals are shown as active-high.

FIGURE 16-5: EXAMPLE OF HALF-BRIDGE APPLICATIONS

Standard Half-Bridge Circuit (“Push-Pull”)

FET
Driver +
P1A
-

Load
FET
Driver
+
P1B
-

Half-Bridge Output Driving a Full-Bridge Circuit

V+

FET FET
Driver Driver
P1A

Load
FET FET
Driver Driver
P1B

DS41303G-page 178  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4.2 FULL-BRIDGE MODE
In Full-Bridge mode, all four pins are used as outputs.
An ex ample of Full-Bridge application is sh own i n
Figure 16-6.
In the For ward mode, pi n C CP1/P1A is dri ven to it s
active state, pin P1D is modulated, while P1B and P1C
will b e dr iven t o th eir in active stat e as s hown i n
Figure 16-7.
In the R everse mode, P1C is drive n to its active state,
pin P1B is modulated, while P1A and P1D will be driven
to their inactive state as shown Figure 16-7.
P1A, P1B, P1C and P1D outputs are multiplexed with
the PORT data latches. The associated TRIS bits must
be cleared to configure the P1A, P1B, P1C and P1D
pins as outputs.

FIGURE 16-6: EXAMPLE OF FULL-BRIDGE APPLICATION

V+

FET QA QC FET
Driver Driver
P1A

Load
P1B
FET FET
Driver Driver

P1C
QB QD

V-
P1D

 2010 Microchip Technology Inc. DS41303G-page 179

PIC18F2XK20/4XK20
FIGURE 16-7: EXAMPLE OF FULL-BRIDGE PWM OUTPUT
Forward Mode
Period

P1A (2)

Pulse Width

P1B(2)

P1C(2)

P1D(2)

(1) (1)

Reverse Mode

Period
Pulse Width

P1A(2)

P1B(2)

P1C(2)

P1D(2)
(1) (1)

Note 1: At this time, the TMR2 register is equal to the PR2 register.
2: Output signal is shown as active-high.

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 PIC18F2XK20/4XK20
16.4.2.1 Direction Change in Full-Bridge The Fu ll-Bridge m ode do es not prov ide d ead-band
Mode delay. As one output is modulated at a time, dead-band
delay i s generally n ot r equired. T here is a s ituation
In the Full-Bridge mode, the P1M1 bit in the CCP1CON
where de ad-band del ay is required. Thi s s ituation
register allows users to cont rol t he f orward/reverse
occurs when both of the following conditions are true:
direction. Wh en t he application fir mware cha nges th is
direction control bit, the module will change to the new 1. The direction of the PWM output changes when
direction on the next PWM cycle. the duty cycle of the output is at or near 100%.
A direction change is initiated in software by changing 2. The turn off time of the power switch, including
the P1M1 bit of the CCP1CON register. The following the po wer d evice and dri ver ci rcuit, i s g reater
sequence occurs prior to the end of the current PWM than the turn on time.
period: Figure 16-9 shows an exa mple of the PW M dir ection
• The modulated outputs (P1B and P1D) are placed changing from forward to reverse, at a near 100% duty
in their inactive state. cycle. In this example, at time t1, the output P1A and
P1D be come in active, while ou tput P1 C becomes
• The associated unmodulated outputs (P1A and
active. Since the turn off time of the power devices is
P1C) are switched to drive in the opposite
longer th an th e t urn o n t ime, a sho ot-through cu rrent
direction.
will f low t hrough p ower devices QC an d QD ( see
• PWM modulation resumes at the beginning of the Figure 16-6) for th e du ration of ‘t ’. The same
next period. phenomenon w ill oc cur to power d evices QA an d QB
See Figure 16-8 for an illustration of this sequence. for PWM direction change from reverse to forward.
If changing PWM direction at high duty cycle is required
for an application, two possible solutions for eliminating
the shoot-through current are:
1. Reduce PWM dut y cy cle fo r one PWM p eriod
before changing directions.
2. Use switch drivers that can drive the switches off
faster than they can drive them on.
Other opt ions to prev ent sh oot-through cu rrent ma y
exist.

FIGURE 16-8: EXAMPLE OF PWM DIRECTION CHANGE

Signal Period(1) Period

P1A (Active-High)

P1B (Active-High)
Pulse Width

P1C (Active-High)

(2)
P1D (Active-High)

Pulse Width

Note 1: The direction bit P1M1 of the CCP1CON register is written any time during the PWM cycle.
2: When changing directions, the P1A and P1C signals switch before the end of the current PWM cycle. The
modulated P1B and P1D signals are inactive at this time. The length of this time is (1/FOSC)  TMR2 prescale
value.

 2010 Microchip Technology Inc. DS41303G-page 181

PIC18F2XK20/4XK20
FIGURE 16-9: EXAMPLE OF PWM DIRECTION CHANGE AT NEAR 100% DUTY CYCLE
Forward Period t1 Reverse Period

P1A

P1B
PW

P1C

P1D PW
TON
External Switch C
TOFF

External Switch D

Potential T = TOFF – TON

Shoot-Through Current

Note 1: All signals are shown as active-high.

2: TON is the turn on delay of power switch QC and its driver.
3: TOFF is the turn off delay of power switch QD and its driver.

16.4.3 START-UP CONSIDERATIONS

When any PWM mode is us ed, the a pplication
hardware must use the proper external pull-up and/or
pull-down resistors on the PWM output pins.
Note: When the microcontroller is released from
Reset, all of the I/O pins are in the
high-impedance state. The e xternal c ir-
cuits must keep the power switch devices
in the O ff state until the microcontroller
drives the I/O pins with the proper signal
levels or activates the PWM output(s).
The C CP1M<1:0> bi ts of the C CP1CON r egister all ow
the user to choose whether the PWM output signals are
active-high or active-low for each pair of PWM output pins
(P1A/P1C and P1 B/P1D). Th e P WM output p olarities
must be selected before the PWM pin output drivers are
enabled. C hanging t he po larity co nfiguration w hile the
PWM pin output drivers are enable is not recommended
since it may result in damage to the application circuits.
The P1A, P1B, P1C and P1D output latches may not be
in the prop er s tates w hen th e PWM m odule i s
initialized. Enabling the PWM pin output drivers at the
same time as the Enhanced PWM modes may cause
damage to the application circuit. The Enhanced PWM
modes must be enabled in the proper Output mode and
complete a full PWM cycle before enabling the PWM
pin output drivers. The completion of a full PWM cycle
is i ndicated by th e TM R2IF bi t o f th e PIR 1 reg ister
being set as the second PWM period begins.

DS41303G-page 182  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4.4 ENHANCED PWM A sh utdown co ndition is in dicated by the ECCPASE
AUTO-SHUTDOWN MODE (Auto-Shutdown Ev ent S tatus) bit of the ECCP1AS
register. If the bit is a ‘0’, the PWM pins are operating
The PWM mode supports an Auto-Shutdown mode that
normally. If the bit is a ‘1’, the PWM outputs are in the
will di sable the PWM output s w hen an external
shutdown state.
shutdown eve nt occ urs. Auto-Shut down mo de plac es
the PWM output pins into a prede termined state. This When a shutdown event occurs, two things happen:
mode is used to help prevent the PWM from dam aging The EC CPASE bit is s et to ‘ 1’. The ECCPASE will
the application. remain set u ntil cle ared in firm ware o r an auto-rest art
The auto-shutdown sources are s elected usin g the occurs (see Section 16.4.5 “Auto-Restart Mode”).
ECCPAS<2:0> bit s of the EC CP1AS register. A The enabled PWM pins are as ynchronously placed in
shutdown event may be generated by: their sh utdown st ates. The PWM ou tput pins are
• A ogic
l ‘0’ on the FLT0 pin grouped into pairs [P1A/P1C] and [P1B/P1D]. The state
• Comparator C1 of each pi n p air is d etermined by the PSSAC and
PSSBD bits of the ECCP1AS register. Each pin pair may
• Comparator C2
be placed into one of three states:
• Setting the ECCPASE bit in firmware
• Drive logic ‘1’
• Drive logic ‘0’
• Tri-state (high-impedance)

REGISTER 16-2: ECCP1AS: ENHANCED CAPTURE/COMPARE/PWM AUTO-SHUTDOWN

CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W -0 R/W-0 R/W-0 R/W-0
ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1 PSSBD0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 ECCPASE: ECCP Auto-Shutdown Event Status bit

1 = A shutdown event has occurred; ECCP outputs are in shutdown state
0 = ECCP outputs are operating
bit 6-4 ECCPAS<2:0>: ECCP Auto-shutdown Source Select bits
000 = Auto-Shutdown is disabled
001 = Comparator C1OUT output is high
010 = Comparator C2OUT output is high
011 = Either Comparator C1OUT or C2OUT is high
100 =VIL on FLT0 pin
101 =VIL on FLT0 pin or Comparator C1OUT output is high
110 =VIL on FLT0 pin or Comparator C2OUT output is high
111 =VIL on FLT0 pin or Comparator C1OUT or Comparator C2OUT is high
bit 3-2 PSSACn: Pins P1A and P1C Shutdown State Control bits
00 = Drive pins P1A and P1C to ‘0’
01 = Drive pins P1A and P1C to ‘1’
1x = Pins P1A and P1C tri-state
bit 1-0 PSSBDn: Pins P1B and P1D Shutdown State Control bits
00 = Drive pins P1B and P1D to ‘0’
01 = Drive pins P1B and P1D to ‘1’
1x = Pins P1B and P1D tri-state

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PIC18F2XK20/4XK20

Note 1: The auto-shutdown c ondition i s a

level-based si gnal, no t an edg e-based
signal. As long as the level is present, the
auto-shutdown will persist.
2: Writing to th e ECCPASE bi t is di sabled
while an a uto-shutdown c ondition
persists.
3: Once the au to-shutdown c ondition has
been rem oved an d th e PWM res tarted
(either thro ugh firmware or au to-restart)
the PWM signal will always restart at the
beginning of the next PWM period.

FIGURE 16-10: PWM AUTO-SHUTDOWN WITH FIRMWARE RESTART (PRSEN = 0)

PWM Period
Shutdown Event

ECCPASE bit

PWM Activity

Normal PWM
ECCPASE
Cleared by
Start of Shutdown Shutdown Firmware PWM
PWM Period Event Occurs Event Clears Resumes

16.4.5 AUTO-RESTART MODE

The En hanced PW M can be c onfigured to a utomati-
cally restart the PWM signal once the auto-shutdown
condition has been removed. Auto-restart is enabled by
setting the PRSEN bit in the PWM1CON register.
If auto-restart is enabled, the ECCPASE bit will remain
set as l ong a s the au to-shutdown c ondition i s active.
When the a uto-shutdown c ondition is r emoved, th e
ECCPASE bit will be cleared via hardware and normal
operation will resume.

FIGURE 16-11: PWM AUTO-SHUTDOWN WITH AUTO-RESTART ENABLED (PRSEN = 1)

PWM Period

Shutdown Event

ECCPASE bit

PWM Activity

Normal PWM

Start of Shutdown Shutdown PWM

PWM Period Event Occurs Event Clears Resumes

DS41303G-page 184  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4.6 PROGRAMMABLE DEAD-BAND FIGURE 16-12: EXAMPLE OF
DELAY MODE HALF-BRIDGE PWM
In H alf-Bridge a pplications w here al l p ower s witches OUTPUT
are m odulated at th e PW M frequency, the po wer Period Period
switches normally require more time to turn off than to
turn on. If both the upper and lower power switches are Pulse Width
switched at the sa me ti me (one tu rned on , an d th e P1A(2)
other turned off), both switches may be on for a short td
period of ti me until one switch c ompletely turn s of f.
td
During thi s bri ef i nterval, a v ery hi gh c urrent P1B(2)
(shoot-through c urrent) will fl ow th rough both po wer
switches, sh orting t he b ridge su pply. To avoid t his (1) (1) (1)
potentially de structive s hoot-through c urrent fro m
flowing during switching, turning on either of the power td = Dead-Band Delay
switches is normally delayed to allow the other switch
to completely turn off. Note 1: At this time, the TMR2 register is equal to the
In Half-Bridge mode, a di gitally pro grammable PR2 register.
dead-band d elay i s a vailable to a void s hoot-through 2: Output signals are shown as active-high.
current from destroying the bridge power switches. The
delay occurs at the signal transition from the non-active
state to th e ac tive s tate. See F igure 16-12 for
illustration. Th e l ower s even b its of th e a ssociated
PWM1CON reg ister (R egister 16-3) se ts t he d elay
period in t erms o f m icrocontroller instruction cycles
(TCY or 4 TOSC).

FIGURE 16-13: EXAMPLE OF HALF-BRIDGE APPLICATIONS

V+
Standard Half-Bridge Circuit (“Push-Pull”)

FET
Driver +
P1A V
-

Load
FET
Driver
+
P1B V
-

V-

 2010 Microchip Technology Inc. DS41303G-page 185

PIC18F2XK20/4XK20

REGISTER 16-3: PWM1CON: ENHANCED PWM CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
PRSEN PDC6 PDC5 PDC4 PDC3 PDC2 PDC1 PDC0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 PRSEN: PWM Restart Enable bit

1 = Upon au to-shutdown, the ECCPASE bit c lears au tomatically once the shutdown event go es
away; the PWM restarts automatically
0 = Upon auto-shutdown, ECCPASE must be cleared by software to restart the PWM
bit 6-0 PDC<6:0>: PWM Delay Count bits
PDCn = Number o f F OSC/4 (4 * TOSC) c ycles bet ween the sc heduled time w hen a PWM s ignal
should transition active and the actual time it transitions active

DS41303G-page 186  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4.7 PULSE STEERING MODE
In Single Output mode, pulse steering allows any of the Note: The associated TR IS bits must be set to
PWM pins to be the modulated signal. Additionally, the output (‘0’) to enable the pin output driver
same PWM signal can be simultaneously available on in order to see the PWM signal on the pin.
multiple pins.
While the PWM Steering mode is active, CCP1M<1:0>
Once th e Si ngle O utput m ode is s elected bits of the CCP1CON register select the PWM output
(CCP1M<3:2> = 11 and P1M<1:0>= 00 of t he polarity for the P1<D:A> pins.
CCP1CON reg ister), the u ser firm ware can bri ng o ut
The PWM auto-shutdown ope ration al so applies to
the same PWM signal to one, two, three or four output
PWM Steering mod e as de scribed in Section 16.4.4
pins by setting the a ppropriate STR<D:A> bi ts of t he
“Enhanced PWM Auto-shutdown mode”. An
PSTRCON register, as shown in Table 16-1.
auto-shutdown ev ent w ill o nly af fect p ins th at h ave
PWM outputs enabled.

REGISTER 16-4: PSTRCON: PULSE STEERING CONTROL REGISTER(1)

U-0 U-0 U-0 R/W-0 R/W -0 R/W-0 R/W-0 R/W-1
— — — STRSYNC STRD STRC STRB STRA
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4 STRSYNC: Steering Sync bit
1 = Output steering update occurs on next PWM period
0 = Output steering update occurs at the beginning of the instruction cycle boundary
bit 3 STRD: Steering Enable bit D
1 = P1D pin has the PWM waveform with polarity control from CCPxM<1:0>
0 = P1D pin is assigned to port pin
bit 2 STRC: Steering Enable bit C
1 = P1C pin has the PWM waveform with polarity control from CCPxM<1:0>
0 = P1C pin is assigned to port pin
bit 1 STRB: Steering Enable bit B
1 = P1B pin has the PWM waveform with polarity control from CCPxM<1:0>
0 = P1B pin is assigned to port pin
bit 0 STRA: Steering Enable bit A
1 = P1A pin has the PWM waveform with polarity control from CCPxM<1:0>
0 = P1A pin is assigned to port pin

Note 1: The PWM Steering mode is available only when the CCP1CON register bits CCP1M<3:2> = 11 and
P1M<1:0> = 00.

 2010 Microchip Technology Inc. DS41303G-page 187

PIC18F2XK20/4XK20
FIGURE 16-14: SIMPLIFIED STEERING
BLOCK DIAGRAM
STRA

P1A Signal P1A pin

CCP1M1 1

PORT Data
0
TRIS
STRB

CCP1M0 1 P1B pin

PORT Data 0
TRIS
STRC

P1C pin
CCP1M1 1

PORT Data 0
TRIS
STRD

CCP1M0 1 P1D pin

PORT Data 0
TRIS

Note 1: Port out puts are configured as show n when

the CCP 1CON regist er bit s P 1M<1:0> = 00
and CCP1M<3:2> = 11.
2: Single P WM out put requires setting at least
one of the STRx bits.

DS41303G-page 188  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
16.4.7.1 Steering Synchronization Figures 16-15 and 16-16 illustrate the timing diagrams
of the PWM ste ering de pending on the STR SYNC
The STRSYNC bit of the PSTRCON register gives the
setting.
user two sel ections of w hen the s teering eve nt w ill
happen. Wh en the STR SYNC b it is ‘ 0’, t he steering
event w ill happen a t th e e nd of the in struction th at
writes to t he PST RCON re gister. In thi s c ase, th e
output si gnal at the P 1<D:A> p ins ma y be an
incomplete PWM w aveform. Thi s ope ration is useful
when the user firmware needs to immediately remove
a PWM signal from the pin.
When the STRSYNC b it i s ‘1’, t he e ffective steering
update will happen at the b eginning of th e next PWM
period. In this case, steering on/off the PWM output will
always produce a complete PWM waveform.

FIGURE 16-15: EXAMPLE OF STEERING EVENT AT END OF INSTRUCTION (STRSYNC = 0)

PWM Period

PWM

STRn

P1<D:A> PORT Data PORT Data

P1n = PWM

FIGURE 16-16: EXAMPLE OF STEERING EVENT AT BEGINNING OF INSTRUCTION

(STRSYNC = 1)

PWM

STRn

P1<D:A> PORT Data PORT Data

P1n = PWM

 2010 Microchip Technology Inc. DS41303G-page 189

PIC18F2XK20/4XK20
16.4.8 OPERATION IN POWER-MANAGED
MODES
In Sleep mode, all clock sources are disabled. Timer2
will not increment and the state of the module will not
change. If the ECCP pin is driving a value, it w ill con-
tinue to drive that value. When the device wakes up, it
will continue from this state. If Two-Speed Start-ups are
enabled, the initial start-up frequency from HFINTOSC
and the postscaler may not be stable immediately.
In PRI_IDLE mode, the primary clock will continue to
clock th e ECCP module without c hange. In a ll other
power-managed modes, the selected power-managed
mode c lock w ill clock Timer2. Ot her power-managed
mode cl ocks will m ost li kely b e dif ferent th an th e
primary clock frequency.

16.4.8.1 Operation with Fail-Safe

Clock Monitor
If the Fail-Safe Clock Monitor is enabled, a clock failure
will force the device into the RC_RUN Power-Managed
mode and the OSCFIF bit of the PIR2 register will be
set. The ECCP will then be cl ocked from the internal
oscillator clock s ource, w hich m ay h ave a different
clock frequency than the primary clock.
See the previous section for additional details.

16.4.9 EFFECTS OF A RESET

Both Power-on Reset and subsequent Resets will force
all ports to In put mode and the CCP registers to their
Reset states.
This fo rces the enhanced C CP m odule to res et to a
state compatible with the standard CCP module.

DS41303G-page 190  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 16-2: REGISTERS ASSOCIATED WITH ECCP1 MODULE AND TIMER1 TO TIMER3
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
RCON IPEN SBOREN — RI TO PD POR BOR 58
PIR1 PSPIF ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
TRISB PORTB Data Direction Control Register 62
TRISC PORTC Data Direction Control Register 62
TRISD PORTD Data Direction Control Register 62
TMR1L Timer1 Register, Low Byte 60
TMR1H Timer1 Register, High Byte 60
T1CON RD16 T1RUN T1CKPS1 T1CKPS0 T1OSCEN T1SYNC TMR1CS TMR1ON 60
TMR2 Timer2 Register 60
T2CON — T2OUTPS3 T2OUTPS2 T2OUTPS1 T2OUTPS0 TMR2ON T2CKPS1 T2CKPS0 60
PR2 Timer2 Period Register 60
TMR3L Timer3 Register, Low Byte 61
TMR3H Timer3 Register, High Byte 61
T3CON RD16 T3CCP2 T3CKPS1 T3CKPS0 T3CCP1 T3SYNC TMR3CS TMR3ON 61
CCPR1L Capture/Compare/PWM Register 1, Low Byte 61
CCPR1H Capture/Compare/PWM Register 1, High Byte 61
CCP1CON P1M1 P1M0 DC1B1 DC1B0 CCP1M3 CCP1M2 CCP1M1 CCP1M0 61
ECCP1AS ECCPASE ECCPAS2 ECCPAS1 ECCPAS0 PSSAC1 PSSAC0 PSSBD1 PSSBD0 61
PWM1CON PRSEN PDC6 PDC5 PDC4 PDC3 PDC2 PDC1 PDC0 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used during ECCP operation.

 2010 Microchip Technology Inc. DS41303G-page 191

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 192  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.0 MASTER SYNCHRONOUS 17.3 SPI Mode
SERIAL PORT (MSSP) The SPI mode allows 8 bits of data to be synchronously
MODULE transmitted and rec eived si multaneously. Al l fo ur
modes of SPI are supported. T o ac complish
17.1 Master SSP (MSSP) Module communication, typically three pins are used:
Overview • Serial Data Out – SDO
• Serial Data In – SDI/SDA
The Master Synchronous Serial Port (MSSP) module is
a serial interface, useful for communicating with other • Serial Clock – SCK/SCL
peripheral or microcontroller devices. These peripheral Additionally, a fourth pin may be used when in a Slave
devices may be serial EEPROMs, shift registers, dis- mode of operation:
play drivers, A/D c onverters, etc . The M SSP m odule • Slave Select – SS
can operate in one of two modes:
Figure 17-1 sh ows the block di agram of the MSSP
• Serial Peripheral Interface (SPI) module when operating in SPI mode.
• Inter-Integrated Circuit (I2C)
- Full Master mode FIGURE 17-1: MSSP BLOCK DIAGRAM
- Slave mode (with general address call) (SPI MODE)
The I 2C i nterface s upports the f ollowing modes i n Internal
hardware: Data Bus

• Master m ode Read Write

• Multi-Master mode
SSPBUF Reg
• Slave mode

17.2 Control Registers SDI/SDA

The M SSP m odule ha s seven as sociated re gisters. SSPSR Reg
These include: SDO bit 0 Shift
Clock
• SSPSTA – STATUS register
• SSPCON1 – First Control register
• SSPCON2 – Second Control register
• SSPBUF – Transmit/Receive buffer SS SS Control
• SSPSR – Shift register (not directly accessible) Enable
• SSPADD – Address register
Edge
• SSPMSK – Address Mask register Select
The use of these registers and their individual Configu-
2
ration bits differ significantly depending on whether the
Clock Select
MSSP module is operated in SPI or I2C mode.
Additional d etails are provided un der the i ndividual SSPM<3:0>
sections.
SCK/SCL
SMP:CKE 4
2 (
TMR2 Output
2
)
Edge
Select Prescaler TOSC
4, 16, 64

Data to TX/RX in SSPSR

TRIS bit

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PIC18F2XK20/4XK20
17.3.1 REGISTERS SSPSR i s the s hift register u sed fo r s hifting da ta i n
and out. SSPBUF provides in direct ac cess to th e
The M SSP m odule ha s fo ur reg isters for SPI mode
SSPSR regi ster. S SPBUF is the buf fer register to
operation. These are:
which d ata bytes a re written, and fro m which data
• SSPCON1 – Control Register bytes are read.
• SSPSTAT – STATUS register In receive operations, SSPSR and SSPBUF together
• SSPBUF – Serial Receive/Transmit Buffer create a double-buffered re ceiver. When SSPSR
• SSPSR – Shift Register (Not directly accessible) receives a complete byte, it is transferred to SSPBUF
SSPCON1 a nd SSPST AT are the c ontrol a nd ST A- and the SSPIF interrupt is set.
TUS registers in SPI mode operation. The SSPCON1 During transmission, the SSPBUF is n ot
register is re adable a nd w ritable. The l ower 6 bits of double-buffered. A wri te to SSPBUF wil l write to both
the SSPSTAT are read-only. The upper two bits of the SSPBUF and SSPSR.
SSPSTAT are read/write.

REGISTER 17-1: SSPSTAT: MSSP STATUS REGISTER (SPI MODE)

R/W-0 R/W -0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P S R/W UA BF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 SMP: Sample bit

SPI Master mode:
1 = Input data sampled at end of data output time
0 = Input data sampled at middle of data output time
SPI Slave mode:
SMP must be cleared when SPI is used in Slave mode.
bit 6 CKE: SPI Clock Select bit(1)
1 = Output data changes on clock transition from active to idle
0 = Output data changes on clock transition from idle to active
bit 5 D/A: Data/Address bit
Used in I2C mode only.
bit 4 P: Stop bit
Used in I2C mode only. This bit is cleared when the MSSP module is disabled, SSPEN is cleared.
bit 3 S: Start bit
Used in I2C mode only.
bit 2 R/W: Read/Write Information bit
Used in I2C mode only.
bit 1 UA: Update Address bit
Used in I2C mode only.
bit 0 BF: Buffer Full Status bit (Receive mode only)
1 = Receive complete, SSPBUF is full
0 = Receive not complete, SSPBUF is empty

Note 1: Polarity of clock state is set by the CKP bit of the SSPCON1 register.

DS41303G-page 194  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 17-2: SSPCON1: MSSP CONTROL 1 REGISTER (SPI MODE)

R/W-0 R/W -0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 WCOL: Write Collision Detect bit (Transmit mode only)

1 = The SSPBUF register is written while it is still transmitting the previous word
(must be cleared by software)
0 = No collision
bit 6 SSPOV: Receive Overflow Indicator bit(1)
SPI Slave mode:
1 = A new byte is received while the SSPBUF register is still holding the previous data. In case of over-
flow, the data in SSPSR is lost. Overflow can only occur in Slave mode. The user must read the
SSPBUF, even if only transmitting data, to avoid setting overflow (must be cleared by software).
0 = No overflow
bit 5 SSPEN: Synchronous Serial Port Enable bit(2)
1 = Enables serial port and configures SCK, SDO, SDI and SS as serial port pins. When enabled, the
SDA and SCL pins must be configured as inputs.
0 = Disables serial port and configures these pins as I/O port pins
bit 4 CKP: Clock Polarity Select bit
1 = Idle state for clock is a high level
0 = Idle state for clock is a low level
bit 3-0 SSPM<3:0>: Synchronous Serial Port Mode Select bits(3)
0101 = SPI Slave mode, clock = SCK pin, SS pin control disabled, SS can be used as I/O pin
0100 = SPI Slave mode, clock = SCK pin, SS pin control enabled
0011 = SPI Master mode, clock = TMR2 output/2
0010 = SPI Master mode, clock = FOSC/64
0001 = SPI Master mode, clock = FOSC/16
0000 = SPI Master mode, clock = FOSC/4

Note 1: In Master mode, the overflow bit is not set since each new reception (and transmission) is initiated by
writing to the SSPBUF register.
2: When enabled, these pins must be properly configured as input or output.
3: Bit combinations not specifically listed here are either reserved or implemented in I2C mode only.

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PIC18F2XK20/4XK20
17.3.2 OPERATION When the a pplication software is expecting to r eceive
valid data, the SSPBUF should be read before the next
When ini tializing th e SPI , se veral options n eed to b e
byte of data to transfer is written to the SSPBUF. The
specified. This is done by programming the appropriate
Buffer Full bit, BF of the SSPSTAT register, indicates
control b its (SSPCO N1<5:0> an d SSPST AT<7:6>).
when SSPBUF has been loaded with the received data
These control bits allow the following to be specified:
(transmission is complete). When the SSPBUF is read,
• Master mode (SCK is the clock output) the BF bit is cleared. This data may be irrelevant if the
• Slave mode (SCK is the clock input) SPI is only a transmitter. Generally, the MSSP interrupt
• Clock Polarity (Idle state of SCK) is used to d etermine when the transmission/reception
• Data Input Sample Phase (middle or end of data has c ompleted. The SSPBUF must be rea d and/or
output time) written. If the interrupt method is not going to be used,
then software polling can be done to ensure that a write
• Clock Edge (output data on rising/falling edge of
collision doe s no t oc cur. Exa mple 17-1 sh ows th e
SCK)
loading of the SSPBUF (SSPSR) for data transmission.
• Clock Rate (Master mode only)
The SSPSR is not directly readable or writable and can
• Slave Select mode (Slave mode only)
only be accessed by addressing the SSPBUF register.
The MSSP consists of a tr ansmit/receive shift register Additionally, the MSSP STATUS re gister (SSPSTAT)
(SSPSR) and a buffer register (SSPBUF). The SSPSR indicates the various status conditions.
shifts the data in and out of the device, MSb first. The
SSPBUF holds the data that was written to the SSPSR
until the received data is ready. Once the 8 bits of data
have been received, that byte is moved to the SSPBUF
register. The n, the Buf fer Fu ll de tect bi t, BF of th e
SSPSTAT register, and the interrupt flag bit, SSPIF, are
set. Th is double-buffering of the re ceived da ta
(SSPBUF) allows the next byte to start reception before
reading the data that was just received. Any write to the
SSPBUF register during transmission/reception of data
will be ignored and the write collision detect bit WCOL
of t he S SPCON1 register, will be se t. U ser so ftware
must clear the WCOL bit so that it can be determined if
the fo llowing w rite(s) to t he SSP BUF reg ister
completed successfully.

EXAMPLE 17-1: LOADING THE SSPBUF (SSPSR) REGISTER

LOOP BTFSS SSPSTAT, BF ;Has data been received (transmit complete)?
BRA LOOP ;No
MOVF SSPBUF, W ;WREG reg = contents of SSPBUF
MOVWF RXDATA ;Save in user RAM, if data is meaningful
MOVF TXDATA, W ;W reg = contents of TXDATA
MOVWF SSPBUF ;New data to xmit

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 PIC18F2XK20/4XK20
17.3.3 ENABLING SPI I/O 17.3.4 TYPICAL CONNECTION
To enable the serial port, SSP Enab le bit, SSPEN of Figure 17-2 sh ows a typ ical c onnection between tw o
the SSPCON1 register, must be set. To reset or recon- microcontrollers. The master c ontroller (Proc essor 1)
figure SPI m ode, clear the SSPEN bit , reinitialize the initiates the data transfer by sending the SCK signal.
SSPCON registers and then s et the SSPEN bi t. This Data is shifted out of bo th shift registers on their pro-
configures the SDI, SDO, SCK and SS pins as serial grammed clock edge and latched on the opposite edge
port pins. For the pins to behave as the serial port func- of the clock. Both processors should be programmed to
tion, some mu st hav e the ir data direction bi ts (in the the same C lock Pol arity (C KP), then bo th controllers
TRIS register) appropriately programmed as follows: would se nd an d receive da ta at th e same ti me.
• SDI is automatically controlled by the SPI module Whether t he data is m eaningful (o r du mmy data)
depends on th e app lication sof tware. This lea ds to
• SDO must have corresponding TRIS bit cleared
three scenarios for data transmission:
• SCK (Master mode) must have corresponding
TRIS bit cleared • Master sends data–Slave sends dummy data
• SCK (Slave mode) must have corresponding • Master sends data–Slave sends data
TRIS bit set • Master sends dummy data–Slave sends data
• SS must have corresponding TRIS bit set
Any serial po rt f unction that is n ot desired may b e
overridden by programming the co rresponding da ta
direction (TRIS) register to the opposite value.

FIGURE 17-2: SPI MASTER/SLAVE CONNECTION

SPI Master SSPM<3:0> = 00xxb SPI Slave SSPM<3:0> = 010xb

SDO SDI

Serial Input Buffer Serial Input Buffer

(SSPBUF) (SSPBUF)

Shift Register SDI SDO Shift Register

(SSPSR) (SSPSR)

MSb LSb MSb LSb

Serial Clock
SCK SCK
Processor 1 Processor 2

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PIC18F2XK20/4XK20
17.3.5 MASTER MODE The c lock p olarity is s elected by ap propriately
programming th e C KP bi t of t he SSP CON1 r egister.
The m aster can in itiate the da ta tra nsfer at a ny time
This then , w ould gi ve w aveforms f or SPI
because it co ntrols t he SC K. The m aster dete rmines
communication as s hown in Fi gure 17-3, Fi gure 17-5
when th e sl ave (Proc essor 2, Fi gure 17-2) is to
and Figure 17-6, where the MSB is transmitted first. In
broadcast data by the software protocol.
Master m ode, the SPI c lock ra te (bi t rate) i s us er
In Ma ster m ode, th e da ta i s t ransmitted/received a s programmable to be one of the following:
soon as the SSPBUF register is written to. If the SPI is
• FOSC/4 (or TCY)
only go ing to re ceive, the SD O o utput c ould be di s-
abled (programmed as an input). The SSPSR register • FOSC/16 (or 4 • TCY)
will continue to shift in the signal present on the SDI pin • FOSC/64 (or 16 • TCY)
at the pro grammed c lock rat e. As ea ch byte is • Timer2 output/2
received, it will be loaded into the SSPBUF register as
This allows a ma ximum data rate ( at 64 M Hz) o f
if a normal rec eived byt e (int errupts and S tatus bit s
16.00 Mbps.
appropriately s et). Thi s c ould be u seful in r eceiver
applications as a “Line Activity Monitor” mode. Figure 17-3 s hows the waveforms for Ma ster m ode.
When the CKE bit is set, the SDO data is valid before
there is a clock edge on SCK. The change of the input
sample is shown based on the state of the SMP bit. The
time when the SSPBUF is loaded w ith the received
data is shown.

FIGURE 17-3: SPI MODE WAVEFORM (MASTER MODE)

Write to
SSPBUF

SCK
(CKP = 0
CKE = 0)

SCK
(CKP = 1
CKE = 0)
4 Clock
SCK Modes
(CKP = 0
CKE = 1)

SCK
(CKP = 1
CKE = 1)

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

(CKE = 0)

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

(CKE = 1)
SDI
(SMP = 0) bit 7 bit 0
Input
Sample
(SMP = 0)
SDI
(SMP = 1)
bit 7 bit 0

Input
Sample
(SMP = 1)
SSPIF
Next Q4 Cycle
SSPSR to after Q2
SSPBUF

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 PIC18F2XK20/4XK20
17.3.6 SLAVE MODE must be high. When the SS pin is low, transmission and
reception are enabled and the SDO pin is driven. When
In Slave mode, the data is transmitted and received as
the SS pin goes high, the SDO pin is no longer driven,
the ex ternal cl ock pul ses ap pear on SC K. When the
even if in the middle of a transmitted byte and becomes
last bit is latched, the SSPIF interrupt flag bit is set.
a floating o utput. E xternal pu ll-up/pull-down res istors
Before enabling the module in SPI Slave mode, the clock may be desirable depending on the application.
line must match the proper Idle state. The clock line can
be obser ved by r eading the S CK pin. The Id le st ate is Note 1: When the SPI is in Slave mode with SS pin
determined by the CKP bit of the SSPCON1 register. control enabled (SSPCON<3:0> = 0100),
the SPI module will reset if the SS pin is set
While in Slave mode, the external clock is supplied by
to VDD.
the external clock source on the SCK pin. This external
clock must meet the minimum high and low times as 2: When the SPI is used in Slave mode with
specified in the electrical specifications. CKE set the SS pin control must also be
enabled.
While in Sle ep m ode, the s lave ca n tran smit/receive
data. When a byte is received, the device will wake-up When the SPI module resets, the bit counter is forced
from Sleep. to ‘0’. This can be done by either forcing the SS pin to
a high level or clearing the SSPEN bit.
17.3.7 SLAVE SELECT To emulate two-wire communication, the SDO pin can
SYNCHRONIZATION be connected to th e SDI pin. When the SPI nee ds to
The SS p in allows a Sy nchronous Slave mode. Th e operate as a receiver, the SDO pin can be configured
SPI must be in Slave mode with SS pin control enabled as an input. This disables transmissions from the SDO.
(SSPCON1<3:0> = 04h). The pin must not be driven The SDI can always be left as an input (SDI function)
low for the SS pin to function as an input. The data latch since it cannot create a bus conflict.

FIGURE 17-4: SLAVE SYNCHRONIZATION WAVEFORM

SS

SCK
(CKP = 0
CKE = 0)

SCK
(CKP = 1
CKE = 0)

Write to
SSPBUF

SDO bit 7 bit 6 bit 7 bit 0

SDI bit 0
(SMP = 0)
bit 7 bit 7
Input
Sample
(SMP = 0)
SSPIF
Interrupt
Flag
Next Q4 Cycle
SSPSR to after Q2
SSPBUF

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PIC18F2XK20/4XK20
FIGURE 17-5: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 0)

SS
Optional

SCK
(CKP = 0
CKE = 0)

SCK
(CKP = 1
CKE = 0)
Write to
SSPBUF

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

SDI
(SMP = 0) bit 7 bit 0
Input
Sample
(SMP = 0)
SSPIF
Interrupt
Flag
Next Q4 Cycle
SSPSR to after Q2
SSPBUF

FIGURE 17-6: SPI MODE WAVEFORM (SLAVE MODE WITH CKE = 1)

SS
Not Optional

SCK
(CKP = 0
CKE = 1)

SCK
(CKP = 1
CKE = 1)
Write to
SSPBUF

SDO bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

SDI
(SMP = 0) bit 7 bit 0
Input
Sample
(SMP = 0)

SSPIF
Interrupt
Flag
Next Q4 Cycle
after Q2
SSPSR to
SSPBUF

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 PIC18F2XK20/4XK20
17.3.8 OPERATION IN POWER-MANAGED Transmit/Receive Shift reg ister. Wh en all 8 bits h ave
MODES been received, the M SSP interrupt flag bit will be set
and if enabled, will wake the device.
In SPI Master mode, module clocks may be operating
at a different speed than when in full power mode; in 17.3.9 EFFECTS OF A RESET
the case of the Sleep mode, all clocks are halted.
A Reset disables the MSSP module and terminates the
In all Idle modes, a clock is provided to the peripherals. current transfer.
That clock could be from the primary clock source, the
secondary c lock (Timer1 os cillator at 32 .768 k Hz) or 17.3.10 BUS MODE COMPATIBILITY
the IN TOSC so urce. S ee Section 3.0 “Power-Man-
Table 17-1 s hows the com patibility between th e
aged Modes” for additional information.
standard SPI modes and th e st ates of the CKP an d
In most c ases, t he s peed that t he m aster clocks S PI CKE control bits.
data is n ot important; ho wever, this should b e
evaluated for each system. TABLE 17-1: SPI BUS MODES
When MSSP interrupts are enabled, after the master Control Bits State
completes sending data, an MSSP interrupt will wake Standard SPI Mode
the controller: Terminology CKP CKE
• from Sleep, in slave mode 0, 0 0 1
• from Idle, in slave or master mode 0, 1 0 0
If an exit from Sleep or Idle mode is not desired, MSSP 1, 0 1 1
interrupts should be disabled. 1, 1 1 0
In SPI master mode, when the Sleep mode is selected,
There is also an SMP bit which controls when the data
all m odule c locks are ha lted and the tra nsmis-
is sampled.
sion/reception will remain in that state until the devices
wakes. After the device returns to Run mode, the mod-
ule will resume transmitting and receiving data.
In SPI Slave m ode, the SPI T ransmit/Receive Shi ft
register operates as ynchronously to the de vice. Thi s
allows the device to be placed in any power-managed
mode an d da ta to be s hifted in to th e SPI

TABLE 17-2: REGISTERS ASSOCIATED WITH SPI OPERATION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF (1)
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
TRISA TRISA7(2) TRISA6(2) TRISA5 TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 62
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 62
SSPBUF SSP Receive Buffer/Transmit Register 60
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 60
SSPSTAT SMP CKE D/A P S R/W UA BF 60
Legend: Shaded cells are not used by the MSSP in SPI mode.
Note 1: These bits are unimplemented in 28-pin devices; always maintain these bits clear.
2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.

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PIC18F2XK20/4XK20
17.4 I2C Mode 17.4.1 REGISTERS
The M SSP m odule in I 2C m ode ful ly im plements al l The M SSP m odule has seven reg isters for I2C
master a nd s lave fu nctions (i ncluding general cal l operation. These are:
support) and provides interrupts on Start and Stop bits • MSSP Control Register 1 (SSPCON1)
in h ardware t o d etermine a fre e b us (m ulti-master • MSSP Control Register 2 (SSPCON2)
function). The MSSP module implements the standard
• MSSP STATUS register (SSPSTAT)
mode s pecifications as w ell a s 7-bit an d 1 0-bit
addressing. • Serial Receive/Transmit Buffer Register
(SSPBUF)
Two pins are used for data transfer:
• MSSP Shift Register (SSPSR) – Not directly
• Serial clock (SCL) – SCK/SCL accessible
• Serial data (SDA) – SDI/SDA • MSSP Address Register (SSPADD)
The user must configure these pins as inputs with the • MSSP Address Mask (SSPMSK)
corresponding TRIS bits. SSPCON1, SSPCON2 and SSPS TAT ar e the control
and S TATUS registers in I2C mod e op eration. The
FIGURE 17-7: MSSP BLOCK DIAGRAM SSPCON1 an d S SPCON2 re gisters a re re adable an d
(I2C™ MODE) writable. The lower 6 bits of the SSPSTAT are read-only.
The upper two bits of the SSPSTAT are read/write.
Internal
Data Bus
SSPSR is the shift register used for shifting data in or
out. SSPBUF is the buffer register to which data bytes
Read Write
are written to or read from.

SSPBUF Reg
When the SSP is configured in Master mode, the lower
SCK/SCL seven bits of SSPADD act as the Baud Rate Generator
Shift
reload value. When the SSP is configured for I2C slave
Clock mode t he SSPADD r egister h olds the sl ave device
address. The SSP can be configured t o resp ond to a
SSPSR Reg
range of a ddresses by qu alifying s elected bits of the
SDI/SDA MSb LSb
address register with the SSPMSK register.
SSPMSK Reg In receive operations, SSPSR and SSPBUF together
create a double-buffered re ceiver. When SSPSR
Match Detect Addr Match receives a complete byte, it is transferred to SSPBUF
and the SSPIF interrupt is set.
SSPADD Reg During transmission, the SSPBUF is n ot
double-buffered. A wri te to SSPBUF wil l write to both
Start and Set, Reset SSPBUF and SSPSR.
Stop bit Detect S, P bits
(SSPSTAT Reg)

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 PIC18F2XK20/4XK20

REGISTER 17-3: SSPADD: MSSP ADDRESS AND BAUD RATE REGISTER (I2C MODE)
R/W-0 R/W -0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADD7 ADD6 ADD5 ADD4 ADD3 ADD2 ADD1 ADD0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

Master mode

bit 7-0 ADD<7:0>: Baud Rate Clock Divider bits

SCL pin clock period = ((ADD<7:0> + 1) *4)/FOSC
10-Bit Slave mode: Most significant address byte

bit 7-3 Not used: Unused for most significant address byte. Bit state of this register is a don’t care. Bit pattern
sent by master is fixed by I2C specification and must be equal to ‘11110’. However, those bits are
compared by hardware and are not affected by the value in this register.
bit 2-1 ADD<9:8>: Two most significant bits of 10-bit address
bit 0 Not used: Unused in this mode. Bit state is a “don’t care”.
10-Bit Slave mode: Least significant address byte

bit 7-0 ADD<7:0>: Eight least significant bits of 10-bit address

7-Bit Slave mode

bit 7-1 ADD<7:1>: 7-bit address

bit 0 Not used: Unused in this mode. Bit state is a “don’t care”.

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PIC18F2XK20/4XK20

REGISTER 17-4: SSPSTAT: MSSP STATUS REGISTER (I2C MODE)

R/W-0 R/W -0 R-0 R-0 R-0 R-0 R-0 R-0
SMP CKE D/A P(1)
S(1)
R/W (2, 3)
UA BF
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 SMP: Slew Rate Control bit

In Master or Slave mode:
1 = Slew rate control disabled for standard speed mode (100 kHz and 1 MHz)
0 = Slew rate control enabled for high-speed mode (400 kHz)
bit 6 CKE: SMBus Select bit
In Master or Slave mode:
1 = Enable SMBus specific inputs
0 = Disable SMBus specific inputs
bit 5 D/A: Data/Address bit
In Master mode:
Reserved.
In Slave mode:
1 = Indicates that the last byte received or transmitted was data
0 = Indicates that the last byte received or transmitted was address
bit 4 P: Stop bit(1)
1 = Indicates that a Stop bit has been detected last
0 = Stop bit was not detected last
bit 3 S: Start bit(1)
1 = Indicates that a Start bit has been detected last
0 = Start bit was not detected last
bit 2 R/W: Read/Write Information bit (I2C mode only)(2, 3)
In Slave mode:
1 = Read
0 = Write
In Master mode:
1 = Transmit is in progress
0 = Transmit is not in progress
bit 1 UA: Update Address bit (10-bit Slave mode only)
1 = Indicates that the user needs to update the address in the SSPADD register
0 = Address does not need to be updated
bit 0 BF: Buffer Full Status bit
In Transmit mode:
1 = SSPBUF is full
0 = SSPBUF is empty
In Receive mode:
1 = SSPBUF is full (does not include the ACK and Stop bits)
0 = SSPBUF is empty (does not include the ACK and Stop bits)

Note 1: This bit is cleared on Reset and when SSPEN is cleared.

2: This bit holds the R/W bit information following the last address match. This bit is only valid from the
address match to the next Start bit, Stop bit or not ACK bit.
3: ORing this bit with SEN, RSEN, PEN, RCEN or ACKEN will indicate if the MSSP is in Active mode.

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 PIC18F2XK20/4XK20

REGISTER 17-5: SSPCON1: MSSP CONTROL 1 REGISTER (I2C MODE)

R/W-0 R/W -0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 WCOL: Write Collision Detect bit

In Master Transmit mode:
1 = A write to the SSPBUF register was attempted while the I2C conditions were not valid for a trans-
mission to be started (must be cleared by software)
0 = No collision
In Slave Transmit mode:
1 = The SSPBUF register is written while it is still transmitting the previous word (must be cleared by
software)
0 = No collision
In Receive mode (Master or Slave modes):
This is a “don’t care” bit.
bit 6 SSPOV: Receive Overflow Indicator bit
In Receive mode:
1 = A byte is received while the SSPBUF register is still holding the previous byte (must be cleared
by software)
0 = No overflow
In Transmit mode:
This is a “don’t care” bit in Transmit mode.
bit 5 SSPEN: Synchronous Serial Port Enable bit
1 = Enab les the ser ial port and co nfigures the SDA and SC L pins as the serial port pi ns. When
enabled, the SDA and SCL pins must be configured as inputs.
0 = Disables serial port and configures these pins as I/O port pins
bit 4 CKP: SCK Release Control bit
In Slave mode:
1 = Release clock
0 = Holds clock low (clock stretch), used to ensure data setup time
In Master mode:
Unused in this mode.
bit 3-0 SSPM<3:0>: Synchronous Serial Port Mode Select bits
1111 = I2C Slave mode, 10-bit address with Start and Stop bit interrupts enabled
1110 = I2C Slave mode, 7-bit address with Start and Stop bit interrupts enabled
1011 = I2C Firmware Controlled Master mode (Slave Idle)
1000 = I2C Master mode, clock = FOSC/(4 * (SSPADD + 1))
0111 = I2C Slave mode, 10-bit address
0110 = I2C Slave mode, 7-bit address
Bit combinations not specifically listed here are either reserved or implemented in SPI mode only.

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PIC18F2XK20/4XK20

REGISTER 17-6: SSPCON2: MSSP CONTROL REGISTER (I2C MODE)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
GCEN ACKSTAT ACKDT (2)
ACKEN(1)
RCEN (1)
PEN (1)
RSEN (1)
SEN(1)
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 GCEN: General Call Enable bit (Slave mode only)

1 = Generate interrupt when a general call address (0000h) is received in the SSPSR
0 = General call address disabled
bit 6 ACKSTAT: Acknowledge Status bit (Master Transmit mode only)
1 = Acknowledge was not received from slave
0 = Acknowledge was received from slave
bit 5 ACKDT: Acknowledge Data bit (Master Receive mode only)(2)
1 = Not Acknowledge
0 = Acknowledge
bit 4 ACKEN: Acknowledge Sequence Enable bit (Master Receive mode only)(1)
1 = Initiate Acknowledge sequence on SDA and SCL pins and transmit ACKDT data bit.
Automatically cleared by hardware.
0 = Acknowledge sequence Idle
bit 3 RCEN: Receive Enable bit (Master mode only)(1)
1 = Enables Receive mode for I2C
0 = Receive Idle
bit 2 PEN: Stop Condition Enable bit (Master mode only)(1)
1 = Initiate Stop condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Stop condition Idle
bit 1 RSEN: Repeated Start Condition Enable bit (Master mode only)(1)
1 = Initiate Repeated Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Repeated Start condition Idle
bit 0 SEN: Start Condition Enable/Stretch Enable bit(1)
In Master mode:
1 = Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware.
0 = Start condition Idle
In Slave mode:
1 = Clock stretching is enabled for both slave transmit and slave receive (stretch enabled)
0 = Clock stretching is disabled for slave received. Slave transmit clock stretching remains enabled.

Note 1: For bits ACKEN, RCEN, PEN, RSEN, SEN: If the I2C module is not in the Idle mode, these bits may not
be set (no spooling) and the SSPBUF may not be written (or writes to the SSPBUF are disabled).
2: Value that will be transmitted when the user initiates an Acknowledge sequence at the end of a receive.

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 PIC18F2XK20/4XK20
17.4.2 OPERATION 17.4.3.1 Addressing
The M SSP m odule fun ctions are ena bled by s etting Once the MSSP module has been enabled, it waits for
SSPEN bit of the SSPCON1 register. a Start condition to occur. Following the Start condition,
The SSPCON1 re gister all ows c ontrol of t he I 2C the 8 b its a re shifted i nto th e SSPSR re gister. Al l
operation. Four mode selection bits of the SSPCON1 incoming bits are s ampled with the rising edge of th e
register al low one of the fo llowing I 2C m odes to b e clock (SCL) line. The value of register SSPSR<7:1> is
selected: compared t o t he v alue o f t he SSPADD r egister. T he
address is compared on the falling edge of the eighth
• I2C Master mode, clock = (FOSC/(4 x clock (SCL) pulse. If the addresses match and the BF
(SSPADD + 1)) and SSPOV bits are clear, the following events occur:
• I 2C Slave mode (7-bit address)
1. The SSPSR reg ister v alue is lo aded in to th e
• I 2C Slave mode (10-bit address) SSPBUF register.
• I 2C Slave mode (7-bit address) with Start and 2. The Buffer Full bit, BF, is set.
Stop bit interrupts enabled
3. An ACK pulse is generated.
• I 2C Slave mode (10-bit address) with Start and
4. MSSP Interrupt Flag bit, SSPIF of the PIR1 reg-
Stop bit interrupts enabled
ister, is set (interrupt is generated, if enabled) on
• I 2C Firmware Controlled Master mode, slave is the falling edge of the ninth SCL pulse.
Idle
In 10-bit Address mode, tw o address bytes need to be
Selection of a ny I 2C m ode with the SSPEN bi t s et, received by the sla ve. The fiv e Mos t S ignificant bits
forces the SCL a nd SD A p ins to be op en-drain, (MSbs) of the first address byte specify if this is a 10-bit
provided these pin s are pro grammed to inp uts by address. Bit R/W of the SSPSTAT register must specify
setting the app ropriate TR IS bits. T o e nsure proper a write s o the slave devic e w ill rec eive the sec ond
operation of t he m odule, pul l-up res istors mu st be address byte. For a 10 -bit address, the firs t byte would
provided externally to the SCL and SDA pins. equal ‘11110 A9 A8 0’, where ‘A9’ and ‘A8’ are the two
MSbs of the address. The sequence of events for 10-bit
17.4.3 SLAVE MODE address is as follow s, w ith steps 7 thr ough 9 for the
In Slave mode, the SCL and SDA pins must be config- slave-transmitter:
ured as inputs. The M SSP m odule will ov erride the 1. Receive first (high) byte of address (bits SSPIF,
input s tate w ith th e ou tput da ta when req uired BF and UA (of the SSPSTAT register are set).
(slave-transmitter).
2. Update the SSPADD register with second (low)
The I 2C Slave mode hardware will always generate an byte of address (clears bit UA and releases the
interrupt on a n address match. T hrough th e m ode SCL line).
select bits, th e us er ca n al so cho ose to i nterrupt on 3. Read the SSPBUF register (clears bit BF) and
Start and Stop bits clear flag bit, SSPIF.
When an address is matched, or the data transfer after 4. Receive s econd ( low) byte of a ddress (bits
an a ddress m atch i s received, th e h ardware SSPIF, BF and UA are set). If th e address
automatically w ill g enerate the Ac knowledge (AC K) matches then the SCL is held until the next step.
pulse and load the SSPBUF register with the received Otherwise the SCL line is not held.
value currently in the SSPSR register. 5. Update the SSPADD register with the first (high)
Any combination of the following conditions will cause byte of a ddress. (T his w ill c lear bi t U A an d
the MSSP module not to give this ACK pulse: release a held SCL line.)
• The Buffer Full bit, BF bit of the SSPSTAT regis- 6. Read the SSPBUF register (clears bit BF) and
ter, is set before the transfer is received. clear flag bit, SSPIF.
• The overflow bit, SSPOV bit of the SSPCON1 7. Receive Repeated Start condition.
register, is set before the transfer is received. 8. Receive first (high) byte of address (bits SSPIF
In this c ase, the SSPSR reg ister v alue is not lo aded and BF are set).
into the SSPBUF, but bit SSPIF of the PIR1 register is 9. Read the SSPBUF register (clears bit BF) and
set. T he BF b it is c leared b y rea ding th e SSPBUF clear flag bit, SSPIF.
register, while bit SSPOV is cleared through software.
The SCL clock input must have a minimum high and
low for proper operation. The high and low times of the
I2C s pecification, as w ell a s t he requirement o f th e
MSSP module, are shown in timing parameter 100 and
parameter 101 (See Table 26-19).

 2010 Microchip Technology Inc. DS41303G-page 207

PIC18F2XK20/4XK20
17.4.3.2 Reception 17.4.3.3 Transmission
When the R/W bit of the address byte is clear and an When the R/W bit of the inc oming address byte is set
address ma tch oc curs, t he R /W bit of the SSPSTAT and a n a ddress m atch occurs, t he R/W bi t of t he
register is cleared. The received address is loaded into SSPSTAT re gister is s et. The rec eived a ddress i s
the SS PBUF re gister and th e SD A line i s held low loaded into the SSPBUF regi ster. The ACK pu lse will
(ACK). be sent on the ninth bit and pin SCK/SCL is held low
When the address byte overflow condition exists, then regardless of SEN (see Section 17.4.4 “Clock
the no Acknowledge (ACK) pulse is given. An overflow Stretching” for m ore detail). By s tretching the c lock,
condition is defined as either bit BF bit of the SSPSTAT the master will be unable to assert another clock pulse
register is s et, or b it S SPOV b it o f th e SSPCON1 until the slave is done preparing the transmit data. The
register is set. transmit data must be loaded into the SSPBUF register
which al so lo ads th e SSPSR register. T hen pi n
An MSSP interrupt is generated for each data transfer SCK/SCL should be enabled by setting the CKP bit of
byte. Fl ag bit, SSPIF of the PIR1 register, m ust b e the SSPCON1 register. The eight data bits are shifted
cleared by software. The SSPSTAT register is used to out on the falling edge of the SCL input. This ensures
determine the status of the byte. that the SDA signal is v alid during the SCL high time
When th e SEN b it of th e SSPCON2 re gister i s set, (Figure 17-9).
SCK/SCL will be he ld lo w ( clock stretch) following The ACK pulse from the master-receiver is latched on
each da ta t ransfer. Th e c lock m ust be re leased by the rising edge of the ninth SCL input pulse. If the SDA
setting th e C KP bit of t he SSPCON1 register. See line is hi gh (no t AC K), then th e d ata tran sfer i s
Section 17.4.4 “Clock Stretching” for more detail. complete. In this case, when the ACK is latched by the
slave, the s lave l ogic is res et (re sets SSPST AT
register) and the slave monitors for another occurrence
of the Start bit. If the SDA line was low (ACK), the next
transmit data must be loaded into the SSPBUF register.
Again, p in SCK/SCL must be en abled by s etting b it
CKP.
An MSSP interrupt is generated for each data transfer
byte. The SSPIF bit must be cleared by software and
the SSPSTAT register is used to determine the status
of the byte. The SSPIF bit is set on the falling edge of
the ninth clock pulse.

DS41303G-page 208  2010 Microchip Technology Inc.

 FIGURE 17-8:

 2010 Microchip Technology Inc.

Receiving Address R/W = 0 Receiving Data ACK Receiving Data ACK

SDA A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S P

SSPIF
Bus master
(PIR1<3>) terminates
transfer

BF (SSPSTAT<0>)
Cleared by software
SSPBUF is read

SSPOV (SSPCON1<6>)

SSPOV is set
because SSPBUF is
still full. ACK is not sent.

CKP (CKP does not reset to ‘0’ when SEN = 0)

I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 7-BIT ADDRESS)

DS41303G-page 209
PIC18F2XK20/4XK20
 FIGURE 17-9:

DS41303G-page 210
Receiving Address R/W = 0 Transmitting Data Transmitting Data
ACK ACK
SDA A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

SCL
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S
Data in SCL held low P
sampled while CPU
responds to SSPIF

SSPIF (PIR1<3>)
PIC18F2XK20/4XK20

BF (SSPSTAT<0>)
Cleared by software Cleared by software
From SSPIF ISR From SSPIF ISR
SSPBUF is written by software SSPBUF is written by software

CKP

CKP is set by software

I2C™ SLAVE MODE TIMING (TRANSMISSION, 7-BIT ADDRESS)

CKP is set by software

 2010 Microchip Technology Inc.

 FIGURE 17-10:

Clock is held low until Clock is held low until

update of SSPADD has update of SSPADD has
taken place taken place

Receive First Byte of Address Receive Second Byte of Address Receive Data Byte Receive Data Byte
R/W = 0 ACK

SDA 1 1 1 1 0 A9 A8 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACK D7 D6 D5 D4 D3 D2 D1 D0

 2010 Microchip Technology Inc.

SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S P

Bus master
terminates
SSPIF transfer
(PIR1<3>)
Cleared by software Cleared by software Cleared by software
Cleared by software

BF (SSPSTAT<0>)

SSPBUF is written with Dummy read of SSPBUF

contents of SSPSR to clear BF flag
SSPOV (SSPCON1<6>)

SSPOV is set
because SSPBUF is
still full. ACK is not sent.

UA (SSPSTAT<1>)

UA is set indicating that Cleared by hardware Cleared by hardware when

the SSPADD needs to be when SSPADD is updated SSPADD is updated with high
updated with low byte of address byte of address

UA is set indicating that

SSPADD needs to be
updated

CKP (CKP does not reset to ‘0’ when SEN = 0)

I2C™ SLAVE MODE TIMING WITH SEN = 0 (RECEPTION, 10-BIT ADDRESS)

DS41303G-page 211
PIC18F2XK20/4XK20
 FIGURE 17-11:

DS41303G-page 212
Bus master
terminates
Clock is held low until Clock is held low until transfer
update of SSPADD has update of SSPADD has Clock is held low until
taken place taken place CKP is set to ‘1’
R/W = 0
Receive First Byte of Address Receive Second Byte of Address Receive First Byte of Address R/W=1 Transmitting Data Byte ACK
SDA 1 1 1 1 0 A9 A8 ACK A7 A6 A5 A4 A3 A2 A1 A0 ACK 1 1 1 1 0 A9 A8 ACK D7 D6 D5 D4 D3 D2 D1 D0

SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S Sr P
PIC18F2XK20/4XK20

SSPIF
(PIR1<3>)
Cleared by software Cleared by software Cleared by software

BF (SSPSTAT<0>)

SSPBUF is written with Dummy read of SSPBUF Dummy read of SSPBUF

contents of SSPSR to clear BF flag BF flag is clear Write of SSPBUF Completion of
to clear BF flag initiates transmit data transmission
at the end of the
UA (SSPSTAT<1>) third address sequence clears BF flag

UA is set indicating that Cleared by hardware when Cleared by hardware when

the SSPADD needs to be SSPADD is updated with low SSPADD is updated with high
updated byte of address byte of address.

UA is set indicating that

SSPADD needs to be
updated
CKP (SSPCON1<4>)

CKP is set by software

CKP is automatically cleared by hardware, holding SCL low

I2C™ SLAVE MODE TIMING (TRANSMISSION, 10-BIT ADDRESS)

 2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.3.4 SSP Mask Register This register m ust be initiated pri or to se tting
2 SSPM<3:0> bits to select the I2C Slave mode (7-bit or
An SSP Mask (SS PMSK) register is av ailable in I C
10-bit address).
Slave mo de a s a m ask fo r the value h eld in th e
SSPSR reg ister duri ng an address comparison The SSP Mask register is active during:
operation. A zero (‘0’) bit in the SSPMSK register has • 7-bit Address mode: address compare of A<7:1>.
the e ffect of making t he c orresponding b it i n th e
• 10-bit Address mode: address compare of A<7:0>
SSPSR register a “don’t care”.
only. The SSP mask has no effect during the
This register is res et to al l ‘ 1’s up on an y R eset reception of the first (high) byte of the address.
condition a nd, therefore, has no ef fect on st andard
SSP operation until written with a mask value.

REGISTER 17-7: SSPMSK: SSP MASK REGISTER

R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1 R/W-1
MSK7 MSK6 MSK5 MSK4 MSK3 MSK2 MSK1 MSK0(1)
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-1 MSK<7:1>: Mask bits

1 = The received address bit n is compared to SSPADD<n> to detect I2C address match
0 = The received address bit n is not used to detect I2C address match
bit 0 MSK<0>: Mask bit for I2C Slave mode, 10-bit Address(1)
I2C Slave mode, 10-bit Address (SSPM<3:0> = 0111):
1 = The received address bit 0 is compared to SSPADD<0> to detect I2C address match
0 = The received address bit 0 is not used to detect I2C address match

Note 1: The MSK0 bit is used only in 10-bit slave mode. In all other modes, this bit has no effect.

 2010 Microchip Technology Inc. DS41303G-page 213

PIC18F2XK20/4XK20
17.4.4 CLOCK STRETCHING 17.4.4.3 Clock Stretching for 7-bit Slave
Both 7 -bit an d 1 0-bit Sl ave m odes implement Transmit Mode
automatic clock stretching during a transmit sequence. 7-bit Slave T ransmit m ode i mplements clock stretch-
The SEN bi t o f th e SSP CON2 register a llows clock ing by clearing the CKP bit after the falling edge of the
stretching to be enabled during receives. Setting SEN ninth clock if the BF bit is clear. This occurs regardless
will cause the SC L pin to be hel d l ow a t th e e nd of of the state of the SEN bit.
each data receive sequence. The user’s ISR must set the CKP bit before transmis-
sion is all owed to continue. By hol ding the SC L lin e
17.4.4.1 Clock Stretching for 7-bit Slave low, the user has time to service the ISR and load the
Receive Mode (SEN = 1) contents of the SSPBUF before the master device can
In 7-bit Slave Receive mode, on the falling edge of the initiate ano ther data tran sfer se quence (se e
ninth clock at the end of the ACK sequence if the BF Figure 17-9).
bit is s et, th e CKP bi t of th e SSPCON1 reg ister i s Note 1: If the user loads the contents of SSPBUF,
automatically cl eared, fo rcing th e SC L out put to be setting the BF bit before the falling edge of
held low. The CKP being cleared to ‘ 0’ will assert the the ni nth c lock, the C KP bi t w ill not be
SCL l ine low. T he C KP bi t must be set i n t he us er’s cleared and clock stretching will not occur.
ISR before reception is allowed to continue. By holding
the SCL line low, the user has time to service the ISR 2: The C KP bit can b e s et by software
and read t he contents of th e SSP BUF b efore th e regardless of the state of the BF bit.
master dev ice can ini tiate another dat a transfer
sequence. Th is w ill p revent buffer ov erruns fro m 17.4.4.4 Clock Stretching for 10-bit Slave
occurring (see Figure 17-13). Transmit Mode
Note 1: If the u ser reads the co ntents of the In 10-bit Slave Transmit mode, clock stretching is con-
SSPBUF b efore the f alling e dge of the trolled during the first tw o address sequences by the
ninth cl ock, t hus cl earing th e BF bi t, the state of the UA bit, just as it is in 10-bit Slave Receive
CKP bi t w ill not be cleared and clock mode. The first two addresses are followed by a third
stretching will not occur. address s equence w hich c ontains the high-order bits
of the 10-bit address and the R/W bit set to ‘ 1’. A fter
2: The C KP bit ca n b e s et by so ftware
the third address sequence is performed, the UA bit is
regardless of the state of the BF bit. The
not se t, the mo dule is now c onfigured in T ransmit
user should be careful to clear the BF bit
mode and clock stretching is controlled by the BF flag
in th e ISR be fore th e n ext re ceive
as in 7-bit Slave Transmit mode (see Figure 17-11).
sequence in order to prevent an overflow
condition.

17.4.4.2 Clock Stretching for 10-bit Slave

Receive Mode (SEN = 1)
In 10 -bit Sl ave R eceive m ode du ring th e address
sequence, cl ock s tretching a utomatically t akes p lace
but CKP is not cleared. During this time, if the UA bit is
set a fter th e ni nth clock, cl ock s tretching i s in itiated.
The UA bit is set after receiving the upper byte of the
10-bit address and following the receive of the second
byte of the 10-bit address with the R/W bit cleared to
‘0’. The release of the clock line occurs upon updating
SSPADD. C lock s tretching w ill o ccur o n ea ch d ata
receive sequence as described in 7-bit mode.
Note: If the user polls the UA bit and clears it by
updating the SSPADD register before the
falling edge of the ninth clock occurs and if
the user hasn’t cleared the BF bit by read-
ing the SSPBUF register before that time,
then the CKP bit will still NOT be asserted
low. C lock s tretching o n th e ba sis o f the
state of the BF bi t onl y oc curs du ring a
data sequence, not an address sequence.

DS41303G-page 214  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.4.5 Clock Synchronization and
the CKP bit
When the CKP bit is cleared, the SCL output is forced
to ‘0’. However, clearing the CKP bit will not assert the
SCL output l ow un til t he S CL output i s already s am-
pled lo w. Th erefore, the C KP b it w ill no t as sert th e
SCL line un til an ex ternal I 2C ma ster de vice h as
already as serted th e SC L li ne. Th e SC L ou tput w ill
remain l ow un til the C KP bit is set and all oth er
devices o n the I 2C b us have de asserted SC L. Thi s
ensures that a write to the CKP bit will not violate the
minimum high ti me req uirement for SC L (se e
Figure 17-12).

FIGURE 17-12: CLOCK SYNCHRONIZATION TIMING

Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4

SDA DX DX – 1

SCL

Master device
CKP asserts clock

Master device
deasserts clock
WR
SSPCON1

 2010 Microchip Technology Inc. DS41303G-page 215

 FIGURE 17-13:

DS41303G-page 216
Clock is not held low
because buffer full bit is
clear prior to falling edge Clock is held low until Clock is not held low
of 9th clock CKP is set to ‘1’ because ACK = 1

Receiving Address R/W = 0 Receiving Data ACK Receiving Data ACK

SDA A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S P
PIC18F2XK20/4XK20

SSPIF
Bus master
(PIR1<3>) terminates
transfer

BF (SSPSTAT<0>)
Cleared by software
SSPBUF is read

SSPOV (SSPCON1<6>)

SSPOV is set
because SSPBUF is
still full. ACK is not sent.

CKP

CKP
If BF is cleared written
prior to the falling to ‘1’ in
edge of the 9th clock, software
CKP will not be reset BF is set after falling
to ‘0’ and no clock edge of the 9th clock,
stretching will occur CKP is reset to ‘0’ and
clock stretching occurs
I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 7-BIT ADDRESS)

 2010 Microchip Technology Inc.

 FIGURE 17-14:

Clock is held low until Clock is held low until

update of SSPADD has update of SSPADD has Clock is not held low
Clock is held low until
taken place taken place because ACK = 1
CKP is set to ‘1’
Receive First Byte of Address Receive Second Byte of Address Receive Data Byte Receive Data Byte
R/W = 0 ACK
ACK ACK
SDA 1 1 1 1 0 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

 2010 Microchip Technology Inc.

ACK

SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S P

SSPIF
Bus master
(PIR1<3>) terminates
Cleared by software Cleared by software Cleared by software transfer
Cleared by software

BF (SSPSTAT<0>)

SSPBUF is written with Dummy read of SSPBUF Dummy read of SSPBUF

contents of SSPSR to clear BF flag to clear BF flag
SSPOV (SSPCON1<6>)

SSPOV is set
because SSPBUF is
still full. ACK is not sent.

UA (SSPSTAT<1>)

UA is set indicating that Cleared by hardware when Cleared by hardware when

the SSPADD needs to be SSPADD is updated with low SSPADD is updated with high
updated byte of address after falling edge byte of address after falling edge
of ninth clock of ninth clock

UA is set indicating that

SSPADD needs to be
updated
CKP
Note: An updat e of the SSPADD
register be fore t he f alling
edge of th e n inth clock will CKP written to ‘1’
have n o ef fect on U A and by software
UA will remain set.

Note: An update of the SSPADD register before

the falling edge of the ninth clock will have
no effect on UA and UA will remain set.
I2C™ SLAVE MODE TIMING WITH SEN = 1 (RECEPTION, 10-BIT ADDRESS)

DS41303G-page 217
PIC18F2XK20/4XK20
PIC18F2XK20/4XK20
17.4.5 GENERAL CALL ADDRESS If the ge neral c all a ddress m atches, the SSPSR i s
SUPPORT transferred to the SSPBUF, the BF flag bit is set (eighth
bit) and on the falling edge of the ninth bit (ACK bit), the
The addressing procedure for the I2C bus is such that
SSPIF interrupt flag bit is set.
the f irst b yte af ter the Start condition u sually
determines which device will be the slave addressed by When the interrupt is se rviced, th e s ource for th e
the master. The exception is the general call address interrupt can be checked by reading the contents of the
which ca n a ddress al l d evices. When th is address i s SSPBUF. Th e v alue can b e u sed to de termine i f th e
used, a ll devices s hould, in the ory, respond w ith a n address was device specific or a general call address.
Acknowledge. In 10-bit mode, the SSPADD is required to be updated
The general c all ad dress is o ne of eight addresses for the second half of the address to match and the UA
reserved for sp ecific purp oses by the I 2C pr otocol. It bit of th e SSPSTAT register is set. If the general call
consists of all ‘0’s with R/W = 0. address is sampled when the GCEN bit is set, while the
slave is configured in 10-b it Add ress mo de, then the
The gen eral cal l add ress is recognized w hen the
second half of the address is not necessary, the UA bit
GCEN bit of the SSPCON2 is set. Following a Start bit
will not be set and the slave will begin receiving data
detect, 8 bit s are shifted in to the SSPSR and the
after the Acknowledge (Figure 17-15).
address is c ompared against t he SSPADD. It i s also
compared to the general call address and fixed in hard-
ware.

FIGURE 17-15: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE

(7 OR 10-BIT ADDRESS MODE)

Address is compared to General Call Address

after ACK, set interrupt

R/W = 0 Receiving Data ACK

SDA General Call Address ACK D7 D6 D5 D4 D3 D2 D1 D0

SCL
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S

SSPIF

BF (SSPSTAT<0>)

Cleared by software
SSPBUF is read
SSPOV (SSPCON1<6>) ‘0’

GCEN (SSPCON2<7>)
‘1’

DS41303G-page 218  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.6 MASTER MODE Note: The M SSP m odule, when configured in
Master m ode is en abled b y s etting and cle aring th e I2C Master mode, does not allow queueing
appropriate SSPM bits in SSPCON1 and by setting the of ev ents. Fo r in stance, the user i s not
SSPEN bit. In M aster m ode, the SCL and SDA lines allowed to in itiate a S tart c ondition and
are manipulated by the MSSP hardware. immediately write the SSPBUF register to
initiate tra nsmission b efore the S tart
Master m ode of ope ration is su pported by in terrupt
condition i s c omplete. In th is ca se, the
generation on the detection of the Start and Stop con-
SSPBUF wil l no t be writte n to an d the
ditions. The Stop (P) and Start (S) bits are cleared from
WCOL bit will be set, indicating that a write
a Reset or when the MSSP module is disabled. Control
to the SSPBUF did not occur.
of the I 2C bus may be taken when the P bit is set, or the
bus is Idle, with both the S and P bits clear. The following events will cause the SSP Interrupt Flag
In Firmware C ontrolled Ma ster mode, us er cod e bit, SSPIF, to be set (SSP interrupt, if enabled):
conducts al l I 2C bu s ope rations based on Start and • Start condition
Stop bit conditions.
• Stop condition
Once M aster m ode is e nabled, the user has si x • Data transfer byte transmitted/received
options.
• Acknowledge transmit
1. Assert a Start condition on SDA and SCL. • Repeated Start
2. Assert a Repeated Start condition on SDA and
SCL.
3. Write to the SSPBUF reg ister in itiating
transmission of data/address.
4. Configure the I2C port to receive data.
5. Generate an Acknowledge condition at the end
of a received byte of data.
6. Generate a Stop condition on SDA and SCL.

FIGURE 17-16: MSSP BLOCK DIAGRAM (I2C™ MASTER MODE)

Internal SSPM<3:0>
Data Bus SSPADD<7:0>
Read Write

SSPBUF Baud
Rate
Generator
SDA Shift
Clock
Clock Arbitrate/WCOL Detect

SDA In
SSPSR
(hold off clock source)

MSb LSb
Receive Enable

Start bit, Stop bit,

Clock Cntl

Acknowledge
Generate
SCL

Start bit Detect

Stop bit Detect
SCL In Write Collision Detect Set/Reset, S, P, WCOL (SSPSTAT)
Clock Arbitration Set SSPIF, BCLIF
Bus Collision State Counter for Reset ACKSTAT, PEN (SSPCON2)
end of XMIT/RCV

 2010 Microchip Technology Inc. DS41303G-page 219

PIC18F2XK20/4XK20
17.4.6.1 I2C Master Mode Operation A typical transmit sequence would go as follows:
The m aster de vice generates al l o f th e s erial clock 1. The user generates a Start condition by setting
pulses and the Start and Stop conditions. A transfer is the SEN bit of the SSPCON2 register.
ended with a S top condition or w ith a R epeated Start 2. SSPIF is s et. Th e M SSP m odule wi ll wa it th e
condition. Since the R epeated Start co ndition is als o required s tart tim e b efore an y ot her o peration
the beginning of the next serial transfer, the I2C bus will takes place.
not be released. 3. The u ser l oads t he SSPBUF wi th the s lave
In Master T ransmitter mo de, serial da ta is output address to transmit.
through SDA, while SCL outputs the serial clock. The 4. Address is shifted out the SDA pin until all 8 bits
first byte transmitted contains the slave address of the are transmitted.
receiving device (7 bits) and the Read/Write (R/W) bit. 5. The MSSP module shifts in the ACK bit from the
In this case, the R/W bit will be logic ‘0’. Serial data is slave d evice and w rites it s v alue in to th e
transmitted 8 bits at a time. After each byte is transmit- ACKSTAT bit of the SSPCON2 register.
ted, an A cknowledge bi t is r eceived. S tart a nd S top
6. The MSSP module generates an interrupt at the
conditions are output to indicate the beginning and the
end of the ninth clock cycle by setting the SSPIF
end of a serial transfer.
bit.
In Master Receive mode, the first byte transmitted con- 7. The user l oads the SSPBUF wit h e ight bits of
tains th e s lave ad dress of t he t ransmitting device data.
(7 bits) and the R/W bit. In this case, the R/W bit will be
8. Data is shifted out the SDA pin until all 8 bits are
logic ‘1’. Thus, the first byte transmitted is a 7-bit slave
transmitted.
address fo llowed by a ‘1’ to indicate the re ceive bi t.
Serial data is received via SDA, while SCL outputs the 9. The MSSP module shifts in the ACK bit from the
serial clock. Serial data is received 8 bits at a time. After slave d evice and w rites it s v alue in to th e
each byte is received, an Acknowledge bit is transmit- ACKSTAT bit of the SSPCON2 register.
ted. S tart and S top conditions i ndicate t he beginning 10. The MSSP module generates an interrupt at the
and end of transmission. end of the ninth clock cycle by setting the SSPIF
bit.
The Bau d R ate G enerator use d for th e SPI mode
operation i s used t o se t t he S CL c lock f requency f or 11. The user generates a Stop condition by setting
either 100 kHz, 400 kHz or 1 MHz I 2C operation. See the PEN bit of the SSPCON2 register.
Section 17.4.7 “Baud Rate” for more detail. 12. Interrupt is generated once the Stop condition is
complete.

DS41303G-page 220  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.7 BAUD RATE Once th e gi ven op eration is co mplete (i.e .,
2 transmission of the last data bit is followed by ACK), the
In I C Master mode, the Baud Rate Generator (BRG)
internal clock will automatically stop counting and the
reload value i s pl aced in th e SSPADD register
SCL pin will remain in its last state.
(Figure 17-17). Wh en a w rite occ urs to SS PBUF, th e
Baud Rate Generator will automatically begin counting. Table 17-3 de monstrates cl ock rate s ba sed on
The BR G co unts dow n to ‘ 0’ an d stops un til an other instruction c ycles an d t he BR G v alue l oaded in to
reload has taken pla ce. The BR G co unt is decre- SSPADD.
mented twice per instruction cycle (TCY) on the Q2 and The minimum SSPADD value for baud rate generation
Q4 cl ocks. In I 2C Master mode, the BRG is reloaded is 0x03.
automatically. O ne h alf o f th e SCL p eriod is e qual to
[(SSPADD+1)  2]/FOSC. T herefore SSP ADD =
(FCY/FSCL) -1.

FIGURE 17-17: BAUD RATE GENERATOR BLOCK DIAGRAM

SSPM<3:0> SSPADD<7:0>

SSPM<3:0> Reload Reload

SCL Control

CLKOUT BRG Down Counter FOSC/2

TABLE 17-3: I2C™ CLOCK RATE W/BRG

FSCL
FOSC FCY BRG Value
(2 Rollovers of BRG)
64 MHz 16 MHz 27h 400 kHz(1)
64 MHz 16 MHz 32h 313.7 kHz
64 MHz 16 MHz 3Fh 250 kHz
40 MHz 10 MHz 18h 400 kHz(1)
40 MHz 10 MHz 1Fh 312.5 kHz
40 MHz 10 MHz 63h 100 kHz
16 MHz 4 MHz 09h 400 kHz(1)
16 MHz 4 MHz 0Ch 308 kHz
16 MHz 4 MHz 27h 100 kHz
4 MHz 1 MHz 09h 100 kHz
Note 1: The I2C interface does not conform to the 400 kHz I2C specification (which applies to rates greater than
100 kHz) in all details, but may be used with care where higher rates are required by the application.

 2010 Microchip Technology Inc. DS41303G-page 221

PIC18F2XK20/4XK20
17.4.7.1 Clock Arbitration
Clock arbitration occurs w hen the master, during any
receive, tra nsmit or R epeated Start/Stop co ndition,
deasserts the SC L p in ( SCL al lowed to flo at h igh).
When the SC L pin i s al lowed to float hi gh, th e Bau d
Rate Gen erator (BRG) is s uspended fro m c ounting
until the SC L pin is actually sampled high. When the
SCL pin is sampled high, the Baud Rate Generator is
reloaded w ith the contents o f SS PADD<7:0> and
begins counting. This ensures that the SCL high time
will always be at lea st one BRG rollover count in the
event that the clock is held low by an external device
(Figure 17-18).

FIGURE 17-18: BAUD RATE GENERATOR TIMING WITH CLOCK ARBITRATION

SDA DX DX – 1

SCL deasserted but slave holds SCL allowed to transition high

SCL low (clock arbitration)
SCL

BRG decrements on
Q2 and Q4 cycles

BRG
03h 02h 01h 00h (hold off) 03h 02h
Value

SCL is sampled high, reload takes

place and BRG starts its count
BRG
Reload

DS41303G-page 222  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.8 I2C MASTER MODE START Note: If a t the be ginning of the Start c ondition,
CONDITION TIMING the SD A and SC L pins are already sam-
To in itiate a S tart c ondition, the us er se ts th e S tart pled low, or if during the Start condition, the
Enable bi t, SEN bi t of t he SSPCON2 re gister. If th e SCL l ine is sa mpled low be fore the SD A
SDA and SCL pins are sampled high, the Baud Rate line is dri ven lo w, a bus col lision oc curs,
Generator is reloaded w ith the co ntents of the Bus Collision Interrupt Flag, BCLIF, is
SSPADD<6:0> and starts its count. If SCL and SDA are set, the Start condition is aborted and the
both sampled hi gh w hen the B aud Rate Ge nerator I2C module is reset into its Idle state.
times out (TBRG), the SDA pin is driven low. The action
of the SD A being driven low while SCL is high is th e 17.4.8.1 WCOL Status Flag
Start condition and causes the S bit of the SSPSTAT1 If the user writes the SSPBUF when a Start sequence
register to be set. Following this, the Baud Rate Gener- is in progress, the WCOL is set and the contents of the
ator is rel oaded w ith the contents of SSPADD<7:0> buffer are unchanged (the write doesn’t occur).
and resumes its count. When the Baud Rate Generator
Note: Because que ueing of ev ents i s n ot
times out (TBRG), the SEN bit of the SSPCON2 register
allowed, w riting to the low er 5 bi ts of
will be aut omatically cleared by hardware; th e Bau d
SSPCON2 i s d isabled unt il the Start
Rate G enerator is s uspended, le aving the SD A lin e
condition is complete.
held low and the Start condition is complete.

FIGURE 17-19: FIRST START BIT TIMING

Set S bit (SSPSTAT<3>)

Write to SEN bit occurs here
SDA = 1,
At completion of Start bit,
SCL = 1
hardware clears SEN bit
and sets SSPIF bit
TBRG TBRG Write to SSPBUF occurs here

1st bit 2nd bit

SDA
TBRG

SCL
TBRG
S

 2010 Microchip Technology Inc. DS41303G-page 223

PIC18F2XK20/4XK20
17.4.9 I2C MASTER MODE REPEATED Note 1: If R SEN is programmed w hile any other
START CONDITION TIMING event is in progress, it will not take effect.
A Repeated Start condition occurs when the RSEN bit 2: A bus collision during the Repeated Start
of the SSPCON2 register is programmed high and the condition occurs if:
I2C logic module is in the Idle state. When the RSEN bit
• SDA is sampled low when SCL goes
is set, the SCL pin is asserted low. When the SCL pin
from low-to-high.
is sampled low, the Baud Rate Generator is loaded with
the c ontents of SSPADD<5:0> an d b egins c ounting. • SCL goes low before SDA is
The SDA pin is released (brought high) for one Baud asserted low. This may indicate that
Rate Generator co unt (T BRG). W hen t he B aud Rate another master is attempting to
Generator times out, if SDA is sampled high, the SCL transmit a data ‘1’.
pin w ill b e dea sserted (b rought h igh). Whe n SC L i s
Immediately following the SSPIF bit getting set, the user
sampled hig h, the Baud R ate G enerator is relo aded
may w rite the SSPBUF w ith the 7-bit add ress i n 7-bit
with the contents of SSPADD<7:0> and begins count-
mode or the default first address in 10-bit mode. After the
ing. SDA and SCL must be sampled high for one TBRG.
first eight bit s are transmitted and an ACK is received,
This action is then followed by assertion of the SDA pin
the u ser may then trans mit an additional eight bi ts of
(SDA = 0) for on e T BRG while SCL is high. Following
address (10-bit mode) or eight bits of data (7-bit mode).
this, the RSEN bit of the SSPCON2 reg ister wil l be
automatically cleared and the Baud Rate Generator will 17.4.9.1 WCOL Status Flag
not be reloaded, leaving the SDA pin held low. As soon
as a S tart condition is detected on the SDA and SCL If the user writes the SSPBUF when a Repeated Start
pins, the S bit of the SSPSTAT register will be set. The sequence is in pro gress, th e W COL is s et and th e
SSPIF bit will not be set until the Baud Rate Generator contents of the buffer are unchanged (the write doesn’t
has timed out. occur).
Note: Because que ueing of ev ents i s n ot
allowed, w riting of the low er 5 bi ts of
SSPCON2 is disabled until the Repeated
Start condition is complete.

FIGURE 17-20: REPEAT START CONDITION WAVEFORM

S bit set by hardware

Write to SSPCON2
SDA = 1,
occurs here. At completion of Start bit,
SDA = 1, SCL = 1
hardware clears RSEN bit
SCL (no change). and sets SSPIF

TBRG TBRG TBRG

SDA 1st bit

RSEN bit set by hardware

on falling edge of ninth clock, Write to SSPBUF occurs here
end of Xmit
TBRG
SCL
TBRG

Sr = Repeated Start

DS41303G-page 224  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.10 I2C MASTER MODE 17.4.10.3 ACKSTAT Status Flag
TRANSMISSION In Transmit mode, the ACKSTAT bit of the SSPCON2
Transmission of a d ata by te, a 7 -bit ad dress or th e register is cleared when the slave has sent an Acknowl-
other half of a 10-bit address is accomplished by simply edge (AC K = 0) and i s s et w hen t he sl ave do es no t
writing a value to the SSPBUF register. This action will Acknowledge (AC K = 1). A slave sends an Acknowl-
set the Buffer Full flag bit, BF and allow the Baud Rate edge when it has recognized its address (including a
Generator to beg in counting and start the next trans- general call), or when the slave has properly received
mission. Eac h b it o f a ddress/data w ill be shifted o ut its data.
onto the SDA pin af ter th e fa lling edg e o f SC L i s
asserted (see da ta ho ld t ime sp ecification 17.4.11 I2C MASTER MODE RECEPTION
parameter 106). S CL is h eld l ow f or one Baud Rate Master mode reception is enabled by programming the
Generator rollover count (T BRG). Data should be valid Receive En able bit, RCEN bit o f t he SSPCON2
before SCL is released high (see data setup time spec- register.
ification parameter 107). When the SCL pin is released
high, it is held that way for TBRG. The data on the SDA Note: The MSSP module must be in an Idle state
pin must remain stable for that duration and some hold before the RCEN bit is set or the RCEN bit
time after the next falling edge of SCL. After the eighth will be disregarded.
bit is shifted out (the falling edge of the eighth clock), The Baud Rate Generator begins counting and on each
the B F f lag i s cleared and t he m aster releases S DA. rollover, t he state of th e SCL pin c hanges
This al lows the sl ave de vice be ing addressed to (high-to-low/low-to-high) an d dat a is sh ifted in to th e
respond with an ACK bit during the ninth bit time if an SSPSR. After the falling edge of the eighth clock, the
address match occurred, or if data was received prop- receive enable flag is automatically cleared, the con-
erly. The status of ACK is written into the ACKDT bit on tents of th e SSPSR are loaded into the SSPBUF, the
the falling edge of the ninth clock. If the master receives BF flag bit is set, the SSPIF flag bit is set and the Baud
an Ac knowledge, t he Acknowledge S tatus bi t, Rate G enerator is s uspended fr om counting, holding
ACKSTAT, is cleared. If not, the bit is set. After the ninth SCL low. The MSSP is now in Id le state awaiting the
clock, the SSPIF bit is set and the master clock (Baud next command. When the buffer is re ad by the CPU,
Rate Generator) is suspended until the next data byte the BF flag bit is au tomatically cleared. The us er can
is loaded into the SSPBUF, leaving SCL low and SDA then send an Acknowledge bit at the end of reception
unchanged (Figure 17-21). by setting the Acknowledge Sequence Enable, ACKEN
After the write to the SSPBUF, each bit of the address bit of the SSPCON2 register.
will be shifted out on the falling edge of SC L until all
seven address bits and the R/W bit are completed. On 17.4.11.1 BF Status Flag
the fal ling ed ge of the eighth c lock, the m aster w ill In receive operation, the BF bit is set when an address
deassert the SD A pin , allowing the sl ave to res pond or data byte is loaded into SSPBUF from SSPSR. It is
with an Acknowledge. On the falling edge of the ninth cleared when the SSPBUF register is read.
clock, the master will sample the SDA pin to see if the
address was recognized by a slave. The status of the 17.4.11.2 SSPOV Status Flag
ACK bit is loaded into the ACKSTAT Status bit of the In receive operation, the SSPOV bit is set when 8 bits
SSPCON2 reg ister. Following the fa lling ed ge of the are rec eived into the SSPSR and t he BF fl ag bit i s
ninth clock transmission of the address, the SSPIF is already set from a previous reception.
set, the BF flag is cleared and the Baud Rate Generator
is turned off until another w rite to the SSPBUF takes 17.4.11.3 WCOL Status Flag
place, holding SCL low and allowing SDA to float.
If the us er writes t he SSPBUF wh en a re ceive i s
17.4.10.1 BF Status Flag already in progress (i.e., SSPSR is still shifting in a data
byte), the WCOL bit is set and the contents of the buffer
In Transmit mode, the BF bit of the SSPSTAT register are unchanged (the write doesn’t occur).
is set when the CPU writes to SSPBUF and is cleared
when all 8 bits are shifted out.

17.4.10.2 WCOL Status Flag

If the us er writ es the SSPBUF whe n a t ransmit i s
already in p rogress (i.e., SSPSR i s still shifting out a
data byte), the WCOL is set and the contents of the buf-
fer are unchanged (the write doesn’t occur).
WCOL must be cleared by software.

 2010 Microchip Technology Inc. DS41303G-page 225

 FIGURE 17-21:

DS41303G-page 226
Write SSPCON2<0> SEN = 1 ACKSTAT in
Start condition begins SSPCON2 = 1
From slave, clear ACKSTAT bit SSPCON2<6>
SEN = 0
Transmitting Data or Second Half
Transmit Address to Slave R/W = 0 ACK
of 10-bit Address
SDA A7 A6 A5 A4 A3 A2 A1 ACK = 0 D7 D6 D5 D4 D3 D2 D1 D0

SSPBUF written with 7-bit address and R/W

start transmit
SCL 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
S P
SCL held low
while CPU
responds to SSPIF
PIC18F2XK20/4XK20

SSPIF
Cleared by software service routine
Cleared by software from SSP interrupt
Cleared by software

BF (SSPSTAT<0>)

SSPBUF written SSPBUF is written by software

SEN

After Start condition, SEN cleared by hardware

PEN

R/W
I 2C™ MASTER MODE WAVEFORM (TRANSMISSION, 7 OR 10-BIT ADDRESS)

 2010 Microchip Technology Inc.

 FIGURE 17-22:

Write to SSPCON2<4>
to start Acknowledge sequence
SDA = ACKDT (SSPCON2<5>) = 0
Write to SSPCON2<0> (SEN = 1),
begin Start condition ACK from Master Set ACKEN, start Acknowledge sequence
Master configured as a receiver SDA = ACKDT = 0 SDA = ACKDT = 1
SEN = 0 by programming SSPCON2<3> (RCEN = 1)

 2010 Microchip Technology Inc.

PEN bit = 1
Write to SSPBUF occurs here, RCEN cleared RCEN = 1, start RCEN cleared
ACK from Slave next receive automatically written here
start XMIT automatically
Transmit Address to Slave R/W = 0 Receiving Data from Slave Receiving Data from Slave
SDA A7 A6 A5 A4 A3 A2 A1 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACK D7 D6 D5 D4 D3 D2 D1 D0 ACK

Bus master
ACK is not sent terminates
transfer
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
SCL S P
Data shifted in on falling edge of CLK Set SSPIF at end
of receive Set SSPIF interrupt
Set SSPIF interrupt at end of Acknow-
Set SSPIF interrupt ledge sequence
at end of receive
at end of Acknowledge
SSPIF sequence

Set P bit
Cleared by software Cleared by software Cleared by software Cleared by software (SSPSTAT<4>)
SDA = 0, SCL = 1 Cleared in
while CPU software and SSPIF
responds to SSPIF

BF
(SSPSTAT<0>) Last bit is shifted into SSPSR and
contents are unloaded into SSPBUF

SSPOV

SSPOV is set because

SSPBUF is still full

ACKEN
I 2C™ MASTER MODE WAVEFORM (RECEPTION, 7-BIT ADDRESS)

DS41303G-page 227
PIC18F2XK20/4XK20
PIC18F2XK20/4XK20
17.4.12 ACKNOWLEDGE SEQUENCE 17.4.13 STOP CONDITION TIMING
TIMING A Stop bit is asserted on th e SDA pin at the end of a
An Ackn owledge seque nce is e nabled by setting the receive/transmit by setting the Stop Sequence Enable
Acknowledge Sequence Enable bit, AC KEN bit of the bit, PEN bit of the SSPCON2 register. At the end of a
SSPCON2 register. When this bit is set, the SCL pin is receive/transmit, t he SCL line is h eld l ow a fter th e
pulled low and the contents of the Acknowledge data bit falling edge of the ninth clock. When the PEN bit is set,
are presented on the SDA pin. If the user wishes to gen- the master will assert the SDA line low. When the SDA
erate an Ack nowledge, then the AC KDT bit sh ould be line is s ampled low, th e Ba ud Rate G enerator i s
cleared. If not, the user should set the ACKDT bit before reloaded and counts down to ‘0’. When the Baud Rate
starting an Acknowledge sequence. The Baud R ate Generator times out, the SC L pin will be brought high
Generator t hen count s for one rollover period (T BRG) and on e T BRG (Bau d R ate Generator rol lover c ount)
and the SC L pin is deasserted (pulled high). When the later, the SDA pin will be deasserted. When the SDA
SCL pin is sampled high (cloc k arbitration), the Baud pin is sampled high while SCL is high, the P bit of the
Rate G enerator counts for TBRG. The SCL pin is then SSPSTAT register is set. A T BRG later, the PEN bit is
pulled low. Following this, the ACKEN bit is automatically cleared and the SSPIF bit is set (Figure 17-24).
cleared, the Baud R ate Generator is turned of f and the
MSSP module then goes into Idle mode (Figure 17-23). 17.4.13.1 WCOL Status Flag
If the user writes the SSPBUF when a Stop sequence
17.4.12.1 WCOL Status Flag is i n pro gress, the n th e W COL bit is se t an d th e
If the user writes the SSPBUF when an Acknowledge contents of the buffer are unchanged (the write doesn’t
sequence i s i n pro gress, the n WC OL i s s et a nd th e occur).
contents of the buffer are unchanged (the write doesn’t
occur).

FIGURE 17-23: ACKNOWLEDGE SEQUENCE WAVEFORM

Acknowledge sequence starts here, ACKEN automatically cleared
write to SSPCON2
ACKEN = 1, ACKDT = 0
TBRG TBRG
SDA D0 ACK

SCL 8 9

SSPIF

Cleared in
SSPIF set at software
the end of receive Cleared in
software SSPIF set at the end
of Acknowledge sequence
Note: TBRG = one Baud Rate Generator period.

FIGURE 17-24: STOP CONDITION RECEIVE OR TRANSMIT MODE

Write to SSPCON2, SCL = 1 for TBRG, followed by SDA = 1 for TBRG
set PEN after SDA sampled high. P bit (SSPSTAT<4>) is set.

Falling edge of PEN bit (SSPCON2<2>) is cleared by

9th clock hardware and the SSPIF bit is set
TBRG
SCL

SDA ACK

P
TBRG TBRG TBRG
SCL brought high after TBRG
SDA asserted low before rising edge of clock
to setup Stop condition

Note: TBRG = one Baud Rate Generator period.

DS41303G-page 228  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
17.4.14 SLEEP OPERATION 17.4.17 MULTI -MASTER COMMUNICATION,
2
While in Sle ep mode, the I C mo dule can rec eive BUS COLLISION AND BUS
addresses or data and when an address match or com- ARBITRATION
plete by te tran sfer oc curs, w ake t he processor fro m Multi-Master mode support is achieved by bus arbitra-
Sleep (if the MSSP interrupt is enabled). tion. When the master outputs address/data bits onto
the SDA pin, arbitration takes place when the master
17.4.15 EFFECTS OF A RESET outputs a ‘1’ on SDA, b y letting SDA f loat h igh an d
A Reset disables the MSSP module and terminates the another master asserts a ‘0’. When the SCL pin floats
current transfer. high, d ata s hould b e s table. I f t he expected d ata o n
SDA is a ‘1’ and the data sampled on the SDA pin = 0,
17.4.16 MULTI-MASTER MODE then a bus collision has taken place. The master will set
In Multi-Master mode, the interrupt generation on th e the Bus C ollision Interrupt Flag, BC LIF and reset the
detection of th e Start and Stop conditions all ows the I2C port to its Idle state (Figure 17-25).
determination of when the bus is free. The Stop (P) and If a tran smit w as i n pro gress w hen t he b us c ollision
Start (S) bit s a re cl eared fro m a R eset or w hen th e occurred, th e t ransmission i s h alted, the BF flag i s
MSSP module is disabled. Control of the I 2C bus may cleared, the SDA and SCL lines are deasserted and the
be taken when the P bit of the SSPSTAT register is set, SSPBUF can be written to. When the user services the
or the bus is Idle, with both the S and P bits clear. When bus c ollision Interrupt Serv ice R outine and if the I2C
the bus is busy, enabling the SSP interrupt will gener- bus i s fre e, th e us er c an res ume co mmunication b y
ate the interrupt when the Stop condition occurs. asserting a Start condition.
In mu lti-master operation, th e SD A lin e m ust be If a Start, Repeated Start, Stop or Acknowledge condi-
monitored for arbitration to see if the signal level is the tion was in progress when the bus collision occurred, the
expected o utput le vel. Th is check is perf ormed b y condition is ab orted, the SDA and SCL lines are deas-
hardware with the result placed in the BCLIF bit. serted and the respec tive control bits in the SS PCON2
The states where arbitration can be lost are: register are cleared. When the user services the bus col-
lision Interrupt Service Routine and if the I2C bus is free,
• Address Transfer the user can resume communication by asserting a Start
• Data Transfer condition.
• A Start Condition The mast er w ill continu e to monito r the S DA and SC L
• A Repeated Start Condition pins. If a Stop condition occurs, the SSPIF bit will be set.
• An Acknowledge Condition A write to the SSPBUF w ill start the tra nsmission of
data at t he f irst da ta b it, regardless o f w here th e
transmitter left off when the bus collision occurred.
In Multi-Master mode, the interrupt generation on th e
detection of Start and Stop conditions allows the deter-
mination of when the bus is free. Control of the I2C bus
can be t aken whe n the P b it is set in the SSPSTAT
register, o r th e bus i s Idle and th e S an d P b its a re
cleared.

FIGURE 17-25: BUS COLLISION TIMING FOR TRANSMIT AND ACKNOWLEDGE

Sample SDA. While SCL is high,
Data changes SDA line pulled low data doesn’t match what is driven
while SCL = 0 by another source by the master.
Bus collision has occurred.
SDA released
by master

SDA

SCL Set bus collision

interrupt (BCLIF)

BCLIF

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PIC18F2XK20/4XK20
17.4.17.1 Bus Collision During a Start If the SD A pi n i s s ampled l ow d uring t his c ount, th e
Condition BRG is res et a nd t he SD A l ine is as serted e arly
(Figure 17-28). If, however, a ‘1’ is sampled on the SDA
During a Start condition, a bus collision occurs if:
pin, the SDA pin is asserted low at the end of the BRG
a) SDA or SCL are sampled low at the beginning of count. The Baud Rate Generator is then reloaded and
the Start condition (Figure 17-26). counts dow n to 0 ; if the SC L pi n i s s ampled a s ‘ 0’
b) SCL is sampled low before SDA is asserted low during this time, a bu s collision does not occur. At the
(Figure 17-27). end of the BRG count, the SCL pin is asserted low.
During a Start co ndition, bo th the S DA an d the S CL Note: The reason that bus collision is not a factor
pins are monitored. during a Start condition is that no two bus
If the SDA pin is already low, or the SCL pin is already masters can assert a Start condition at the
low, then all of the following occur: exact sa me time. Th erefore, o ne m aster
will a lways as sert SD A b efore t he o ther.
• the Start condition is aborted,
This condition does not cause a bus colli-
• the BCLIF flag is set and sion be cause th e two m asters m ust b e
• the MSSP module is reset to its Idle state allowed to arbi trate the first add ress fo l-
(Figure 17-26). lowing the Start condition. If the address is
The Start condition begins with the SDA and SCL pins the sa me, arbitration m ust be al lowed to
deasserted. W hen t he SDA p in is sampled hi gh, th e continue i nto th e d ata p ortion, Repeated
Baud Rate G enerator i s loaded f rom SSP ADD<7:0> Start or Stop conditions.
and counts down to 0. If the SC L pin is sampled low
while SDA is high, a bus collision occurs because it is
assumed that another master is attempting to drive a
data ‘1’ during the Start condition.

FIGURE 17-26: BUS COLLISION DURING START CONDITION (SDA ONLY)

SDA goes low before the SEN bit is set.
Set BCLIF,
S bit and SSPIF set because
SDA = 0, SCL = 1.

SDA

SCL
Set SEN, enable Start SEN cleared automatically because of bus collision.
condition if SDA = 1, SCL = 1 SSP module reset into Idle state.
SEN
SDA sampled low before
Start condition. Set BCLIF.
S bit and SSPIF set because
BCLIF SDA = 0, SCL = 1.
SSPIF and BCLIF are
cleared by software

SSPIF

SSPIF and BCLIF are

cleared by software

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 PIC18F2XK20/4XK20
FIGURE 17-27: BUS COLLISION DURING START CONDITION (SCL = 0)
SDA = 0, SCL = 1

TBRG TBRG

SDA

SCL Set SEN, enable Start

sequence if SDA = 1, SCL = 1
SCL = 0 before SDA = 0,
bus collision occurs. Set BCLIF.
SEN
SCL = 0 before BRG time-out,
bus collision occurs. Set BCLIF.
BCLIF
Interrupt cleared
by software
S ‘0’ ‘0’

SSPIF ‘0’ ‘0’

FIGURE 17-28: BRG RESET DUE TO SDA ARBITRATION DURING START CONDITION
SDA = 0, SCL = 1
Set S Set SSPIF
Less than TBRG
TBRG

SDA SDA pulled low by other master.

Reset BRG and assert SDA.

SCL S
SCL pulled low after BRG
time-out
SEN
Set SEN, enable START
sequence if SDA = 1, SCL = 1
BCLIF ‘0’

SSPIF
SDA = 0, SCL = 1, Interrupts cleared
set SSPIF by software

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PIC18F2XK20/4XK20
17.4.17.2 Bus Collision During a Repeated If SDA is low, a bus collision has occurred (i.e., another
Start Condition master is attempting to transmit a data ‘0’, Figure 17-29).
If SDA is sampled high, the BRG is reloaded and begins
During a R epeated S tart c ondition, a bus c ollision
counting. If SDA goes from high-to-low before the BRG
occurs if:
times out, no bus c ollision occurs bec ause no tw o
a) A low level is sampled on SDA when SCL goes masters can assert SDA at exactly the same time.
from low level to high level.
If SCL goes from high-to-low before the BRG times out
b) SCL go es l ow before SDA i s asserted l ow, and SDA has not already been asserted, a bus collision
indicating th at a nother master is at tempting to occurs. In t his c ase, another master i s attempting to
transmit a data ‘1’. transmit a data ‘1’ during the Repeated Start condition,
When the user deasserts SDA and the pin is allowed to see Figure 17-30.
float high, the BRG is loaded with SSPADD<7:0> and If, at the end of the BRG time-out, both SCL and SDA
counts down to 0. The SCL pin is then deasserted and are still high, the SDA pin is driven low and the BRG is
when sampled high, the SDA pin is sampled. reloaded and begins counting. At the end of the count,
regardless of the status of the SCL pin, the SCL pin is
driven low and the R epeated S tart co ndition is
complete.

FIGURE 17-29: BUS COLLISION DURING A REPEATED START CONDITION (CASE 1)

SDA

SCL

Sample SDA when SCL goes high.

If SDA = 0, set BCLIF and release SDA and SCL.

RSEN

BCLIF

Cleared by software
S ‘0’

SSPIF ‘0’

FIGURE 17-30: BUS COLLISION DURING REPEATED START CONDITION (CASE 2)

TBRG TBRG

SDA

SCL

SCL goes low before SDA,

BCLIF set BCLIF. Release SDA and SCL.
Interrupt cleared
by software
RSEN

S ‘0’

SSPIF

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 PIC18F2XK20/4XK20
17.4.17.3 Bus Collision During a Stop The S top co ndition beg ins w ith SDA as serted low.
Condition When SDA is sampled low, the SCL pin is allowed to
float. When the pin is sampled high (clock arbitration),
Bus collision occurs during a Stop condition if:
the Baud Rate Generator is loaded with SSPADD<7:0>
a) After t he SDA p in has b een d easserted an d and counts down to 0. After the BRG times out, SDA is
allowed to float high, SDA is sampled low after sampled. If SDA is sampled low, a bus co llision ha s
the BRG has timed out. occurred. This is due to an other master attempting to
b) After the SCL pin is deasserted, SCL is sampled drive a da ta ‘ 0’ (Fi gure 17-31). If th e SC L pi n i s
low before SDA goes high. sampled low before SDA is allowed to float high, a bus
collision occurs. This is another case of another master
attempting to drive a data ‘0’ (Figure 17-32).

FIGURE 17-31: BUS COLLISION DURING A STOP CONDITION (CASE 1)

TBRG TBRG TBRG SDA sampled

low after TBRG,
set BCLIF
SDA

SDA asserted low

SCL

PEN

BCLIF

P ‘0’

SSPIF ‘0’

FIGURE 17-32: BUS COLLISION DURING A STOP CONDITION (CASE 2)

TBRG TBRG TBRG

SDA

Assert SDA SCL goes low before SDA goes high,

set BCLIF
SCL

PEN

BCLIF

P ‘0’

SSPIF ‘0’

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PIC18F2XK20/4XK20
TABLE 17-4: SUMMARY OF REGISTERS ASSOCIATED WITH I2C™
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values on
page
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
SSPADD SSP Address Register in I2C™ Slave Mode. SSP Baud Rate Reload Register in I2C Master Mode. 60
SSPBUF SSP Receive Buffer/Transmit Register 60
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 60
SSPCON2 GCEN ACKSTAT ACKDT ACKEN RCEN PEN RSEN SEN 60
SSPMSK MSK7 MSK6 MSK5 MSK4 MSK3 MSK2 MSK1 MSK0 63
SSPSTAT SMP CKE D/A P S R/W UA BF 60
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by PORTA.
Note 1: Not implemented on PIC18F2XK20 devices

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 PIC18F2XK20/4XK20
NOTES:

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PIC18F2XK20/4XK20

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 PIC18F2XK20/4XK20
18.0 ENHANCED UNIVERSAL The EUSART module includes the following capabilities:
SYNCHRONOUS • Full-duplex asynchronous transmit and receive
ASYNCHRONOUS RECEIVER • Two-character input buffer
TRANSMITTER (EUSART) • One-character output buffer
• Programmable 8-bit or 9-bit character length
The Enhanced Universal Synchronous Asynchronous
• Address detection in 9-bit mode
Receiver Transmitter (EUSART) module is a serial I/O
communications pe ripheral. It co ntains all the cl ock • Input buffer overrun error detection
generators, shift registers and data buffers necessary • Received character framing error detection
to p erform an in put or o utput se rial da ta t ransfer • Half-duplex synchronous master
independent of dev ice p rogram execution. Th e • Half-duplex synchronous slave
EUSART, als o kn own as a Seri al C ommunications • Programmable clock and data polarity
Interface ( SCI), ca n b e co nfigured as a fu ll-duplex
asynchronous s ystem o r ha lf-duplex sy nchronous The E USART module i mplements t he following
system. Fu ll-Duplex mo de i s u seful for additional features, making it ideally suited for use in
communications with peripheral systems, such as CRT Local Interconnect Network (LIN) bus systems:
terminals and p ersonal c omputers. H alf-Duplex • Automatic detection and calibration of the baud rate
Synchronous m ode is i ntended for c ommunications • Wake-up on Break reception
with peripheral devices, such as A/D or D/A integrated
• 13-bit Break character transmit
circuits, s erial EEPRO Ms or ot her m icrocontrollers.
These devices typically do not have internal clocks for Block di agrams of the EU SART tra nsmitter an d
baud rate gen eration an d re quire th e ex ternal cl ock receiver are shown in Figure 18-1 and Figure 18-2.
signal provided by a master synchronous device.

FIGURE 18-1: EUSART TRANSMIT BLOCK DIAGRAM

Data Bus
TXIE
Interrupt
TXREG Register TXIF
8
MSb LSb TX/CK pin
Pin Buffer
(8) • •• 0
and Control
Transmit Shift Register (TSR)

TXEN

TRMT
Baud Rate Generator FOSC
÷n
TX9
BRG16 n
+1 Multiplier x4 x16 x64
TX9D
SYNC 1 X 0 0 0
SPBRGH SPBRG BRGH X 1 1 0 0
BRG16 X 1 0 1 0

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PIC18F2XK20/4XK20
FIGURE 18-2: EUSART RECEIVE BLOCK DIAGRAM

CREN OERR RCIDL

RX/DT pin MSb RSR Register LSb

Pin Buffer Data
and Control Recovery
Stop (8) 7 ••• 1 0 START

Baud Rate Generator FOSC RX9

÷n

BRG16
+1 n
Multiplier x4 x16 x64
SYNC 1 X 0 0 0
SPBRGH SPBRG BRGH FIFO
X 1 1 0 0 FERR RX9D RCREG Register
BRG16 X 1 0 1 0
8
Data Bus

RCIF Interrupt
RCIE

The o peration of the EU SART m odule is co ntrolled

through three registers:
• Transmit Status and Control (TXSTA)
• Receive Status and Control (RCSTA)
• Baud Rate Control (BAUDCON)
These r egisters are de tailed in Register 18-1,
Register 18-2 and Register 18-3, respectively.
For al l mo des o f E USART op eration, t he T RIS co ntrol
bits corresponding to the RX/DT and TX/CK pins should
be se t to ‘1’. The EU SART c ontrol will au tomatically
reconfigure the pin from input to output, as needed.
When the receiver or transmitter section is no t enabled
then the corresponding RX or TX p in may be used for
general purpose input and output.

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 PIC18F2XK20/4XK20
18.1 EUSART Asynchronous Mode 18.1.1.2 Transmitting Data
The EU SART tran smits and r eceives data using the A transmission is initiated by writing a character to the
standard non-r eturn-to-zero ( NRZ) f ormat. NRZ is TXREG register . If this is the first characte r, or the
implemented w ith two levels: a V OH mar k state w hich previous character has be en completely flushed f rom
represents a ‘1’ data bit, and a VOL space state which the TS R, the dat a in t he TXR EG is imm ediately
represents a ‘ 0’ dat a bit. N RZ ref ers to t he fact th at transferred to the TSR register. If the TSR still contains
consecutively tr ansmitted data bit s of t he same value all or p art of a previous chara cter, the new characte r
stay at the output level of that bit without returning to a data is held in the TX REG until the S top bit of the
neutral level betw een each bit t ransmission. A n N RZ previous character has been t ransmitted. The pe nding
transmission port idles in the mark state. Each character character in the TXR EG is then transferred to the TSR
transmission consists of one Start bit followed by eig ht in one T CY immediately f ollowing t he Stop bit
or nine data bit s a nd is alw ays ter minated by one or transmission. The transmission of the Start bit, data bits
more Stop bits. The Start bit is always a space and the and S top bit sequence commences imm ediately
Stop bit s ar e alw ays marks. T he m ost com mon da ta following the transfer of the dat a to the TSR from the
format is 8 bits. Each transmitted bit persists for a period TXREG.
of 1/(Baud Rate). An on-chip dedicated 8-bit/16-bit Baud
Rate Generator is used to derive st andard baud rate 18.1.1.3 Transmit Data Polarity
frequencies from the s ystem oscillator. See Table 18-5 The polarity of the transmit data can be controlled with
for examples of baud rate configurations. the CKTXP bit of the BAUDCON re gister. The default
The EUSART transmits and receives the LSb first. The state of this bit is ‘0’ which se lects high t rue tr ansmit
EUSART’s tran smitter and receiver are fun ctionally idle and data bits. Setting the CKTXP bit to ‘1’ will invert
independent, but share the same data format and baud the transmit data resulting in low true idle and data bits.
rate. Parity is not supported by the hardware, but can The C KTXP bit controls transmit data polarity only in
be i mplemented in s oftware a nd stored as th e ninth Asynchronous mode. In Sy nchronous mo de th e
data bit. CKTXP bit has a different function.

18.1.1 EUSART ASYNCHRONOUS 18.1.1.4 Transmit Interrupt Flag

TRANSMITTER The T XIF inter rupt flag bit of the P IR1 reg ister i s set
whenever the E USART transmitt er is enabled and no
The EU SART tra nsmitter bl ock dia gram is shown in
character is b eing held for transmission in the TXREG.
Figure 18-1. The hea rt of the tran smitter is th e s erial
In other words, the TXIF bit is only clear when the TSR
Transmit Shift R egister (TSR ), w hich is no t directly
is busy with a character and a new character has been
accessible by software. The TSR obtains its data from
queued for transmission in the TXR EG. The TXI F flag
the transmit buffer, which is the TXREG register.
bit i s not clear ed immediately upon w riting TXR EG.
18.1.1.1 Enabling the Transmitter TXIF becomes valid in the second instr uction cycle
following the write execution. Polling TXIF immediately
The EUSART transmitter is enabled for asynchronous following the TXREG write will return invalid results. The
operations by c onfiguring th e fo llowing th ree co ntrol TXIF bit is read- only, it cannot be set or cleared by
bits: software.
• TXEN = 1 The TXIF interrupt can be enabled by setting the TXIE
• SYNC = 0 interrupt enable bit of th e PIE1 re gister. However, the
• SPEN = 1 TXIF flag bit will be set whenever the TXREG is empty,
regardless of the state of TXIE enable bit.
All ot her E USART c ontrol b its are as sumed to be i n
their default state. To use interrupts when transmitting data, set the TXIE
bit only w hen there is more da ta to send. Clea r the
Setting the TXEN bit of the TXSTA register enables the
TXIE interrupt enable bit upon writing the last character
transmitter circuitry of the EUSART. Clearing the SYNC
of the transmission to the TXREG.
bit of the TX STA regist er configur es the EUSART for
asynchronous op eration. Set ting th e SP EN bit of t he
RCSTA register enables the EUSART and
automatically configures the TX/CK I/O pin as an output.
If the TX/CK pin is shared with an analog peripheral the
analog I/O function must be disabled by clearing the
corresponding ANSEL bit.

Note: The T XIF t ransmitter in terrupt f lag is s et

when the TXEN enable bit is set.

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PIC18F2XK20/4XK20
18.1.1.5 TSR Status 18.1.1.7 Asynchronous Transmission Set-up:
The TR MT bit of the TXST A regi ster indicates the 1. Initialize the SPBRGH:SPBRG register pair and
status of the TSR register. This is a read-only bit. The the BRGH and BRG16 bits to achieve the desired
TRMT bit is set when the TSR register is empty and is baud r ate (s ee Section 18.3 “EUSART Baud
cleared w hen a c haracter is t ransferred t o t he T SR Rate Generator (BRG)”).
register from the TXREG. The TRMT bit remains clear 2. Set the RX/DT and TX/CK TRIS controls to ‘1’.
until all bits have been shifted out of the TSR register. 3. Enable the asynchronous serial port by clearing
No interrupt logic is tied to this bit, so the user needs to the SYNC bit and setting the SPEN bit.
poll this bit to determine the TSR status.
4. If 9-bit transmission is desired, set the TX9 con-
Note: The TSR re gister i s n ot m apped i n da ta trol bit. A set ninth data bit will indicate that the 8
memory, so it is not available to the user. Least Significant data bits are an address when
the receiver is set for address detection.
18.1.1.6 Transmitting 9-Bit Characters 5. Set th e CKTXP c ontrol bi t i f i nverted t ransmit
The EU SART supports 9-bit character transmissions. data polarity is desired.
When the TX9 bi t of the TXSTA reg ister is set the 6. Enable the tran smission by setting the TXEN
EUSART will shift 9 bits out for each character transmit- control bit. This will cause the TXIF interrupt bit
ted. The TX9D bit of th e TXSTA register is the ninth, to be set.
and Most Significant, data bit. When transmitting 9-bit 7. If interrupts are desired, set the TXIE interrupt
data, the TX9D data bit must be written before writing enable b it. An in terrupt w ill oc cur immediately
the 8 Least Significant bits into the TXREG. All nine bits provided that the GIE and PEIE bits of the INT-
of d ata w ill be t ransferred t o t he T SR sh ift r egister CON register are also set.
immediately after the TXREG is written.
8. If 9 -bit transmission is selected, the ni nth b it
A special 9-bit Address mode is available for use with should be loaded into the TX9D data bit.
multiple r eceivers. S ee Section 18.1.2.8 “Address 9. Load 8-bit da ta int o the TXR EG register. Thi s
Detection” for more information on the Address mode. will start the transmission.

FIGURE 18-3: ASYNCHRONOUS TRANSMISSION

Write to TXREG
Word 1
BRG Output
(Shift Clock)
RC4/C2OUT/TX/CK
pin Start bit bit 0 bit 1 bit 7/8 Stop bit
Word 1
TXIF bit
(Transmit Buffer 1 TCY
Reg. Empty Flag)

TRMT bit Word 1

Transmit Shift Reg
(Transmit Shift
Reg. Empty Flag)

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 PIC18F2XK20/4XK20
FIGURE 18-4: ASYNCHRONOUS TRANSMISSION (BACK-TO-BACK)

Write to TXREG
Word 1 Word 2
BRG Output
(Shift Clock)
RC4/C2OUT/TX/CK
pin Start bit bit 0 bit 1 bit 7/8 Stop bit Start bit bit 0
TXIF bit 1 TCY Word 1 Word 2
(Interrupt Reg. Flag)
1 TCY
TRMT bit Word 1 Word 2
(Transmit Shift Transmit Shift Reg
Reg. Empty Flag) Transmit Shift Reg

Note: This timing diagram shows two consecutive transmissions.

TABLE 18-1: REGISTERS ASSOCIATED WITH ASYNCHRONOUS TRANSMISSION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
TXREG EUSART Transmit Register 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous transmission.
Note 1: Reserved in PIC18F2XK20 devices; always maintain these bits clear.

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PIC18F2XK20/4XK20
18.1.2 EUSART ASYNCHRONOUS 18.1.2.2 Receiving Data
RECEIVER The receiver d ata r ecovery circuit i nitiates character
The As ynchronous m ode w ould typically be used i n reception on the falling edge of the first bit. The first bit,
RS-232 systems. The receiver block diagram is shown also known as the Start bit, is always a zero. The data
in Figure 18-2. The data is received on the RX/DT pin recovery circuit counts one-half bit time to the center of
and drives the data recovery block. The data recovery the Start bit and verifies that the bit is still a zero. If it is
block is actually a hig h-speed sh ifter operating at 16 not a z ero the n the dat a rec overy ci rcuit a borts
times the baud rate, whereas the serial Receive Shift character re ception, w ithout g enerating an error, an d
Register (RSR) operates at the bit rate. When all 8 or 9 resumes looking for th e falling edge of t he Start bit. If
bits o f th e character ha ve b een s hifted in , t hey a re the Start b it z ero v erification s ucceeds the n th e dat a
immediately tran sferred t o a tw o c haracter recovery circuit counts a full bit time to the center of the
First-In-First-Out (FI FO) m emory. The FIFO b uffering next bit. The b it is then sampled by a m ajority detect
allows re ception of tw o c omplete c haracters an d th e circuit and the resulting ‘0’ or ‘1’ is shifted into the RSR.
start of a third character be fore s oftware must start This repeats until all data bits have been sampled and
servicing the EU SART rec eiver. The FI FO and R SR shifted into the RSR. One final bit time is measured and
registers are no t directly ac cessible by software. the level sampled. This is the Stop bit, which is always
Access to the received data is via the RCREG register. a ‘ 1’. I f th e d ata r ecovery circuit s amples a ‘0’ i n t he
Stop bit pos ition the n a f raming erro r is se t for thi s
18.1.2.1 Enabling the Receiver character, otherwise the framing error is cleared for this
The EU SART rec eiver i s e nabled for a synchronous character. Se e Section 18.1.2.5 “Receive Framing
operation by configuring the following three control bits: Error” for more information on framing errors.

• CREN = 1 Immediately af ter al l dat a bits and the S top bi t have

been received, the character in the RSR is transferred
• SYNC = 0
to the EUSART rec eive FIFO and the RC IF in terrupt
• SPEN = 1 flag bit of the PIR1 register is set. The top character in
All ot her E USART c ontrol b its are as sumed to be i n the FIFO is transferred out of the FIFO by reading the
their default state. RCREG register.
Setting the CREN bit of the RCSTA register enables the Note: If the receive FIFO is overrun, no additional
receiver circuitry of the EUSART. Clearing the SYNC bit characters will be received until the overrun
of t he TX STA r egister configur es the EUSART for condition is cleared. S ee Section 18.1.2.6
asynchronous op eration. Set ting th e SP EN b it of t he “Receive Overrun Error” for m ore
RCSTA register enables t he EUSART. The RX/DT I/O information on overrun errors.
pin must be confi gured as an inpu t by set ting t he
corresponding TR IS contr ol bit. If the R X/DT pi n is 18.1.2.3 Receive Data Polarity
shared with an analog peripheral the analog I/O function The polarity of the receive data can be controlled with
must be disabled by clearing the corresponding ANSEL the DTRXP bit of the BAUDCON register. The default
bit. state of this bit is ‘0’ which selects high true receive idle
and data bits. Setting the DTRXP bit to ‘1’ will invert the
receive data resulting in low true idle and data bits. The
DTRXP bit controls receive data polarity only in Asyn-
chronous mode. In synchronous mode the DTRXP bit
has a different function.

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 PIC18F2XK20/4XK20
18.1.2.4 Receive Interrupts 18.1.2.7 Receiving 9-bit Characters
The RCIF interrupt flag bit of the PIR1 register is set The EUSART supports 9-bit character reception. When
whenever the EUSART receiver is enabled and there is the RX9 bit of the RCSTA register is set, the EUSART
an un read ch aracter i n th e rec eive FIFO. Th e R CIF will s hift 9 bits i nto the RSR for e ach c haracter
interrupt flag bit is read-only, it cannot be set or cleared received. T he RX9D b it of the R CSTA r egister i s the
by software. ninth an d M ost Sig nificant dat a b it o f th e to p u nread
RCIF inte rrupts are enabled by setting the foll owing character in the receive FIFO. When reading 9-bit data
bits: from the receive FIFO buffer, the R X9D data bit must
be read before reading the 8 Least Significant bits from
• RCIE interrupt enable bit of the PIE1 register the RCREG.
• PEIE peripheral interrupt enable bit of the INT-
CON register 18.1.2.8 Address Detection
• GIE global interrupt enable bit of the INTCON A special Address Detection mode is available for use
register when multiple receivers share the same transmission
The RCIF interrupt flag bit will be set when there is an line, such as in RS-485 systems. Address detection is
unread character in the FIFO, regardless of the state of enabled by s etting the AD DEN bi t o f th e R CSTA
interrupt enable bits. register.
Address detection req uires 9 -bit ch aracter rec eption.
18.1.2.5 Receive Framing Error When a ddress detection i s enabled, o nly characters
Each ch aracter in the rec eive FIFO b uffer h as a with t he n inth da ta bit se t w ill be t ransferred t o t he
corresponding framing error Status bit. A framing error receive FIFO buffer, thereby setting the RCIF interrupt
indicates that a Stop bit was not seen at the expected bit. All other characters will be ignored.
time. Th e framing error sta tus is ac cessed vi a t he Upon re ceiving an address c haracter, user s oftware
FERR bi t of t he R CSTA register. T he F ERR bi t determines if the add ress matches its ow n. U pon
represents the status of the top unread character in the address ma tch, u ser so ftware mu st disable a ddress
receive F IFO. Therefore, t he F ERR bi t mu st be r ead detection by clearing the AD DEN bit be fore the nex t
before reading the RCREG. Stop bit occurs. When user software detects the end of
The FERR bit is read-only and only applies to the top the mes sage, determined by the me ssage protocol
unread character in the receive FIFO. A framing error used, so ftware pla ces th e rec eiver b ack in to th e
(FERR = 1) does not preclude reception of additional Address Detection mode by setting the ADDEN bit.
characters. It is not necessary to cl ear the FERR bit.
Reading the next ch aracter from the FIFO bu ffer will
advance the FIFO to th e next character and the next
corresponding framing error.
The FERR bit can be forced clear by clearing the SPEN
bit of the RCSTA reg ister w hich res ets the EU SART.
Clearing the CREN bit of the RCSTA register does not
affect the FERR bit. A framing error by itself does not
generate an interrupt.
Note: If al l re ceive c haracters i n th e receive
FIFO have framing errors, repeated reads
of the RCREG will not clear the FERR bit.

18.1.2.6 Receive Overrun Error

The receive FIFO buffer can hold two characters. An
overrun error will be generated If a third character, in its
entirety, is received before the FIFO is accessed. When
this ha ppens the OERR b it o f th e R CSTA reg ister i s
set. The characters already in the FIFO buffer can be
read but no additional characters will be received until
the error is cleared. The error must be cleared by either
clearing th e C REN bi t of the RCSTA re gister or b y
resetting the EUSART by clearing the SPEN bit of the
RCSTA register.

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PIC18F2XK20/4XK20
18.1.2.9 Asynchronous Reception Set-up: 18.1.2.10 9-bit Address Detection Mode Set-up
1. Initialize the SPBRGH:SPBRG register pair and This mode would typically be used in RS-485 systems.
the B RGH and BRG16 b its t o achieve t he To set up a n As ynchronous R eception with Address
desired baud rate (see Section 18.3 “EUSART Detect Enable:
Baud Rate Generator (BRG)”). 1. Initialize the SPBRGH, SPBRG register pair and
2. Set the RX/DT and TX/CK TRIS controls to ‘1’. the BR GH and BR G16 bit s to achieve th e
3. Enable the serial po rt by s etting th e SPEN bit desired baud rate (see Section 18.3 “EUSART
and the RX/DT pin TRIS bit. The SYNC bit must Baud Rate Generator (BRG)”).
be clear for asynchronous operation. 2. Set the RX/DT and TX/CK TRIS controls to ‘1’.
4. If interrupts are desired, set the RCIE interrupt 3. Enable the serial port by setting the SPEN bit.
enable bit and set the GIE and PEIE bits of the The S YNC b it must b e clear f or asynchronous
INTCON register. operation.
5. If 9-bit reception is desired, set the RX9 bit. 4. If interrupts are desired, set the RCIE interrupt
6. Set th e D TRXP if inverted r eceive p olarity i s enable bit and set the GIE and PEIE bits of the
desired. INTCON register.
7. Enable reception by setting the CREN bit. 5. Enable 9-bit reception by setting the RX9 bit.
8. The R CIF i nterrupt flag bit w ill b e se t w hen a 6. Enable address detection by setting the ADDEN
character is transferred fro m the RSR to the bit.
receive buffer. An interrupt w ill be generated if 7. Set th e D TRXP if i nverted re ceive p olarity i s
the RCIE interrupt enable bit was also set. desired.
9. Read the RCSTA register to get the error flags 8. Enable reception by setting the CREN bit.
and, if 9-bit data reception is enabled, the ninth 9. The R CIF i nterrupt fl ag bit w ill b e se t w hen a
data bit. character w ith the ni nth b it se t is tra nsferred
10. Get the rec eived 8 L east S ignificant d ata bits from the RSR to the receive buffer. An interrupt
from the receive buffer by reading the RCREG will be generated if the RCIE interrupt enable bit
register. was also set.
11. If an overrun occurred, clear the OERR flag by 10. Read the RCSTA register to get the error flags.
clearing the CREN receiver enable bit. The ninth data bit will always be set.
11. Get the received 8 L east Si gnificant da ta bits
from the receive buffer by reading the RCREG
register. Software det ermines if this is th e
device’s address.
12. If an overrun occurred, clear the OERR flag by
clearing the CREN receiver enable bit.
13. If th e de vice h as been addressed, cl ear th e
ADDEN bi t to al low a ll re ceived da ta in to th e
receive buffer and generate interrupts.

DS41303G-page 244  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 18-5: ASYNCHRONOUS RECEPTION
Start Start Start
RX/DT pin bit bit 0 bit 1 bit 7/8 Stop bit bit 0 bit 7/8 Stop bit bit 7/8 Stop
bit bit bit
Rcv Shift
Reg
Rcv Buffer Reg
Word 1 Word 2
RCREG RCREG
RCIDL

Read Rcv
Buffer Reg
RCREG

RCIF
(Interrupt Flag)

OERR bit
CREN

Note: This timing diagram shows three words appearing on the RX input. The RCREG (receive buffer) is read after the third word,
causing the OERR (overrun) bit to be set.

TABLE 18-2: REGISTERS ASSOCIATED WITH ASYNCHRONOUS RECEPTION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
RCREG EUSART Receive Register 61
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 62
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented locations read as ‘0’. Shaded cells are not used for asynchronous reception.
Note 1: Reserved in PIC18F2XK20 devices; always maintain these bits clear.

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PIC18F2XK20/4XK20
18.2 Clock Accuracy with The fir st (preferred) method uses the O SCTUNE
Asynchronous Operation register to adjust the H FINTOSC output. Adjusting the
value in the OSCTUNE register allows for fine resolution
The factory calibrates the internal oscillator block out- changes to the s ystem clock source. See Section 2.5
put (HFINTOSC). However, the HFINTOSC frequency “Internal Clock Modes” for more information.
may dri ft as V DD or te mperature c hanges, and thi s
The other method adjusts the value in the Baud Rate
directly affects the asynchronous baud rate. Two meth-
Generator. Th is can be d one auto matically with th e
ods may be used to adjust the baud rate clock, but both
Auto-Baud D etect fe ature (s ee Section 18.3.1
require a reference clock source of some kind.
“Auto-Baud Detect”). There may not be fine enough
resolution when adjusting the Baud Rate Generator to
compensate fo r a g radual ch ange i n th e pe ripheral
clock frequency.

REGISTER 18-1: TXSTA: TRANSMIT STATUS AND CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-1 R/W-0
CSRC TX9 TXEN(1) SYNC SENDB BRGH TRMT TX9D
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 CSRC: Clock Source Select bit

Asynchronous mode:
Don’t care
Synchronous mode:
1 = Master mode (clock generated internally from BRG)
0 = Slave mode (clock from external source)
bit 6 TX9: 9-bit Transmit Enable bit
1 = Selects 9-bit transmission
0 = Selects 8-bit transmission
bit 5 TXEN: Transmit Enable bit(1)
1 = Transmit enabled
0 = Transmit disabled
bit 4 SYNC: EUSART Mode Select bit
1 = Synchronous mode
0 = Asynchronous mode
bit 3 SENDB: Send Break Character bit
Asynchronous mode:
1 = Send Sync Break on next transmission (cleared by hardware upon completion)
0 = Sync Break transmission completed
Synchronous mode:
Don’t care
bit 2 BRGH: High Baud Rate Select bit
Asynchronous mode:
1 = High speed
0 = Low speed
Synchronous mode:
Unused in this mode
bit 1 TRMT: Transmit Shift Register Status bit
1 = TSR empty
0 = TSR full
bit 0 TX9D: Ninth bit of Transmit Data
Can be address/data bit or a parity bit.

Note 1: SREN/CREN overrides TXEN in Sync mode.

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 PIC18F2XK20/4XK20

REGISTER 18-2: RCSTA: RECEIVE STATUS AND CONTROL REGISTER(1)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R-0 R-0 R-x
SPEN RX9 SREN CREN ADDEN FERR OERR RX9D
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 SPEN: Serial Port Enable bit

1 = Serial port enabled (configures RX/DT and TX/CK pins as serial port pins)
0 = Serial port disabled (held in Reset)
bit 6 RX9: 9-bit Receive Enable bit
1 = Selects 9-bit reception
0 = Selects 8-bit reception
bit 5 SREN: Single Receive Enable bit
Asynchronous mode:
Don’t care
Synchronous mode – Master:
1 = Enables single receive
0 = Disables single receive
This bit is cleared after reception is complete.
Synchronous mode – Slave
Don’t care
bit 4 CREN: Continuous Receive Enable bit
Asynchronous mode:
1 = Enables receiver
0 = Disables receiver
Synchronous mode:
1 = Enables continuous receive until enable bit CREN is cleared (CREN overrides SREN)
0 = Disables continuous receive
bit 3 ADDEN: Address Detect Enable bit
Asynchronous mode 9-bit (RX9 = 1):
1 = Enables address detection, enable interrupt and load the receive buffer when RSR<8> is set
0 = Disables address detection, all bytes are received and ninth bit can be used as parity bit
Asynchronous mode 8-bit (RX9 = 0):
Don’t care
bit 2 FERR: Framing Error bit
1 = Framing error (can be updated by reading RCREG register and receive next valid byte)
0 = No framing error
bit 1 OERR: Overrun Error bit
1 = Overrun error (can be cleared by clearing bit CREN)
0 = No overrun error
bit 0 RX9D: Ninth bit of Received Data
This can be address/data bit or a parity bit and must be calculated by user firmware.

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PIC18F2XK20/4XK20

REGISTER 18-3: BAUDCON: BAUD RATE CONTROL REGISTER

R/W-0 R-1 R/W-0 R/W-0 R/W-0 U-0 R/W-0 R/W-0
ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 ABDOVF: Auto-Baud Detect Overflow bit

Asynchronous mode:
1 = Auto-baud timer overflowed
0 = Auto-baud timer did not overflow
Synchronous mode:
Don’t care
bit 6 RCIDL: Receive Idle Flag bit
Asynchronous mode:
1 = Receiver is Idle
0 = Start bit has been detected and the receiver is active
Synchronous mode:
Don’t care
bit 5 DTRXP: Data/Receive Polarity Select bit
Asynchronous mode:
1 = Receive data (RX) is inverted (active-low)
0 = Receive data (RX) is not inverted (active-high)
Synchronous mode:
1 = Data (DT) is inverted (active-low)
0 = Data (DT) is not inverted (active-high)
bit 4 CKTXP: Clock/Transmit Polarity Select bit
Asynchronous mode:
1 = Idle state for transmit (TX) is low
0 = Idle state for transmit (TX) is high
Synchronous mode:
1 = Data changes on the falling edge of the clock and is sampled on the rising edge of the clock
0 = Data changes on the rising edge of the clock and is sampled on the falling edge of the clock
bit 3 BRG16: 16-bit Baud Rate Generator bit
1 = 16-bit Baud Rate Generator is used (SPBRGH:SPBRG)
0 = 8-bit Baud Rate Generator is used (SPBRG)
bit 2 Unimplemented: Read as ‘0’
bit 1 WUE: Wake-up Enable bit
Asynchronous mode:
1 = Re ceiver is waiting for a falling edge. No character will be received but RCIF will be set on the falling
edge. WUE will automatically clear on the rising edge.
0 = Receiver is operating normally
Synchronous mode:
Don’t care
bit 0 ABDEN: Auto-Baud Detect Enable bit
Asynchronous mode:
1 = Auto-Baud Detect mode is enabled (clears when auto-baud is complete)
0 = Auto-Baud Detect mode is disabled
Synchronous mode:
Don’t care

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 PIC18F2XK20/4XK20
18.3 EUSART Baud Rate Generator If the system clock is changed during an active receive
(BRG) operation, a receive error or dat a loss may result. To
avoid this problem, check the status of the RCIDL bit to
The Baud Rate Generator (BRG) is an 8-bit or 1 6-bit make sure that the rec eive ope ration is Idl e before
timer that is dedicated to the support of both the changing the system clock.
asynchronous and sy nchronous EU SART o peration.
By default, the BRG operates in 8-bit mode. Setting the EXAMPLE 18-1: CALCULATING BAUD
BRG16 b it o f t he BAUDCON re gister se lects 1 6-bit RATE ERROR
mode.
For a device with FOSC of 16 MHz, desired baud rate
The S PBRGH:SPBRG r egister pair determines the of 9600, Asynchronous mode, 8-bit BRG:
period of the free running baud rate ti mer. In
F OS C
Asynchronous m ode the m ultiplier of the baud rate Desired Baud Rate = ---------------------------------------------------------------------
64  [SPBRGH:SPBRG] + 1 
period is determined by both the BRGH bit of the TXSTA
register and the BRG16 bit of the BAUDCON register. In Solving for SPBRGH:SPBRG:
Synchronous mode, the BRGH bit is ignored.
FOSC
---------------------------------------------
Table 18-3 contains the fo rmulas fo r dete rmining th e Desired Baud Rate
X = --------------------------------------------- – 1
baud rate. Example 18-1 provides a sample calculation 64
for determining the baud rate and baud rate error. 16000000
------------------------
Typical b aud rate s a nd e rror v alues for various 9600
= ------------------------ – 1
asynchronous mo des have bee n co mputed for yo ur 64
convenience and are shown in Table 18-5. It may be =  25.042  = 25
advantageous to use the high baud rate (BRGH = 1),
or the 16-bit BRG (BRG16 = 1) to reduce the baud rate 16000000
Calculated Baud Rate = ---------------------------
64  25 + 1 
error. Th e 16 -bit BR G mo de is us ed to achieve sl ow
baud rates for fast oscillator frequencies. = 9615
Writing a new value to the SPBRGH, SPBRG register
Calc. Baud Rate – Desired Baud Rate
pair causes the BRG timer to be reset (or cleared). This Error = --------------------------------------------------------------------------------------------
Desired Baud Rate
ensures that the BRG does not wait for a timer overflow
before outputting the new baud rate.  9615 – 9600 
= ---------------------------------- = 0.16%
9600

TABLE 18-3: BAUD RATE FORMULAS

Configuration Bits
BRG/EUSART Mode Baud Rate Formula
SYNC BRG16 BRGH

0 0 0 8-bit/Asynchronous FOSC/[64 (n+1)]

0 0 1 8-bit/Asynchronous
FOSC/[16 (n+1)]
0 1 0 16-bit/Asynchronous
0 1 1 16-bit/Asynchronous
1 0 x 8-bit/Synchronous FOSC/[4 (n+1)]
1 1 x 16-bit/Synchronous
Legend: x = Don’t care, n = value of SPBRGH, SPBRG register pair

TABLE 18-4: REGISTERS ASSOCIATED WITH BAUD RATE GENERATOR

Reset Values
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
on page
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the BRG.

 2010 Microchip Technology Inc. DS41303G-page 249

PIC18F2XK20/4XK20

TABLE 18-5: BAUD RATES FOR ASYNCHRONOUS MODES

SYNC = 0, BRGH = 0, BRG16 = 0
FOSC = 64.000 MHz FOSC = 18.432 MHz FOSC = 16.000 MHz FOSC = 11.0592 MHz
BAUD
RATE SPBRG SPBRG SPBRG SPBRG
Actual % Actual % Actual % Actual %
value value value value
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 — — — — — — — — — — — —
1200 — — — 1200 0.00 239 1202 0.16 207 1200 0.00 143
2400 — — — 2400 0.00 119 2404 0.16 103 2400 0.00 71
9600 9615 0.16 103 9600 0.00 29 9615 0.16 25 9600 0.00 17
10417 10417 0.00 95 10286 -1.26 27 10417 0.00 23 10165 -2.42 16
19.2k 19.23k 0.16 51 19.20k 0.00 14 19.23k 0.16 12 19.20k 0.00 8
57.6k 58.82k 2.12 16 57.60k 0.00 7 — — — 57.60k 0.00 2
115.2k 111.11k -3.55 8 — — — — — — — — —

SYNC = 0, BRGH = 0, BRG16 = 0

FOSC = 8.000 MHz FOSC = 4.000 MHz FOSC = 3.6864 MHz FOSC = 1.000 MHz
BAUD
RATE SPBRG SPBRG SPBRG SPBRG
Actual % Actual % Actual % Actual %
value value value value
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 — — — 300 0.16 207 300 0.00 191 300 0.16 51
1200 1202 0.16 103 1202 0.16 51 1200 0.00 47 1202 0.16 12
2400 2404 0.16 51 2404 0.16 25 2400 0.00 23 — — —
9600 9615 0.16 12 — — — 9600 0.00 5 — — —
10417 10417 0.00 11 10417 0.00 5 — — — — — —
19.2k — — — — — — 19.20k 0.00 2 — — —
57.6k — — — — — — 57.60k 0.00 0 — — —
115.2k — — — — — — — — — — — —

SYNC = 0, BRGH = 1, BRG16 = 0

BAUD FOSC = 64.000 MHz FOSC = 18.432 MHz FOSC = 16.000 MHz FOSC = 11.0592 MHz
RATE SPBRG SPBRG SPBRG SPBRG
Actual % Actual % Actual % Actual %
value value value value
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 — — — — — — — — — — — —
1200 — — — — — — — — — — — —
2400 — — — — — — — — — — — —
9600 — — — 9600 0.00 119 9615 0.16 103 9600 0.00 71
10417 — — — 10378 -0.37 110 10417 0.00 95 10473 0.53 65
19.2k 19.23k 0.16 207 19.20k 0.00 59 19.23k 0.16 51 19.20k 0.00 35
57.6k 57.97k 0.64 68 57.60k 0.00 19 58.82k 2.12 16 57.60k 0.00 11
115.2k 114.29k -0.79 34 115.2k 0.00 9 111.1k -3.55 8 115.2k 0.00 5

DS41303G-page 250  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 18-5: BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)
SYNC = 0, BRGH = 1, BRG16 = 0

BAUD FOSC = 8.000 MHz FOSC = 4.000 MHz FOSC = 3.6864 MHz FOSC = 1.000 MHz
RATE SPBRG SPBRG SPBRG SPBRG
Actual % Actual % Actual % Actual %
value value value value
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 — — — — — — — — — 300 0.16 207
1200 — — — 1202 0.16 207 1200 0.00 191 1202 0.16 51
2400 2404 0.16 207 2404 0.16 103 2400 0.00 95 2404 0.16 25
9600 9615 0.16 51 9615 0.16 25 9600 0.00 23 — — —
10417 10417 0.00 47 10417 0.00 23 10473 0.53 21 10417 0.00 5
19.2k 19231 0.16 25 19.23k 0.16 12 19.2k 0.00 11 — — —
57.6k 55556 -3.55 8 — — — 57.60k 0.00 3 — — —
115.2k — — — — — — 115.2k 0.00 1 — — —

SYNC = 0, BRGH = 0, BRG16 = 1

BAUD FOSC = 64.000 MHz FOSC = 18.432 MHz FOSC = 16.000 MHz FOSC = 11.0592 MHz
RATE SPBRGH SPBRGH SPBRGH SPBRGH
Actual % Actual % Actual % Actual %
:SPBRG :SPBRG :SPBRG :SPBRG
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 300.0 0.00 13332 300.0 0.00 3839 300.03 0.01 3332 300.0 0.00 2303
1200 1200.1 0.01 3332 1200 0.00 959 1200.5 0.04 832 1200 0.00 575
2400 2399 -0.02 1666 2400 0.00 479 2398 -0.08 416 2400 0.00 287
9600 9592 -0.08 416 9600 0.00 119 9615 0.16 103 9600 0.00 71
10417 10417 0.00 383 10378 -0.37 110 10417 0.00 95 10473 0.53 65
19.2k 19.23k 0.16 207 19.20k 0.00 59 19.23k 0.16 51 19.20k 0.00 35
57.6k 57.97k 0.64 68 57.60k 0.00 19 58.82k 2.12 16 57.60k 0.00 11
115.2k 114.29k -0.79 34 115.2k 0.00 9 111.11k -3.55 8 115.2k 0.00 5

SYNC = 0, BRGH = 0, BRG16 = 1

BAUD FOSC = 8.000 MHz FOSC = 4.000 MHz FOSC = 3.6864 MHz FOSC = 1.000 MHz
RATE SPBRGH SPBRGH SPBRGH SPBRGH
Actual % Actual % Actual % Actual %
:SPBRG :SPBRG :SPBRG :SPBRG
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 299.9 -0.02 1666 300.1 0.04 832 300.0 0.00 767 300.5 0.16 207
1200 1199 -0.08 416 1202 0.16 207 1200 0.00 191 1202 0.16 51
2400 2404 0.16 207 2404 0.16 103 2400 0.00 95 2404 0.16 25
9600 9615 0.16 51 9615 0.16 25 9600 0.00 23 — — —
10417 10417 0.00 47 10417 0.00 23 10473 0.53 21 10417 0.00 5
19.2k 19.23k 0.16 25 19.23k 0.16 12 19.20k 0.00 11 — — —
57.6k 55556 -3.55 8 — — — 57.60k 0.00 3 — — —
115.2k — — — — — — 115.2k 0.00 1 — — —

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PIC18F2XK20/4XK20
TABLE 18-5: BAUD RATES FOR ASYNCHRONOUS MODES (CONTINUED)
SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1

BAUD FOSC = 64.000 MHz FOSC = 18.432 MHz FOSC = 16.000 MHz FOSC = 11.0592 MHz
RATE SPBRGH SPBRGH SPBRGH SPBRGH
Actual % Actual % Actual % Actual %
:SPBRG :SPBRG :SPBRG :SPBRG
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 300 0.00 53332 300.0 0.00 15359 300.0 0.00 13332 300.0 0.00 9215
1200 1200 0.00 13332 1200 0.00 3839 1200.1 0.01 3332 1200 0.00 2303
2400 2400 0.00 6666 2400 0.00 1919 2399.5 -0.02 1666 2400 0.00 1151
9600 9598.1 -0.02 1666 9600 0.00 479 9592 -0.08 416 9600 0.00 287
10417 10417 0.00 1535 10425 0.08 441 10417 0.00 383 10433 0.16 264
19.2k 19.21k 0.04 832 19.20k 0.00 239 19.23k 0.16 207 19.20k 0.00 143
57.6k 57.55k -0.08 277 57.60k 0.00 79 57.97k 0.64 68 57.60k 0.00 47
115.2k 115.11k -0.08 138 115.2k 0.00 39 114.29k -0.79 34 115.2k 0.00 23

SYNC = 0, BRGH = 1, BRG16 = 1 or SYNC = 1, BRG16 = 1

BAUD FOSC = 8.000 MHz FOSC = 4.000 MHz FOSC = 3.6864 MHz FOSC = 1.000 MHz
RATE SPBRGH SPBRGH SPBRGH SPBRGH
Actual % Actual % Actual % Actual %
:SPBRG :SPBRG :SPBRG :SPBRG
Rate Error Rate Error Rate Error Rate Error
(decimal) (decimal) (decimal) (decimal)
300 300.0 0.00 6666 300.0 0.01 3332 300.0 0.00 3071 300.1 0.04 832
1200 1200 -0.02 1666 1200 0.04 832 1200 0.00 767 1202 0.16 207
2400 2401 0.04 832 2398 0.08 416 2400 0.00 383 2404 0.16 103
9600 9615 0.16 207 9615 0.16 103 9600 0.00 95 9615 0.16 25
10417 10417 0.00 191 10417 0.00 95 10473 0.53 87 10417 0.00 23
19.2k 19.23k 0.16 103 19.23k 0.16 51 19.20k 0.00 47 19.23k 0.16 12
57.6k 57.14k -0.79 34 58.82k 2.12 16 57.60k 0.00 15 — — —
115.2k 117.6k 2.12 16 111.1k -3.55 8 115.2k 0.00 7 — — —

DS41303G-page 252  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
18.3.1 AUTO-BAUD DETECT and SPBRG registers a re clocked at 1/ 8th th e BRG
base clock rate. The resulting byte measurement is the
The EUSART m odule s upports a utomatic de tection
average bit time when clocked at full speed.
and calibration of the baud rate.
In the Auto-Baud Detect (ABD) mode, the clock to the Note 1: If the WUE bit is set with the ABDEN bit,
BRG i s reversed. Rat her than the BRG c locking th e auto-baud detection will occur on the byte
incoming RX signal, the RX signal is timing the BRG. following th e Bre ak character (se e
The Baud Rate Generator is used to time the period of Section 18.3.3 “Auto-Wake-up on
a received 55h (ASCII “U”) which is the Sync character Break”).
for the LIN bus. The unique feature of this character is 2: It is up to the user to deter mine that the
that it has five rising edges including the Stop bit edge. incoming character baud rate is within the
Setting the ABDEN bit of the BAUDCON register starts range of th e select ed B RG clo ck sour ce.
the au to-baud cal ibration s equence (Fi gure 18.3.2). Some combinations of oscillator frequency
While t he A BD s equence ta kes p lace, t he E USART and EUSART baud rates are not possible.
state machine is held in Idle. On the first rising edge of 3: During th e auto-baud process, the
the receive line, after the Start bit, the SPBRG begins auto-baud counter st arts count ing at 1 .
counting up using the BRG counter clock as shown in Upon comple tion of t he aut o-baud
Table 18-6. The fifth rising edge will occur on the RX pin sequence, to achieve maximum a ccuracy,
at the en d of the eig hth b it per iod. At that ti me, an subtract 1 fr om the SPBRGH:SPBRG
accumulated value t otaling the prop er BR G peri od i s register pair.
left in the SPBRGH:SPBRG register pair, the ABDEN
bit is automatically cleared, and the RCIF interrupt flag TABLE 18-6: BRG COUNTER CLOCK RATES
is set. A read o peration on the RCREG n eeds t o b e
BRG Base BRG ABD
performed to clear the RCIF interrupt. RCREG content BRG16 BRGH
Clock Clock
should be discarded. When calibrating for modes that
do not use the SPBRGH register the us er c an v erify 0 0 FOSC/64 FOSC/512
that the SPBRG register did not overflow by checking
for 00h in the SPBRGH register. 0 1 FOSC/16 FOSC/128

The BRG auto-baud clock is determined by the BRG16 1 0 FOSC/16 FOSC/128

and BRGH bits as shown in Table 18-6. During ABD, 1 1 FOSC/4 FOSC/32
both the SPBRGH and SPBRG registers are used as a Note: During the ABD sequ ence, SP BRG and
16-bit counter, independent of the BR G16 bit setting. SPBRGH registers are both used as a 16-bit
While c alibrating th e b aud rate pe riod, t he SP BRGH counter, independent of BRG16 setting.

FIGURE 18-6: AUTOMATIC BAUD RATE CALIBRATION

BRG Value XXXXh 0000h 001Ch

Edge #1 Edge #2 Edge #3 Edge #4 Edge #5

RX pin Start bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7 Stop bit

BRG Clock

Set by User Auto Cleared

ABDEN bit

RCIDL

RCIF bit
(Interrupt)

Read
RCREG

SPBRG XXh 1Ch

SPBRGH XXh 00h

Note 1: The ABD sequence requires the EUSART module to be configured in Asynchronous mode.

 2010 Microchip Technology Inc. DS41303G-page 253

PIC18F2XK20/4XK20
18.3.2 AUTO-BAUD OVERFLOW 18.3.3.1 Special Considerations
During the c ourse of a utomatic b aud detection, the Break Character
ABDOVF bit of the BAUDCON register will be set if the To av oid c haracter er rors or c haracter fra gments
baud rate counter overflows before the fifth rising edge during a w ake-up event, the w ake-up character must
is detected on th e RX pin. The ABDOVF bit indicates be all zeros.
that the counter has exceeded the maximum count that
can fit in the 1 6 bits of the SPBRGH:SPBRG reg ister When the w ake-up is en abled the fun ction works
pair. After the ABDOVF has been set, the counter con- independent of the low time on the data stream. If the
tinues to count until the fifth rising edge is detected on WUE bit i s set a nd a v alid no n-zero character i s
the RX pin. Upon detecting the fifth RX edge, the hard- received, the low time from the Start bit to the first rising
ware w ill s et th e R CIF int errupt fl ag a nd c lear th e edge will b e in terpreted as the wake-up e vent. Th e
ABDEN bit of the BAUDCON re gister. The RCIF fl ag remaining bi ts in the character w ill be received as a
can be su bsequently cl eared b y reading the RCREG. fragmented character and subsequent characters can
The ABDOVF flag can be cleared by software directly. result in framing or overrun errors.

To term inate the auto-baud process before the R CIF Therefore, the initial character in the transmission must
flag is set, clear the ABDEN bit then clear the ABDOVF be all ‘0’s. Th is must be 10 or mo re bi t times, 13-bit
bit. The ABDOVF bit will remain set if the ABDEN bit is times recommended for LIN bus, or any number of bit
not cleared first. times for standard RS-232 devices.
Oscillator Startup Time
18.3.3 AUTO-WAKE-UP ON BREAK
Oscillator start-up time must be considered, especially
During Slee p m ode, al l c locks to the EU SART a re in ap plications u sing o scillators w ith lo nger st art-up
suspended. Because of this, the Baud Rate Generator intervals (i.e., LP, XT o r HS/PL L mode). Th e Sync
is inactive and a proper character reception cannot be Break (or wake-up s ignal) c haracter m ust b e of
performed. The Auto-Wake-up feat ure al lows the sufficient l ength, and be fol lowed b y a s ufficient
controller to wake-up due to activity on the RX/DT line. interval, to allow enough time for the selected oscillator
This feature is available only in Asynchronous mode. to start and provide proper initialization of the EUSART.
The Au to-Wake-up fea ture is enabled by s etting t he WUE Bit
WUE bit of the BAUDCON register. Once set, the normal
The w ake-up eve nt c auses a rec eive in terrupt b y
receive s equence on R X/DT is disabled, and the
setting the R CIF bi t. The W UE bi t is cleared by
EUSART rem ains in an Idle s tate, m onitoring for a
hardware by a ris ing edg e on RX/DT. Th e in terrupt
wake-up e vent independent o f th e CPU mode. A
condition is then cl eared by so ftware by read ing the
wake-up event consists of a high-to-low transition on the
RCREG register and discarding its contents.
RX/DT line. (This coincides with the start of a Sync Break
or a wake-up signal character for the LIN protocol.) To ensure that no actual data is lost, check the RCIDL
bit to verify that a receive operation is not in p rocess
The E USART mod ule generates an R CIF interrupt
before setting the WUE bit. If a receive operation is not
coincident w ith the w ake-up e vent. The interrupt is
occurring, the WUE bit ma y the n be s et jus t pri or to
generated synchronously to the Q clocks in normal CPU
entering the Sleep mode.
operating m odes (Figure 18-7), an d as ynchronously if
the device is in Sleep mode (Figure 18-8). The interrupt
condition is cleared by reading the RCREG register.
The WUE bit is automatically cleared by the low-to-high
transition on the R X line at the end of the Break. This
signals to the user that the Break event is over. At this
point, the EUSART module is in Idl e mode waiting to
receive the next character.

DS41303G-page 254  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 18-7: AUTO-WAKE-UP BIT (WUE) TIMING DURING NORMAL OPERATION
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
OSC1
Bit set by user Auto Cleared
WUE bit
RX/DT Line

RCIF
Cleared due to User Read of RCREG

Note 1: The EUSART remains in Idle while the WUE bit is set.

FIGURE 18-8: AUTO-WAKE-UP BIT (WUE) TIMINGS DURING SLEEP

Q1Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1Q2 Q3 Q4

OSC1
Bit Set by User Auto Cleared
WUE bit
RX/DT Line Note 1
RCIF
Cleared due to User Read of RCREG
Sleep Command Executed Sleep Ends

Note 1: If the wake-up event requires long oscillator warm-up time, the automatic clearing of the WUE bit can occur while the stposc signal is
still active. This sequence should not depend on the presence of Q clocks.
2: The EUSART remains in Idle while the WUE bit is set.

 2010 Microchip Technology Inc. DS41303G-page 255

PIC18F2XK20/4XK20
18.3.4 BREAK CHARACTER SEQUENCE When the TXREG becomes empty, as indicated by the
TXIF, the next data byte can be written to TXREG.
The EUSART module has the capability of sending the
special Break character sequences that are required by
18.3.5 RECEIVING A BREAK CHARACTER
the LIN bus standard. A Break character consists of a
Start bit, followed by 12 ‘0’ bits and a Stop bit. The Enhanced EUSART module can receive a Break
character in two ways.
To send a Break character, set the SENDB and TXEN
bits of the TXSTA register. The Break character trans- The first method to detect a Break character uses the
mission is then initiated by a write to the TXREG. The FERR bit of the RCSTA register and the Received data
value of data written to TXREG will be ignored and all as indicated by RCREG. The Baud Rate Generator is
‘0’s will be transmitted. assumed to have been initialized to the expected baud
rate.
The SENDB bit is automatically reset by hardware after
the corresponding Stop bit is sent. This allows the user A Break character has been received when;
to preload the transmit FIFO with the next transmit byte • RCIF bit is set
following the Bre ak character (ty pically, th e Syn c • FERR bit is set
character in the LIN specification).
• RCREG = 00h
The TRMT bit of the TXSTA register indicates when the
The s econd m ethod uses the Auto -Wake-up fe ature
transmit operation is active or Idle, just as it does during
described in Section 18.3.3 “Auto-Wake-up on
normal transmission. S ee Figure 18-9 for the tim ing of
Break”. By ena bling this feature, th e EU SART w ill
the Break character sequence.
sample the nex t tw o tran sitions on RX/DT, ca use an
18.3.4.1 Break and Sync Transmit Sequence RCIF interrupt, and receive the next data byte followed
by another interrupt.
The fol lowing se quence w ill start a m essage fram e
header made up of a Break, followed by an auto-baud Note tha t fol lowing a Bre ak character, th e us er w ill
Sync by te. Th is sequence is t ypical of a LIN bu s typically want to enable the Auto-Baud Detect feature.
master. For both methods, the user can set the ABDEN bit of
the BAUDCON register before placing the EUSART in
1. Configure the EUSART for the desired mode. Sleep mode.
2. Set th e T XEN an d SENDB bi ts to enable th e
Break sequence.
3. Load the TXR EG w ith a du mmy ch aracter to
initiate transmission (the value is ignored).
4. Write ‘55h’ to TXREG to load the Sync character
into the transmit FIFO buffer.
5. After the Break has been sent, the SENDB bit is
reset by hard ware an d the Sy nc ch aracter is
then transmitted.

FIGURE 18-9: SEND BREAK CHARACTER SEQUENCE

Write to TXREG
Dummy Write

BRG Output
(Shift Clock)

TX (pin) Start bit bit 0 bit 1 bit 11 Stop bit

Break
TXIF bit
(Transmit
interrupt Flag)
TRMT bit
(Transmit Shift
Reg. Empty Flag)
SENDB Sampled Here Auto Cleared
SENDB
(send Break
control bit)

DS41303G-page 256  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
18.4 EUSART Synchronous Mode 18.4.1.2 Clock Polarity
Synchronous serial communications are typically used A c lock pol arity o ption i s pro vided for M icrowire
in sy stems w ith a single master an d on e or mo re compatibility. Clock polarity is selected with the CKTXP
slaves. Th e m aster device c ontains t he n ecessary bit o f th e BAUDCO N re gister. Se tting th e CKTXP b it
circuitry for baud rate generation and supplies the clock sets the clock Idle state as high. When the CKTXP bit
for all devices in the system. S lave devices can take is s et, the data c hanges on the fal ling e dge of e ach
advantage o f the master clock by eliminating th e clock and is sampled on the rising edge of each clock.
internal clock generation circuitry. Clearing the CKTXP bit sets the Idle state as low. When
the C KTXP bit is cl eared, the data changes on the
There are tw o s ignal lines i n Sy nchronous mode: a rising edge of each clock and is sampled on the falling
bidirectional data line and a clock line. Slaves use the edge of each clock.
external clock supplied by the master to shift the serial
data in to a nd out of their re spective re ceive an d 18.4.1.3 Synchronous Master Transmission
transmit sh ift regi sters. Sinc e t he d ata lin e i s
Data is transferred out of the device on the RX/DT pin.
bidirectional, s ynchronous op eration i s h alf-duplex
The RX/DT and TX/CK pin output drivers are automat-
only. H alf-duplex ref ers to t he f act tha t ma ster an d
ically e nabled w hen the EU SART i s configured f or
slave de vices ca n receive a nd t ransmit da ta but no t
synchronous master transmit operation.
both simultaneously. T he EUSART c an o perate as
either a master or slave device. A transmission is initiated by writing a character to the
TXREG register. If the TSR still contains all or part of a
Start an d S top bi ts are not us ed in sy nchronous
previous character the new character data is held in the
transmissions.
TXREG until the last bit of the previous character has
18.4.1 SYNCHRONOUS MASTER MODE been transmitted. If this is the first character, or the pre-
vious character has been completely flushed from the
The following bits are used to configure the EUSART TSR, the data in the TXREG is immediately transferred
for Synchronous Master operation: to th e T SR. T he transmission of the c haracter c om-
• SYNC = 1 mences immediately following the transfer of the data
• CSRC = 1 to the TSR from the TXREG.
• SREN = 0 (for transmit); SREN = 1 (for receive) Each data bit changes on the leading edge of the mas-
• CREN = 0 (for transmit); CREN = 1 (for receive) ter clock and remains valid until the subsequent leading
clock edge.
• SPEN = 1
Setting the SYNC bit of th e TXSTA register configures Note: The TSR reg ister i s no t ma pped i n dat a
the device for synchronous operation. Setting the CSRC memory, so it is not available to the user.
bit of th e T XSTA r egister c onfigures th e device a s a
master. Clearing the SREN and CREN bits of the RCSTA 18.4.1.4 Data Polarity
register ensures that the device is in the Transmit mode, The polarity of th e transmit an d receive da ta ca n be
otherwise the device will be configured to receive. Setting controlled with the DTRXP bit of the BAUDCON regis-
the S PEN bi t o f th e R CSTA re gister e nables th e ter. The default state of this bit is ‘0’ which selects high
EUSART. If the RX/DT or TX/CK pins are shared with an true transmit and receive data. Setting the DTRXP bit
analog pe ripheral th e a nalog I/O fu nctions m ust b e to ‘1’ will invert the da ta resulting in low true transmit
disabled by clearing the corresponding ANSEL bits. and receive data.
The TRIS bits corresponding to the RX/DT and TX/CK
pins should be set.

18.4.1.1 Master Clock

Synchronous data transfers use a s eparate clock line,
which is synchronous with the data. A device configured
as a master transmits the clock on the TX /CK line. The
TX/CK pin output driver is automatically enabled when
the EUSART is configured for synchronous transmit or
receive operation. Serial data bits change on the leading
edge to ensure they are valid at the trailing edge of each
clock. One clock cyc le is generated for eac h data bit.
Only as many clock cycles are gene rated as there are
data bits.

 2010 Microchip Technology Inc. DS41303G-page 257

PIC18F2XK20/4XK20
18.4.1.5 Synchronous Master Transmission 4. Disable Receive mo de by cl earing bi ts S REN
Set-up: and CREN.
1. Initialize the SPBRGH, SPBRG register pair and 5. Enable Transmit mode by setting the TXEN bit.
the B RGH and BRG16 b its t o achieve t he 6. If 9-bit transmission is desired, set the TX9 bit.
desired baud rate (see Section 18.3 “EUSART 7. If interrupts are desired, set the TXIE, GIE and
Baud Rate Generator (BRG)”). PEIE interrupt enable bits.
2. Set the RX/DT and TX/CK TRIS controls to ‘1’. 8. If 9 -bit transmission is selected, the ni nth b it
3. Enable t he sy nchronous m aster se rial po rt by should be loaded in the TX9D bit.
setting bits SYNC, SPEN an d CSRC. Set th e 9. Start tra nsmission b y l oading d ata to th e
TRIS bi ts corresponding t o th e R X/DT an d TXREG register.
TX/CK I/O pins.

FIGURE 18-10: SYNCHRONOUS TRANSMISSION

RX/DT
pin bit 0 bit 1 bit 2 bit 7 bit 0 bit 1 bit 7
Word 1 Word 2
TX/CK pin
(SCKP = 0)

TX/CK pin
(SCKP = 1)
Write to
TXREG Reg Write Word 1 Write Word 2
TXIF bit
(Interrupt Flag)

TRMT bit

‘1’ ‘1’
TXEN bit

Note: Sync Master mode, SPBRG = 0, continuous transmission of two 8-bit words.

FIGURE 18-11: SYNCHRONOUS TRANSMISSION (THROUGH TXEN)

RX/DT pin bit 0 bit 1 bit 2 bit 6 bit 7

TX/CK pin

Write to
TXREG reg

TXIF bit

TRMT bit

TXEN bit

DS41303G-page 258  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 18-7: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER TRANSMISSION
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 62
TXREG EUSART Transmit Register 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission.
Note 1: Reserved in PIC18F2XK20 devices; always maintain these bits clear.

 2010 Microchip Technology Inc. DS41303G-page 259

PIC18F2XK20/4XK20
18.4.1.6 Synchronous Master Reception 18.4.1.8 Receive Overrun Error
Data i s re ceived at t he R X/DT pi n. T he RX/DT pi n The receive FIFO buffer can hold two characters. An
output dri ver mu st b e di sabled by s etting th e overrun error will be generated if a third character, in its
corresponding TR IS bits when th e EU SART i s entirety, is received before RCREG is read to access
configured for synchronous master receive operation. the F IFO. W hen th is happens the O ERR bi t o f th e
In Synchronous mode, reception is enabled by setting RCSTA register is set. Previous data in the FIFO will
either t he S ingle R eceive E nable b it ( SREN of t he not be overwritten. Th e tw o c haracters in th e FIFO
RCSTA register) or the Continuous Receive Enable bit buffer can be read, however, no a dditional characters
(CREN of the RCSTA register). will be received until the error is cleared. The OERR bit
can only be cleared by clearing the overrun condition.
When SREN is set and CREN is clear, only as many If the overrun error occurred when the SREN bit is set
clock cycles are generated as there are data bits in a and CREN is clear then the error is cleared by reading
single character. The SREN bit is automatically cleared RCREG. If the overrun occurred when the CREN bit is
at the completion of one character. When CREN is set, set then the error condition is cleared by either clearing
clocks are continuously generated unt il C REN is the CREN bit of the RCSTA register or by clearing the
cleared. If CREN is cleared in the middle of a character SPEN bit which resets the EUSART.
the CK clock stops immediately and the partial charac-
ter is discarded. If SREN and CREN are both set, then 18.4.1.9 Receiving 9-bit Characters
SREN is cleared at the completion of the first character
The EUSART supports 9-bit character reception. When
and CREN takes precedence.
the RX9 bit of the RCSTA register is set the EUSART
To initiate reception, set either SREN or CREN. Data is will s hift 9-bi ts into the RSR fo r eac h c haracter
sampled at the R X/DT pin on the trailing edge of the received. T he RX9D b it of the R CSTA r egister i s the
TX/CK c lock pin a nd is s hifted in to the R eceive Shi ft ninth, and Most Significant, data bit of the top u nread
Register (R SR). W hen a co mplete cha racter i s character in the receive FIFO. When reading 9-bit data
received in to th e R SR, the R CIF b it is set and th e from the receive FIFO buffer, the R X9D data bit must
character i s automatically tra nsferred t o t he two be read before reading the 8 Least Significant bits from
character receive FIFO. The Least Significant eight bits the RCREG.
of the top character in the receive FIFO are available in
RCREG. The RCIF bit remains set as long as there are 18.4.1.10 Synchronous Master Reception
un-read characters in the receive FIFO. Set-up:
18.4.1.7 Slave Clock 1. Initialize the SPBRGH, SPBRG register pair for
the ap propriate ba ud rat e. Set or cl ear th e
Synchronous data transfers use a s eparate clock line, BRGH and BRG16 bits, as required, to achieve
which is synchronous with the data. A device configured the desired baud rate.
as a sl ave rece ives the cloc k on the TX/C K l ine. The
2. Set the RX/DT and TX/CK TRIS controls to ‘1’.
TX/CK pin output driver must be disabled by setting the
associated TRIS bit w hen the device is config ured for 3. Enable th e s ynchronous ma ster se rial po rt b y
synchronous slave transmit or receive operation. Serial setting b its SYNC, SPEN an d CSRC. Dis able
data bits change on the leading edge to ensure they are RX/DT and TX/CK output drivers by setting the
valid at the trailing edge of each clock. One data bit is corresponding TRIS bits.
transferred for eac h cloc k cyc le. Onl y as m any clo ck 4. Ensure bits CREN and SREN are clear.
cycles should be received as there are data bits. 5. If using interrupts, set the GIE and PEIE bits of
the INTCON register and set RCIE.
6. If 9-bit reception is desired, set bit RX9.
7. Start reception by se tting the SR EN bit or for
continuous reception, set the CREN bit.
8. Interrupt flag bit RCIF will be set when reception
of a character i s c omplete. A n i nterrupt w ill be
generated if the enable bit RCIE was set.
9. Read the RCSTA register to get the ninth bit (if
enabled) and de termine if an y erro r occurred
during reception.
10. Read t he 8 -bit rec eived da ta by rea ding th e
RCREG register.
11. If an overrun error oc curs, c lear the error by
either cl earing the C REN b it of the R CSTA
register or by clearing the SPEN bit which resets
the EUSART.

DS41303G-page 260  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 18-12: SYNCHRONOUS RECEPTION (MASTER MODE, SREN)

RX/DT
pin bit 0 bit 1 bit 2 bit 3 bit 4 bit 5 bit 6 bit 7

TX/CK pin
(SCKP = 0)

TX/CK pin
(SCKP = 1)

Write to
bit SREN

SREN bit

CREN bit ‘0’ ‘0’

RCIF bit
(Interrupt)
Read
RXREG

Note: Timing diagram demonstrates Sync Master mode with bit SREN = 1 and bit BRGH = 0.

TABLE 18-8: REGISTERS ASSOCIATED WITH SYNCHRONOUS MASTER RECEPTION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
RCREG EUSART Receive Register 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master reception.
Note 1: Reserved in 28-pin devices; always maintain these bits clear.

 2010 Microchip Technology Inc. DS41303G-page 261

PIC18F2XK20/4XK20
18.4.2 SYNCHRONOUS SLAVE MODE If tw o words are written to the TXR EG and then the
SLEEP instruction is executed, the following will occur:
The following bits are used to configure the EUSART
for Synchronous slave operation: 1. The firs t c haracter w ill immediately tran sfer to
the TSR register and transmit.
• SYNC = 1
2. The second word will remain in TXREG register.
• CSRC = 0
3. The TXIF bit will not be set.
• SREN = 0 (for transmit); SREN = 1 (for receive)
4. After the first character h as been shif ted out of
• CREN = 0 (for transmit); CREN = 1 (for receive)
TSR, the TXREG register will transfer the second
• SPEN = 1 character to the TSR and the TXIF bit will now be
Setting the SYNC bit of th e TX STA re gister configures set.
the device for synch ronous operation. C learing th e 5. If the PEIE a nd TXIE bits are set, the interrupt
CSRC bit of the TXSTA register configures the device as will wake the device from Sleep and execute the
a slave. Clearing the SREN and CREN bits of the RCSTA next in struction. If t he GIE b it is a lso s et, th e
register ensures that the device is in the Transmit mode, program will call the Interrupt Service Routine.
otherwise the device will be configured to receive. Setting
the S PEN bit of the R CSTA r egister ena bles th e 18.4.2.2 Synchronous Slave Transmission
EUSART. If the RX/DT or TX/CK pins are shared with an Set-up:
analog pe ripheral t he analog I /O f unctions must b e
1. Set the SYNC and SPEN bi ts an d c lear the
disabled by clearing the corresponding ANSEL bits.
CSRC bit.
RX/DT and TX/CK pin output drivers must be disabled 2. Set the RX/DT and TX/CK TRIS controls to ‘1’.
by setting the corresponding TRIS bits.
3. Clear the CREN and SREN bits.
18.4.2.1 EUSART Synchronous Slave 4. If using interrupts, ensure that the GIE and PEIE
Transmit bits of the INTCON register are set and set the
TXIE bit.
The oper ation of the Synchronous M aster and Sl ave
5. If 9-bit transmission is desired, set the TX9 bit.
modes ar e ident ical ( see Section 18.4.1.3
“Synchronous Master Transmission”), except in t he 6. Enable transmission by setting the TXEN bit.
case of the Sleep mode. 7. If 9-bit transmission is selected, insert the Most
Significant bit into the TX9D bit.
8. Start tra nsmission by w riting th e L east
Significant 8 bits to the TXREG register.

TABLE 18-9: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE TRANSMISSION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
TRISC TRISC7 TRISC6 TRISC5 TRISC4 TRISC3 TRISC2 TRISC1 TRISC0 62
TXREG EUSART Transmit Register 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous master transmission.
Note 1: Reserved in PIC18F2XK20 devices; always maintain these bits clear.

DS41303G-page 262  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
18.4.2.3 EUSART Synchronous Slave 18.4.2.4 Synchronous Slave Reception
Reception Set-up:
The operation of the Sy nchronous M aster an d S lave 1. Set the SYNC and SPEN bi ts an d c lear the
modes is ide ntical ( Section 18.4.1.6 “Synchronous CSRC bit.
Master Reception”), with the following exceptions: 2. Set the RX/DT and TX/CK TRIS controls to ‘1’.
• Sleep 3. If using interrupts, ensure that the GIE and PEIE
• CREN bit is always set, therefore the receiver is bits of the INTCON register are set and set the
never Idle RCIE bit.
• SREN bit, which is a “don't care” in Slave mode 4. If 9-bit reception is desired, set the RX9 bit.
A character may be re ceived while in Sleep mode by 5. Set the CREN bit to enable reception.
setting the CREN bit prior to entering Sleep. Once the 6. The R CIF bit w ill be s et when r eception is
word is received, the RSR register will transfer the data complete. An inte rrupt will be g enerated if th e
to the RCREG register. If the RCIE enable bit is set, the RCIE bit was set.
interrupt g enerated w ill wake th e dev ice from Slee p 7. If 9-bit mo de is e nabled, re trieve t he M ost
and execute the next instruction. If the GIE bit is also Significant bit from the RX9D bit of the RCSTA
set, the program will branch to the interrupt vector. register.
8. Retrieve th e 8 L east Si gnificant bit s fro m th e
receive FIFO by reading the RCREG register.
9. If an overrun error oc curs, cl ear the error by
either cl earing the C REN bi t of the R CSTA
register or by clearing the SPEN bit which resets
the EUSART.

TABLE 18-10: REGISTERS ASSOCIATED WITH SYNCHRONOUS SLAVE RECEPTION

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE(1) ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
RCSTA SPEN RX9 SREN CREN ADDEN FERR OERR RX9D 61
RCREG EUSART Receive Register 61
TXSTA CSRC TX9 TXEN SYNC SENDB BRGH TRMT TX9D 61
BAUDCON ABDOVF RCIDL DTRXP CKTXP BRG16 — WUE ABDEN 61
SPBRGH EUSART Baud Rate Generator Register, High Byte 61
SPBRG EUSART Baud Rate Generator Register, Low Byte 61
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for synchronous slave reception.
Note 1: Reserved in 28-pin devices; always maintain these bits clear.

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PIC18F2XK20/4XK20
NOTES:

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 PIC18F2XK20/4XK20
19.0 ANALOG-TO-DIGITAL
CONVERTER (ADC) MODULE
The Ana log-to-Digital C onverter (AD C) allows
conversion of an analog input signal to a 10-bit binary
representation of that signal. This device uses analog
inputs, which are multiplexed into a single sample and
hold ci rcuit. The ou tput of t he sample a nd hold i s
connected to the input of the converter. The converter
generates a 1 0-bit b inary r esult vi a su ccessive
approximation and stores the conversion result into the
ADC result registers (ADRESL and ADRESH).
The AD C volt age reference is software se lectable to
either VDD or a voltage applied to the external reference
pins.
The ADC can generate an interrupt upon completion of
a conversion. This interrupt can be used to wake-up the
device from Sleep.
Figure 19-1 shows the block diagram of the ADC.

FIGURE 19-1: ADC BLOCK DIAGRAM

VCFG1 = 0
AVSS
VREF- VCFG1 = 1
AVDD
VCFG0 = 0

VREF+ VCFG0 = 1

AN0 0000
AN1 0001
AN2 0010
AN3 0011
AN4 0100
AN5 0101
AN6 0110
AN7 0111
ADC
AN8 1000
GO/DONE 10
AN9 1001
AN10 1010 0 = Left Justify
ADFM
AN11 1011 1 = Right Justify

AN12 1100 ADON 10

Unused 1101
VSS ADRESH ADRESL
Unused 1110
FVR 1111

CHS<3:0>

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PIC18F2XK20/4XK20
19.1 ADC Configuration 19.1.4 SELECTING AND CONFIGURING
ACQUISITION TIME
When c onfiguring a nd using t he ADC th e following
functions must be considered: The AD CON2 r egister al lows th e u ser to select a n
acquisition time that occurs each time the GO/DONE
• Port configuration
bit is set.
• Channel selection
Acquisition time is set with the ACQT<2:0> bits of the
• ADC voltage reference selection
ADCON2 register. Acquisition delays cover a range of
• ADC conversion clock source 2 to 20 TAD. W hen th e GO/DONE bit is set , the A/D
• Interrupt control module continues to sample the input for the selected
• Results formatting acquisition tim e, th en aut omatically begins a co nver-
sion. Since the acquisition time is programmed, there is
19.1.1 PORT CONFIGURATION no need to wait for an acquisition time between select-
The ANSEL, ANSELH, TRISA, TRISB and TRISE reg- ing a channel and setting the GO/DONE bit.
isters al l con figure th e A/D port pin s. Any port pin Manual ac quisition is selected w hen
needed as an analog input should have its correspond- ACQT<2:0> = 000. W hen the G O/DONE bi t is se t,
ing ANSx bit set to disable the digital input buffer and sampling is stopped and a conversion begins. The user
TRISx bit set to disable the digital output driver. If the is responsible for ensuring the required acquisition time
TRISx bi t is cleared, th e digital ou tput le vel ( VOH or has p assed be tween se lecting th e de sired i nput
VOL) will be converted. channel a nd s etting th e GO/DONE bit. This option is
The A/D ope ration is ind ependent of the state of the also the default Reset state of the ACQT<2:0> bits and
ANSx bits and the TRIS bits. is c ompatible with devices th at d o n ot offer
programmable acquisition times.
Note 1: When reading the PORT register, all pins
In either case, when the conversion is completed, the
with the ir co rresponding AN Sx bit s et
GO/DONE bit is cleared, the ADIF flag is set and the
read as c leared (a l ow level). Ho wever,
A/D b egins sampling the cur rently s elected c hannel
analog conversion of pins configured as
again. When an acquisition time is programmed, there
digital inputs (AN Sx bi t cl eared an d
is no indication of when the acquisition time ends and
TRISx b it s et) will be a ccurately
the conversion begins.
converted.
2: Analog levels on any pin with the corre- 19.1.5 CONVERSION CLOCK
sponding ANSx bit cleared may cause the The source of the conversion clock is software select-
digital input buffer to consume current out able via the ADCS bits of the ADCON2 register. There
of the device’s specification limits. are seven possible clock options:
3: The PBADEN bi t in Confi guration • FOSC/2
Register 3H configures PORTB pin s to
• FOSC/4
reset as a nalog or digital p ins b y
controlling how the bit s in AN SELH are • FOSC/8
reset. • FOSC/16
• FOSC/32
19.1.2 CHANNEL SELECTION • FOSC/64
The CHS bits of the ADCON0 register determine which • FRC (dedicated internal oscillator)
channel is connected to the sample and hold circuit.
The time to complete one bit conversion is defined as
When changing c hannels, a de lay is required before TAD. One full 10-bit conversion requires 11 TAD periods
starting th e n ext co nversion. R efer t o Section 19.2 as shown in Figure 19-3.
“ADC Operation” for more information.
For correct conversion, the appropriate TAD specification
19.1.3 ADC VOLTAGE REFERENCE must be met. See A/D conversion re quirements in
Table 26-25 f or more i nformation. T able 19-1 g ives
The VC FG bits of the ADCON1 reg ister pro vide examples of appropriate ADC clock selections.
independent c ontrol of t he positive an d n egative
voltage references. The positive voltage reference can Note: Unless using the FRC, any changes in the
be either V DD or an external voltage source. Likewise, system c lock f requency w ill ch ange th e
the negative voltage reference can be either VSS or an ADC c lock freq uency, w hich may
external voltage source. adversely affect the ADC result.

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 PIC18F2XK20/4XK20
19.1.6 INTERRUPTS This interrupt ca n be g enerated w hile th e dev ice i s
operating or while in Sleep. If the device is in Sleep, the
The ADC module allows for the ability to g enerate an
interrupt w ill wake-up the device. Upon w aking from
interrupt up on com pletion of an Anal og-to-Digital
Sleep, t he next instruction fo llowing th e SLEEP
Conversion. T he A DC i nterrupt f lag is t he A DIF bi t in
instruction is always executed. If the user is attempting
the PIR1 register. The ADC interrupt enable is the ADIE
to w ake-up fro m S leep a nd r esume in -line c ode
bit in the PIE1 register. The ADIF bit must be cleared by
execution, the global interrupt must be disabled. If the
software.
global interrupt is enabled, execution will switch to the
Note: The ADIF b it is set a t th e c ompletion of Interrupt Service Routine. Please see Section 19.1.6
every c onversion, reg ardless o f w hether “Interrupts” for more information.
or not the ADC interrupt is enabled.

TABLE 19-1: ADC CLOCK PERIOD (TAD) VS. DEVICE OPERATING FREQUENCIES
ADC Clock Period (TAD) Device Frequency (FOSC)

ADC Clock Source ADCS<2:0> 64 MHz 16 MHz 4 MHz 1 MHz

FOSC/2 000 31.25 ns(2) 125 ns(2) 500 ns(2) 2.0 s
FOSC/4 100 62.5 ns(2) 250 ns(2) 1.0 s 4.0 s(3)
FOSC/8 001 400 ns(2) 500 ns(2) 2.0 s 8.0 s(3)
FOSC/16 101 250 ns(2) 1.0 s 4.0 s(3) 16.0 s(3)
FOSC/32 010 500 ns(2) 2.0 s 8.0 s(3) 32.0 s(3)
FOSC/64 110 1.0 s 4.0 s(3) 16.0 s(3) 64.0 s(3)
FRC x11 1-4 s(1,4) 1-4 s(1,4) 1-4 s(1,4) 1-4 s(1,4)
Legend: Shaded cells are outside of recommended range.
Note 1: The FRC source has a typical TAD time of 1.7 s.
2: These values violate the minimum required TAD time.
3: For faster conversion times, the selection of another clock source is recommended.
4: When the device frequency is greater than 1 MHz, the FRC clock source is only recommended if the
conversion will be performed during Sleep.

19.1.7 RESULT FORMATTING

The 10-bit A/D conversion result can be supplied in two
formats, left justified or right justified. The ADFM bit of
the ADCON2 register controls the output format.
Figure 19-2 shows the two output formats.

FIGURE 19-2: 10-BIT A/D CONVERSION RESULT FORMAT

ADRESH ADRESL
(ADFM = 0) MSB LSB
bit 7 bit 0 bit 7 bit 0

10-bit A/D Result Unimplemented: Read as ‘0’

(ADFM = 1) MSB LSB

bit 7 bit 0 bit 7 bit 0

Unimplemented: Read as ‘0’ 10-bit A/D Result

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PIC18F2XK20/4XK20
19.2 ADC Operation Figure 19-3 shows the operation of th e A/D converter
after the GO bit has been set and the ACQT<2:0> bits
19.2.1 STARTING A CONVERSION are cleared. A conversion is started after the following
instruction to al low entry into SLEEP mode before the
To enable th e AD C module, the AD ON bi t o f th e
conversion begins.
ADCON0 register must be set to a ‘1’. Setting the GO/
DONE bit of the ADCON0 register to a ‘1’ will, depend- Figure 19-4 shows the operation of th e A/D converter
ing on the ACQT bits of the ADCON2 register, either after the GO bit has been set and the ACQT<2:0> bits
immediately st art the Anal og-to-Digital c onversion or are set to ‘010’ which selects a 4 T AD acquisition time
start an ac quisition d elay followed b y t he Analog-to- before the conversion starts.
Digital conversion.
Note: The GO/DONE bit should not be set in the
same in struction t hat tu rns o n t he A DC.
Refer to Section 19.2.9 “A/D Conver-
sion Procedure”.

FIGURE 19-3: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 000, TACQ = 0)

TCY - TAD TAD1 TAD2 TAD3 TAD4 TAD5 TAD6 TAD7 TAD8 TAD9 TAD10 TAD11 2 TAD
b9 b8 b7 b6 b5 b4 b3 b2 b1 b0

Conversion starts Discharge

Holding capacitor is disconnected from analog input (typically 100 ns)

Set GO bit
On the following cycle:
ADRESH:ADRESL is loaded, GO bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.

FIGURE 19-4: A/D CONVERSION TAD CYCLES (ACQT<2:0> = 010, TACQ = 4 TAD)

TACQT Cycles TAD Cycles

1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 2 TAD
b9 b8 b7 b6 b5 b4 b3 b2 b1 b0
Automatic
Acquisition Conversion starts Discharge
Time (Holding capacitor is disconnected from analog input)

Set GO bit
(Holding capacitor continues On the following cycle:
acquiring input) ADRESH:ADRESL is loaded, GO bit is cleared,
ADIF bit is set, holding capacitor is connected to analog input.

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 PIC18F2XK20/4XK20
19.2.2 COMPLETION OF A CONVERSION 19.2.7 ADC OPERATION DURING SLEEP
When the conversion is complete, the ADC module will: The AD C mod ule ca n ope rate during Sl eep. Thi s
• Clear the GO/DONE bit requires t he A DC cl ock s ource to be se t to th e FRC
option. Wh en th e F RC cl ock source is se lected, t he
• Set the ADIF flag bit
ADC waits one additional instruction before starting the
• Update the ADRESH:ADRESL registers with new conversion. Th is al lows the SLEEP in struction to b e
conversion result executed, w hich can reduce system noise during the
conversion. If the ADC interrupt is enabled, the device
19.2.3 DISCHARGE will w ake-up fro m Sl eep when t he c onversion
The discharge phase is used to initialize the value of completes. If the ADC interrupt is di sabled, the ADC
the capacitor array. The array is discharged after every module is tu rned of f a fter the c onversion c ompletes,
sample. T his fe ature h elps t o o ptimize the un ity-gain although the ADON bit remains set.
amplifier, as th e c ircuit a lways needs to ch arge th e When the A DC clock source is something other than
capacitor array, rather than charge/discharge based on FRC, a SLEEP instruction causes the present conver-
previous measure values. sion to be aborted and the AD C module is turned off,
although the ADON bit remains set.
19.2.4 TERMINATING A CONVERSION
If a conversion must be terminated before completion, 19.2.8 SPECIAL EVENT TRIGGER
the GO/DONE bit ca n b e c leared by so ftware. Th e The CCP2 Special Event Trigger allows periodic ADC
ADRESH:ADRESL reg isters w ill no t be up dated w ith measurements w ithout s oftware i ntervention. When
the p artially co mplete Ana log-to-Digital c onversion this trigger occurs, the GO/DONE bit is set by hardware
sample. Ins tead, th e ADRESH:ADRESL reg ister p air and the Timer1 or Timer3 counter resets to zero.
will retain the value of the previous conversion.
Using the S pecial Eve nt T rigger do es not as sure
Note: A device Reset forces all registers to their proper AD C t iming. It is t he user’s res ponsibility to
Reset st ate. T hus, th e AD C mo dule i s ensure that the ADC timing requirements are met.
turned off and any pending conversion is
See Section 11.3.4 “Special Event Trigger” for more
terminated.
information.
19.2.5 DELAY BETWEEN CONVERSIONS
After t he A/D c onversion i s completed o r a borted, a
2 TAD wait is required before the next acquisition can
be s tarted. Af ter t his wai t, th e c urrently s elected
channel is reconnected to the charge holding capacitor
commencing the next acquisition.

19.2.6 ADC OPERATION IN POWER-

MANAGED MODES
The selection of the automatic acquisition time and A/D
conversion clock is determ ined in p art by the clo ck
source and frequency while in a power-managed mode.
If the A/D is expected to operate while the device is in
a power-managed m ode, th e AC QT<2:0> an d
ADCS<2:0> bits in AD CON2 sh ould be updated in
accordance wi th t he clock s ource t o be u sed in t hat
mode. A fter e ntering the mode, an A /D ac quisition o r
conversion m ay be st arted. O nce s tarted, the device
should co ntinue to be cl ocked by the sa me cl ock
source until the conversion has been completed.
If de sired, the de vice m ay be pl aced into th e
corresponding Idle mode during the conversion. If the
device clock frequency is less than 1 MHz, the A/D FRC
clock source should be selected.

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PIC18F2XK20/4XK20
19.2.9 A/D CONVERSION PROCEDURE EXAMPLE 19-1: A/D CONVERSION
This is an exa mple procedure for u sing the AD C to ;This code block configures the ADC
perform an Analog-to-Digital conversion: ;for polling, Vdd and Vss as reference, Frc
clock and AN0 input.
1. Configure Port: ;
• Disable pin output driver (See TRIS register) ;Conversion start & polling for completion
• Configure pin as analog ; are included.
;
2. Configure the ADC module: MOVLW B’10101111’ ;right justify, Frc,
• Select ADC conversion clock MOVWF ADCON2 ; & 12 TAD ACQ time
• Configure voltage reference MOVLW B’00000000’ ;ADC ref = Vdd,Vss
MOVWF ADCON1 ;
• Select ADC input channel
BSF TRISA,0 ;Set RA0 to input
• Select result format BSF ANSEL,0 ;Set RA0 to analog
• Select acquisition delay MOVLW B’00000001’ ;AN0, ADC on
• Turn on ADC module MOVWF ADCON0 ;
BSF ADCON0,GO ;Start conversion
3. Configure ADC interrupt (optional): ADCPoll:
• Clear ADC interrupt flag BTFSC ADCON0,GO ;Is conversion done?
• Enable ADC interrupt BRA ADCPoll ;No, test again
; Result is complete - store 2 MSbits in
• Enable peripheral interrupt
; RESULTHI and 8 LSbits in RESULTLO
• Enable global interrupt(1) MOVFF ADRESH,RESULTHI
4. Wait the required acquisition time(2). MOVFF ADRESL,RESULTLO
5. Start conversion by setting the GO/DONE bit.
6. Wait for ADC conversion to complete by one of
the following:
• Polling the GO/DONE bit
• Waiting for the ADC interrupt (interrupts
enabled)
7. Read ADC Result
8. Clear the ADC interrupt flag (required if interrupt
is enabled).

Note 1: The global interrupt can be disabled if the

user is attempting to wake-up from Sleep
and resume in-line code execution.
2: Software delay required if ACQT bits are
set to zero delay. See Section 19.3 “A/D
Acquisition Requirements”.

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 PIC18F2XK20/4XK20
19.2.10 ADC REGISTER DEFINITIONS
The following registers are used to control the opera-
tion of the ADC.
Note: Analog pi n control is pe rformed b y th e
ANSEL and ANSELH registers. For ANSEL
and AN SELH registers, see Register 10-2
and Register 10-3, respectively.

REGISTER 19-1: ADCON0: A/D CONTROL REGISTER 0

U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 Unimplemented: Read as ‘0’

bit 5-2 CHS<3:0>: Analog Channel Select bits
0000 = AN0
0001 = AN1
0010 = AN2
0011 = AN3
0100 = AN4
0101 = AN5(1)
0110 = AN6(1)
0111 = AN7(1)
1000 = AN8
1001 = AN9
1010 = AN10
1011 = AN11
1100 = AN12
1101 = Reserved
1110 = Reserved
1111 = FVR (1.2 Volt Fixed Voltage Reference)(2)
bit 1 GO/DONE: A/D Conversion Status bit
1 = A/D conversion cycle in progress. Setting this bit starts an A/D conversion cycle.
This bit is automatically cleared by hardware when the A/D conversion has completed.
0 = A/D conversion completed/not in progress
bit 0 ADON: ADC Enable bit
1 = ADC is enabled
0 = ADC is disabled and consumes no operating current

Note 1: These channels are not implemented on PIC18F2XK20 devices.

2: Allow greater than 15 s acquisition time when measuring the Fixed Voltage Reference.

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PIC18F2XK20/4XK20

REGISTER 19-2: ADCON1: A/D CONTROL REGISTER 1

U-0 U-0 R/W-0 R/W-0 U-0 U-0 U-0 U-0
— — VCFG1 VCFG0 — — — —
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 Unimplemented: Read as ‘0’

bit 5 VCFG1: Negative Voltage Reference select bit
1 = Negative voltage reference supplied externally through VREF- pin.
0 = Negative voltage reference supplied internally by VSS.
bit 4 VCFG0: Positive Voltage Reference select bit
1 = Positive voltage reference supplied externally through VREF+ pin.
0 = Positive voltage reference supplied internally by VDD.
bit 3-0 Unimplemented: Read as ‘0’

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 PIC18F2XK20/4XK20

REGISTER 19-3: ADCON2: A/D CONTROL REGISTER 2

R/W-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 ADFM: A/D Conversion Result Format Select bit

1 = Right justified
0 = Left justified
bit 6 Unimplemented: Read as ‘0’
bit 5-3 ACQT<2:0>: A/D Acquisition time select bits. Acquisition time is the duration that the A/D charge hold-
ing capacitor remains connected to A/D channel from the instant the GO/DONE bit is set until conver-
sions begins.
000 = 0(1)
001 = 2 TAD
010 = 4 TAD
011 = 6 TAD
100 = 8 TAD
101 = 12 TAD
110 = 16 TAD
111 = 20 TAD
bit 2-0 ADCS<2:0>: A/D Conversion Clock Select bits
000 = FOSC/2
001 = FOSC/8
010 = FOSC/32
011 = FRC(1) (clock derived from a dedicated internal oscillator = 600 kHz nominal)
100 = FOSC/4
101 = FOSC/16
110 = FOSC/64
111 = FRC(1) (clock derived from a dedicated internal oscillator = 600 kHz nominal)
Note 1: When the A/D clock source is selected as FRC then the start of conversion is delayed by one instruction
cycle after the GO/DONE bit is set to allow the SLEEP instruction to be executed.

 2010 Microchip Technology Inc. DS41303G-page 273

PIC18F2XK20/4XK20

REGISTER 19-4: ADRESH: ADC RESULT REGISTER HIGH (ADRESH) ADFM = 0

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
ADRES9 ADRES8 ADRES7 ADRES6 ADRES5 ADRES4 ADRES3 ADRES2
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 ADRES<9:2>: ADC Result Register bits

Upper 8 bits of 10-bit conversion result

REGISTER 19-5: ADRESL: ADC RESULT REGISTER LOW (ADRESL) ADFM = 0

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
ADRES1 ADRES0 — — — — — —
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 ADRES<1:0>: ADC Result Register bits

Lower 2 bits of 10-bit conversion result
bit 5-0 Reserved: Do not use.

REGISTER 19-6: ADRESH: ADC RESULT REGISTER HIGH (ADRESH) ADFM = 1

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
— — — — — — ADRES9 ADRES8
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-2 Reserved: Do not use.

bit 1-0 ADRES<9:8>: ADC Result Register bits
Upper 2 bits of 10-bit conversion result

REGISTER 19-7: ADRESL: ADC RESULT REGISTER LOW (ADRESL) ADFM = 1

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x
ADRES7 ADRES6 ADRES5 ADRES4 ADRES3 ADRES2 ADRES1 ADRES0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 ADRES<7:0>: ADC Result Register bits

Lower 8 bits of 10-bit conversion result

DS41303G-page 274  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
19.3 A/D Acquisition Requirements an A/D acquisition must be done before the conversion
can be s tarted. To calculate the minimum acquisition
For the ADC to meet its specified accuracy, the charge time, Equation 19-1 may be u sed. T his equat ion
holding cap acitor (C HOLD) must be a llowed to f ully assumes that 1/2 LSb er ror is used (1024 step s for the
charge to the input c hannel voltage level. The Analog ADC). The 1/2 LSb error is the maximum error allowed
Input model is show n in Figure 19-5. The sou rce for the ADC to meet its specified resolution.
impedance (RS) and the internal sampling switch (RSS)
impedance directly affect the time required to charge the
capacitor CHOLD. The sampling switch (RSS) impedance
varies over t he device volt age (VDD), see Figur e 19-5.
The maximum recommended impedance for analog
sources is 10 k. As the s ource impedance is
decreased, the a cquisition t ime may be decrea sed.
After the analog input channel is selected (or changed),

EQUATION 19-1: ACQUISITION TIME EXAMPLE

Assumptions: Temperature = 50°C and external impedance of 10k  3.0V V DD

T ACQ = Amplifier Settling Time + Hold Capacitor Charging Time + Temperature Coefficient
= T AMP + T C + T COFF
= 5µs + T C +   Temperature - 25°C   0.05µs/°C  

The value for TC can be approximated with the following equations:

V APPLIE D  1 – ------------ = V CHOL D

1
;[1] VCHOLD charged to within 1/2 lsb
 2047
–TC
 ----------
RC
V APPLIE D  1 – e  = V CHOL D ;[2] VCHOLD charge response to VAPPLIED
 
– Tc
 ---------
V APPLI ED  1 – e  = V APPL IED  1 – ------------ ;combining [1] and [2]
RC 1
   2047

Solving for TC:

T C = – C HOLD  R IC + R SS + R S  ln(1/2047)
= – 13.5pF  1k  + 700  + 10k   ln(0.0004885)
= 1.20 µs
Therefore:
T ACQ = 5µs + 1.20µs +   50°C- 25°C   0.05  s/ °C  
= 7.45µs

Note 1: The reference voltage (VREF) has no effect on the equation, since it cancels itself out.
2: The charge holding capacitor (CHOLD) is discharged after each conversion.
3: The maximum recommended impedance for analog sources is 10 k. This is required to meet the pin
leakage specification.

 2010 Microchip Technology Inc. DS41303G-page 275

PIC18F2XK20/4XK20
FIGURE 19-5: ANALOG INPUT MODEL
VDD
Sampling
Switch
Rs ANx RIC  1k SS Rss

VA CPIN I LEAKAGE(1) CHOLD = 13.5 pF

5 pF
Discharge VSS/VREF-
Switch

3.5V
Legend: CPIN = Input Capacitance 3.0V
I LEAKAGE = Leakage current at the pin due to

VDD
various junctions 2.5V
RIC = Interconnect Resistance 2.0V
SS = Sampling Switch 1.5V
CHOLD = Sample/Hold Capacitance
.1 1 10 100
Rss (k)
Note 1: See Section 26.0 “Electrical Characteristics”.

FIGURE 19-6: ADC TRANSFER FUNCTION

Full-Scale Range

3FFh
3FEh
3FDh
3FCh
ADC Output Code

1/2 LSB ideal

3FBh

Full-Scale
004h Transition

003h
002h
001h
000h Analog Input Voltage
1/2 LSB ideal

VSS/VREF- Zero-Scale VDD/VREF+

Transition

DS41303G-page 276  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 19-2: REGISTERS ASSOCIATED WITH A/D OPERATION
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR1 PSPIF(1) ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 62
PIE1 PSPIE (1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 62
IPR1 PSPIP(1) ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 62
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
ADRESH A/D Result Register, High Byte 61
ADRESL A/D Result Register, Low Byte 61
ADCON0 — — CHS3 CHS2 CHS1 CHS0 GO/DONE ADON 61
ADCON1 — — VCFG1 VCFG0 — — — — 61
ADCON2 ADFM — ACQT2 ACQT1 ACQT0 ADCS2 ADCS1 ADCS0 61
ANSEL ANS7(1) ANS6(1) ANS5(1) ANS4 ANS3 ANS2 ANS1 ANS0 62
ANSELH — — — ANS12 ANS11 ANS10 ANS9 ANS8 62
PORTA RA7(2) RA6(2) RA5 RA4 RA3 RA2 RA1 RA0 62
TRISA TRISA7(2) TRISA6(2) PORTA Data Direction Control Register 62
PORTB RB7 RB6 RB5 RB4 RB3 RB2 RB1 RB0 62
TRISB PORTB Data Direction Control Register 62
LATB PORTB Data Latch Register (Read and Write to Data Latch) 62
PORTE(4) — — — — RE3(3) RE2 RE1 RE0 62
TRISE(4) IBF OBF IBOV PSPMODE — TRISE2 TRISE1 TRISE0 62
LATE(4) — — — — — PORTE Data Latch Register 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used for A/D conversion.
Note 1: These bits are unimplemented on PIC18F2XK20 devices; always maintain these bits clear.
2: PORTA<7:6> and their direction bits are individually configured as port pins based on various primary
oscillator modes. When disabled, these bits read as ‘0’.
3: RE3 port bit is available only as an input pin when the MCLRE Configuration bit is ‘0’.
4: These registers are not implemented on PIC18F2XK20 devices.

 2010 Microchip Technology Inc. DS41303G-page 277

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 278  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
20.0 COMPARATOR MODULE FIGURE 20-1: SINGLE COMPARATOR
Comparators are used to inter face analog circuit s to a
digital circuit by comp aring tw o analog v oltages and VIN+ +
providing a digital indication of their relative magnitudes. Output
The comparators are very useful mixed signal building VIN- –
blocks because t hey pro vide analog functionality
independent of the progr am execution. The An alog
Comparator module includes the following features:
• Independent comparator control VIN-
• Programmable input selection VIN+
• Comparator output is available internally/externally
• Programmable output polarity
• Interrupt-on-change
• Wake-up from Sleep Output
• Programmable Speed/Power optimization
• PWM hutdown
s
Note: The b lack a reas of t he output o f the
• Programmable and fixed voltage reference
comparator rep resents th e unc ertainty
20.1 Comparator Overview due to input offsets and response time.

A single comparator is shown in Figure 20-1 along with

the re lationship between the an alog i nput l evels an d
the digital output. When the analog voltage at V IN+ is
less than the analog voltage at VIN-, the output of the
comparator is a dig ital lo w lev el. Whe n th e an alog
voltage at V IN+ is g reater t han th e a nalog voltage at
VIN-, the output of the comparator is a digital high level.

 2010 Microchip Technology Inc. DS41303G-page 279

PIC18F2XK20/4XK20
FIGURE 20-2: COMPARATOR C1 SIMPLIFIED BLOCK DIAGRAM

C1CH<1:0>
2 To
D Q Data Bus
Q1
C12IN0- 0 EN
RD_CM1CON0
C12IN1- 1
MUX Set C1IF
D Q
C12IN2- 2
Q3*RD_CM1CON0
EN
C12IN3- 3 To PWM Logic
CL
Reset
C1ON(1)
C1R C1OE
C1VIN- -
C1IN+ C1OUT
C1VIN+ C1
0
MUX +
FVR 1 C1OUT pin(2)
0 C1SP C1POL
MUX
CVREF C1VREF
1

C1RSEL Note 1: When C1ON = 0, the C1 comparator will produce a ‘0’ output to the XOR Gate.
2: Output shown for reference only. See I/O port pin block diagram for more detail.
3: Q1 and Q3 are phases of the four-phase system clock (FOSC).
4: Q1 is held high during Sleep mode.

FIGURE 20-3: COMPARATOR C2 SIMPLIFIED BLOCK DIAGRAM

To
D Q
Data Bus
Q1
EN
RD_CM2CON0
C2CH<1:0> Set C2IF
2 D Q
Q3*RD_CM2CON0
EN To PWM Logic
C12IN0- 0 C2ON(1)
CL
C2OE
C12IN1- 1 NRESET
MUX C2VIN-
C12IN2- 2 C2 C2OUT
C2VIN+
C12IN3- C2OUT pin(2)
3 C2SP

C2POL
C2R

C2IN+ 0
MUX
FVR 1
0
MUX
CVREF 1 C2VREF
Note 1: When C2ON = 0, the C2 comparator will produce a ‘0’ output to the XOR Gate.
C2RSEL 2: Output shown for reference only. See I/O port pin block diagram for more detail.
3: Q1 and Q3 are phases of the four-phase system clock (FOSC).
4: Q1 is held high during Sleep mode.

DS41303G-page 280  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
20.2 Comparator Control
Each comparator has a separate control and Configu- Note 1: The C xOE bit ov errides the PO RT dat a
ration re gister: C M1CON0 f or C omparator C 1 an d latch. Setting the CxON has no impact on
CM2CON0 for Comparator C2. In addition, Compara- the port override.
tor C 2 h as a s econd control reg ister, C M2CON1, for 2: The i nternal ou tput of the comparator i s
controlling the in teraction w ith Timer1 and simultane- latched w ith e ach i nstruction cycle.
ous reading of both comparator outputs. Unless ot herwise s pecified, ex ternal
The C M1CON0 and CM2CON0 reg isters (s ee Regis- outputs are not latched.
ters 20 -1 an d 20-2 , res pectively) c ontain the co ntrol
and Status bits for the following: 20.2.5 COMPARATOR OUTPUT POLARITY
• Enable Inverting t he output of th e c omparator i s functionally
• Input selection equivalent to s wapping th e comparator i nputs. Th e
polarity of th e co mparator ou tput ca n be inv erted b y
• Reference selection
setting th e C xPOL bit of the C MxCON0 register.
• Output election
s Clearing the CxPOL bit results in a non-inverted output.
• Output polarity
Table 20-1 sh ows the output st ate ve rsus input
• Speed selection conditions, including polarity control.
20.2.1 COMPARATOR ENABLE TABLE 20-1: COMPARATOR OUTPUT
STATE VS. INPUT
Setting the CxON bit of the CMxCON0 register enables
CONDITIONS
the c omparator fo r ope ration. Clearing the C xON b it
disables the comparator resulting in minimum current Input Condition CxPOL CxOUT
consumption. CxVIN- > CxVIN+ 0 0
20.2.2 COMPARATOR INPUT SELECTION CxVIN- < CxVIN+ 0 1

The C xCH<1:0> bits of the C MxCON0 register direct CxVIN- > CxVIN+ 1 1
one o f fo ur a nalog input p ins to the co mparator CxVIN- < CxVIN+ 1 0
inverting input.
20.2.6 COMPARATOR SPEED SELECTION
Note: To use CxIN+ and C12INx- pins as analog
inputs, the appropriate bits must be set in The t rade-off be tween s peed o r po wer c an be opt i-
the ANSEL register and the corresponding mized during program execution with the CxSP control
TRIS bits must also be set to disable the bit. The default state for this bit is ‘1’ which selects the
output drivers. normal s peed m ode. D evice pow er con sumption ca n
be optimized at the cost of slower comparator propaga-
20.2.3 COMPARATOR REFERENCE tion delay by clearing the CxSP bit to ‘0’.
SELECTION
20.3 Comparator Response Time
Setting the CxR bit of the CMxCON0 register directs an
internal voltage reference or an analog input pin to the The comparator output is indeterminate for a period of
non-inverting i nput of th e co mparator. See time after the change of an input source or the selection
Section 21.0 “VOLTAGE REFERENCES” for m ore of a new reference voltage. This period is referred to as
information on the Internal Voltage Reference module. the re sponse time. The res ponse t ime o f th e
comparator differs from the settling time of the voltage
20.2.4 COMPARATOR OUTPUT reference. T herefore, bo th o f t hese t imes m ust be
SELECTION considered when determining the total response time
The o utput o f th e c omparator can be m onitored b y to a comparator input change. See the Comparator and
reading either the CxOUT bit of the CMxCON0 register Voltage R eference S pecifications i n Section 26.0
or the MCxOUT bit of the CM2CON1 register. In order “Electrical Characteristics” for more details.
to make the output available for an external connection,
the following conditions must be true:
• CxOE bit of the CMxCON0 register must be set
• Corresponding TRIS bit must be cleared
• CxON bit of the CMxCON0 register must be set

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PIC18F2XK20/4XK20
20.4 Comparator Interrupt Operation 20.4.1 PRESETTING THE MISMATCH
LATCHES
The co mparator inte rrupt flag can be set w henever
there is a change in the output value of the comparator. The comparator mismatch latches can be preset to the
Changes are recognized by m eans of a mi smatch desired state befo re the comparators are enabled.
circuit which consists of two latches and an exclusive- When the comparator is off the CxPOL bit controls the
or gate (see Figure 20-2 and Figure 20-3). One latch is CxOUT level. Set the CxPOL bit to the desired CxOUT
updated w ith t he comparator output l evel when th e non-interrupt level while the CxON bit is cleared. Then,
CMxCON0 register is read. This latch retains the value configure the desired CxPOL level in the same instruc-
until the ne xt re ad of th e C MxCON0 register or the tion that the CxON bit is set. Since all register writes are
occurrence of a Reset. The other latch of the mismatch performed as a R ead-Modify-Write, the m ismatch
circuit is up dated on every Q1 system cl ock. A latches w ill be c leared du ring t he instruction R ead
mismatch co ndition w ill oc cur w hen a co mparator phase and the ac tual co nfiguration of the CxON an d
output change is clocked through the second latch on CxPOL bits will be occur in the final Write phase.
the Q 1 cl ock c ycle. At thi s po int the tw o mi smatch
latches have opposite output levels which is detected FIGURE 20-4: COMPARATOR
by th e ex clusive-or ga te an d fe d to th e in terrupt INTERRUPT TIMING W/O
circuitry. The mi smatch con dition persists unti l either CMxCON0 READ
the CMxCON0 re gister i s read o r t he comparator
output returns to the previous state. Q1
Q3
Note 1: A w rite operation to the C MxCON0
CxIN+ TRT
register w ill als o clear the mism atch
condition because all writes include a read CxOUT
operation at the beginning of the write Set CxIF (edge)
cycle. CxIF

2: Comparator interrupts will operate correctly reset by software

regardless of the state of CxOE.
The comparator interrupt is set by the mismatch edge FIGURE 20-5: COMPARATOR
and not the mismatch level. This means that the inter- INTERRUPT TIMING WITH
rupt fl ag ca n be res et without t he a dditional s tep of CMxCON0 READ
reading or writing the CMxCON0 register to c lear the
mismatch registers. When the mismatch registers are Q1
cleared, an interrupt will occur upon the comparator’s Q3
return to the previous state, otherwise no interrupt will CxIN+ TRT
be generated. CxOUT
Software will need to maintain informatio n about the Set CxIF (edge)
status of the co mparator output, as r ead from the CxIF
CMxCON0 register, or CM2CON1 register, to determine cleared by CMxCON0 read reset by software
the actual change that has oc curred. See Figures 20-4
and 20-5.
The C xIF bi t of t he PI R2 reg ister is th e co mparator
interrupt fl ag. This bit m ust b e r eset b y software b y Note 1: If a change in the C MxCON0 register
clearing it to ‘0’. Since it is also possible to write a ‘1’ to (CxOUT) should occur when a read oper-
this register, an interrupt can be generated. ation is bei ng ex ecuted (st art of the Q 2
In mi d-range C ompatibility mode th e C xIE b it of th e cycle), then the CxIF interrupt flag of the
PIE2 register and the PEIE and GIE bits of the INTCON PIR2 register may not get set.
register must all be set to enable comparator interrupts. 2: When either comparator is fir st enabled,
If any o f t hese bits are c leared, t he interrupt i s not bias cir cuitry i n the Comparator module
enabled, although the CxIF bit of the PIR2 register will may cause an invalid o utput from the
still be set if an interrupt condition occurs. comparator until the bias circuitry is stable.
Allow about 1 s for bias settling then clear
the mismatch condition and interrupt flags
before enabling comparator interrupts.

DS41303G-page 282  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
20.5 Operation During Sleep
The comparator, if enabled before entering Sleep mode,
remains ac tive d uring Sleep. Th e addition al current
consumed by the comparator is shown separately in the
Section 26.0 “Electrical Characteristics”. If the
comparator is not used to w ake the dev ice, po wer
consumption can be minimized while in Sleep mode by
turning off the comparator. Each comparator is turned off
by clearing the CxON bit of the CMxCON0 register.
A ch ange to the comparator out put can w ake-up the
device from Sleep. To enable the comparator to wake
the device from Sleep, the CxIE bit of the PIE2 register
and the PEIE bit of the INTCON register must be set.
The instruction following the SLEEP instruction always
executes following a wake from Sleep. If the GIE bit of
the I NTCON register is a lso s et, the de vice will the n
execute the Interrupt Service Routine.

20.6 Effects of a Reset

A device Reset forces the CMxCON0 and CM2CON1
registers to the ir R eset st ates. Th is forc es bo th
comparators and the vo ltage ref erences to the ir Of f
states.

 2010 Microchip Technology Inc. DS41303G-page 283

PIC18F2XK20/4XK20

REGISTER 20-1: CM1CON0: COMPARATOR 1 CONTROL REGISTER 0

R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
C1ON C1OUT C1OE C1POL C1SP C1R C1CH1 C1CH0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 C1ON: Comparator C1 Enable bit

1 = Comparator C1 is enabled
0 = Comparator C1 is disabled
bit 6 C1OUT: Comparator C1 Output bit
If C1POL = 1 (inverted polarity):
C1OUT = 0 when C1VIN+ > C1VIN-
C1OUT = 1 when C1VIN+ < C1VIN-
If C1POL = 0 (non-inverted polarity):
C1OUT = 1 when C1VIN+ > C1VIN-
C1OUT = 0 when C1VIN+ < C1VIN-
bit 5 C1OE: Comparator C1 Output Enable bit
1 = C1OUT is present on the C1OUT pin(1)
0 = C1OUT is internal only
bit 4 C1POL: Comparator C1 Output Polarity Select bit
1 = C1OUT logic is inverted
0 = C1OUT logic is not inverted
bit 3 C1SP: Comparator C1 Speed/Power Select bit
1 = C1 operates in normal power, higher speed mode
0 = C1 operates in low-power, low-speed mode
bit 2 C1R: Comparator C1 Reference Select bit (non-inverting input)
1 = C1VIN+ connects to C1VREF output
0 = C1VIN+ connects to C1IN+ pin
bit 1-0 C1CH<1:0>: Comparator C1 Channel Select bit
00 = C12IN0- pin of C1 connects to C1VIN-
01 = C12IN1- pin of C1 connects to C1VIN-
10 = C12IN2- pin of C1 connects to C1VIN-
11 = C12IN3- pin of C1 connects to C1VIN-

Note 1: Comparator output requires the following three conditions: C1OE = 1, C1ON = 1 and corresponding port
TRIS bit = 0.

DS41303G-page 284  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 20-2: CM2CON0: COMPARATOR 2 CONTROL REGISTER 0

R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
C2ON C2OUT C2OE C2POL C2SP C2R C2CH1 C2CH0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 C2ON: Comparator C2 Enable bit

1 = Comparator C2 is enabled
0 = Comparator C2 is disabled
bit 6 C2OUT: Comparator C2 Output bit
If C2POL = 1 (inverted polarity):
C2OUT = 0 when C2VIN+ > C2VIN-
C2OUT = 1 when C2VIN+ < C2VIN-
If C2POL = 0 (non-inverted polarity):
C2OUT = 1 when C2VIN+ > C2VIN-
C2OUT = 0 when C2VIN+ < C2VIN-
bit 5 C2OE: Comparator C2 Output Enable bit
1 = C2OUT is present on C2OUT pin(1)
0 = C2OUT is internal only
bit 4 C2POL: Comparator C2 Output Polarity Select bit
1 = C2OUT logic is inverted
0 = C2OUT logic is not inverted
bit 3 C2SP: Comparator C2 Speed/Power Select bit
1 = C2 operates in normal power, higher speed mode
0 = C2 operates in low-power, low-speed mode
bit 2 C2R: Comparator C2 Reference Select bits (non-inverting input)
1 = C2VIN+ connects to C2VREF
0 = C2VIN+ connects to C2IN+ pin
bit 1-0 C2CH<1:0>: Comparator C2 Channel Select bits
00 = C12IN0- pin of C2 connects to C2VIN-
01 = C12IN1- pin of C2 connects to C2VIN-
10 = C12IN2- pin of C2 connects to C2VIN-
11 = C12IN3- pin of C2 connects to C2VIN-

Note 1: Comparator output requires the following three conditions: C2OE = 1, C2ON = 1 and corresponding port
TRIS bit = 0.

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PIC18F2XK20/4XK20
20.7 Analog Input Connection
Considerations Note 1: When re ading a PORT register, all pins
configured as analog inputs will read as a
A simplified c ircuit fo r an a nalog input is s hown i n
‘0’. Pins c onfigured as d igital i nputs w ill
Figure 20-6. Si nce the an alog in put p ins share the ir
convert as an analog input, according to
connection w ith a di gital input, they hav e rev erse
the input specification.
biased ESD prot ection dio des to V DD an d V SS. Th e
analog input, therefore, must be between VSS and VDD. 2: Analog le vels on any pi n d efined as a
If the input voltage deviates from this range by more digital input, may cause the input buffer to
than 0.6V in ei ther di rection, o ne of t he diodes i s consume more current than is specified.
forward biased and a latch-up may occur.
A maximum source impedance of 10 k is recommended
for the anal og sources. Also, any exter nal componen t
connected to an analog input pin, such as a capacitor or
a Zener diode, should h ave very lit tle leakage current to
minimize inaccuracies introduced.

FIGURE 20-6: ANALOG INPUT MODEL

VDD

Rs < 10K RIC

AIN
CPIN ILEAKAGE(1)
VA
5 pF

Vss

Legend: CPIN = Input Capacitance

ILEAKAGE = Leakage Current at the pin due to various junctions
RIC = Interconnect Resistance
RS = Source Impedance
VA = Analog Voltage

Note 1: See Section 26.0 “Electrical Characteristics”.

DS41303G-page 286  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
20.8 Additional Comparator Features 20.8.2 INTERNAL REFERENCE
SELECTION
There are two additional comparator features:
There are t wo internal voltage references available to
• Simultaneous read of comparator outputs
the non-inverting in put of eac h co mparator. On e of
• Internal reference selection these is the 1.2V Fixed Voltage Reference (FVR) and
the other is the variable Comparator Voltage Reference
20.8.1 SIMULTANEOUS COMPARATOR (CVREF). T he C xRSEL b it o f th e C M2CON reg ister
OUTPUT READ determines which of these references is routed to the
The M C1OUT an d M C2OUT bi ts of t he C M2CON1 Comparator Voltage refe rence out put (CXVREF). F ur-
register are mirror copies of both comparator outputs. ther routing to the comparator is accomplished by the
The ability to read both outputs simultaneously from a CxR b it of t he C MxCON0 r egister. S ee Section 21.1
single r egister e liminates t he t iming sk ew of r eading “Comparator Voltage Reference” a nd Figure 20-2
separate registers. and Figure 20-3 for more detail.
Note 1: Obtaining the status of C1OUT or C2OUT
by reading CM2CON1 does not affect the
comparator interrupt mismatch registers.

REGISTER 20-3: CM2CON1: COMPARATOR 2 CONTROL REGISTER 1

R-0 R-0 R/W-0 R/W-0 U-0 U-0 U-0 U-0
MC1OUT MC2OUT C1RSEL C2RSEL — — — —
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 MC1OUT: Mirror Copy of C1OUT bit

bit 6 MC2OUT: Mirror Copy of C2OUT bit
bit 5 C1RSEL: Comparator C1 Reference Select bit
1 = CVREF routed to C1VREF input
0 = FVR (1.2 Volt fixed voltage reference) routed to C1VREF input
bit 4 C2RSEL: Comparator C2 Reference Select bit
1 = CVREF routed to C2VREF input
0 = FVR (1.2 Volt fixed voltage reference) routed to C2VREF input
bit 3-0 Unimplemented: Read as ‘0’

 2010 Microchip Technology Inc. DS41303G-page 287

PIC18F2XK20/4XK20
TABLE 20-2: REGISTERS ASSOCIATED WITH COMPARATOR MODULE
Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
CM1CON0 C1ON C1OUT C1OE C1POL C1SP C1R C1CH1 C1CH0 62
CM2CON0 C2ON C2OUT C2OE C2POL C2SP C2R C2CH1 C2CH0 62
CM2CON1 MC1OUT MC2OUT C1RSEL C2RSEL — — — — 63
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 61
CVRCON2 FVREN FVRST — — — — — — 61
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
PORTA RA7(1) RA6(1) RA5 RA4 RA3 RA2 RA1 RA0 62
LATA LATA7(1) LATA6(1) PORTA Data Latch Register (Read and Write to Data Latch) 62
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the comparator module.
Note 1: PORTA<7:6> and their direction and latch bits are individually configured as port pins based on various
primary oscillator modes. When disabled, these bits read as ‘0’.

DS41303G-page 288  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
21.0 VOLTAGE REFERENCES 21.1.3 OUTPUT CLAMPED TO VSS
There are tw o in dependent v oltage ref erences The CV REF output voltage can be s et to Vs s w ith no
available: power consumption by c onfiguring C VRCON a s
follows:
• Programmable Comparator Voltage Reference
• CVREN = 0
• 1.2V Fixed Voltage Reference
• CVRR = 1
21.1 Comparator Voltage Reference • CVR<3:0> = 0000
This allows th e c omparator to dete ct a zero -crossing
The C omparator V oltage R eference module pr ovides while not consuming additional CVREF module current.
an internally generated voltage reference for the com-
parators. The following features are available: 21.1.4 OUTPUT RATIOMETRIC TO VDD
• Independent from Comparator operation The comparator vo ltage re ference is V DD derived and
• Two 16-level voltage ranges therefore, the CVREF output changes with fluctuations in
• Output clamped to VSS VDD. The tested absolute accuracy of the Comparator
• Ratiometric with VDD Voltage R eference can be fo und in Section 26.0
“Electrical Characteristics”.
• 1.2 Fixed Reference Voltage (FVR)
The C VRCON re gister (Register 21-1) co ntrols th e 21.1.5 VOLTAGE REFERENCE OUTPUT
Voltage Reference module shown in Figure 21-1.
The CV REF voltage refe rence c an be output to th e
device CVREF pin by setting the CVROE bit of the CVR-
21.1.1 INDEPENDENT OPERATION
CON register to ‘1’. Selecting the reference voltage for
The comparator v oltage re ference i s i ndependent of output on the C VREF pi n a utomatically overrides t he
the comparator configuration. Setting the CVREN bit of digital output buffer and digital input threshold detector
the CVRCON register will enable the voltage reference functions o f that pin. R eading the C VREF pi n w hen it
by allowing current to flow in the CVREF voltage divider. has been configured for refe rence voltage output will
When both the CVREN bit is cleared, current flow in the always return a ‘0’.
CVREF voltage divider is disabled minimizing the power
Due to the limited current drive capability, a buffer must
drain of the voltage reference peripheral.
be us ed o n th e v oltage refer ence o utput for external
21.1.2 OUTPUT VOLTAGE SELECTION connections to CVREF. Figure 21-2 shows an example
buffering technique.
The CVREF voltage ref erence has 2 ran ges w ith 16
voltage lev els in eac h ra nge. R ange se lection i s 21.1.6 OPERATION DURING SLEEP
controlled by the C VRR bit of th e C VRCON regi ster.
When the de vice w akes up from Sl eep th rough a n
The 1 6 le vels are set w ith the C VR<3:0> bi ts of th e
interrupt or a Watchdog Timer time-out, the contents of
CVRCON register.
the C VRCON re gister ar e n ot affected. To m inimize
The C VREF output vol tage is det ermined by th e current co nsumption in S leep mo de, t he vo ltage
following equations: reference should be disabled.

EQUATION 21-1: CVREF OUTPUT VOLTAGE 21.1.7 EFFECTS OF A RESET

CV RR = 1 (low range): A device Reset affects the following:
CVREF = (CVRSRC/24) X CVR<3:0> + VREF- • Comparator voltage reference is disabled
• Fixed voltage reference is disabled
CV RR = 0 (high range):
• CVREF is removed from the CVREF pin
CVREF = (CVRSRC/32) X (8 + CVR<3:0>) + VREF- • The high-voltage range is selected
CV RSRC = V DD or [(VREF+) - (VREF-)] • The CVR<3:0> range select bits are cleared

Note: VREF- is 0 when CVRSS = 0

The full range of VSS to VDD cannot be realized due to

the construction of the module. See Figure 21-1.

 2010 Microchip Technology Inc. DS41303G-page 289

PIC18F2XK20/4XK20
21.2 FVR Reference Module 21.2.1 FVR STABILIZATION PERIOD
The FVR reference is a stable fixed voltage reference, When the Fixed Voltage Reference module is enabled, it
independent of VDD, with a nominal output voltage of will require some time for the reference and its amplifier
1.2V. Thi s refe rence ca n be en abled by setting the circuits to st abilize. T he u ser pr ogram m ust in clude a
FVREN bit of the CVRCO N2 register to ‘ 1’. The FVR small del ay ro utine t o allow the mod ule to set tle. Th e
defaults to on when any one or more of the HFINTOSC, FVRST stable bit of the CVRCON2 register also indicates
HLVD, or BOR functions are enabled. The FVR voltage that the FVR reference has been operating long enough
reference can be routed to the comparators or an ADC to be s table. Se e Section 26.0 “Electrical
input channel. Characteristics” for the minimum delay requirement.

FIGURE 21-1: VOLTAGE REFERENCE BLOCK DIAGRAM

CVRSS = 1
VREF+

VDD
CVRSS = 0 8R
CVR<3:0>

CVREN R

16-to-1 MUX
16 Steps
CVREF

R
R

CVRR
8R
CVRSS = 1
VREF-

CVRSS = 0

FVR
1.2 Volt Fixed
FVREN Reference
From HVLD and FVRST
EN
BOR circuits

DS41303G-page 290  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 21-2: VOLTAGE REFERENCE OUTPUT BUFFER EXAMPLE

PIC18F2XK20/4XK20

CVREF
R(1)
Module
+
Voltage CVREF Buffered CVREF Output
–
Reference
Output
Impedance

Note 1: R is dependent upon the voltage reference Configuration bits, CVR<3:0> and CVRR.

REGISTER 21-1: CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
CVREN CVROE (1)
CVRR CVRSS CVR3 CVR2 CVR1 CVR0
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 CVREN: Comparator Voltage Reference Enable bit

1 =CVREF circuit powered on
0 =CVREF circuit powered down
bit 6 CVROE: Comparator VREF Output Enable bit(1)
1 =CVREF voltage level is also output on the CVREF pin
0 =CVREF voltage is disconnected from the CVREF pin
bit 5 CVRR: Comparator VREF Range Selection bit
1 = 0 to 0.667 CVRSRC, with CVRSRC/24 step size (low range)
0 =0 .25 CVRSRC to 0.75 CVRSRC, with CVRSRC/32 step size (high range)
bit 4 CVRSS: Comparator VREF Source Selection bit
1 = Comparator reference source, CVRSRC = (VREF+) – (VREF-)
0 = Comparator reference source, CVRSRC = VDD – VSS
bit 3-0 CVR<3:0>: Comparator VREF Value Selection bits (0  (CVR<3:0>)  15)
When CVRR = 1:
CVREF = ((CVR<3:0>)/24)  (CVRSRC) + VREF-
When CVRR = 0:
CVREF = (CVRSRC/4) + ((CVR<3:0>)/32)  (CVRSRC) + VREF-

Note 1: CVROE overrides the TRISA<2> bit setting.

 2010 Microchip Technology Inc. DS41303G-page 291

PIC18F2XK20/4XK20

REGISTER 21-2: CVRCON2: COMPARATOR VOLTAGE REFERENCE CONTROL 2 REGISTER

R/W-0 R-0 U-0 U-0 U-0 U-0 U-0 U-0
FVREN FVRST — — — — — —
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 FVREN: Fixed Voltage Reference Enable bit

1 = FVR circuit powered on
0 = FVR circuit not enabled by FVREN. Other peripherals may enable FVR.
bit 6 FVRST: Fixed Voltage Stable Status bit
1 = FVR is stable and can be used.
0 = FVR is not stable and should not be used.
bit 5-0 Unimplemented: Read as ‘0’.

TABLE 21-1: REGISTERS ASSOCIATED WITH COMPARATOR VOLTAGE REFERENCE

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page
CVRCON CVREN CVROE CVRR CVRSS CVR3 CVR2 CVR1 CVR0 62
CVRCON2 FVREN FVRST — — — — — — 61
CM1CON0 C1ON C1OUT C1OE C1POL C1SP C1R C1CH1 C1CH0 62
CM2CON0 C2ON C2OUT C2OE C2POL C2SP C2R C2CH1 C2CH0 62
CM2CON1 MC1OUT MC2OUT C1RSEL C2RSEL — — — — 63
TRISA TRISA7(1) TRISA6(1) PORTA Data Direction Control Register 62
Legend: Shaded cells are not used with the comparator voltage reference.
Note 1: PORTA pins are enabled based on oscillator configuration.

DS41303G-page 292  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
22.0 HIGH/LOW-VOLTAGE The block d iagram fo r th e HLVD module is s hown i n
Figure 22-1.
DETECT (HLVD)
The m odule is en abled by setting th e H LVDEN bi t.
PIC18F2XK20/4XK20 devices have a High/Low-Voltage Each t ime th at th e H LVD m odule i s e nabled, th e c ir-
Detect module (HLVD). This is a programmab le circuit cuitry requires some time to stabilize. The IRVST bit is
that allows the user to specify both a device voltage trip a read-only bit and is used to indicate when the circuit
point and the di rection of c hange from that point. If the is s table. T he m odule ca n on ly gen erate an in terrupt
device ex periences an excursion p ast the trip point in after the circuit is stable and IRVST is set.
that direction, an interrupt flag is set. If the interrupt is
enabled, the program execution will branch to the inter- The VDIRMAG bit determines the overall operation of
rupt vector address and the software can then respond the m odule. W hen VD IRMAG is c leared, t he module
to the interrupt. monitors for drops in V DD below a pre determined set
point. When the bit is set, the module monitors for rises
The High/Low-Voltage D etect C ontrol register in VDD above the set point.
(Register 22-1) completely controls the operation of the
HLVD m odule. This a llows the circuitry to be “t urned
off” by the us er under software control, w hich
minimizes the current consumption for the device.

REGISTER 22-1: HLVDCON: HIGH/LOW-VOLTAGE DETECT CONTROL REGISTER

R/W-0 U-0 R-0 R/W-0 R/W-0 R/W-1 R/W-0 R/W-1
VDIRMAG — IRVST HLVDEN HLVDL3(1) HLVDL2(1) HLVDL1(1) HLVDL0(1)
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented C = Clearable only bit
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 VDIRMAG: Voltage Direction Magnitude Select bit

1 = Event occurs when voltage equals or exceeds trip point (HLVDL<3:0>)
0 = Event occurs when voltage equals or falls below trip point (HLVDL<3:0>)
bit 6 Unimplemented: Read as ‘0’
bit 5 IRVST: Internal Reference Voltage Stable Flag bit
1 = Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage range
0 = Indicates that the voltage detect logic will not generate the interrupt flag at the specified voltage
range and the HLVD interrupt should not be enabled
bit 4 HLVDEN: High/Low-Voltage Detect Power Enable bit
1 = HLVD enabled
0 = HLVD disabled
bit 3-0 HLVDL<3:0>: Voltage Detection Limit bits(1)
1111 = External analog input is used (input comes from the HLVDIN pin)
1110 = Maximum setting
.
.
.
0000 = Minimum setting

Note 1: See Table 26-4 for specifications.

 2010 Microchip Technology Inc. DS41303G-page 293

PIC18F2XK20/4XK20
22.1 Operation The trip point voltage is software programmable to any
one o f 16 va lues. The tri p po int is se lected b y
When the HLVD module is enabled, a comparator uses programming th e H LVDL<3:0> bi ts of the HLVDCON
an int ernally gen erated re ference vol tage as the s et register.
point. Th e s et po int is co mpared w ith t he t rip p oint,
where eac h no de in the resistor divider represents a The HLVD module has an additional feature that allows
trip point voltage. The “trip point” voltage is the voltage the user to supply the trip voltage to the module from
level at which the device detects a high or low-voltage an e xternal s ource. Th is m ode is e nabled w hen bits
event, depending on the configuration of the module. HLVDL<3:0> are se t to ‘1111’. In thi s st ate, the
When the supply voltage is equal to the trip point, the comparator input is multiplexed from the external input
voltage tapped off of th e resistor array is equal to the pin, H LVDIN. T his gi ves us ers fl exibility because it
internal re ference v oltage g enerated by th e voltage allows them to configure the High/Low-Voltage Detect
reference module. The comparator then generates an interrupt to occur at any voltage in the valid operating
interrupt signal by setting the HLVDIF bit. range.

FIGURE 22-1: HLVD MODULE BLOCK DIAGRAM (WITH EXTERNAL INPUT)

Externally Generated
Trip Point
VDD

VDD HLVDL<3:0> HLVDCON

Register

HLVDIN HLVDEN VDIRMAG

HLVDIN

Set
16-to-1 MUX

HLVDIF

HLVDEN

Internal Voltage
BOREN Reference

DS41303G-page 294  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
22.2 HLVD Setup Depending on the application, the HLVD module does
not need to be operating constantly. To decrease the
The following st eps are ne eded t o set up the H LVD current requirements, the H LVD cir cuitry may only
module: need to be enabled for short periods where the voltage
1. Write t he value t o the H LVDL<3:0> bi ts t hat is ch ecked. Af ter doi ng th e c heck, the H LVD mo dule
selects the desired HLVD trip point. may be disabled.
2. Set the VD IRMAG bit to dete ct high vol tage
(VDIRMAG = 1) or low voltage (VDIRMAG = 0). 22.4 HLVD Start-up Time
3. Enable the H LVD mo dule by se tting the The int ernal refer ence vo ltage of the HLVD module,
HLVDEN bit. specified in el ectrical specification p arameter D 420,
4. Clear th e H LVD i nterrupt fl ag bi t of th e PIR 2 may be us ed by o ther in ternal circuitry, such as th e
register, w hich ma y have b een s et f rom a Programmable Brown-out Reset. If the HLVD or other
previous interrupt. circuits u sing the voltage r eference a re d isabled to
5. Enable t he H LVD i nterrupt i f i nterrupts ar e lower the device’s current consumption, the reference
desired by s etting th e HLVDIE bit o f th e PIE2 voltage circuit will require time to become stable before
register, and the GIE and PEIE bits of the INT- a lo w or hig h-voltage condition ca n be reliably
CON register. An interrupt will not be generated detected. This start-up time, TIRVST, is an interval that
until the IRVST bit is set. is independent of device clock speed. It is specified in
electrical specification parameter 36.
22.3 Current Consumption The HLVD interrupt flag is not enabled until T IRVST has
expired an d a s table r eference v oltage i s r eached. F or
When the mo dule i s e nabled, th e H LVD co mparator
this r eason, brief e xcursions beyond t he s et point may
and voltage divider are enabled and will consume static
not be detected during this interval. Refer to Figure 22-2
current. The total current consumption, when enabled,
or Figure 22-3.
is specified in electrical specification parameter D024B.

FIGURE 22-2: LOW-VOLTAGE DETECT OPERATION (VDIRMAG = 0)

CASE 1:
HLVDIF may not be set

VDD

VHLVD

HLVDIF

Enable HLVD

TIVRST
IRVST
HLVDIF cleared by software
Internal Reference is stable

CASE 2:

VDD
VHLVD

HLVDIF

Enable HLVD

TIVRST
IRVST
Internal Reference is stable
HLVDIF cleared by software

HLVDIF cleared by software,

HLVDIF remains set since HLVD condition still exists

 2010 Microchip Technology Inc. DS41303G-page 295

PIC18F2XK20/4XK20
FIGURE 22-3: HIGH-VOLTAGE DETECT OPERATION (VDIRMAG = 1)
CASE 1:
HLVDIF may not be set

VHLVD
VDD

HLVDIF

Enable HLVD

IRVST TIVRST

HLVDIF cleared by software

Internal Reference is stable

CASE 2:

VHLVD
VDD

HLVDIF

Enable HLVD

IRVST TIVRST

Internal Reference is stable

HLVDIF cleared by software

HLVDIF cleared by software,

HLVDIF remains set since HLVD condition still exists

DS41303G-page 296  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
22.5 Applications FIGURE 22-4: TYPICAL LOW-VOLTAGE
DETECT APPLICATION
In many applications, the ability to detect a drop below,
or ris e ab ove, a p articular t hreshold i s d esirable. For
example, the H LVD m odule c ould be periodically
enabled to detect Universal Serial Bus (USB) attach or
detach. This assumes the device is powered by a lower
voltage source than the USB when detached. An attach VA
would indicate a high-voltage detect from, for example, VB
3.3V to 5V (th e voltage on USB) and vice versa for a

Voltage
detach. This feature could save a design a few extra
components and an attach signal (input pin).
For general battery applications, Figure 22-4 shows a
possible voltage curve. Over time, the device voltage
decreases. When the device voltage reaches voltage
VA, the HLVD logic generates an interrupt at time TA.
The interrupt c ould c ause the e xecution of an ISR, Time TA TB
which w ould a llow the a pplication t o pe rform
“housekeeping t asks” an d pe rform a co ntrolled Legend: VA = HLVD trip point
shutdown before the device vol tage ex its the v alid VB = Minimum valid device
operating range at TB. The HLVD, thus, would give the operating voltage
application a ti me window, repre sented by the
difference between TA and TB, to safely exit.

TABLE 22-1: REGISTERS ASSOCIATED WITH HIGH/LOW-VOLTAGE DETECT MODULE

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on Page
HLVDCON VDIRMAG — IRVST HLVDEN HLVDL3 HLVDL2 HLVDL1 HLVDL0 60
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 59
PIR2 OSCFIF C1IF C2IF EEIF BCLIF HLVDIF TMR3IF CCP2IF 62
PIE2 OSCFIE C1IE C2IE EEIE BCLIE HLVDIE TMR3IE CCP2IE 62
IPR2 OSCFIP C1IP C2IP EEIP BCLIP HLVDIP TMR3IP CCP2IP 62
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the HLVD module.

 2010 Microchip Technology Inc. DS41303G-page 297

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 298  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
23.0 SPECIAL FEATURES OF
THE CPU
PIC18F2XK20/4XK20 devices inc lude several f eatures
intended to maximize reliability and minimize cost through
elimination of external components. These are:
• Oscillator Selection
• Resets:
- Power-on Reset (POR)
- Power-up Timer (PWRT)
- Oscillator Start-up Timer (OST)
- Brown-out Reset (BOR)
• Interrupts
• Watchdog Timer (WDT)
• Code Protection
• ID Locations
• In-Circuit Serial Programming™
The o scillator ca n b e c onfigured f or th e a pplication
depending on frequency, power, accuracy and cost. All
of th e o ptions a re discussed in de tail i n Section 2.0
“Oscillator Module (With Fail-Safe Clock Monitor)”.
A complete discussion of device Resets and interrupts
is available in previous sections of this data sheet.
In additio n to their Pow er-up and Os cillator S tart-up
Timers provided for R esets, PIC 18F2XK20/4XK20
devices have a W atchdog T imer, w hich is either
permanently enabled v ia th e C onfiguration bit s or
software controlled (if configured as disabled).
The inclusion of an internal RC oscillator also provides
the ad ditional b enefits of a Fai l-Safe C lock Mo nitor
(FSCM) and Two-Speed Start-up. FSCM provides for
background mo nitoring o f the peri pheral cl ock an d
automatic s witchover in the ev ent o f i ts failure. Two-
Speed S tart-up ena bles c ode to be exe cuted alm ost
immediately on start-up, while the primary clock source
completes its start-up delays.
All of thes e fe atures are e nabled an d c onfigured b y
setting the appropriate Configuration register bits.

 2010 Microchip Technology Inc. DS41303G-page 299

PIC18F2XK20/4XK20
23.1 Configuration Bits
The C onfiguration bit s ca n be prog rammed (read as
‘0’) or left unprogrammed (read as ‘1’) to select various
device configurations. These bits are mapped starting
at program memory location 300000h.
The user will not e tha t ad dress 300000h is be yond t he
user program memor y sp ace. In fact, it b elongs to t he
configuration memory space (300000h-3FFFFFh), which
can only be accessed using table reads and table writes.
Programming the Configuration registers is done in a
manner similar to programming the Flash memory. The
WR bit in the EECON1 register starts a self-timed write
to the Configuration register. In normal operation mode,
a TBLWT in struction with the TBLP TR po inting to th e
Configuration register sets up the address and the data
for the Configuration register write. Setting the WR bit
starts a lo ng write to the Configuration re gister. Th e
Configuration registers are written a byte at a time. To
write or erase a configuration cell, a TBLWT instruction
can write a ‘1’ or a ‘0’ into the cell. For additional details
on Flash programming, refer to Section 6.5 “Writing
to Flash Program Memory”.

TABLE 23-1: CONFIGURATION BITS AND DEVICE IDs

Default/
File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Unprogrammed
Value
300001h CONFIG1H IESO FCMEN — — FOSC3 FOSC2 FOSC1 FOSC0 00-- 0111
300002h CONFIG2L — — — BORV1 BORV0 BOREN1 BOREN0 PWRTEN ---1 1111
300003h CONFIG2H — — — WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN ---1 1111
300005h CONFIG3H MCLRE — — — HFOFST LPT1OSC PBADEN CCP2MX 1--- 1011
300006h CONFIG4L DEBUG XINST — — — LVP — STVREN 10-- -1-1
300008h CONFIG5L — — — — CP3(1) CP2(1) CP1 CP0 ---- 1111
300009h CONFIG5H CPD CPB — — — — — — 11-- ----
30000Ah CONFIG6L — — — — WRT3(1) WRT2(1) WRT1 WRT0 ---- 1111
30000Bh CONFIG6H WRTD WRTB WRTC — — — — — 111- ----
30000Ch CONFIG7L — — — — EBTR3(1) EBTR2(1) EBTR1 EBTR0 ---- 1111
30000Dh CONFIG7H — EBTRB — — — — — — -1-- ----
3FFFFEh DEVID1(2) DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0 qqqq qqqq(2)
3FFFFFh DEVID2 (2)
DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3 0000 1100
Legend: x = unknown, u = unchanged, – = unimplemented, q = value depends on condition.
Shaded cells are unimplemented, read as ‘0’.
Note 1: Implemented but not used in PIC18FX3K20 and PIC18FX4K20 devices; maintain this bit set.
2: See Register 23-12 for DEVID1 values. DEVID registers are read-only and cannot be programmed by the user.

DS41303G-page 300  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 23-1: CONFIG1H: CONFIGURATION REGISTER 1 HIGH

R/P-0 R/P-0 U-0 U-0 R/P-0 R/P-1 R/P-1 R/P-1
IESO FCMEN — — FOSC3 FOSC2 FOSC1 FOSC0
bit 7 bit 0

Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown

bit 7 IESO: Internal/External Oscillator Switchover bit

1 = Oscillator Switchover mode enabled
0 = Oscillator Switchover mode disabled
bit 6 FCMEN: Fail-Safe Clock Monitor Enable bit
1 = Fail-Safe Clock Monitor enabled
0 = Fail-Safe Clock Monitor disabled
bit 5-4 Unimplemented: Read as ‘0’
bit 3-0 FOSC<3:0>: Oscillator Selection bits
11xx = External RC oscillator, CLKOUT function on RA6
101x = External RC oscillator, CLKOUT function on RA6
1001 = Internal oscillator block, CLKOUT function on RA6, port function on RA7
1000 = Internal oscillator block, port function on RA6 and RA7
0111 = External RC oscillator, port function on RA6
0110 = HS oscillator, PLL enabled (Clock Frequency = 4 x FOSC1)
0101 = EC oscillator, port function on RA6
0100 = EC oscillator, CLKOUT function on RA6
0011 = External RC oscillator, CLKOUT function on RA6
0010 = HS oscillator
0001 = XT oscillator
0000 = LP oscillator

 2010 Microchip Technology Inc. DS41303G-page 301

PIC18F2XK20/4XK20

REGISTER 23-2: CONFIG2L: CONFIGURATION REGISTER 2 LOW

U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1
— — — BORV1(1) BORV0(1) BOREN1(2) BOREN0(2) PWRTEN(2)
bit 7 bit 0

Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4-3 BORV<1:0>: Brown-out Reset Voltage bits(1)
11 = VBOR set to 1.8V nominal
10 = VBOR set to 2.2V nominal
01 = VBOR set to 2.7V nominal
00 = VBOR set to 3.0V nominal
bit 2-1 BOREN<1:0>: Brown-out Reset Enable bits(2)
11 = Brown-out Reset enabled in hardware only (SBOREN is disabled)
10 = Brown-out Reset enabled in hardware only and disabled in Sleep mode
(SBOREN is disabled)
01 = Brown-out Reset enabled and controlled by software (SBOREN is enabled)
00 = Brown-out Reset disabled in hardware and software
bit 0 PWRTEN: Power-up Timer Enable bit(2)
1 = PWRT disabled
0 = PWRT enabled

Note 1: See Section 26.1 “DC Characteristics: Supply Voltage” for specifications.
2: The Power-up Timer is decoupled from Brown-out Reset, allowing these features to be independently controlled.

REGISTER 23-3: CONFIG2H: CONFIGURATION REGISTER 2 HIGH

U-0 U-0 U-0 R/P-1 R/P-1 R/P-1 R/P-1 R/P-1
— — — WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN
bit 7 bit 0

Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown

bit 7-5 Unimplemented: Read as ‘0’

bit 4-1 WDTPS<3:0>: Watchdog Timer Postscale Select bits
1111 = 1:32,768
1110 = 1:16,384
1101 = 1:8,192
1100 = 1:4,096
1011 = 1:2,048
1010 = 1:1,024
1001 = 1:512
1000 = 1:256
0111 = 1:128
0110 = 1:64
0101 = 1:32
0100 = 1:16
0011 = 1:8
0010 = 1:4
0001 = 1:2
0000 = 1:1
bit 0 WDTEN: Watchdog Timer Enable bit
1 = WDT is always enabled. SWDTEN bit has no effect
0 = WDT is controlled by SWDTEN bit of the WDTCON register

DS41303G-page 302  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
REGISTER 23-4: CONFIG3H: CONFIGURATION REGISTER 3 HIGH
R/P-1 U-0 U-0 U-0 R/P-1 R/P-0 R/P-1 R/P-1
MCLRE — — — HFOFST LPT1OSC PBADEN CCP2MX
bit 7 bit 0

Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown

bit 7 MCLRE: MCLR Pin Enable bit

1 = MCLR pin enabled; RE3 input pin disabled
0 = RE3 input pin enabled; MCLR disabled
bit 6-4 Unimplemented: Read as ‘0’
bit 3 HFOFST: HFINTOSC Fast Start-up
1 = HFINTOSC starts clocking the CPU without waiting for the oscillator to stabilize.
0 = The system clock is held off until the HFINTOSC is stable.
bit 2 LPT1OSC: Low-Power Timer1 Oscillator Enable bit
1 = Timer1 configured for low-power operation
0 = Timer1 configured for higher power operation
bit 1 PBADEN: PORTB A/D Enable bit
(Affects ANSELH Reset state. ANSELH controls PORTB<4:0> pin configuration.)
1 = PORTB<4:0> pins are configured as analog input channels on Reset
0 = PORTB<4:0> pins are configured as digital I/O on Reset
bit 0 CCP2MX: CCP2 MUX bit
1 = CCP2 input/output is multiplexed with RC1
0 = CCP2 input/output is multiplexed with RB3

REGISTER 23-5: CONFIG4L: CONFIGURATION REGISTER 4 LOW

R/P-1 R/P-0 U-0 U-0 U-0 R/P-1 U-0 R/P-1
DEBUG XINST — — — LVP (1)
— STVREN
bit 7 bit 0

Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown

bit 7 DEBUG: Background Debugger Enable bit

1 = Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins
0 = Background debugger enabled, RB6 and RB7 are dedicated to In-Circuit Debug
bit 6 XINST: Extended Instruction Set Enable bit
1 = Instruction set extension and Indexed Addressing mode enabled
0 = Instruction set extension and Indexed Addressing mode disabled (Legacy mode)
bit 5-3 Unimplemented: Read as ‘0’
bit 2 LVP: Single-Supply ICSP Enable bit
1 = Single-Supply ICSP enabled
0 = Single-Supply ICSP disabled
bit 1 Unimplemented: Read as ‘0’
bit 0 STVREN: Stack Full/Underflow Reset Enable bit
1 = Stack full/underflow will cause Reset
0 = Stack full/underflow will not cause Reset
Note 1: Can only be changed by a programmer in high-voltage programming mode.

 2010 Microchip Technology Inc. DS41303G-page 303

PIC18F2XK20/4XK20

REGISTER 23-6: CONFIG5L: CONFIGURATION REGISTER 5 LOW

U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1
— — — — CP3 (1)
CP2 (1)
CP1 CP0
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7-4 Unimplemented: Read as ‘0’

bit 3 CP3: Code Protection bit(1)
1 = Block 3 not code-protected
0 = Block 3 code-protected
bit 2 CP2: Code Protection bit(1)
1 = Block 2 not code-protected
0 = Block 2 code-protected
bit 1 CP1: Code Protection bit
1 = Block 1 not code-protected
0 = Block 1 code-protected
bit 0 CP0: Code Protection bit
1 = Block 0 not code-protected
0 = Block 0 code-protected

Note 1: Implemented, but not used in PIC18FX3K20 and PIC18FX4K20 devices.

REGISTER 23-7: CONFIG5H: CONFIGURATION REGISTER 5 HIGH

R/C-1 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0
CPD CPB — — — — — —
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7 CPD: Data EEPROM Code Protection bit

1 = Data EEPROM not code-protected
0 = Data EEPROM code-protected
bit 6 CPB: Boot Block Code Protection bit
1 = Boot Block not code-protected
0 = Boot Block code-protected
bit 5-0 Unimplemented: Read as ‘0’

DS41303G-page 304  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 23-8: CONFIG6L: CONFIGURATION REGISTER 6 LOW

U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1
— — — — WRT3(1) WRT2(1) WRT1 WRT0
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7-4 Unimplemented: Read as ‘0’

bit 3 WRT3: Write Protection bit(1)
1 = Block 3 not write-protected
0 = Block 3 write-protected
bit 2 WRT2: Write Protection bit(1)
1 = Block 2 not write-protected
0 = Block 2 write-protected
bit 1 WRT1: Write Protection bit
1 = Block 1 not write-protected
0 = Block 1 write-protected
bit 0 WRT0: Write Protection bit
1 = Block 0 not write-protected
0 = Block 0 write-protected

Note 1: Implemented, but not used in PIC18FX3K20 and PIC18FX4K20 devices.

REGISTER 23-9: CONFIG6H: CONFIGURATION REGISTER 6 HIGH

R/C-1 R/C-1 R-1 U-0 U-0 U-0 U-0 U-0
WRTD WRTB WRTC(1) — — — — —
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7 WRTD: Data EEPROM Write Protection bit

1 = Data EEPROM not write-protected
0 = Data EEPROM write-protected
bit 6 WRTB: Boot Block Write Protection bit
1 = Boot Block not write-protected
0 = Boot Block write-protected
bit 5 WRTC: Configuration Register Write Protection bit(1)
1 = Configuration registers not write-protected
0 = Configuration registers write-protected
bit 4-0 Unimplemented: Read as ‘0’

Note 1: This bit is read-only in normal execution mode; it can be written only in Program mode.

 2010 Microchip Technology Inc. DS41303G-page 305

PIC18F2XK20/4XK20

REGISTER 23-10: CONFIG7L: CONFIGURATION REGISTER 7 LOW

U-0 U-0 U-0 U-0 R/C-1 R/C-1 R/C-1 R/C-1
— — — — EBTR3(1) EBTR2(1) EBTR1 EBTR0
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7-4 Unimplemented: Read as ‘0’

bit 3 EBTR3: Table Read Protection bit(1)
1 = Block 3 not protected from table reads executed in other blocks
0 = Block 3 protected from table reads executed in other blocks
bit 2 EBTR2: Table Read Protection bit(1)
1 = Block 2 not protected from table reads executed in other blocks
0 = Block 2 protected from table reads executed in other blocks
bit 1 EBTR1: Table Read Protection bit
1 = Block 1 not protected from table reads executed in other blocks
0 = Block 1 protected from table reads executed in other blocks
bit 0 EBTR0: Table Read Protection bit
1 = Block 0 not protected from table reads executed in other blocks
0 = Block 0 protected from table reads executed in other blocks

Note 1: Implemented, but not used in PIC18FX3K20 and PIC18FX4K20 devices.

REGISTER 23-11: CONFIG7H: CONFIGURATION REGISTER 7 HIGH

U-0 R/C-1 U-0 U-0 U-0 U-0 U-0 U-0
— EBTRB — — — — — —
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7 Unimplemented: Read as ‘0’

bit 6 EBTRB: Boot Block Table Read Protection bit
1 = Boot Block not protected from table reads executed in other blocks
0 = Boot Block protected from table reads executed in other blocks
bit 5-0 Unimplemented: Read as ‘0’

DS41303G-page 306  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

REGISTER 23-12: DEVID1: DEVICE ID REGISTER 1 FOR PIC18F2XK20/4XK20

R R R R R R R R
DEV2 DEV1 DEV0 REV4 REV3 REV2 REV1 REV0
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7-5 DEV<2:0>: Device ID bits

000 = PIC18F46K20
001 = PIC18F26K20
010 = PIC18F45K20
011 = PIC18F25K20
100 = PIC18F44K20
101 = PIC18F24K20
110 = PIC18F43K20
111 = PIC18F23K20
bit 4-0 REV<4:0>: Revision ID bits
These bits are used to indicate the device revision.

REGISTER 23-13: DEVID2: DEVICE ID REGISTER 2 FOR PIC18F2XK20/4XK20

R R R R R R R R
DEV10 DEV9 DEV8 DEV7 DEV6 DEV5 DEV4 DEV3
bit 7 bit 0

Legend:
R = Readable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed C = Clearable only bit

bit 7-0 DEV<10:3>: Device ID bits

These bits are used with the DEV<2:0> bits in the Device ID Register 1 to identify the
part number.
0010 0000 = PIC18F2XK20/4XK20 devices

Note 1: These values for DEV<10:3> may be shared with other devices. The specific device is always identified
by using the entire DEV<10:0> bit sequence.

 2010 Microchip Technology Inc. DS41303G-page 307

PIC18F2XK20/4XK20
23.2 Watchdog Timer (WDT)
For PIC18F2XK20/4XK20 devices, the WDT is driven
by the LFINTOSC source. When the WDT is enabled,
the cl ock source is als o ena bled. Th e nominal WD T
period is 4 ms and has the same stability as the LFIN-
TOSC oscillator.
The 4 ms period of the WDT is multiplied by a 16-bit
postscaler. Any output of the WD T po stscaler is
selected by a multiplexer, controlled by bits in Configu-
ration Register 2H. Available periods range from 4 ms
to 13 1.072 seconds (2 .18 minutes). Th e W DT an d
postscaler are cleared when any of the following events
occur: a SLEEP or CLRWDT instruction is executed, the
IRCF bits of the O SCCON register are changed or a
clock failure has occurred.
Note 1: The CLRWDT an d SLEEP in structions
clear th e W DT a nd postscaler counts
when executed.
2: Changing t he s etting o f t he I RCF b its o f
the O SCCON re gister clears t he WDT
and postscaler counts.
3: When a CLRWDT instruction is executed,
the postscaler count will be cleared.

FIGURE 23-1: WDT BLOCK DIAGRAM

SWDTEN Enable WDT

WDTEN
WDT Counter

LFINTOSC Source 128 Wake-up

from Power
Managed Modes
Change on IRCF bits
Programmable Postscaler Reset WDT
CLRWDT
1:1 to 1:32,768 Reset
All Device Resets

WDTPS<3:0> 4

Sleep

DS41303G-page 308  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
23.2.1 CONTROL REGISTER
Register 23-14 shows the WDTCON register. This is a
readable and writable register which contains a control
bit tha t al lows sof tware to ov erride th e WD T en able
Configuration bit, but only if the Configuration bit has
disabled the WDT.

REGISTER 23-14: WDTCON: WATCHDOG TIMER CONTROL REGISTER

U-0 U-0 U-0 U-0 U-0 U-0 U-0 R/W-0
— — — — — — — SWDTEN(1)
bit 7 bit 0

Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-1 Unimplemented: Read as ‘0’

bit 0 SWDTEN: Software Enable or Disable the Watchdog Timer bit(1)
1 = WDT is turned on
0 = WDT is turned off (Reset value)

Note 1: This bit has no effect if the Configuration bit, WDTEN, is enabled.

TABLE 23-2: SUMMARY OF WATCHDOG TIMER REGISTERS

Reset
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Values
on page

RCON IPEN SBOREN — RI TO PD POR BOR 58

WDTCON — — — — — — — SWDTEN 60
CONFIG2H WDTPS3 WDTPS2 WDTPS1 WDTPS0 WDTEN 302
Legend: — = unimplemented, read as ‘0’. Shaded cells are not used by the Watchdog Timer.

 2010 Microchip Technology Inc. DS41303G-page 309

PIC18F2XK20/4XK20
23.3 Program Verification and Each of the blocks has three code protection bits asso-
Code Protection ciated with them. They are:
• Code-Protect bit (CPn)
The ov erall s tructure of the cod e pro tection on th e
PIC18 F lash d evices differs s ignificantly f rom oth er • Write-Protect bit (WRTn)
PIC® microcontroller devices. • External Block Table Read bit (EBTRn)
The user program memory is divided into three or five Figure 23-2 shows the program memory organization
blocks, dep ending on the device. On e of the se is a for 8, 16 and 32-Kbyte devices and the specific code
Boot Block of 0.5K o r 2K b ytes, d epending on th e protection bit associated with eac h blo ck. The ac tual
device. Th e rem ainder of the memory is di vided in to locations of the bits are summarized in Table 23-3.
individual blocks on binary boundaries.

FIGURE 23-2: CODE-PROTECTED PROGRAM MEMORY FOR PIC18F2XK20/4XK20

MEMORY SIZE/DEVICE
Block Code Protection
8 Kbytes 16 Kbytes 32 Kbytes 64 Kbytes Controlled By:
(PIC18FX3K20) (PIC18FX4K20) (PIC18FX5K20) (PIC18FX6K20)
Boot Block Boot Block Boot Block Boot Block
CPB, WRTB, EBTRB
(000h-1FFh) (000h-7FFh) (000h-7FFh) (000h-7FFh)
Block 0 Block 0 Block 0 Block 0
CP0, WRT0, EBTR0
(200h-FFFh) (800h-1FFFh) (800h-1FFFh) (800h-3FFFh)
Block 1 Block 1 Block 1 Block 1
CP1, WRT1, EBTR1
(1000h-1FFFh) (2000h-3FFFh) (2000h-3FFFh) (4000h-7FFFh)
Block 2 Block 2
CP2, WRT2, EBTR2
(4000h-5FFFh) (8000h-BFFFh)
Block 3 Block 3
CP3, WRT3, EBTR3
(6000h-7FFFh) (C000h-FFFFh)

Unimplemented Unimplemented
Read ‘0’s Read ‘0’s
(2000h-1FFFFFh) (4000h-1FFFFFh)
Unimplemented Unimplemented (Unimplemented
Read ‘0’s Read ‘0’s Memory Space)
(8000h-1FFFFFh) (10000h-1FFFFFh)

TABLE 23-3: SUMMARY OF CODE PROTECTION REGISTERS

File Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

300008h CONFIG5L — — — — CP3(1) CP2(1) CP1 CP0

300009h CONFIG5H CPD CPB — — — — — —
30000Ah CONFIG6L — — — — WRT3(1) WRT2(1) WRT1 WRT0
30000Bh CONFIG6H WRTD WRTB WRTC — — — — —
30000Ch CONFIG7L — — — — EBTR3(1) EBTR2(1) EBTR1 EBTR0
30000Dh CONFIG7H — EBTRB — — — — — —
Legend: Shaded cells are unimplemented.
Note 1: Implemented, but not used in PIC18FX3K20 and PIC18FX4K20 devices.

DS41303G-page 310  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
23.3.1 PROGRAM MEMORY instruction that executes from a locatio n outside of that
CODE PROTECTION block is not allowed to read and will result in reading ‘0’s.
Figures 23-3 through 23-5 illustrate table write and table
The program memory may be read to or written from
read protection.
any location us ing the t able rea d a nd t able w rite
instructions. The de vice ID ma y b e re ad with t able Note: Code protection bits may only be written to
reads. Th e C onfiguration regi sters ma y b e rea d an d a ‘0’ f rom a ‘1’ state. It is not possible to
written with the table read and table write instructions. write a ‘1’ to a bit in the ‘0’ state. Code pro-
In normal execution mode, the CPn bits have no direct tection bits are only set to ‘1’ by a full chip
effect. CPn bits inhibit external reads and writes. A block erase or block erase function. The full chip
of user memory may be protected from table writes if the erase and block erase functions can only
WRTn C onfiguration bit is ‘ 0’. The EBTR n b its control be in itiated via ICSP or an ex ternal
table reads. For a block of user memory with the EBTRn programmer.
bit cleared to ‘0’, a table READ instruction that executes
from w ithin that block is allow ed to read. A t able read

FIGURE 23-3: TABLE WRITE (WRTn) DISALLOWED

Register Values Program Memory Configuration Bit Settings

000000h
WRTB, EBTRB = 11
0007FFh
000800h

TBLPTR = 0008FFh
WRT0, EBTR0 = 01

PC = 001FFEh TBLWT* 001FFFh

002000h
WRT1, EBTR1 = 11
003FFFh
004000h
PC = 005FFEh TBLWT* WRT2, EBTR2 = 11
005FFFh
006000h
WRT3, EBTR3 = 11

007FFFh

Results: All table writes disabled to Blockn whenever WRTn = 0.

 2010 Microchip Technology Inc. DS41303G-page 311

PIC18F2XK20/4XK20
FIGURE 23-4: EXTERNAL BLOCK TABLE READ (EBTRn) DISALLOWED

Register Values Program Memory Configuration Bit Settings

000000h
WRTB, EBTRB = 11
0007FFh
000800h
TBLPTR = 0008FFh
WRT0, EBTR0 = 10

001FFFh
002000h
PC = 003FFEh TBLRD* WRT1, EBTR1 = 11
003FFFh
004000h
WRT2, EBTR2 = 11
005FFFh
006000h
WRT3, EBTR3 = 11

007FFFh

Results: All table reads from external blocks to Blockn are disabled whenever EBTRn = 0.
TABLAT register returns a value of ‘0’.

FIGURE 23-5: EXTERNAL BLOCK TABLE READ (EBTRn) ALLOWED

Register Values Program Memory Configuration Bit Settings

000000h
WRTB, EBTRB = 11
0007FFh
000800h

TBLPTR = 0008FFh WRT0, EBTR0 = 10

PC = 001FFEh TBLRD* 001FFFh

002000h
WRT1, EBTR1 = 11
003FFFh
004000h
WRT2, EBTR2 = 11
005FFFh
006000h
WRT3, EBTR3 = 11

007FFFh

Results: Table reads permitted within Blockn, even when EBTRBn = 0.

TABLAT register returns the value of the data at the location TBLPTR.

DS41303G-page 312  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
23.3.2 DATA EEPROM To use the In-Circuit D ebugger function of the micro-
CODE PROTECTION controller, the design must implement In-Circuit Serial
Programming connections to the following pins:
The en tire dat a EEPROM is pro tected from ex ternal
reads a nd writes by tw o bi ts: C PD a nd WRTD. C PD • MCLR/VPP/RE3
inhibits ex ternal rea ds and write s of dat a EEPRO M. • VDD
WRTD inhibits int ernal and external writes to da ta • VSS
EEPROM. The CPU can always read data EEPROM • RB7
under normal operation, regardless of the protection bit
• RB6
settings.
This will in terface to the In- Circuit D ebugger mo dule
23.3.3 CONFIGURATION REGISTER available from Microchip or one of the third party devel-
PROTECTION opment tool companies.
The Configuration re gisters can b e w rite-protected.
The WRTC bit controls protection of the Configuration 23.7 Single-Supply ICSP Programming
registers. In no rmal execution mode, the WRTC bit is The LVP Configuration bit enables Single-Supply ICSP
readable only. WRTC can only be written via ICSP or Programming (formerly kn own a s Low -Voltage IC SP
an external programmer. Programming or L VP). When Sing le-Supply Program-
ming is enabled, the microcontroller can be programmed
23.4 ID Locations without requiring high vol tage being applied to the
MCLR/VPP/RE3 pin, but the RB5/KBI1/PGM pin is then
Eight m emory l ocations (200000h-200007h) a re
dedicated to controlling Program mode entry and is not
designated as ID locations, where the user can store
available as a general purpose I/O pin.
checksum or other code identification numbers. These
locations are both readable and writable during normal While programming, using Single-Supply Programming
execution through the TBLRD and TBLWT instructions mode, V DD is applied to the MCLR/VPP/RE3 pin as in
or during program/verify. The ID locations can be read normal execution mode. To enter Programming mode,
when the device is code-protected. VDD is applied to the PGM pin.
Note 1: High-voltage prog ramming i s al ways
23.5 In-Circuit Serial Programming available, regardless of the state of th e
PIC18F2XK20/4XK20 dev ices can be s erially LVP bit or the PGM pin, by applying VIHH
programmed while in the end application circuit. This is to the MCLR pin.
simply done with two lines for clock and data and three 2: By def ault, Sin gle-Supply IC SP i s
other li nes fo r po wer, ground and th e p rogramming enabled i n unprogrammed d evices (as
voltage. This allows customers to manufacture boards supplied fro m M icrochip) an d era sed
with un programmed d evices and the n pro gram th e devices.
microcontroller j ust be fore sh ipping th e pro duct. This 3: When Si ngle-Supply Prog ramming i s
also al lows the m ost rec ent firm ware or a custom enabled, th e RB5 p in c an no lo nger b e
firmware to be programmed. used as a general purpose I/O pin.
4: When LVP is enabled, externally pull the
23.6 In-Circuit Debugger
PGM pin to VSS to allow normal program
When the DEBUG Configuration bit is programmed to execution.
a ‘0’, the In-Circuit Debugger functionality is enabled. If Single-Supply ICSP Programming mode will not be
This function allows simple debugging functions when used, the LVP bit can be cleared. RB5/KBI1/PGM then
used with MPLAB® IDE. When the microcontroller has becomes available as the digital I/O pin, RB5. The LVP
this feature enabled, some resources are not available bit m ay b e se t or c leared o nly w hen us ing standard
for general use. Table 23-4 shows which resources are high-voltage programming (VIHH applied to the MCLR/
required by the background debugger. VPP/RE3 pin). Once LVP has been disabled, only the
standard high-voltage pro gramming is av ailable an d
TABLE 23-4: DEBUGGER RESOURCES must be used to program the device.
I/O pins: RB6, RB7 Memory that is not code-protected can be erased using
Stack: 2 levels either a block erase, or erased row by row, then written
Program Memory: 512 bytes at any specified VDD. If code-protected memory is to be
erased, a block erase is required.
Data Memory: 10 bytes

 2010 Microchip Technology Inc. DS41303G-page 313

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 314  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
24.0 INSTRUCTION SET SUMMARY The literal instructions may use some of the following
operands:
PIC18F2XK20/4XK20 devices incorporate the standard
• A literal value to be loaded into a file register
set of 75 PIC18 core instructions, as well as an extended
(specified by ‘k’)
set of 8 new instructions, for the optimization of code that
is r ecursive or that utili zes a sof tware st ack. The • The desired FSR register to load the literal value
extended set is discussed later in this section. into (specified by ‘f’)
• No operand required
24.1 Standard Instruction Set (specified by ‘—’)
The control instructions may use some of the following
The st andard PIC 18 ins truction s et ad ds many
operands:
enhancements to th e p revious PIC® M CU instruction
sets, w hile m aintaining a n e asy migration from t hese • A program memory address (specified by ‘n’)
PIC® MCU instruction sets. Most instructions are a sin- • The mode of the CALL or RETURN instructions
gle program memory word (16 bits), but there are four (specified by ‘s’)
instructions th at re quire tw o pr ogram m emory loca- • The mode of the table read and table write
tions. instructions (specified by ‘m’)
Each si ngle-word in struction is a 16-bit word d ivided • No operand required
into an opcode, which specifies the instruction type and (specified by ‘—’)
one or m ore op erands, which furth er sp ecify the All i nstructions are a s ingle word, e xcept fo r fo ur
operation of the instruction. double-word i nstructions. The se in structions w ere
The instruction set is highly orthogonal and is grouped made double-word to contain the required information
into four basic categories: in 32 bits. In the second word, the 4 MSbs are ‘1’s. If
• Byte-oriented operations this second w ord is ex ecuted as a n ins truction (b y
itself), it will execute as a NOP.
• Bit-oriented operations
• Literal operations All sin gle-word instructions are ex ecuted in a si ngle
instruction cycle, unless a conditional test is true or the
• Control operations
program counter is changed as a result of the instruc-
The PIC18 instruction set summary in Table 24-2 lists tion. In these cases, the execution takes two instruction
byte-oriented, bit-oriented, literal a nd control cycles, with the additional instruction cycle(s) executed
operations. T able 24-1 sh ows the o pcode fiel d as a NOP.
descriptions.
The double-word instructions execute in two instruction
Most byte-oriented instructions have three operands: cycles.
1. The file register (specified by ‘f’) One instruction cycle consists of four oscillator periods.
2. The destination of the result (specified by ‘d’) Thus, for an oscillator frequency of 4 MHz, the normal
3. The accessed memory (specified by ‘a’) instruction execution time is 1 s. If a conditional test is
true, or the program counter is changed as a result of
The f ile reg ister d esignator ‘f’ s pecifies w hich fil e an i nstruction, t he i nstruction execution time i s 2 s.
register is to be used by the instruction. The destination Two-word branch instructions (if true) would take 3 s.
designator ‘d’ specifies where the result of the opera-
tion is to be placed. If ‘d’ is zero, the result is placed in Figure 24-1 shows the general formats that the instruc-
the WREG register. If ‘d’ is one, the result is placed in tions can have. All examples use the convention ‘nnh’
the file register specified in the instruction. to represent a hexadecimal number.

All bit-oriented instructions have three operands: The I nstruction Se t Sum mary, shown in Table 24-2,
lists th e st andard in structions r ecognized by th e
1. The file register (specified by ‘f’) Microchip Assembler (MPASMTM).
2. The bit in the file register (specified by ‘b’)
Section 24.1.1 “Standard Instruction Set” pr ovides
3. The accessed memory (specified by ‘a’) a description of each instruction.
The bit field designator ‘b’ selects the number of the bit
affected b y th e op eration, w hile the file reg ister
designator ‘f’ represents the number of the file in which
the bit is located.

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PIC18F2XK20/4XK20
TABLE 24-1: OPCODE FIELD DESCRIPTIONS
Field Description
a RAM access bit
a = 0: RAM location in Access RAM (BSR register is ignored)
a = 1: RAM bank is specified by BSR register
bbb Bit address within an 8-bit file register (0 to 7).
BSR Bank Select Register. Used to select the current RAM bank.
C, DC, Z, OV, N ALU Status bits: Carry, Digit Carry, Zero, Overflow, Negative.
d Destination select bit
d = 0: store result in WREG
d = 1: store result in file register f
dest Destination: either the WREG register or the specified register file location.
f 8-bit Register file address (00h to FFh) or 2-bit FSR designator (0h to 3h).
fs 12-bit Register file address (000h to FFFh). This is the source address.
fd 12-bit Register file address (000h to FFFh). This is the destination address.
GIE Global Interrupt Enable bit.
k Literal field, constant data or label (may be either an 8-bit, 12-bit or a 20-bit value).
label Label name.
mm The mode of the TBLPTR register for the table read and table write instructions.
Only used with table read and table write instructions:
* No change to register (such as TBLPTR with table reads and writes)
*+ Post-Increment register (such as TBLPTR with table reads and writes)
*- Post-Decrement register (such as TBLPTR with table reads and writes)
+* Pre-Increment register (such as TBLPTR with table reads and writes)
n The relative address (2’s complement number) for relative branch instructions or the direct address for
CALL/BRANCH and RETURN instructions.
PC Program Counter.
PCL Program Counter Low Byte.
PCH Program Counter High Byte.
PCLATH Program Counter High Byte Latch.
PCLATU Program Counter Upper Byte Latch.
PD Power-down bit.
PRODH Product of Multiply High Byte.
PRODL Product of Multiply Low Byte.
s Fast Call/Return mode select bit
s = 0: do not update into/from shadow registers
s = 1: certain registers loaded into/from shadow registers (Fast mode)
TBLPTR 21-bit Table Pointer (points to a Program Memory location).
TABLAT 8-bit Table Latch.
TO Time-out bit.
TOS Top-of-Stack.
u Unused or unchanged.
WDT Watchdog Timer.
WREG Working register (accumulator).
x Don’t care (‘0’ or ‘1’). The assembler will generate code with x = 0. It is the recommended form of use for
compatibility with all Microchip software tools.
zs 7-bit offset value for indirect addressing of register files (source).
zd 7-bit offset value for indirect addressing of register files (destination).
{ } Optional argument.
[text] Indicates an indexed address.
(text) The contents of text.
[expr]<n> Specifies bit n of the register indicated by the pointer expr.
 Assigned to.
< > Register bit field.
 In the set of.
italics User defined term (font is Courier).

DS41303G-page 316  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 24-1: GENERAL FORMAT FOR INSTRUCTIONS
Byte-oriented file register operations Example Instruction
15 10 9 8 7 0
OPCODE d a f (FILE #) ADDWF MYREG, W, B
d = 0 for result destination to be WREG register
d = 1 for result destination to be file register (f)
a = 0 to force Access Bank
a = 1 for BSR to select bank
f = 8-bit file register address

Byte to Byte move operations (2-word)

15 12 11 0
OPCODE f (Source FILE #) MOVFF MYREG1, MYREG2
15 12 11 0
1111 f (Destination FILE #)

f = 12-bit file register address

Bit-oriented file register operations

15 12 11 9 8 7 0
OPCODE b (BIT #) a f (FILE #) BSF MYREG, bit, B

b = 3-bit position of bit in file register (f)

a = 0 to force Access Bank
a = 1 for BSR to select bank
f = 8-bit file register address

Literal operations
15 8 7 0
OPCODE k (literal) MOVLW 7Fh

k = 8-bit immediate value

Control operations
CALL, GOTO and Branch operations
15 8 7 0
OPCODE n<7:0> (literal) GOTO Label
15 12 11 0
1111 n<19:8> (literal)

n = 20-bit immediate value

15 8 7 0
OPCODE S n<7:0> (literal) CALL MYFUNC
15 12 11 0
1111 n<19:8> (literal)
S = Fast bit

15 11 10 0
OPCODE n<10:0> (literal) BRA MYFUNC

15 8 7 0
OPCODE n<7:0> (literal) BC MYFUNC

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PIC18F2XK20/4XK20

TABLE 24-2: PIC18FXXXX INSTRUCTION SET

Mnemonic, 16-Bit Instruction Word Status
Description Cycles Notes
Operands MSb LSb Affected

BYTE-ORIENTED OPERATIONS
ADDWF f, d, a Add WREG and f 1 0010 01da0 ffff ffff C, DC, Z, OV, N 1, 2
ADDWFC f, d, a Add WREG and CARRY bit to f 1 0010 0da ffff ffff C, DC, Z, OV, N 1, 2
ANDWF f, d, a AND WREG with f 1 0001 01da ffff ffff Z, N 1,2
CLRF f, a Clear f 1 0110 101a ffff ffff Z 2
COMF f, d, a Complement f 1 0001 11da ffff ffff Z, N 1, 2
CPFSEQ f, a Compare f with WREG, skip = 1 (2 or 3) 0110 001a ffff ffff None 4
CPFSGT f, a Compare f with WREG, skip > 1 (2 or 3) 0110 010a ffff ffff None 4
CPFSLT f, a Compare f with WREG, skip < 1 (2 or 3) 0110 000a ffff ffff None 1, 2
DECF f, d, a Decrement f 1 0000 01da ffff ffff C, DC, Z, OV, N 1, 2, 3, 4
DECFSZ f, d, a Decrement f, Skip if 0 1 (2 or 3) 0010 11da ffff ffff None 1, 2, 3, 4
DCFSNZ f, d, a Decrement f, Skip if Not 0 1 (2 or 3) 0100 11da ffff ffff None 1, 2
INCF f, d, a Increment f 1 0010 10da ffff ffff C, DC, Z, OV, N 1, 2, 3, 4
INCFSZ f, d, a Increment f, Skip if 0 1 (2 or 3) 0011 11da ffff ffff None 4
INFSNZ f, d, a Increment f, Skip if Not 0 1 (2 or 3) 0100 10da ffff ffff None 1, 2
IORWF f, d, a Inclusive OR WREG with f 1 0001 00da ffff ffff Z, N 1, 2
MOVF f, d, a Move f 1 0101 00da ffff ffff Z, N 1
MOVFF fs, fd Move fs (source) to 1st word 2 1100 ffff ffff ffff None
fd (destination) 2nd word 1111 ffff ffff ffff
MOVWF f, a Move WREG to f 1 0110 111a ffff ffff None
MULWF f, a Multiply WREG with f 1 0000 001a ffff ffff None 1, 2
NEGF f, a Negate f 1 0110 110a ffff ffff C, DC, Z, OV, N
RLCF f, d, a Rotate Left f through Carry 1 0011 01da ffff ffff C, Z, N 1, 2
RLNCF f, d, a Rotate Left f (No Carry) 1 0100 01da ffff ffff Z, N
RRCF f, d, a Rotate Right f through Carry 1 0011 00da ffff ffff C, Z, N
RRNCF f, d, a Rotate Right f (No Carry) 1 0100 00da ffff ffff Z, N
SETF f, a Set f 1 0110 100a ffff ffff None 1, 2
SUBFWB f, d, a Subtract f from WREG with 1 0101 01da ffff ffff C, DC, Z, OV, N
borrow
SUBWF f, d, a Subtract WREG from f 1 0101 11da ffff ffff C, DC, Z, OV, N 1, 2
SUBWFB f, d, a Subtract WREG from f with 1 0101 10da ffff ffff C, DC, Z, OV, N
borrow
SWAPF f, d, a Swap nibbles in f 1 0011 10da ffff ffff None 4
TSTFSZ f, a Test f, skip if 0 1 (2 or 3) 0110 011a ffff ffff None 1, 2
XORWF f, d, a Exclusive OR WREG with f 1 0001 10da ffff ffff Z, N
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is
executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.

DS41303G-page 318  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 24-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)
Mnemonic, 16-Bit Instruction Word Status
Description Cycles Notes
Operands MSb LSb Affected

BIT-ORIENTED OPERATIONS
BCF f, b, a Bit Clear f 1 1001 bbba ffff ffff None 1, 2
BSF f, b, a Bit Set f 1 1000 bbba ffff ffff None 1, 2
BTFSC f, b, a Bit Test f, Skip if Clear 1 (2 or 3) 1011 bbba ffff ffff None 3, 4
BTFSS f, b, a Bit Test f, Skip if Set 1 (2 or 3) 1010 bbba ffff ffff None 3, 4
BTG f, d, a Bit Toggle f 1 0111 bbba ffff ffff None 1, 2
CONTROL OPERATIONS
BC n Branch if Carry 1 (2) 1110 0010 nnnn nnnn None
BN n Branch if Negative 1 (2) 1110 0110 nnnn nnnn None
BNC n Branch if Not Carry 1 (2) 1110 0011 nnnn nnnn None
BNN n Branch if Not Negative 1 (2) 1110 0111 nnnn nnnn None
BNOV n Branch if Not Overflow 1 (2) 1110 0101 nnnn nnnn None
BNZ n Branch if Not Zero 1 (2) 1110 0001 nnnn nnnn None
BOV n Branch if Overflow 1 (2) 1110 0100 nnnn nnnn None
BRA n Branch Unconditionally 2 1101 0nnn nnnn nnnn None
BZ n Branch if Zero 1 (2) 1110 0000 nnnn nnnn None
CALL n, s Call subroutine 1st word 2 1110 110s kkkk kkkk None
2nd word 1111 kkkk kkkk kkkk
CLRWDT — Clear Watchdog Timer 1 0000 0000 0000 0100 TO, PD
DAW — Decimal Adjust WREG 1 0000 0000 0000 0111 C
GOTO n Go to address 1st word 2 1110 1111 kkkk kkkk None
2nd word 1111 kkkk kkkk kkkk
NOP — No Operation 1 0000 0000 0000 0000 None
NOP — No Operation 1 1111 xxxx xxxx xxxx None 4
POP — Pop top of return stack (TOS) 1 0000 0000 0000 0110 None
PUSH — Push top of return stack (TOS) 1 0000 0000 0000 0101 None
RCALL n Relative Call 2 1101 1nnn nnnn nnnn None
RESET Software device Reset 1 0000 0000 1111 1111 All
RETFIE s Return from interrupt enable 2 0000 0000 0001 000s GIE/GIEH,
PEIE/GIEL
RETLW k Return with literal in WREG 2 0000 1100 kkkk kkkk None
RETURN s Return from Subroutine 2 0000 0000 0001 001s None
SLEEP — Go into Standby mode 1 0000 0000 0000 0011 TO, PD
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is
executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.

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PIC18F2XK20/4XK20
TABLE 24-2: PIC18FXXXX INSTRUCTION SET (CONTINUED)
Mnemonic, 16-Bit Instruction Word Status
Description Cycles Notes
Operands MSb LSb Affected

LITERAL OPERATIONS
ADDLW k Add literal and WREG 1 0000 1111 kkkk kkkk C, DC, Z, OV, N
ANDLW k AND literal with WREG 1 0000 1011 kkkk kkkk Z, N
IORLW k Inclusive OR literal with WREG 1 0000 1001 kkkk kkkk Z, N
LFSR f, k Move literal (12-bit) 2nd word 2 1110 1110 00ff kkkk None
to FSR(f) 1st word 1111 0000 kkkk kkkk
MOVLB k Move literal to BSR<3:0> 1 0000 0001 0000 kkkk None
MOVLW k Move literal to WREG 1 0000 1110 kkkk kkkk None
MULLW k Multiply literal with WREG 1 0000 1101 kkkk kkkk None
RETLW k Return with literal in WREG 2 0000 1100 kkkk kkkk None
SUBLW k Subtract WREG from literal 1 0000 1000 kkkk kkkk C, DC, Z, OV, N
XORLW k Exclusive OR literal with WREG 1 0000 1010 kkkk kkkk Z, N
DATA MEMORY  PROGRAM MEMORY OPERATIONS
TBLRD* Table Read 2 0000 0000 0000 1000 None
TBLRD*+ Table Read with post-increment 0000 0000 0000 1001 None
TBLRD*- Table Read with post-decrement 0000 0000 0000 1010 None
TBLRD+* Table Read with pre-increment 0000 0000 0000 1011 None
TBLWT* Table Write 2 0000 0000 0000 1100 None
TBLWT*+ Table Write with post-increment 0000 0000 0000 1101 None
TBLWT*- Table Write with post-decrement 0000 0000 0000 1110 None
TBLWT+* Table Write with pre-increment 0000 0000 0000 1111 None
Note 1: When a PORT register is modified as a function of itself (e.g., MOVF PORTB, 1, 0), the value used will be that value
present on the pins themselves. For example, if the data latch is ‘1’ for a pin configured as input and is driven low by an
external device, the data will be written back with a ‘0’.
2: If this instruction is executed on the TMR0 register (and where applicable, ‘d’ = 1), the prescaler will be cleared if
assigned.
3: If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is
executed as a NOP.
4: Some instructions are two-word instructions. The second word of these instructions will be executed as a NOP unless the
first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory
locations have a valid instruction.

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 PIC18F2XK20/4XK20
24.1.1 STANDARD INSTRUCTION SET

ADDLW ADD literal to W ADDWF ADD W to f

Syntax: ADDLW k Syntax: ADDWF f {,d {,a}}
Operands: 0  k  255 Operands: 0  f  255
Operation: (W) + k  W d  [0,1]
a  [0,1]
Status Affected: N, OV, C, DC, Z
Operation: (W) + (f)  dest
Encoding: 0000 1111 kkkk kkkk
Status Affected: N, OV, C, DC, Z
Description: The contents of W are added to the
Encoding: 0010 01da ffff ffff
8-bit literal ‘k’ and the result is placed in
W. Description: Add W to register ‘f’. If ‘d’ is ‘0’, the
result is stored in W. If ‘d’ is ‘1’, the
Words: 1
result is stored back in register ‘f’
Cycles: 1 (default).
Q Cycle Activity: If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
Q1 Q2 Q3 Q4
GPR bank.
Decode Read Process Write to W If ‘a’ is ‘0’ and the extended instruction
literal ‘k’ Data set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Example: ADDLW 15h Section 24.2.3 “Byte-Oriented and
Before Instruction Bit-Oriented Instructions in Indexed
W = 10h Literal Offset Mode” for details.
After Instruction Words: 1
W= 25h Cycles: 1

Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write to
register ‘f’ Data destination

Example: ADDWF REG, 0, 0

Before Instruction
W = 17h
REG = 0C2h
After Instruction
W = 0D9h
REG = 0C2h

Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in
symbolic addressing. If a label is used, the instruction format then becomes: {label} instruction argument(s).

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PIC18F2XK20/4XK20

ADDWFC ADD W and CARRY bit to f ANDLW AND literal with W

Syntax: ADDWFC f {,d {,a}} Syntax: ANDLW k
Operands: 0  f  255 Operands: 0  k  255
d [0,1]
Operation: (W) .AND. k  W
a [0,1]
Status Affected: N, Z
Operation: (W) + (f) + (C)  dest
Encoding: 0000 1011 kkkk kkkk
Status Affected: N,OV, C, DC, Z
Description: The contents of W are AND’ed with the
Encoding: 0010 00da ffff ffff 8-bit literal ‘k’. The result is placed in W.
Description: Add W, the CARRY flag and data mem-
Words: 1
ory location ‘f’. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is Cycles: 1
placed in data memory location ‘f’. Q Cycle Activity:
If ‘a’ is ‘0’, the Access Bank is selected.
Q1 Q2 Q3 Q4
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank. Decode Read literal Process Write to W
If ‘a’ is ‘0’ and the extended instruction ‘k’ Data
set is enabled, this instruction operates
in Indexed Literal Offset Addressing Example: ANDLW 05Fh
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Before Instruction
Bit-Oriented Instructions in Indexed W = A3h
Literal Offset Mode” for details. After Instruction
Words: 1 W= 03h
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write to
register ‘f’ Data destination

Example: ADDWFC REG, 0, 1

Before Instruction
CARRY bit = 1
REG = 02h
W = 4Dh
After Instruction
CARRY bit = 0
REG = 02h
W = 50h

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 PIC18F2XK20/4XK20

ANDWF AND W with f BC Branch if Carry

Syntax: ANDWF f {,d {,a}} Syntax: BC n
Operands: 0  f  255 Operands: -128  n  127
d [0,1]
Operation: if CARRY bit is ‘1’
a [0,1]
(PC) + 2 + 2n  PC
Operation: (W) .AND. (f)  dest
Status Affected: None
Status Affected: N, Z
Encoding: 1110 0010 nnnn nnnn
Encoding: 0001 01da ffff ffff Description: If the CARRY bit is ‘1’, then the program
Description: The contents of W are AND’ed with will branch.
register ‘f’. If ‘d’ is ‘0’, the result is stored The 2’s complement number ‘2n’ is
in W. If ‘d’ is ‘1’, the result is stored back added to the PC. Since the PC will have
in register ‘f’ (default). incremented to fetch the next
If ‘a’ is ‘0’, the Access Bank is selected. instruction, the new address will be
If ‘a’ is ‘1’, the BSR is used to select the PC + 2 + 2n. This instruction is then a
GPR bank. two-cycle instruction.
If ‘a’ is ‘0’ and the extended instruction Words: 1
set is enabled, this instruction operates
in Indexed Literal Offset Addressing Cycles: 1(2)
mode whenever f 95 (5Fh). See Q Cycle Activity:
Section 24.2.3 “Byte-Oriented and If Jump:
Bit-Oriented Instructions in Indexed
Q1 Q2 Q3 Q4
Literal Offset Mode” for details.
Decode Read literal Process Write to PC
Words: 1 ‘n’ Data
Cycles: 1 No No No No
operation operation operation operation
Q Cycle Activity:
If No Jump:
Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4
Decode Read Process Write to
Decode Read literal Process No
register ‘f’ Data destination
‘n’ Data operation

Example: ANDWF REG, 0, 0

Example: HERE BC 5
Before Instruction
Before Instruction
W = 17h PC = address (HERE)
REG = C2h
After Instruction
After Instruction
If CARRY = 1;
W = 02h PC = addres s (HERE + 12)
REG = C2h If CARRY = 0;
PC = addres s (HERE + 2)

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BCF Bit Clear f BN Branch if Negative

Syntax: BCF f, b {,a} Syntax: BN n
Operands: 0  f  255 Operands: -128  n  127
0b7
Operation: if NEGATIVE bit is ‘1’
a [0,1]
(PC) + 2 + 2n  PC
Operation: 0  f<b>
Status Affected: None
Status Affected: None
Encoding: 1110 0110 nnnn nnnn
Encoding: 1001 bbba ffff ffff Description: If the NEGATIVE bit is ‘1’, then the
Description: Bit ‘b’ in register ‘f’ is cleared. program will branch.
If ‘a’ is ‘0’, the Access Bank is selected. The 2’s complement number ‘2n’ is
If ‘a’ is ‘1’, the BSR is used to select the added to the PC. Since the PC will have
GPR bank. incremented to fetch the next
If ‘a’ is ‘0’ and the extended instruction instruction, the new address will be
set is enabled, this instruction operates PC + 2 + 2n. This instruction is then a
in Indexed Literal Offset Addressing two-cycle instruction.
mode whenever f 95 (5Fh). See Words: 1
Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed Cycles: 1(2)
Literal Offset Mode” for details. Q Cycle Activity:
Words: 1 If Jump:
Q1 Q2 Q3 Q4
Cycles: 1
Decode Read literal Process Write to PC
Q Cycle Activity: ‘n’ Data
Q1 Q2 Q3 Q4 No No No No
Decode Read Process Write operation operation operation operation
register ‘f’ Data register ‘f’ If No Jump:
Q1 Q2 Q3 Q4
Example: BCF FLAG_REG, 7, 0 Decode Read literal Process No
Before Instruction ‘n’ Data operation
FLAG_REG = C7h
After Instruction Example: HERE BN Jump
FLAG_REG = 47h
Before Instruction
PC = address (HERE)
After Instruction
If NEGATIVE = 1;
PC = addres s (Jump)
If NEGATIVE = 0;
PC = addres s (HERE + 2)

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 PIC18F2XK20/4XK20

BNC Branch if Not Carry BNN Branch if Not Negative

Syntax: BNC n Syntax: BNN n
Operands: -128  n  127 Operands: -128  n  127
Operation: if CARRY bit is ‘0’ Operation: if NEGATIVE bit is ‘0’
(PC) + 2 + 2n  PC (PC) + 2 + 2n  PC
Status Affected: None Status Affected: None
Encoding: 1110 0011 nnnn nnnn Encoding: 1110 0111 nnnn nnnn
Description: If the CARRY bit is ‘0’, then the program Description: If the NEGATIVE bit is ‘0’, then the
will branch. program will branch.
The 2’s complement number ‘2n’ is The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have added to the PC. Since the PC will have
incremented to fetch the next incremented to fetch the next
instruction, the new address will be instruction, the new address will be
PC + 2 + 2n. This instruction is then a PC + 2 + 2n. This instruction is then a
two-cycle instruction. two-cycle instruction.
Words: 1 Words: 1
Cycles: 1(2) Cycles: 1(2)
Q Cycle Activity: Q Cycle Activity:
If Jump: If Jump:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read literal Process Write to PC Decode Read literal Process Write to PC
‘n’ Data ‘n’ Data
No No No No No No No No
operation operation operation operation operation operation operation operation
If No Jump: If No Jump:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read literal Process No Decode Read literal Process No
‘n’ Data operation ‘n’ Data operation

Example: HERE BNC Jump Example: HERE BNN Jump

Before Instruction Before Instruction
PC = address (HERE) PC = address (HERE)
After Instruction After Instruction
If CARRY = 0; If NEGATIVE = 0;
PC = addres s (Jump) PC = addres s (Jump)
If CARRY = 1; If NEGATIVE = 1;
PC = addres s (HERE + 2) PC = addres s (HERE + 2)

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PIC18F2XK20/4XK20

BNOV Branch if Not Overflow BNZ Branch if Not Zero

Syntax: BNOV n Syntax: BNZ n
Operands: -128  n  127 Operands: -128  n  127
Operation: if OVERFLOW bit is ‘0’ Operation: if ZERO bit is ‘0’
(PC) + 2 + 2n  PC (PC) + 2 + 2n  PC
Status Affected: None Status Affected: None
Encoding: 1110 0101 nnnn nnnn Encoding: 1110 0001 nnnn nnnn
Description: If the OVERFLOW bit is ‘0’, then the Description: If the ZERO bit is ‘0’, then the program
program will branch. will branch.
The 2’s complement number ‘2n’ is The 2’s complement number ‘2n’ is
added to the PC. Since the PC will have added to the PC. Since the PC will have
incremented to fetch the next incremented to fetch the next
instruction, the new address will be instruction, the new address will be
PC + 2 + 2n. This instruction is then a PC + 2 + 2n. This instruction is then a
two-cycle instruction. two-cycle instruction.
Words: 1 Words: 1
Cycles: 1(2) Cycles: 1(2)
Q Cycle Activity: Q Cycle Activity:
If Jump: If Jump:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read literal Process Write to PC Decode Read literal Process Write to PC
‘n’ Data ‘n’ Data
No No No No No No No No
operation operation operation operation operation operation operation operation
If No Jump: If No Jump:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read literal Process No Decode Read literal Process No
‘n’ Data operation ‘n’ Data operation

Example: HERE BNOV Jump Example: HERE BNZ Jump

Before Instruction Before Instruction
PC = address (HERE) PC = address (HERE)
After Instruction After Instruction
If OVERFLOW = 0; If ZERO = 0;
PC = addres s (Jump) PC = addres s (Jump)
If OVERFLOW = 1; If ZERO = 1;
PC = addres s (HERE + 2) PC = addres s (HERE + 2)

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 PIC18F2XK20/4XK20

BRA Unconditional Branch BSF Bit Set f

Syntax: BRA n Syntax: BSF f, b {,a}
Operands: -1024  n  1023 Operands: 0  f  255
0b7
Operation: (PC) + 2 + 2n  PC
a [0,1]
Status Affected: None
Operation: 1  f<b>
Encoding: 1101 0nnn nnnn nnnn
Status Affected: None
Description: Add the 2’s complement number ‘2n’ to
the PC. Since the PC will have incre- Encoding: 1000 bbba ffff ffff
mented to fetch the next instruction, the Description: Bit ‘b’ in register ‘f’ is set.
new address will be PC + 2 + 2n. This If ‘a’ is ‘0’, the Access Bank is selected.
instruction is a two-cycle instruction. If ‘a’ is ‘1’, the BSR is used to select the
GPR bank.
Words: 1
If ‘a’ is ‘0’ and the extended instruction
Cycles: 2 set is enabled, this instruction operates
Q Cycle Activity: in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Q1 Q2 Q3 Q4
Section 24.2.3 “Byte-Oriented and
Decode Read literal Process Write to PC Bit-Oriented Instructions in Indexed
‘n’ Data Literal Offset Mode” for details.
No No No No
Words: 1
operation operation operation operation
Cycles: 1
Q Cycle Activity:
Example: HERE BRA Jump
Q1 Q2 Q3 Q4
Before Instruction
Decode Read Process Write
PC = address (HERE)
register ‘f’ Data register ‘f’
After Instruction
PC = addres s (Jump)
Example: BSF FLAG_REG, 7, 1
Before Instruction
FLAG_REG = 0Ah
After Instruction
FLAG_REG = 8Ah

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PIC18F2XK20/4XK20

BTFSC Bit Test File, Skip if Clear BTFSS Bit Test File, Skip if Set
Syntax: BTFSC f, b {,a} Syntax: BTFSS f, b {,a}
Operands: 0  f  255 Operands: 0  f  255
0b7 0b<7
a [0,1] a [0,1]
Operation: skip if (f<b>) = 0 Operation: skip if (f<b>) = 1
Status Affected: None Status Affected: None
Encoding: 1011 bbba ffff ffff Encoding: 1010 bbba ffff ffff
Description: If bit ‘b’ in register ‘f’ is ‘0’, then the next Description: If bit ‘b’ in register ‘f’ is ‘1’, then the next
instruction is skipped. If bit ‘b’ is ‘0’, then instruction is skipped. If bit ‘b’ is ‘1’, then
the next instruction fetched during the the next instruction fetched during the
current instruction execution is discarded current instruction execution is discarded
and a NOP is executed instead, making and a NOP is executed instead, making
this a two-cycle instruction. this a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected. If If ‘a’ is ‘0’, the Access Bank is selected. If
‘a’ is ‘1’, the BSR is used to select the ‘a’ is ‘1’, the BSR is used to select the
GPR bank. GPR bank.
If ‘a’ is ‘0’ and the extended instruction If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates in set is enabled, this instruction operates
Indexed Literal Offset Addressing in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). mode whenever f 95 (5Fh).
See Section 24.2.3 “Byte-Oriented and See Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details. Literal Offset Mode” for details.
Words: 1 Words: 1
Cycles: 1(2) Cycles: 1(2)
Note: 3 cycles if skip and followed Note: 3 cycles if skip and followed
by a 2-word instruction. by a 2-word instruction.
Q Cycle Activity: Q Cycle Activity:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read Process No Decode Read Process No
register ‘f’ Data operation register ‘f’ Data operation
If skip: If skip:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
No No No No No No No No
operation operation operation operation operation operation operation operation
If skip and followed by 2-word instruction: If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
No No No No No No No No
operation operation operation operation operation operation operation operation
No No No No No No No No
operation operation operation operation operation operation operation operation

Example: HERE BTFSC FLAG, 1, 0 Example: HERE BTFSS FLAG, 1, 0

FALSE : FALSE :
TRUE : TRUE :
Before Instruction Before Instruction
PC = address (HERE) PC = addres s (HERE)
After Instruction After Instruction
If FLAG<1> = 0; If FLAG<1> = 0;
PC = addres s (TRUE) PC = addres s (FALSE)
If FLAG<1> = 1; If FLAG<1> = 1;
PC = addres s (FALSE) PC = addres s (TRUE)

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 PIC18F2XK20/4XK20

BTG Bit Toggle f BOV Branch if Overflow

Syntax: BTG f, b {,a} Syntax: BOV n
Operands: 0  f  255 Operands: -128  n  127
0b<7
Operation: if OVERFLOW bit is ‘1’
a [0,1]
(PC) + 2 + 2n  PC
Operation: (f<b>)  f<b>
Status Affected: None
Status Affected: None
Encoding: 1110 0100 nnnn nnnn
Encoding: 0111 bbba ffff ffff
Description: If the OVERFLOW bit is ‘1’, then the
Description: Bit ‘b’ in data memory location ‘f’ is program will branch.
inverted. The 2’s complement number ‘2n’ is
If ‘a’ is ‘0’, the Access Bank is selected. added to the PC. Since the PC will have
If ‘a’ is ‘1’, the BSR is used to select the incremented to fetch the next
GPR bank. instruction, the new address will be
If ‘a’ is ‘0’ and the extended instruction PC + 2 + 2n. This instruction is then a
set is enabled, this instruction operates two-cycle instruction.
in Indexed Literal Offset Addressing
Words: 1
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Cycles: 1(2)
Bit-Oriented Instructions in Indexed Q Cycle Activity:
Literal Offset Mode” for details. If Jump:
Words: 1 Q1 Q2 Q3 Q4
Cycles: 1 Decode Read literal Process Write to PC
‘n’ Data
Q Cycle Activity:
No No No No
Q1 Q2 Q3 Q4 operation operation operation operation
Decode Read Process Write If No Jump:
register ‘f’ Data register ‘f’
Q1 Q2 Q3 Q4
Decode Read literal Process No
Example: BTG PORTC, 4, 0 ‘n’ Data operation
Before Instruction:
PORTC = 0111 0101 [75h]
Example: HERE BOV Jump
After Instruction:
PORTC = 0110 0101 [65h] Before Instruction
PC = address (HERE)
After Instruction
If OVERFLOW = 1;
PC = addres s (Jump)
If OVERFLOW = 0;
PC = addres s (HERE + 2)

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PIC18F2XK20/4XK20

BZ Branch if Zero CALL Subroutine Call

Syntax: BZ n Syntax: CALL k {,s}
Operands: -128  n  127 Operands: 0  k  1048575
s [0,1]
Operation: if ZERO bit is ‘1’
(PC) + 2 + 2n  PC Operation: (PC) + 4  TOS,
k  PC<20:1>,
Status Affected: None
if s = 1
Encoding: 1110 0000 nnnn nnnn (W)  WS,
Description: If the ZERO bit is ‘1’, then the program (Status)  STATUSS,
will branch. (BSR)  BSRS
The 2’s complement number ‘2n’ is Status Affected: None
added to the PC. Since the PC will
Encoding:
have incremented to fetch the next
1st word (k<7:0>) 1110 110s k7kkk kkkk0
instruction, the new address will be
PC + 2 + 2n. This instruction is then a 2nd word(k<19:8>) 1111 k19kkk kkkk kkkk8
two-cycle instruction. Description: Subroutine call of entire 2-Mbyte
memory range. First, return address
Words: 1
(PC + 4) is pushed onto the return
Cycles: 1(2) stack. If ‘s’ = 1, the W, Status and BSR
Q Cycle Activity: registers are also pushed into their
If Jump: respective shadow registers, WS,
STATUSS and BSRS. If ‘s’ = 0, no
Q1 Q2 Q3 Q4
update occurs (default). Then, the
Decode Read literal Process Write to PC 20-bit value ‘k’ is loaded into PC<20:1>.
‘n’ Data CALL is a two-cycle instruction.
No No No No
Words: 2
operation operation operation operation
If No Jump: Cycles: 2
Q1 Q2 Q3 Q4 Q Cycle Activity:
Decode Read literal Process No Q1 Q2 Q3 Q4
‘n’ Data operation Decode Read literal PUSH PC to Read literal
‘k’<7:0>, stack ‘k’<19:8>,
Example: HERE BZ Jump Write to PC
No No No No
Before Instruction
PC = address (HERE) operation operation operation operation
After Instruction
If ZERO = 1; Example: HERE CALL THERE, 1
PC = addres s (Jump)
If ZERO = 0; Before Instruction
PC = addres s (HERE + 2) PC = address (HERE)
After Instruction
PC = address (THERE)
TOS = address (HERE + 4)
WS = W
BSRS = BSR
STATUSS = S tatus

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 PIC18F2XK20/4XK20

CLRF Clear f CLRWDT Clear Watchdog Timer

Syntax: CLRF f {,a} Syntax: CLRWDT
Operands: 0  f  255 Operands: None
a [0,1]
Operation: 000h  WDT,
Operation: 000h  f 000h  WDT postscaler,
1Z 1  TO,
1  PD
Status Affected: Z
Status Affected: TO, PD
Encoding: 0110 101a ffff ffff
Encoding: 0000 0000 0000 0100
Description: Clears the contents of the specified
register. Description: CLRWDT instruction resets the
If ‘a’ is ‘0’, the Access Bank is selected. Watchdog Timer. It also resets the
If ‘a’ is ‘1’, the BSR is used to select the postscaler of the WDT. Status bits, TO
GPR bank. and PD, are set.
If ‘a’ is ‘0’ and the extended instruction Words: 1
set is enabled, this instruction operates
in Indexed Literal Offset Addressing Cycles: 1
mode whenever f 95 (5Fh). See Q Cycle Activity:
Section 24.2.3 “Byte-Oriented and
Q1 Q2 Q3 Q4
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details. Decode No Process No
operation Data operation
Words: 1
Cycles: 1
Example: CLRWDT
Q Cycle Activity: Before Instruction
Q1 Q2 Q3 Q4 WDT Counter = ?
Decode Read Process Write After Instruction
register ‘f’ Data register ‘f’ WDT Counter = 00h
WDT Postscaler = 0
TO = 1
Example: CLRF FLAG_REG, 1 PD = 1
Before Instruction
FLAG_REG = 5Ah
After Instruction
FLAG_REG = 00h

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PIC18F2XK20/4XK20

COMF Complement f CPFSEQ Compare f with W, skip if f = W

Syntax: COMF f {,d {,a}} Syntax: CPFSEQ f {,a}

Operands: 0  f  255 Operands: 0  f  255

d  [0,1] a  [0,1]
a  [0,1] Operation: (f) – (W),
skip if (f) = (W)
Operation: (f)  dest
(unsigned comparison)
Status Affected: N, Z
Status Affected: None
Encoding: 0001 11da ffff ffff Encoding: 0110 001a ffff ffff
Description: The contents of register ‘f’ are Description: Compares the contents of data memory
complemented. If ‘d’ is ‘0’, the result is location ‘f’ to the contents of W by
stored in W. If ‘d’ is ‘1’, the result is performing an unsigned subtraction.
stored back in register ‘f’ (default). If ‘f’ = W, then the fetched instruction is
If ‘a’ is ‘0’, the Access Bank is selected. discarded and a NOP is executed
If ‘a’ is ‘1’, the BSR is used to select the instead, making this a two-cycle
GPR bank. instruction.
If ‘a’ is ‘0’ and the extended instruction If ‘a’ is ‘0’, the Access Bank is selected.
set is enabled, this instruction operates If ‘a’ is ‘1’, the BSR is used to select the
in Indexed Literal Offset Addressing GPR bank.
mode whenever f 95 (5Fh). See If ‘a’ is ‘0’ and the extended instruction
Section 24.2.3 “Byte-Oriented and set is enabled, this instruction operates
Bit-Oriented Instructions in Indexed in Indexed Literal Offset Addressing
Literal Offset Mode” for details. mode whenever f 95 (5Fh). See
Words: 1 Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Cycles: 1
Literal Offset Mode” for details.
Q Cycle Activity: Words: 1
Q1 Q2 Q3 Q4 Cycles: 1(2)
Decode Read Process Write to Note: 3 cycles if skip and followed
register ‘f’ Data destination by a 2-word instruction.
Q Cycle Activity:
Example: COMF REG, 0, 0 Q1 Q2 Q3 Q4
Before Instruction Decode Read Process No
REG = 13h register ‘f’ Data operation
After Instruction If skip:
REG = 13h Q1 Q2 Q3 Q4
W = ECh No No No No
operation operation operation operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No No No No
operation operation operation operation
No No No No
operation operation operation operation

Example: HERE CPFSEQ REG, 0

NEQUAL :
EQUAL :
Before Instruction
PC Address = HERE
W = ?
REG = ?
After Instruction
If REG = W;
=PC Address (EQUAL)
If REG  W;
=PC Address (NEQUAL)

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 PIC18F2XK20/4XK20

CPFSGT Compare f with W, skip if f > W CPFSLT Compare f with W, skip if f < W
Syntax: CPFSGT f {,a} Syntax: CPFSLT f {,a}
Operands: 0  f  255 Operands: 0  f  255
a  [0,1] a  [0,1]
Operation: (f) –W), Operation: (f) –W),
skip if (f) > (W) skip if (f) < (W)
(unsigned comparison) (unsigned comparison)
Status Affected: None
Status Affected: None
Encoding: 0110 010a ffff ffff
Encoding: 0110 000a ffff ffff
Description: Compares the contents of data memory
location ‘f’ to the contents of the W by Description: Compares the contents of data memory
performing an unsigned subtraction. location ‘f’ to the contents of W by
performing an unsigned subtraction.
If the contents of ‘f’ are greater than the
contents of WREG, then the fetched If the contents of ‘f’ are less than the
instruction is discarded and a NOP is contents of W, then the fetched
instruction is discarded and a NOP is
executed instead, making this a
two-cycle instruction. executed instead, making this a
If ‘a’ is ‘0’, the Access Bank is selected. two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank. If ‘a’ is ‘1’, the BSR is used to select the
If ‘a’ is ‘0’ and the extended instruction GPR bank.
set is enabled, this instruction operates Words: 1
in Indexed Literal Offset Addressing
Cycles: 1(2)
mode whenever f 95 (5Fh). See
Note: 3 cycles if skip and followed
Section 24.2.3 “Byte-Oriented and
by a 2-word instruction.
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details. Q Cycle Activity:
Words: 1 Q1 Q2 Q3 Q4
Cycles: 1(2) Decode Read Process No
Note: 3 cycles if skip and followed register ‘f’ Data operation
by a 2-word instruction. If skip:
Q Cycle Activity: Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4 No No No No
Decode Read Process No operation operation operation operation
register ‘f’ Data operation If skip and followed by 2-word instruction:
If skip: Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4 No No No No
No No No No operation operation operation operation
operation operation operation operation No No No No
If skip and followed by 2-word instruction: operation operation operation operation
Q1 Q2 Q3 Q4
No No No No
Example: HERE CPFSLT REG, 1
operation operation operation operation NLESS :
No No No No LESS :
operation operation operation operation
Before Instruction
= PC Address (HERE)
Example: HERE CPFSGT REG, 0 W = ?
NGREATER : After Instruction
GREATER :
If REG < W;
Before Instruction PC = Addr ess (LESS)
= PC Address (HERE) If REG  W;
W = ? =PC Address (NLESS)
After Instruction
If REG  W;
=PC Address (GREATER)
If REG  W;
PC = Addr ess (NGREATER)

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PIC18F2XK20/4XK20

DAW Decimal Adjust W Register DECF Decrement f

Syntax: DAW Syntax: DECF f {,d {,a}}
Operands: None Operands: 0  f  255
d  [0,1]
Operation: If [W<3:0> > 9] or [DC = 1] then
a  [0,1]
(W<3:0>) + 6  W<3:0>;
else Operation: (f) – 1  dest
(W<3:0>)  W<3:0>; Status Affected: C, DC, N, OV, Z

If [W<7:4> + DC > 9] or [C = 1] then Encoding: 0000 01da ffff ffff

(W<7:4>) + 6 + DC  W<7:4>; Description: Decrement register ‘f’. If ‘d’ is ‘0’, the
else result is stored in W. If ‘d’ is ‘1’, the
(W<7:4>) + DC  W<7:4> result is stored back in register ‘f’
Status Affected: C (default).
If ‘a’ is ‘0’, the Access Bank is selected.
Encoding: 0000 0000 0000 0111
If ‘a’ is ‘1’, the BSR is used to select the
Description: DAW adjusts the eight-bit value in W, GPR bank.
resulting from the earlier addition of two If ‘a’ is ‘0’ and the extended instruction
variables (each in packed BCD format) set is enabled, this instruction operates
and produces a correct packed BCD in Indexed Literal Offset Addressing
result. mode whenever f 95 (5Fh). See
Words: 1 Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Cycles: 1 Literal Offset Mode” for details.
Q Cycle Activity: Words: 1
Q1 Q2 Q3 Q4 Cycles: 1
Decode Read Process Write
Q Cycle Activity:
register W Data W
Example1: Q1 Q2 Q3 Q4

DAW Decode Read Process Write to

register ‘f’ Data destination
Before Instruction
W = A5h
Example: DECF CNT, 1, 0
C = 0
DC = 0 Before Instruction
After Instruction CNT = 01h
W = 05h Z = 0
C = 1 After Instruction
DC = 0 CNT = 00h
Example 2: Z = 1
Before Instruction
W = CEh
C = 0
DC = 0
After Instruction
W = 34h
C = 1
DC = 0

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 PIC18F2XK20/4XK20

DECFSZ Decrement f, skip if 0 DCFSNZ Decrement f, skip if not 0

Syntax: DECFSZ f {,d {,a}} Syntax: DCFSNZ f {,d {,a}}
Operands: 0  f  255 Operands: 0  f  255
d  [0,1] d  [0,1]
a  [0,1] a  [0,1]
Operation: (f) – 1  dest, Operation: (f) – 1  dest,
skip if result = 0 skip if result  0
Status Affected: None Status Affected: None
Encoding: 0010 11da ffff ffff Encoding: 0100 11da ffff ffff
Description: The contents of register ‘f’ are Description: The contents of register ‘f’ are
decremented. If ‘d’ is ‘0’, the result is decremented. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is placed in W. If ‘d’ is ‘1’, the result is
placed back in register ‘f’ (default). placed back in register ‘f’ (default).
If the result is ‘0’, the next instruction, If the result is not ‘0’, the next
which is already fetched, is discarded instruction, which is already fetched, is
and a NOP is executed instead, making discarded and a NOP is executed
it a two-cycle instruction. instead, making it a two-cycle
If ‘a’ is ‘0’, the Access Bank is selected. instruction.
If ‘a’ is ‘1’, the BSR is used to select the If ‘a’ is ‘0’, the Access Bank is selected.
GPR bank. If ‘a’ is ‘1’, the BSR is used to select the
If ‘a’ is ‘0’ and the extended instruction GPR bank.
set is enabled, this instruction operates If ‘a’ is ‘0’ and the extended instruction
in Indexed Literal Offset Addressing set is enabled, this instruction operates
mode whenever f 95 (5Fh). See in Indexed Literal Offset Addressing
Section 24.2.3 “Byte-Oriented and mode whenever f 95 (5Fh). See
Bit-Oriented Instructions in Indexed Section 24.2.3 “Byte-Oriented and
Literal Offset Mode” for details. Bit-Oriented Instructions in Indexed
Words: 1 Literal Offset Mode” for details.
Words: 1
Cycles: 1(2)
Note: 3 cycles if skip and followed Cycles: 1(2)
by a 2-word instruction. Note: 3 cycles if skip and followed
Q Cycle Activity: by a 2-word instruction.

Q1 Q2 Q3 Q4 Q Cycle Activity:
Decode Read Process Write to Q1 Q2 Q3 Q4
register ‘f’ Data destination Decode Read Process Write to
If skip: register ‘f’ Data destination
Q1 Q2 Q3 Q4 If skip:
No No No No Q1 Q2 Q3 Q4
operation operation operation operation No No No No
If skip and followed by 2-word instruction: operation operation operation operation
Q1 Q2 Q3 Q4 If skip and followed by 2-word instruction:
No No No No Q1 Q2 Q3 Q4
operation operation operation operation No No No No
No No No No operation operation operation operation
operation operation operation operation No No No No
operation operation operation operation
Example: HERE DECFSZ CNT, 1, 1
GOTO LOOP Example: HERE DCFSNZ TEMP, 1, 0
CONTINUE ZERO :
NZERO :
Before Instruction
= PC Address (HERE) Before Instruction
After Instruction TEMP = ?
CNT = CNT - 1 After Instruction
If CNT = 0; TEMP = TEMP – 1,
PC = Address (CONTINUE) If TEMP = 0;
If CNT  0; = PC Address (ZERO)
PC = Address (HERE + 2) If TEMP  0;
= PC Address (NZERO)

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GOTO Unconditional Branch INCF Increment f

Syntax: GOTO k Syntax: INCF f {,d {,a}}
Operands: 0  k  1048575 Operands: 0  f  255
d  [0,1]
Operation: k  PC<20:1>
a  [0,1]
Status Affected: None
Operation: (f) + 1  dest
Encoding:
Status Affected: C, DC, N, OV, Z
1st word (k<7:0>) 1110 1111 k7kkk kkkk0
2nd word(k<19:8>) 1111 k19kkk kkkk kkkk8 Encoding: 0010 10da ffff ffff
Description: GOTO allows an unconditional branch Description: The contents of register ‘f’ are
anywhere within entire incremented. If ‘d’ is ‘0’, the result is
2-Mbyte memory range. The 20-bit placed in W. If ‘d’ is ‘1’, the result is
value ‘k’ is loaded into PC<20:1>. placed back in register ‘f’ (default).
GOTO is always a two-cycle If ‘a’ is ‘0’, the Access Bank is selected.
instruction. If ‘a’ is ‘1’, the BSR is used to select the
GPR bank.
Words: 2
If ‘a’ is ‘0’ and the extended instruction
Cycles: 2 set is enabled, this instruction operates
Q Cycle Activity: in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Q1 Q2 Q3 Q4
Section 24.2.3 “Byte-Oriented and
Decode Read literal No Read literal Bit-Oriented Instructions in Indexed
‘k’<7:0>, operation ‘k’<19:8>, Literal Offset Mode” for details.
Write to PC
Words: 1
No No No No
operation operation operation operation Cycles: 1
Q Cycle Activity:
Example: GOTO THERE Q1 Q2 Q3 Q4
After Instruction Decode Read Process Write to
PC = Address (THERE) register ‘f’ Data destination

Example: INCF CNT, 1, 0

Before Instruction
CNT = FFh
Z = 0
C = ?
DC = ?
After Instruction
CNT = 00h
Z = 1
C = 1
DC = 1

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 PIC18F2XK20/4XK20

INCFSZ Increment f, skip if 0 INFSNZ Increment f, skip if not 0

Syntax: INCFSZ f {,d {,a}} Syntax: INFSNZ f {,d {,a}}

Operands: 0  f  255 Operands: 0  f  255

d  [0,1] d  [0,1]
a  [0,1] a  [0,1]
Operation: (f) + 1  dest,
Operation: (f) + 1  dest,
skip if result  0
skip if result = 0
Status Affected: None
Status Affected: None
Encoding: 0100 10da ffff ffff
Encoding: 0011 11da ffff ffff
Description: The contents of register ‘f’ are
Description: The contents of register ‘f’ are incremented. If ‘d’ is ‘0’, the result is
incremented. If ‘d’ is ‘0’, the result is placed in W. If ‘d’ is ‘1’, the result is
placed in W. If ‘d’ is ‘1’, the result is placed back in register ‘f’ (default).
placed back in register ‘f’ (default). If the result is not ‘0’, the next
If the result is ‘0’, the next instruction, instruction, which is already fetched, is
which is already fetched, is discarded discarded and a NOP is executed
and a NOP is executed instead, making instead, making it a two-cycle
it a two-cycle instruction. instruction.
If ‘a’ is ‘0’, the Access Bank is selected. If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the If ‘a’ is ‘1’, the BSR is used to select the
GPR bank. GPR bank.
If ‘a’ is ‘0’ and the extended instruction If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates set is enabled, this instruction operates
in Indexed Literal Offset Addressing in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details. Literal Offset Mode” for details.
Words: 1 Words: 1
Cycles: 1(2) Cycles: 1(2)
Note: 3 cycles if skip and followed Note: 3 cycles if skip and followed
by a 2-word instruction. by a 2-word instruction.
Q Cycle Activity: Q Cycle Activity:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Decode Read Process Write to Decode Read Process Write to
register ‘f’ Data destination register ‘f’ Data destination
If skip: If skip:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
No No No No No No No No
operation operation operation operation operation operation operation operation
If skip and followed by 2-word instruction: If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
No No No No No No No No
operation operation operation operation operation operation operation operation
No No No No No No No No
operation operation operation operation operation operation operation operation

Example: HERE INCFSZ CNT, 1, 0 Example: HERE INFSNZ REG, 1, 0

NZERO : ZERO
ZERO : NZERO
Before Instruction Before Instruction
= PC Address (HERE) = PC Address (HERE)
After Instruction After Instruction
CNT = CNT + 1 REG = REG + 1
If CNT = 0; If REG  0;
PC = Addr ess (ZERO) = PC Address (NZERO)
If CNT  0; If REG = 0;
= PC Address (NZERO) = PC Address (ZERO)

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PIC18F2XK20/4XK20

IORLW Inclusive OR literal with W IORWF Inclusive OR W with f

Syntax: IORLW k Syntax: IORWF f {,d {,a}}
Operands: 0  k  255 Operands: 0  f  255
d  [0,1]
Operation: (W) .OR. k  W
a  [0,1]
Status Affected: N, Z
Operation: (W) .OR. (f)  dest
Encoding: 0000 1001 kkkk kkkk
Status Affected: N, Z
Description: The contents of W are ORed with the
eight-bit literal ‘k’. The result is placed in Encoding: 0001 00da ffff ffff
W. Description: Inclusive OR W with register ‘f’. If ‘d’ is
‘0’, the result is placed in W. If ‘d’ is ‘1’,
Words: 1
the result is placed back in register ‘f’
Cycles: 1 (default).
Q Cycle Activity: If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
Q1 Q2 Q3 Q4
GPR bank.
Decode Read Process Write to W If ‘a’ is ‘0’ and the extended instruction
literal ‘k’ Data set is enabled, this instruction operates
in Indexed Literal Offset Addressing
Example: IORLW 35h mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and
Before Instruction
Bit-Oriented Instructions in Indexed
W = 9Ah Literal Offset Mode” for details.
After Instruction
Words: 1
W = BFh
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write to
register ‘f’ Data destination

Example: IORWF RESULT, 0, 1

Before Instruction
RESULT = 13h
W = 91h
After Instruction
RESULT = 13h
W = 93h

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 PIC18F2XK20/4XK20

LFSR Load FSR MOVF Move f

Syntax: LFSR f, k Syntax: MOVF f {,d {,a}}
Operands: 0f2 Operands: 0  f  255
0  k  4095 d  [0,1]
a  [0,1]
Operation: k  FSRf
Operation: f  dest
Status Affected: None
Status Affected: N, Z
Encoding: 1110 1110 00ff k11kkk
1111 0000 k7kkk kkkk Encoding: 0101 00da ffff ffff
Description: The 12-bit literal ‘k’ is loaded into the Description: The contents of register ‘f’ are moved to
File Select Register pointed to by ‘f’. a destination dependent upon the
Words: 2 status of ‘d’. If ‘d’ is ‘0’, the result is
placed in W. If ‘d’ is ‘1’, the result is
Cycles: 2 placed back in register ‘f’ (default).
Q Cycle Activity: Location ‘f’ can be anywhere in the
256-byte bank.
Q1 Q2 Q3 Q4
If ‘a’ is ‘0’, the Access Bank is selected.
Decode Read literal Process Write If ‘a’ is ‘1’, the BSR is used to select the
‘k’ MSB Data literal ‘k’ GPR bank.
MSB to If ‘a’ is ‘0’ and the extended instruction
FSRfH set is enabled, this instruction operates
Decode Read literal Process Write literal in Indexed Literal Offset Addressing
‘k’ LSB Data ‘k’ to FSRfL mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Example: LFSR 2, 3ABh
Literal Offset Mode” for details.
After Instruction
Words: 1
FSR2H
= 03h
FSR2L = ABh Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write W
register ‘f’ Data

Example: MOVF REG, 0, 0

Before Instruction
REG = 22h
W = FFh
After Instruction
REG = 22h
W = 22h

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PIC18F2XK20/4XK20

MOVFF Move f to f MOVLB Move literal to low nibble in BSR

Syntax: MOVFF fs,fd Syntax: MOVLW k
Operands: 0  fs  4095 Operands: 0  k  255
0  fd  4095
Operation: k  BSR
Operation: (fs)  fd Status Affected: None
Status Affected: None
Encoding: 0000 0001 kkkk kkkk
Encoding:
Description: The eight-bit literal ‘k’ is loaded into the
1st word (source) 1100 ffff ffff ffffs
Bank Select Register (BSR). The value
2nd word (destin.) 1111 ffff ffff ffffd
of BSR<7:4> always remains ‘0’,
Description: The contents of source register ‘fs’ are regardless of the value of k7:k4.
moved to destination register ‘fd’.
Words: 1
Location of source ‘fs’ can be anywhere
in the 4096-byte data space (000h to Cycles: 1
FFFh) and location of destination ‘fd’ Q Cycle Activity:
can also be anywhere from 000h to
Q1 Q2 Q3 Q4
FFFh.
Either source or destination can be W Decode Read Process Write literal
(a useful special situation). literal ‘k’ Data ‘k’ to BSR
MOVFF is particularly useful for
transferring a data memory location to a Example: MOVLB 5
peripheral register (such as the transmit
Before Instruction
buffer or an I/O port).
BSR Register = 02h
The MOVFF instruction cannot use the
After Instruction
PCL, TOSU, TOSH or TOSL as the
BSR Register = 05h
destination register.
Words: 2
Cycles: 2 (3)
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process No
register ‘f’ Data operation
(src)
Decode No No Write
operation operation register ‘f’
No dummy (dest)
read

Example: MOVFF REG1, REG2

Before Instruction
REG1 = 33h
REG2 = 11h
After Instruction
REG1 = 33h
REG2 = 33h

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 PIC18F2XK20/4XK20

MOVLW Move literal to W MOVWF Move W to f

Syntax: MOVLW k Syntax: MOVWF f {,a}
Operands: 0  k  255 Operands: 0  f  255
a  [0,1]
Operation: kW
Operation: (W)  f
Status Affected: None
Status Affected: None
Encoding: 0000 1110 kkkk kkkk
Encoding: 0110 111a ffff ffff
Description: The eight-bit literal ‘k’ is loaded into W.
Description: Move data from W to register ‘f’.
Words: 1
Location ‘f’ can be anywhere in the
Cycles: 1 256-byte bank.
Q Cycle Activity: If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
Q1 Q2 Q3 Q4
GPR bank.
Decode Read Process Write to W If ‘a’ is ‘0’ and the extended instruction
literal ‘k’ Data set is enabled, this instruction operates
in Indexed Literal Offset Addressing
Example: MOVLW 5Ah mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and
After Instruction
Bit-Oriented Instructions in Indexed
W = 5Ah Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write
register ‘f’ Data register ‘f’

Example: MOVWF REG, 0

Before Instruction
W = 4Fh
REG = FFh
After Instruction
W = 4Fh
REG = 4Fh

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PIC18F2XK20/4XK20

MULLW Multiply literal with W MULWF Multiply W with f

Syntax: MULLW k Syntax: MULWF f {,a}
Operands: 0  k  255 Operands: 0  f  255
a  [0,1]
Operation: (W) x k  PRODH:PRODL
Operation: (W) x (f)  PRODH:PRODL
Status Affected: None
Status Affected: None
Encoding: 0000 1101 kkkk kkkk
Encoding: 0000 001a ffff ffff
Description: An unsigned multiplication is carried
out between the contents of W and the Description: An unsigned multiplication is carried
8-bit literal ‘k’. The 16-bit result is out between the contents of W and the
placed in the PRODH:PRODL register register file location ‘f’. The 16-bit
pair. PRODH contains the high byte. result is stored in the PRODH:PRODL
W is unchanged. register pair. PRODH contains the
None of the Status flags are affected. high byte. Both W and ‘f’ are
Note that neither overflow nor carry is unchanged.
possible in this operation. A zero result None of the Status flags are affected.
is possible but not detected. Note that neither overflow nor carry is
Words: 1 possible in this operation. A zero
result is possible but not detected.
Cycles: 1 If ‘a’ is ‘0’, the Access Bank is
Q Cycle Activity: selected. If ‘a’ is ‘1’, the BSR is used
to select the GPR bank.
Q1 Q2 Q3 Q4
If ‘a’ is ‘0’ and the extended instruction
Decode Read Process Write set is enabled, this instruction
literal ‘k’ Data registers operates in Indexed Literal Offset
PRODH: Addressing mode whenever
PRODL f 95 (5Fh). See Section 24.2.3
“Byte-Oriented and Bit-Oriented
Example: MULLW 0C4h Instructions in Indexed Literal Offset
Mode” for details.
Before Instruction
Words: 1
W = E2h
PRODH = ? Cycles: 1
PRODL = ?
After Instruction Q Cycle Activity:

W = E2h Q1 Q2 Q3 Q4
PRODH = ADh Decode Read Process Write
PRODL = 08h register ‘f’ Data registers
PRODH:
PRODL

Example: MULWF REG, 1

Before Instruction
W = C4h
REG = B5h
PRODH = ?
PRODL = ?
After Instruction
W = C4h
REG = B5h
PRODH = 8Ah
PRODL = 94h

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 PIC18F2XK20/4XK20

NEGF Negate f NOP No Operation

Syntax: NEGF f {,a} Syntax: NOP
Operands: 0  f  255 Operands: None
a  [0,1]
Operation: No operation
Operation: (f)+1f
Status Affected: None
Status Affected: N, OV, C, DC, Z
Encoding: 0000 0000 0000 0000
Encoding: 0110 110a ffff ffff 1111 xxxx xxxx xxxx
Description: Location ‘f’ is negated using two’s Description: No operation.
complement. The result is placed in the
Words: 1
data memory location ‘f’.
If ‘a’ is ‘0’, the Access Bank is selected. Cycles: 1
If ‘a’ is ‘1’, the BSR is used to select the Q Cycle Activity:
GPR bank.
Q1 Q2 Q3 Q4
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates Decode No No No
in Indexed Literal Offset Addressing operation operation operation
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Example:
Bit-Oriented Instructions in Indexed
None.
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write
register ‘f’ Data register ‘f’

Example: NEGF REG, 1

Before Instruction
REG = 0011 1010 [3Ah]
After Instruction
REG = 1100 0110 [C6h]

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PIC18F2XK20/4XK20

POP Pop Top of Return Stack PUSH Push Top of Return Stack
Syntax: POP Syntax: PUSH
Operands: None Operands: None
Operation: (TOS)  bit bucket Operation: (PC + 2)  TOS
Status Affected: None Status Affected: None
Encoding: 0000 0000 0000 0110 Encoding: 0000 0000 0000 0101
Description: The TOS value is pulled off the return Description: The PC + 2 is pushed onto the top of
stack and is discarded. The TOS value the return stack. The previous TOS
then becomes the previous value that value is pushed down on the stack.
was pushed onto the return stack. This instruction allows implementing a
This instruction is provided to enable software stack by modifying TOS and
the user to properly manage the return then pushing it onto the return stack.
stack to incorporate a software stack.
Words: 1
Words: 1
Cycles: 1
Cycles: 1
Q Cycle Activity:
Q Cycle Activity: Q1 Q2 Q3 Q4
Q1 Q2 Q3 Q4 Decode PUSH No No
Decode No POP TOS No PC + 2 onto operation operation
operation value operation return stack

Example: POP Example: PUSH

GOTO NEW
Before Instruction
Before Instruction TOS = 345Ah
TOS = 0031A2h PC = 0124h
Stack (1 level down) = 014332h
After Instruction
After Instruction PC = 0126h
TOS = 014332h TOS = 0126h
PC = NEW Stack (1 level down) = 345Ah

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 PIC18F2XK20/4XK20

RCALL Relative Call RESET Reset

Syntax: RCALL n Syntax: RESET
Operands: -1024  n  1023 Operands: None
Operation: (PC) + 2  TOS, Operation: Reset all registers and flags that are
(PC) + 2 + 2n  PC affected by a MCLR Reset.
Status Affected: None Status Affected: All
Encoding: 1101 1nnn nnnn nnnn Encoding: 0000 0000 1111 1111
Description: Subroutine call with a jump up to 1K Description: This instruction provides a way to
from the current location. First, return execute a MCLR Reset by software.
address (PC + 2) is pushed onto the Words: 1
stack. Then, add the 2’s complement
number ‘2n’ to the PC. Since the PC will Cycles: 1
have incremented to fetch the next Q Cycle Activity:
instruction, the new address will be
Q1 Q2 Q3 Q4
PC + 2 + 2n. This instruction is a
two-cycle instruction. Decode Start No No
Reset operation operation
Words: 1
Cycles: 2 Example: RESET
Q Cycle Activity: After Instruction
Q1 Q2 Q3 Q4 Registers = Reset Value
Decode Read literal Process Write to PC Flags* = Reset Value
‘n’ Data
PUSH PC to
stack
No No No No
operation operation operation operation

Example: HERE RCALL Jump

Before Instruction
PC = Address (HERE)
After Instruction
PC = Address (Jump)
TOS = Address (HERE + 2)

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PIC18F2XK20/4XK20

RETFIE Return from Interrupt RETLW Return literal to W

Syntax: RETFIE {s} Syntax: RETLW k
Operands: s  [0,1] Operands: 0  k  255
Operation: (TOS)  PC, Operation: k  W,
1  GIE/GIEH or PEIE/GIEL, (TOS)  PC,
if s = 1 PCLATU, PCLATH are unchanged
(WS)  W, Status Affected: None
(STATUSS)  Status,
(BSRS)  BSR, Encoding: 0000 1100 kkkk kkkk
PCLATU, PCLATH are unchanged. Description: W is loaded with the eight-bit literal ‘k’.
Status Affected: GIE/GIEH, PEIE/GIEL. The program counter is loaded from the
top of the stack (the return address).
Encoding: 0000 0000 0001 000s
The high address latch (PCLATH)
Description: Return from interrupt. Stack is popped remains unchanged.
and Top-of-Stack (TOS) is loaded into Words: 1
the PC. Interrupts are enabled by
setting either the high or low priority Cycles: 2
global interrupt enable bit. If ‘s’ = 1, the Q Cycle Activity:
contents of the shadow registers, WS,
Q1 Q2 Q3 Q4
STATUSS and BSRS, are loaded into
their corresponding registers, W, Decode Read Process POP PC
Status and BSR. If ‘s’ = 0, no update of literal ‘k’ Data from stack,
these registers occurs (default). Write to W
No No No No
Words: 1
operation operation operation operation
Cycles: 2
Q Cycle Activity: Example:
Q1 Q2 Q3 Q4
Decode No No POP PC CALL TABLE ; W contains table
operation operation from stack ; offset value
; W now has
Set GIEH or
; table value
GIEL
:
No No No No TABLE
operation operation operation operation ADDWF PCL ; W = offset
RETLW k0 ; Begin table
Example: RETFIE 1 RETLW k1 ;
:
After Interrupt
:
PC = TOS
W = WS RETLW kn ; End of table
BSR = BSRS
Status = STATUSS
GIE/GIEH, PEIE/GIEL = 1 Before Instruction
W = 07h
After Instruction
W = value of kn

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 PIC18F2XK20/4XK20

RETURN Return from Subroutine RLCF Rotate Left f through Carry

Syntax: RETURN {s} Syntax: RLCF f {,d {,a}}
Operands: s  [0,1] Operands: 0  f  255
d  [0,1]
Operation: (TOS)  PC,
a  [0,1]
if s = 1
(WS)  W, Operation: (f<n>)  dest<n + 1>,
(STATUSS)  Status, (f<7>)  C,
(BSRS)  BSR, (C)  dest<0>
PCLATU, PCLATH are unchanged
Status Affected: C, N, Z
Status Affected: None Encoding: 0011 01da ffff ffff
Encoding: 0000 0000 0001 001s
Description: The contents of register ‘f’ are rotated
Description: Return from subroutine. The stack is one bit to the left through the CARRY
popped and the top of the stack (TOS) flag. If ‘d’ is ‘0’, the result is placed in
is loaded into the program counter. If W. If ‘d’ is ‘1’, the result is stored back
‘s’= 1, the contents of the shadow in register ‘f’ (default).
registers, WS, STATUSS and BSRS, If ‘a’ is ‘0’, the Access Bank is
are loaded into their corresponding selected. If ‘a’ is ‘1’, the BSR is used to
registers, W, Status and BSR. If select the GPR bank.
‘s’ = 0, no update of these registers If ‘a’ is ‘0’ and the extended instruction
occurs (default). set is enabled, this instruction
operates in Indexed Literal Offset
Words: 1
Addressing mode whenever
Cycles: 2 f 95 (5Fh). See Section 24.2.3
Q Cycle Activity: “Byte-Oriented and Bit-Oriented
Instructions in Indexed Literal Offset
Q1 Q2 Q3 Q4
Mode” for details.
Decode No Process POP PC
operation Data from stack C register f
No No No No
operation operation operation operation Words: 1
Cycles: 1
Q Cycle Activity:
Example: RETURN Q1 Q2 Q3 Q4
After Instruction: Decode Read Process Write to
PC = TOS register ‘f’ Data destination

Example: RLCF REG, 0, 0

Before Instruction
REG = 1110 0110
C = 0
After Instruction
REG = 1110 0110
W = 1100 1100
C = 1

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PIC18F2XK20/4XK20

RLNCF Rotate Left f (No Carry) RRCF Rotate Right f through Carry
Syntax: RLNCF f {,d {,a}} Syntax: RRCF f {,d {,a}}
Operands: 0  f  255 Operands: 0  f  255
d  [0,1] d  [0,1]
a  [0,1] a  [0,1]
Operation: (f<n>)  dest<n + 1>, Operation: (f<n>)  dest<n – 1>,
(f<7>)  dest<0> (f<0>)  C,
(C)  dest<7>
Status Affected: N, Z
Status Affected: C, N, Z
Encoding: 0100 01da ffff ffff
Encoding: 0011 00da ffff ffff
Description: The contents of register ‘f’ are rotated
one bit to the left. If ‘d’ is ‘0’, the result Description: The contents of register ‘f’ are rotated
is placed in W. If ‘d’ is ‘1’, the result is one bit to the right through the CARRY
stored back in register ‘f’ (default). flag. If ‘d’ is ‘0’, the result is placed in W.
If ‘a’ is ‘0’, the Access Bank is selected. If ‘d’ is ‘1’, the result is placed back in
If ‘a’ is ‘1’, the BSR is used to select the register ‘f’ (default).
GPR bank. If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘0’ and the extended instruction If ‘a’ is ‘1’, the BSR is used to select the
set is enabled, this instruction operates GPR bank.
in Indexed Literal Offset Addressing If ‘a’ is ‘0’ and the extended instruction
mode whenever f 95 (5Fh). See set is enabled, this instruction operates
Section 24.2.3 “Byte-Oriented and in Indexed Literal Offset Addressing
Bit-Oriented Instructions in Indexed mode whenever f 95 (5Fh). See
Literal Offset Mode” for details. Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
register f
Literal Offset Mode” for details.

Words: 1 C register f
Cycles: 1
Words: 1
Q Cycle Activity:
Cycles: 1
Q1 Q2 Q3 Q4
Decode Read Process Write to Q Cycle Activity:
register ‘f’ Data destination Q1 Q2 Q3 Q4
Decode Read Process Write to
Example: RLNCF REG, 1, 0 register ‘f’ Data destination

Before Instruction
REG = 1010 1011 Example: RRCF REG, 0, 0
After Instruction Before Instruction
REG = 0101 0111 REG = 1110 0110
C = 0
After Instruction
REG = 1110 0110
W = 0111 0011
C = 0

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 PIC18F2XK20/4XK20

RRNCF Rotate Right f (No Carry) SETF Set f

Syntax: RRNCF f {,d {,a}} Syntax: SETF f {,a}
Operands: 0  f  255 Operands: 0  f  255
d  [0,1] a [0,1]
a  [0,1]
Operation: FFh  f
Operation: (f<n>)  dest<n – 1>,
Status Affected: None
(f<0>)  dest<7>
Encoding: 0110 100a ffff ffff
Status Affected: N, Z
Description: The contents of the specified register
Encoding: 0100 00da ffff ffff
are set to FFh.
Description: The contents of register ‘f’ are rotated If ‘a’ is ‘0’, the Access Bank is selected.
one bit to the right. If ‘d’ is ‘0’, the result If ‘a’ is ‘1’, the BSR is used to select the
is placed in W. If ‘d’ is ‘1’, the result is GPR bank.
placed back in register ‘f’ (default). If ‘a’ is ‘0’ and the extended instruction
If ‘a’ is ‘0’, the Access Bank will be set is enabled, this instruction operates
selected (default), overriding the BSR in Indexed Literal Offset Addressing
value. If ‘a’ is ‘1’, then the bank will be mode whenever f 95 (5Fh). See
selected as per the BSR value. Section 24.2.3 “Byte-Oriented and
If ‘a’ is ‘0’ and the extended instruction Bit-Oriented Instructions in Indexed
set is enabled, this instruction operates Literal Offset Mode” for details.
in Indexed Literal Offset Addressing Words: 1
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Cycles: 1
Bit-Oriented Instructions in Indexed Q Cycle Activity:
Literal Offset Mode” for details.
Q1 Q2 Q3 Q4
register f Decode Read Process Write
register ‘f’ Data register ‘f’
Words: 1
Cycles: 1 Example: SETF REG, 1
Q Cycle Activity: Before Instruction
Q1 Q2 Q3 Q4 REG = 5Ah
After Instruction
Decode Read Process Write to
REG = FFh
register ‘f’ Data destination

Example 1: RRNCF REG, 1, 0

Before Instruction
REG = 1101 0111
After Instruction
REG = 1110 1011

Example 2: RRNCF REG, 0, 0

Before Instruction
W = ?
REG = 1101 0111
After Instruction
W = 1110 1011
REG = 1101 0111

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PIC18F2XK20/4XK20

SLEEP Enter Sleep mode SUBFWB Subtract f from W with borrow

Syntax: SLEEP Syntax: SUBFWB f {,d {,a}}
Operands: None Operands: 0 f 255
d  [0,1]
Operation: 00h  WDT,
a  [0,1]
0  WDT postscaler,
1  TO, Operation: (W) – (f) – (C) dest
0  PD Status Affected: N, OV, C, DC, Z
Status Affected: TO, PD
Encoding: 0101 01da ffff ffff
Encoding: 0000 0000 0000 0011
Description: Subtract register ‘f’ and CARRY flag
Description: The Power-down Status bit (PD) is (borrow) from W (2’s complement
cleared. The Time-out Status bit (TO) method). If ‘d’ is ‘0’, the result is stored
is set. Watchdog Timer and its in W. If ‘d’ is ‘1’, the result is stored in
postscaler are cleared. register ‘f’ (default).
The processor is put into Sleep mode If ‘a’ is ‘0’, the Access Bank is
with the oscillator stopped. selected. If ‘a’ is ‘1’, the BSR is used
Words: 1 to select the GPR bank.
If ‘a’ is ‘0’ and the extended instruction
Cycles: 1 set is enabled, this instruction
Q Cycle Activity: operates in Indexed Literal Offset
Addressing mode whenever
Q1 Q2 Q3 Q4
f 95 (5Fh). See Section 24.2.3
Decode No Process Go to “Byte-Oriented and Bit-Oriented
operation Data Sleep Instructions in Indexed Literal Offset
Mode” for details.
Example: SLEEP Words: 1
Before Instruction Cycles: 1
TO = ?
Q Cycle Activity:
PD = ?
After Instruction Q1 Q2 Q3 Q4
TO =1 † Decode Read Process Write to
PD = 0 register ‘f’ Data destination
Example 1: SUBFWB REG, 1, 0
† If WDT causes wake-up, this bit is cleared.
Before Instruction
REG = 3
W = 2
C = 1
After Instruction
REG = FF
W = 2
C = 0
Z = 0
N = 1 ; result is negative
Example 2: SUBFWB REG, 0, 0
Before Instruction
REG = 2
W = 5
C = 1
After Instruction
REG = 2
W = 3
C = 1
Z = 0
N = 0 ; result is positive
Example 3: SUBFWB REG, 1, 0
Before Instruction
REG = 1
W = 2
C = 0
After Instruction
REG = 0
W = 2
C = 1
Z = 1 ; result is zero
N = 0

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 PIC18F2XK20/4XK20

SUBLW Subtract W from literal SUBWF Subtract W from f

Syntax: SUBLW k Syntax: SUBWF f {,d {,a}}
Operands: 0 k 255 Operands: 0 f 255
d  [0,1]
Operation: k – (W) W
a  [0,1]
Status Affected: N, OV, C, DC, Z
Operation: (f) – (W) dest
Encoding: 0000 1000 kkkk kkkk
Status Affected: N, OV, C, DC, Z
Description W is subtracted from the eight-bit
literal ‘k’. The result is placed in W. Encoding: 0101 11da ffff ffff
Description: Subtract W from register ‘f’ (2’s
Words: 1
complement method). If ‘d’ is ‘0’, the
Cycles: 1 result is stored in W. If ‘d’ is ‘1’, the
Q Cycle Activity: result is stored back in register ‘f’
(default).
Q1 Q2 Q3 Q4
If ‘a’ is ‘0’, the Access Bank is
Decode Read Process Write to W selected. If ‘a’ is ‘1’, the BSR is used
literal ‘k’ Data to select the GPR bank.
If ‘a’ is ‘0’ and the extended instruction
Example 1: SUBLW 02h
set is enabled, this instruction
Before Instruction operates in Indexed Literal Offset
W = 01h Addressing mode whenever
C = ?
f 95 (5Fh). See Section 24.2.3
After Instruction
W = 01h “Byte-Oriented and Bit-Oriented
C = 1 ; result is positive Instructions in Indexed Literal Offset
Z = 0 Mode” for details.
N = 0
Words: 1
Example 2: SUBLW 02h
Cycles: 1
Before Instruction
W = 02h Q Cycle Activity:
C = ?
Q1 Q2 Q3 Q4
After Instruction
W = 00h Decode Read Process Write to
C = 1 ; result is zero register ‘f’ Data destination
Z = 1
N = 0 Example 1: SUBWF REG, 1, 0
Example 3: SUBLW 02h Before Instruction
REG = 3
Before Instruction W = 2
W = 03h C = ?
C = ? After Instruction
After Instruction REG = 1
W = FFh ; (2’s complement) W = 2
C = 0 ; result is negative C = 1 ; result is positive
Z = 0 Z = 0
N = 1 N = 0
Example 2: SUBWF REG, 0, 0
Before Instruction
REG = 2
W = 2
C = ?
After Instruction
REG = 2
W = 0
C = 1 ; esult is r ero z
Z = 1
N = 0
Example 3: SUBWF REG, 1, 0
Before Instruction
REG = 1
W = 2
C = ?
After Instruction
REG = FFh ;(2’s complement)
W = 2
C = 0 ; result is negative
Z = 0
N = 1

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PIC18F2XK20/4XK20

SUBWFB Subtract W from f with Borrow SWAPF Swap f

Syntax: SUBWFB f {,d {,a}} Syntax: SWAPF f {,d {,a}}
Operands: 0  f  255 Operands: 0  f  255
d  [0,1] d  [0,1]
a  [0,1] a  [0,1]
Operation: (f) – (W) – (C) dest Operation: (f<3:0>)  dest<7:4>,
Status Affected: N, OV, C, DC, Z (f<7:4>)  dest<3:0>
Encoding: 0101 10da ffff ffff Status Affected: None
Description: Subtract W and the CARRY flag Encoding: 0011 10da ffff ffff
(borrow) from register ‘f’ (2’s comple-
ment method). If ‘d’ is ‘0’, the result is Description: The upper and lower nibbles of register
stored in W. If ‘d’ is ‘1’, the result is ‘f’ are exchanged. If ‘d’ is ‘0’, the result
stored back in register ‘f’ (default). is placed in W. If ‘d’ is ‘1’, the result is
If ‘a’ is ‘0’, the Access Bank is selected. placed in register ‘f’ (default).
If ‘a’ is ‘1’, the BSR is used to select the If ‘a’ is ‘0’, the Access Bank is selected.
GPR bank. If ‘a’ is ‘1’, the BSR is used to select the
If ‘a’ is ‘0’ and the extended instruction GPR bank.
set is enabled, this instruction operates If ‘a’ is ‘0’ and the extended instruction
in Indexed Literal Offset Addressing set is enabled, this instruction operates
mode whenever f 95 (5Fh). See in Indexed Literal Offset Addressing
Section 24.2.3 “Byte-Oriented and mode whenever f 95 (5Fh). See
Bit-Oriented Instructions in Indexed Section 24.2.3 “Byte-Oriented and
Literal Offset Mode” for details. Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Words: 1
Cycles: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4 Q Cycle Activity:
Decode Read Process Write to Q1 Q2 Q3 Q4
register ‘f’ Data destination Decode Read Process Write to
Example 1: SUBWFB REG, 1, 0 register ‘f’ Data destination
Before Instruction
REG = 19h (0001 1001) Example: SWAPF REG, 1, 0
W = 0Dh (0000 1101)
C = 1 Before Instruction
After Instruction REG = 53h
REG = 0Ch (0000 1100) After Instruction
W = 0Dh (0000 1101)
C = 1 REG = 35h
Z = 0
N = 0 ; result is positive
Example 2: SUBWFB REG, 0, 0
Before Instruction
REG = 1Bh (0001 1011)
W = 1Ah (0001 1010)
C = 0
After Instruction
REG = 1Bh (0001 1011)
W = 00h
C = 1
Z = 1 ; result is zero
N = 0
Example 3: SUBWFB REG, 1, 0
Before Instruction
REG = 03h (0000 0011)
W = 0Eh (0000 1110)
C = 1
After Instruction
REG = F5h (1111 0101)
; [2’s comp]
W = 0Eh (0000 1110)
C = 0
Z = 0
N = 1 ; result is negative

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 PIC18F2XK20/4XK20

TBLRD Table Read TBLRD Table Read (Continued)

Syntax: TBLRD ( *; *+; *-; +*) Example1: TBLRD *+ ;
Operands: None Before Instruction
TABLAT = 55h
Operation: if TBLRD *, TBLPTR = 00A356h
(Prog Mem (TBLPTR))  TABLAT; MEMORY (00A356h) = 34h
TBLPTR – No Change; After Instruction
if TBLRD *+, TABLAT = 34h
(Prog Mem (TBLPTR))  TABLAT; TBLPTR = 00A357h
(TBLPTR) + 1  TBLPTR;
Example2: TBLRD +* ;
if TBLRD *-,
(Prog Mem (TBLPTR))  TABLAT; Before Instruction
(TBLPTR) – 1  TBLPTR; TABLAT = AAh
TBLPTR = 01A357h
if TBLRD +*, MEMORY (01A357h) = 12h
(TBLPTR) + 1  TBLPTR; MEMORY (01A358h) = 34h
(Prog Mem (TBLPTR))  TABLAT; After Instruction
Status Affected: None TABLAT = 34h
TBLPTR = 01A358h
Encoding: 0000 0000 0000 10nn
nn=0 *
=1 *+
=2 *-
=3 +*
Description: This instruction is used to read the contents
of Program Memory (P.M.). To address the
program memory, a pointer called Table
Pointer (TBLPTR) is used.
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory. TBLPTR
has a 2-Mbyte address range.
TBLPTR[0] = 0: Least Significant Byte
of Program Memory
Word
TBLPTR[0] = 1: Most Significant Byte
of Program Memory
Word
The TBLRD instruction can modify the value
of TBLPTR as follows:
• no change
• post-increment
• post-decrement
• pre-increment
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No No No
operation operation operation
No No operation No No operation
operation (Read Program operation (Write TABLAT)
Memory)

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PIC18F2XK20/4XK20

TBLWT Table Write TBLWT Table Write (Continued)

Syntax: TBLWT ( *; *+; *-; +*) Example1: TBLWT *+;
Operands: None
Before Instruction
Operation: if TBLWT*, = TABLAT 55h
(TABLAT)  Holding Register; TBLPTR = 00A356h
TBLPTR – No Change; HOLDING REGISTER
(00A356h) = FFh
if TBLWT*+,
After Instructions (table write completion)
(TABLAT)  Holding Register;
TABLAT = 55h
(TBLPTR) + 1  TBLPTR; TBLPTR = 00A357h
if TBLWT*-, HOLDING REGISTER
(TABLAT)  Holding Register; (00A356h) = 55h
(TBLPTR) – 1  TBLPTR; Example 2: TBLWT +*;
if TBLWT+*,
(TBLPTR) + 1  TBLPTR; Before Instruction
(TABLAT)  Holding Register; TABLAT = 34h
TBLPTR = 01389Ah
Status Affected: None HOLDING REGISTER
(01389Ah) = FFh
Encoding: 0000 0000 0000 11nn HOLDING REGISTER
nn=0 * (01389Bh) = FFh
=1 *+ After Instruction (table write completion)
=2 *- TABLAT = 34h
=3 +* TBLPTR = 01389Bh
HOLDING REGISTER
Description: This instruction uses the 3 LSBs of (01389Ah) = FFh
TBLPTR to determine which of the HOLDING REGISTER
8 holding registers the TABLAT is written (01389Bh) = 34h
to. The holding registers are used to
program the contents of Program
Memory (P.M.). (Refer to Section 6.0
“Flash Program Memory” for additional
details on programming Flash memory.)
The TBLPTR (a 21-bit pointer) points to
each byte in the program memory.
TBLPTR has a 2-MByte address range.
The LSb of the TBLPTR selects which
byte of the program memory location to
access.
TBLPTR[0] = 0: Least Significant
Byte of Program
Memory Word
TBLPTR[0] = 1: Most Significant
Byte of Program
Memory Word
The TBLWT instruction can modify the
value of TBLPTR as follows:
• no change
• post-increment
• post-decrement
• pre-increment
Words: 1
Cycles: 2
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode No No No
operation operation operation
No No No No
operation operation operation operation
(Read (Write to
TABLAT) Holding
Register )

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 PIC18F2XK20/4XK20

TSTFSZ Test f, skip if 0 XORLW Exclusive OR literal with W

Syntax: TSTFSZ f {,a} Syntax: XORLW k
Operands: 0  f  255 Operands: 0 k 255
a  [0,1]
Operation: (W) .XOR. k W
Operation: skip if f = 0
Status Affected: N, Z
Status Affected: None
Encoding: 0000 1010 kkkk kkkk
Encoding: 0110 011a ffff ffff
Description: The contents of W are XORed with
Description: If ‘f’ = 0, the next instruction fetched the 8-bit literal ‘k’. The result is placed
during the current instruction execution in W.
is discarded and a NOP is executed,
Words: 1
making this a two-cycle instruction.
If ‘a’ is ‘0’, the Access Bank is selected. Cycles: 1
If ‘a’ is ‘1’, the BSR is used to select the Q Cycle Activity:
GPR bank.
Q1 Q2 Q3 Q4
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates Decode Read Process Write to W
in Indexed Literal Offset Addressing literal ‘k’ Data
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and Example: XORLW 0AFh
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details. Before Instruction
W = B5h
Words: 1
After Instruction
Cycles: 1(2)
W = 1Ah
Note: 3 cycles if skip and followed
by a 2-word instruction.
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process No
register ‘f’ Data operation
If skip:
Q1 Q2 Q3 Q4
No No No No
operation operation operation operation
If skip and followed by 2-word instruction:
Q1 Q2 Q3 Q4
No No No No
operation operation operation operation
No No No No
operation operation operation operation

Example: HERE TSTFSZ CNT, 1

NZERO :
ZERO :
Before Instruction
= PC Address (HERE)
After Instruction
If CNT = 00h,
= PC Address (ZERO)
If CNT  00h,
= PC Address (NZERO)

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PIC18F2XK20/4XK20

XORWF Exclusive OR W with f

Syntax: XORWF f {,d {,a}}
Operands: 0  f  255
d  [0,1]
a  [0,1]
Operation: (W) .XOR. (f) dest
Status Affected: N, Z
Encoding: 0001 10da ffff ffff
Description: Exclusive OR the contents of W with
register ‘f’. If ‘d’ is ‘0’, the result is stored
in W. If ‘d’ is ‘1’, the result is stored back
in the register ‘f’ (default).
If ‘a’ is ‘0’, the Access Bank is selected.
If ‘a’ is ‘1’, the BSR is used to select the
GPR bank.
If ‘a’ is ‘0’ and the extended instruction
set is enabled, this instruction operates
in Indexed Literal Offset Addressing
mode whenever f 95 (5Fh). See
Section 24.2.3 “Byte-Oriented and
Bit-Oriented Instructions in Indexed
Literal Offset Mode” for details.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read Process Write to
register ‘f’ Data destination

Example: XORWF REG, 1, 0

Before Instruction
REG = AFh
W = B5h
After Instruction
REG = 1Ah
W = B5h

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 PIC18F2XK20/4XK20
24.2 Extended Instruction Set A summary of the instructions in the extended instruc-
tion set is provided in Table 24-3. Detailed descriptions
In addition to the standard 75 instructions of the PIC18 are provided in Section 24.2.2 “Extended Instruction
instruction s et, PIC 18F2XK20/4XK20 de vices also Set”. The opcode field descriptions in Table 24-1 apply
provide an op tional ex tension to t he core C PU to bo th the standard and ex tended PIC 18 i nstruction
functionality. Th e add ed fe atures include eig ht sets.
additional in structions that au gment in direct an d
indexed addressing operations and the implementation Note: The in struction se t ex tension an d th e
of Indexed Literal Offset Addressing mode for many of Indexed Literal Of fset Addre ssing mode
the standard PIC18 instructions. were designed for optimizing applications
written in C; the user may likely never use
The additional features of the extended instruction set
these i nstructions directly i n assembler.
are disabled by default. To enable them, users must set
The s yntax for th ese co mmands i s p ro-
the XINST Configuration bit.
vided as a reference for users who may be
The in structions in th e ext ended s et ca n all be reviewing co de that ha s be en ge nerated
classified as literal operations, which either manipulate by a compiler.
the F ile Sel ect R egisters, or use th em for i ndexed
addressing. T wo of the instructions, ADDFSR an d 24.2.1 EXTENDED INSTRUCTION SYNTAX
SUBFSR, each have an additional special instantiation
Most of the ex tended instructions us e i ndexed
for u sing F SR2. These versions ( ADDULNK an d
arguments, using one of the File Select Registers and
SUBULNK) allow for automatic return after execution.
some offset to specify a source or destination register.
The extended instructions are specifically implemented When an argument for an instruction serves as part of
to optimize re-entrant program code (that is, code that indexed addressing, it is enclosed in s quare brackets
is r ecursive o r t hat uses a s oftware stack) written in (“[ ]”). This is done to indicate that the argument is used
high-level la nguages, particularly C . Am ong oth er as an index or offset. MPASM™ Assembler will flag an
things, th ey allow users w orking i n high-level error if it determines that an index or offset value is not
languages to perform ce rtain ope rations on da ta bracketed.
structures more efficiently. These include:
When the extended instruction set is enabled, brackets
• dynamic allocation and deallocation of software are als o us ed to indicate ind ex arguments in byt e-
stack space when entering and leaving oriented and bit-oriented instructions. This is in addition
subroutines to other changes in their syntax. For more details, see
• function pointer invocation Section 24.2.3.1 “Extended Instruction Syntax with
• software Stack Pointer manipulation Standard PIC18 Commands”.
• manipulation of variables located in a software Note: In the p ast, sq uare brackets h ave bee n
stack used to denote optional arguments in the
PIC18 and earlier instruction sets. In this
text and goi ng forw ard, o ptional
arguments are denoted by braces (“{ }”).

TABLE 24-3: EXTENSIONS TO THE PIC18 INSTRUCTION SET

Mnemonic, 16-Bit Instruction Word Status

Description Cycles
Operands MSb LSb Affected

ADDFSR f, k Add literal to FSR 1 1110 1000 ffkk kkkk None

ADDULNK k Add literal to FSR2 and return 2 1110 1000 11kk kkkk None
CALLW Call subroutine using WREG 2 0000 0000 0001 0100 None
MOVSF zs, fd Move zs (source) to 1st word 2 1110 1011 0zzz zzzz None
fd (destination) 2nd word 1111 ffff ffff ffff
MOVSS zs, zd Move zs (source) to 1st word 2 1110 1011 1zzz zzzz None
zd (destination) 2nd word 1111 xxxx xzzz zzzz
PUSHL k Store literal at FSR2, 1 1110 1010 kkkk kkkk None
decrement FSR2
SUBFSR f, k Subtract literal from FSR 1 1110 1001 ffkk kkkk None
SUBULNK k Subtract literal from FSR2 and 2 1110 1001 11kk kkkk None
return

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PIC18F2XK20/4XK20
24.2.2 EXTENDED INSTRUCTION SET

ADDFSR Add Literal to FSR ADDULNK Add Literal to FSR2 and Return
Syntax: ADDFSR f, k Syntax: ADDULNK k
Operands: 0  k  63 Operands: 0  k  63
f  [ 0, 1, 2 ] Operation: FSR2 + k  FSR2,
Operation: FSR(f) + k  FSR(f) (TOS) PC
Status Affected: None Status Affected: None
Encoding: 1110 1000 ffkk kkkk Encoding: 1110 1000 11kk kkkk
Description: The 6-bit literal ‘k’ is added to the Description: The 6-bit literal ‘k’ is added to the
contents of the FSR specified by ‘f’. contents of FSR2. A RETURN is then
Words: 1 executed by loading the PC with the
Cycles: 1 TOS.
The instruction takes two cycles to
Q Cycle Activity:
execute; a NOP is performed during
Q1 Q2 Q3 Q4
the second cycle.
Decode Read Process Write to This may be thought of as a special
literal ‘k’ Data FSR case of the ADDFSR instruction,
where f = 3 (binary ‘11’); it operates
only on FSR2.
Example: ADDFSR 2, 23h Words: 1
Before Instruction Cycles: 2
FSR2 = 03FFh
After Instruction
Q Cycle Activity:
FSR2 = 0422h
Q1 Q2 Q3 Q4
Decode Read Process Write to
literal ‘k’ Data FSR
No No No No
Operation Operation Operation Operation

Example: ADDULNK 23h

Before Instruction
FSR2 = 03FFh
PC = 0100h
After Instruction
FSR2 = 0422h
PC = (TOS)

Note: All PIC18 instructions may take an optional label argument preceding the instruction mnemonic for use in
symbolic addressing. If a label is used, the instruction syntax then becomes: {label} instruction argument(s).

DS41303G-page 358  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

CALLW Subroutine Call Using WREG MOVSF Move Indexed to f

Syntax: CALLW Syntax: MOVSF [zs], fd
Operands: None Operands: 0  zs  127
0  fd  4095
Operation: (PC + 2)  TOS,
(W)  PCL, Operation: ((FSR2) + zs)  fd
(PCLATH)  PCH,
Status Affected: None
(PCLATU)  PCU
Encoding:
Status Affected: None
1st word (source) 1110 1011 0zzz zzzzs
Encoding: 0000 0000 0001 0100 2nd word (destin.) 1111 ffff ffff ffffd
Description First, the return address (PC + 2) is Description: The contents of the source register are
pushed onto the return stack. Next, the moved to destination register ‘fd’. The
contents of W are written to PCL; the actual address of the source register is
existing value is discarded. Then, the determined by adding the 7-bit literal
contents of PCLATH and PCLATU are offset ‘zs’ in the first word to the value of
latched into PCH and PCU, FSR2. The address of the destination
respectively. The second cycle is register is specified by the 12-bit literal
executed as a NOP instruction while the ‘fd’ in the second word. Both addresses
new next instruction is fetched. can be anywhere in the 4096-byte data
Unlike CALL, there is no option to space (000h to FFFh).
update W, Status or BSR. The MOVSF instruction cannot use the
PCL, TOSU, TOSH or TOSL as the
Words: 1
destination register.
Cycles: 2 If the resultant source address points to
Q Cycle Activity: an indirect addressing register, the
value returned will be 00h.
Q1 Q2 Q3 Q4
Decode Read PUSH PC to No Words: 2
WREG stack operation Cycles: 2
No No No No Q Cycle Activity:
operation operation operation operation
Q1 Q2 Q3 Q4
Decode Determine Determine Read
Example: HERE CALLW source addr source addr source reg
Decode No No Write
Before Instruction
PC = address (HERE) operation operation register ‘f’
PCLATH = 10h No dummy (dest)
PCLATU = 00h read
W = 06h
After Instruction
PC = 001006h
TOS = address (HERE + 2) Example: MOVSF [05h], REG2
PCLATH = 10h Before Instruction
PCLATU= 00h FSR2 = 80h
W = 06h
Contents
of 85h = 33h
REG2 = 11h
After Instruction
FSR2 = 80h
Contents
of 85h = 33h
REG2 = 33h

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PIC18F2XK20/4XK20

MOVSS Move Indexed to Indexed PUSHL Store Literal at FSR2, Decrement FSR2
Syntax: MOVSS [zs], [zd] Syntax: PUSHL k
Operands: 0  zs  127 Operands: 0k  255
0  zd  127
Operation: k  (FSR2),
Operation: ((FSR2) + zs)  ((FSR2) + zd) FSR2 – 1  FSR2
Status Affected: None
Status Affected: None
Encoding:
Encoding: 1111 1010 kkkk kkkk
1st word (source) 1110 1011 1zzz zzzzs
2nd word (dest.) 1111 xxxx xzzz zzzzd Description: The 8-bit literal ‘k’ is written to the data
memory address specified by FSR2. FSR2
Description The contents of the source register are
moved to the destination register. The is decremented by 1 after the operation.
addresses of the source and destination This instruction allows users to push values
onto a software stack.
registers are determined by adding the
7-bit literal offsets ‘zs’ or ‘zd’, Words: 1
respectively, to the value of FSR2. Both
Cycles: 1
registers can be located anywhere in
the 4096-byte data memory space Q Cycle Activity:
(000h to FFFh). Q1 Q2 Q3 Q4
The MOVSS instruction cannot use the Decode Read ‘k’ Process Write to
PCL, TOSU, TOSH or TOSL as the data destination
destination register.
If the resultant source address points to
an indirect addressing register, the Example: PUSHL 08h
value returned will be 00h. If the
resultant destination address points to Before Instruction
an indirect addressing register, the FSR2H:FSR2L = 01ECh
Memory (01ECh) = 00h
instruction will execute as a NOP.
Words: 2 After Instruction
Cycles: 2 FSR2H:FSR2L = 01EBh
Memory (01ECh) = 08h
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Determine Determine Read
source addr source addr source reg
Decode Determine Determine Write
dest addr dest addr to dest reg

Example: MOVSS [05h], [06h]

Before Instruction
FSR2 = 80h
Contents
of 85h = 33h
Contents
of 86h = 11h
After Instruction
FSR2 = 80h
Contents
of 85h = 33h
Contents
of 86h = 33h

DS41303G-page 360  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

SUBFSR Subtract Literal from FSR SUBULNK Subtract Literal from FSR2 and Return
Syntax: SUBFSR f, k Syntax: SUBULNK k
Operands: 0  k  63 Operands: 0  k  63
f  [ 0, 1, 2 ] Operation: FSR2 – k  FSR2
Operation: FSR(f) – k  FSRf (TOS) PC
Status Affected: None Status Affected: None
Encoding: 1110 1001 ffkk kkkk Encoding: 1110 1001 11kk kkkk
Description: The 6-bit literal ‘k’ is subtracted from Description: The 6-bit literal ‘k’ is subtracted from the
the contents of the FSR specified by contents of the FSR2. A RETURN is then
‘f’. executed by loading the PC with the TOS.
Words: 1 The instruction takes two cycles to
execute; a NOP is performed during the
Cycles: 1
second cycle.
Q Cycle Activity:
This may be thought of as a special case of
Q1 Q2 Q3 Q4 the SUBFSR instruction, where f = 3 (binary
Decode Read Process Write to ‘11’); it operates only on FSR2.
register ‘f’ Data destination Words: 1
Cycles: 2
Q Cycle Activity:
Example: SUBFSR 2, 23h
Before Instruction Q1 Q2 Q3 Q4
FSR2 = 03FFh Decode Read Process Write to
register ‘f’ Data destination
After Instruction
FSR2 = 03DCh No No No No
Operation Operation Operation Operation

Example: SUBULNK 23h

Before Instruction
FSR2 = 03FFh
PC = 0100h
After Instruction
FSR2 = 03DCh
PC = (TOS)

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PIC18F2XK20/4XK20
24.2.3 BYTE-ORIENTED AND 24.2.3.1 Extended Instruction Syntax with
BIT-ORIENTED INSTRUCTIONS IN Standard PIC18 Commands
INDEXED LITERAL OFFSET MODE When the extended instruction set is enabled, the file
Note: Enabling th e PIC 18 i nstruction s et register argument, ‘f’, in the standard byte-oriented and
extension m ay c ause legacy applications bit-oriented commands is replaced with the literal offset
to behave erratically or fail entirely. value, ‘k’. As already noted, this occurs only when ‘f’ is
less than or equal to 5Fh. When an offset value is used,
In addition to eight new commands in the extended set, it must be indicated by square brackets (“[ ]”). As with
enabling th e ex tended in struction se t al so e nables the extended instructions, the use of brackets indicates
Indexed Literal Offset Addressing mode (Section 5.5.1 to the compiler that the value is to be interpreted as an
“Indexed Addressing with Literal Offset”). This has index o r an of fset. O mitting the brackets, or using a
a significant impact on the way that many commands of value greater than 5Fh within brackets, will generate an
the standard PIC18 instruction set are interpreted. error in the MPASM Assembler.
When th e e xtended set i s disabled, addresses If the index argument is properly bracketed for Indexed
embedded in op codes a re t reated as li teral memory Literal Offset Addressing, the Access RAM argument is
locations: either as a location in the Access Bank (‘a’ = never specified; it will automatically be assumed to be
0), or in a GPR bank designated by the BSR (‘a’ = 1). ‘0’. This is in contrast to standard operation (extended
When the extended instruction set is enabled and ‘a’ = instruction set disabled) when ‘a’ is set on the basis of
0, however, a file register argument of 5Fh or less is the t arget a ddress. Declaring the Ac cess R AM bi t i n
interpreted as an offset from the pointer value in FSR2 this mo de will al so generate a n er ror i n th e M PASM
and not as a literal address. For practical purposes, this Assembler.
means that all instructions that use the Access RAM bit
as an argu ment – that is , all byt e-oriented and bit- The destination argument, ‘d’, functions as before.
oriented instructions, or almost half of the core PIC18 In the la test ve rsions of the MPASM™ a ssembler,
instructions – m ay behave differently w hen the language support for the extended instruction set must
extended instruction set is enabled. be ex plicitly in voked. Th is i s d one w ith eith er th e
When the content of FSR2 is 00h, the boundaries of the command lin e option, /y, or t he PE di rective i n th e
Access RAM are essentially remapped to their original source listing.
values. Thi s m ay be us eful in creating bac kward
compatible code. If th is te chnique i s used, it m ay b e 24.2.4 CONSIDERATIONS WHEN
necessary to save t he v alue o f FSR 2 and res tore it ENABLING THE EXTENDED
when moving back and forth between C and assembly INSTRUCTION SET
routines in ord er to pre serve the Stack Pointer. Users It is important to note that the extensions to the instruc-
must also keep in mind the syntax requirements of the tion set may not be beneficial to all users. In particular,
extended i nstruction s et (see Section 24.2.3.1 users w ho are not w riting code tha t use s a s oftware
“Extended Instruction Syntax with Standard PIC18 stack may not benefit from using the extensions to the
Commands”). instruction set.
Although the Indexed Literal Offset Addressing mode Additionally, th e In dexed Li teral O ffset Addr essing
can b e v ery useful for dy namic s tack a nd po inter mode ma y c reate i ssues w ith le gacy applications
manipulation, it c an also be very annoying if a simple written to th e PIC1 8 as sembler. Thi s i s b ecause
arithmetic ope ration i s c arried out o n th e w rong instructions in the legacy code may attempt to address
register. U sers who a re a ccustomed to th e PI C18 registers in the Access Bank below 5Fh. Since these
programming m ust ke ep i n m ind th at, w hen th e addresses are int erpreted as li teral of fsets to FSR2
extended instruction set is enabled, register addresses when the ins truction s et ex tension is ena bled, th e
of 5Fh or le ss are use d for Ind exed Li teral Of fset application ma y rea d or w rite to the w rong dat a
Addressing. addresses.
Representative examples of typical byte-oriented and When po rting a n a pplication to t he PIC18F2XK20/
bit-oriented i nstructions i n t he I ndexed Li teral O ffset 4XK20, it is very important to consider the type of code.
Addressing mode are provided on the following page to A large, re-entrant application that is written in ‘C’ and
show ho w execution is af fected. The operand c ondi- would ben efit fro m efficient c ompilation will do w ell
tions s hown in t he e xamples are app licable t o al l when us ing th e in struction set extensions. Leg acy
instructions of these types. applications that heavily use the Access Bank will most
likely no t be nefit f rom us ing th e e xtended i nstruction
set.

DS41303G-page 362  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

ADD W to Indexed Bit Set Indexed

ADDWF BSF
(Indexed Literal Offset mode) (Indexed Literal Offset mode)
Syntax: ADDWF [k] {,d} Syntax: BSF [k], b
Operands: 0  k  95 Operands: 0  f  95
d  [0,1] 0b7
Operation: (W) + ((FSR2) + k)  dest Operation: 1  ((FSR2) + k)<b>
Status Affected: N, OV, C, DC, Z Status Affected: None
Encoding: 0010 01d0 kkkk kkkk Encoding: 1000 bbb0 kkkk kkkk
Description: The contents of W are added to the Description: Bit ‘b’ of the register indicated by FSR2,
contents of the register indicated by offset by the value ‘k’, is set.
FSR2, offset by the value ‘k’.
Words: 1
If ‘d’ is ‘0’, the result is stored in W. If ‘d’
is ‘1’, the result is stored back in Cycles: 1
register ‘f’ (default). Q Cycle Activity:
Words: 1 Q1 Q2 Q3 Q4
Cycles: 1 Decode Read Process Write to
register ‘f’ Data destination
Q Cycle Activity:
Q1 Q2 Q3 Q4
Example: BSF [FLAG_OFST], 7
Decode Read ‘k’ Process Write to
Before Instruction
Data destination
FLAG_OFST = 0Ah
FSR2 = 0A00h
Example: ADDWF [OFST] , 0 Contents
of 0A0Ah = 55h
Before Instruction
After Instruction
W = 17h Contents
OFST = 2Ch of 0A0Ah = D5h
FSR2 = 0A00h
Contents
of 0A2Ch = 20h
After Instruction
W = 37h
Contents
Set Indexed
SETF
of 0A2Ch = 20h (Indexed Literal Offset mode)
Syntax: SETF [k]
Operands: 0  k  95
Operation: FFh  ((FSR2) + k)
Status Affected: None
Encoding: 0110 1000 kkkk kkkk
Description: The contents of the register indicated by
FSR2, offset by ‘k’, are set to FFh.
Words: 1
Cycles: 1
Q Cycle Activity:
Q1 Q2 Q3 Q4
Decode Read ‘k’ Process Write
Data register

Example: SETF [OFST]

Before Instruction
OFST = 2Ch
FSR2 = 0A00h
Contents
of 0A2Ch = 00h
After Instruction
Contents
of 0A2Ch = FFh

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PIC18F2XK20/4XK20
24.2.5 SPECIAL CONSIDERATIONS WITH
MICROCHIP MPLAB® IDE TOOLS
The latest versions of Microchip’s software tools have
been designed to fully support the extended instruction
set of the PIC18F2XK20/4XK20 family of devices. This
includes t he M PLAB C 18 C c ompiler, MP ASM
assembly la nguage an d M PLAB I ntegrated
Development Environment (IDE).
When se lecting a t arget device f or s oftware
development, MPLAB IDE will automatically set default
Configuration bits for that device. The default setting for
the XIN ST C onfiguration b it is ‘0’, dis abling th e
extended i nstruction s et a nd Ind exed L iteral Offset
Addressing mode. For proper execution of applications
developed to take adv antage of the extended
instruction se t, X INST m ust be se t du ring
programming.
To d evelop s oftware for the extended in struction se t,
the user must enable support for the instructions and
the Indexed Addressing mode in their language tool(s).
Depending on the environment being used, this may be
done in several ways:
• A menu option, or dialog box within the
environment, that allows the user to configure the
language tool and its settings for the project
• A command line option
• A directive in the source code
These options vary betw een dif ferent com pilers,
assemblers and development environments. Users are
encouraged to review the documentation accompanying
their dev elopment system s for the appropriate
information.

DS41303G-page 364  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
25.0 DEVELOPMENT SUPPORT 25.1 MPLAB Integrated Development
Environment Software
The P IC® microcontrollers a nd d sPIC® di gital signal
controllers are supported with a f ull range of software The MPLAB IDE software brings an ease of s oftware
and hardware development tools: development pre viously unseen in the 8/1 6/32-bit
• Integrated Development Environment microcontroller market. The MPLAB IDE is a Windows®
operating system-based application that contains:
- MPLAB® IDE Software
• Compilers/Assemblers/Linkers • A single graphical interface to all debugging tools
- MPLAB C Compiler for Various Device - Simulator
Families - Programmer (sold separately)
- HI-TECH C for Various Device Families - In-Circuit Emulator (sold separately)
- MPASMTM Assembler - In-Circuit Debugger (sold separately)
- MPLINKTM Object Linker/ • A full-featured editor with color-coded context
MPLIBTM Object Librarian • A multiple project manager
- MPLAB Assembler/Linker/Librarian for • Customizable data windows with direct edit of
Various Device Families contents
• Simulators • High-level source code debugging
- MPLAB SIM Software Simulator • Mouse over variable inspection
• Emulators • Drag and drop variables from source to watch
- MPLAB REAL ICE™ In-Circuit Emulator windows
• In-Circuit Debuggers • Extensive on-line help
- MPLAB ICD 3 • Integration of select third party tools, such as
- PICkit™ 3 Debug Express IAR C Compilers
• Device Programmers The MPLAB IDE allows you to:
- PICkit™ 2 Programmer • Edit your source files (either C or assembly)
- MPLAB PM3 Device Programmer • One-touch compile or assemble, and download to
• Low-Cost Demonstration/Development Boards, emulator and simulator tools (automatically
Evaluation Kits, and Starter Kits updates all project information)
• Debug using:
- Source files (C or assembly)
- Mixed C and assembly
- Machine code
MPLAB IDE s upports multiple d ebugging to ols i n a
single dev elopment p aradigm, from th e co st-effective
simulators, t hrough low-cost i n-circuit de buggers, to
full-featured emu lators. Thi s el iminates the learning
curve when upgrading to tools with increased flexibility
and power.

 2010 Microchip Technology Inc. DS41303G-page 365

PIC18F2XK20/4XK20
25.2 MPLAB C Compilers for Various 25.5 MPLINK Object Linker/
Device Families MPLIB Object Librarian
The M PLAB C C ompiler co de development sy stems The M PLINK O bject L inker c ombines relocatable
are complete ANSI C compilers for Microchip’s PIC18, objects c reated b y t he MPASM Assembler an d th e
PIC24 and PIC32 families of microcontrollers and the MPLAB C18 C Compiler. It can link relocatable objects
dsPIC30 and dsPIC33 families of digital signal control- from p recompiled l ibraries, using d irectives f rom a
lers. T hese compilers p rovide p owerful integration linker script.
capabilities, s uperior co de o ptimization an d ea se of The MPLIB Object Librarian manages the creation and
use. modification of library files of precompiled code. When
For easy source level debugging, the compilers provide a routine from a library is called from a source file, only
symbol information that is optimized to the MPLAB IDE the modules that contain that routine will be linked in
debugger. with the ap plication. This all ows la rge li braries to be
used efficiently in many different applications.
25.3 HI-TECH C for Various Device The object linker/library features include:
Families • Efficient linking of single libraries instead of many
The HI-TECH C Compiler code development systems smaller files
are co mplete AN SI C com pilers for Microchip’s PIC • Enhanced code maintainability by grouping
family of microcontrollers and the dsPIC family of digital related modules together
signal controllers. T hese c ompilers p rovide po werful • Flexible creation of libraries with easy module
integration c apabilities, o mniscient code ge neration listing, replacement, deletion and extraction
and ease of use.
For easy source level debugging, the compilers provide 25.6 MPLAB Assembler, Linker and
symbol information that is optimized to the MPLAB IDE Librarian for Various Device
debugger. Families
The compilers include a macro assembler, linker, pre-
MPLAB As sembler p roduces re locatable m achine
processor, and one-step driver, and can run on multiple
code from sy mbolic as sembly la nguage for PIC24,
platforms.
PIC32 an d ds PIC de vices. MP LAB C Compiler us es
the assembler to produce its object file. The assembler
25.4 MPASM Assembler generates rel ocatable obj ect fi les tha t ca n th en b e
The MP ASM Assembler is a full -featured, un iversal archived or linked with other relocatable object files and
macro assembler for PIC10/12/16/18 MCUs. archives to create an executable file. Notable features
of the assembler include:
The M PASM As sembler g enerates re locatable ob ject
files for the MPLINK Object Linker, Intel® standard HEX • Support for the entire device instruction set
files, M AP file s to det ail memory us age and symbol • Support for fixed-point and floating-point data
reference, absolute LST files that contain source lines • Command line interface
and g enerated m achine c ode and C OFF fil es for • Rich directive set
debugging.
• Flexible macro language
The MPASM Assembler features include: • MPLAB IDE compatibility
• Integration into MPLAB IDE projects
• User-defined macros to streamline
assembly code
• Conditional assembly for multi-purpose
source files
• Directives that allow complete control over the
assembly process

DS41303G-page 366  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
25.7 MPLAB SIM Software Simulator 25.9 MPLAB ICD 3 In-Circuit Debugger
The M PLAB SIM Sof tware Sim ulator al lows c ode
System
development in a P C-hosted en vironment by si mulat- MPLAB IC D 3 In-C ircuit D ebugger System is Micro-
ing the PIC MCUs and dsPIC® DSCs on an instruction chip's m ost cost e ffective h igh-speed ha rdware
level. On any given instruction, the data areas can be debugger/programmer for Microchip Flash Digital Sig-
examined or modified and stimuli can be applied from nal Con troller (DSC) an d m icrocontroller (MCU)
a comprehensive stimulus controller. Registers can be devices. It debugs and programs PIC® Flash microcon-
logged to files for further run-time analysis. The trace trollers and dsPIC® DSCs with the powerful, yet easy-
buffer and logic analyzer display extend the po wer of to-use graphical user int erface of MPL AB Integrated
the s imulator t o rec ord and trac k p rogram exe cution, Development Environment (IDE).
actions on I/O, most peripherals and internal registers.
The MPLAB ICD 3 In-Circuit D ebugger probe is con-
The M PLAB SIM So ftware Simulator ful ly supports nected to the design engineer's PC using a high-speed
symbolic de bugging u sing the MPL AB C Compilers, USB 2.0 interface and is connected to the target with a
and t he M PASM a nd M PLAB Ass emblers. The so ft- connector compatible with the MPLAB ICD 2 or MPLAB
ware s imulator o ffers the fl exibility to develop an d REAL ICE systems (RJ-11). MPLAB ICD 3 supports all
debug c ode o utside of the ha rdware l aboratory e nvi- MPLAB ICD 2 headers.
ronment, making it an excellent, economical software
development tool. 25.10 PICkit 3 In-Circuit Debugger/
Programmer and
25.8 MPLAB REAL ICE In-Circuit
PICkit 3 Debug Express
Emulator System
The MPLAB PICkit 3 allows debugging and program-
MPLAB REAL IC E In-C ircuit Emulator Sy stem is ming of PIC ® and dsPIC® Flash microcontrollers at a
Microchip’s next generation high-spee d emulator for most affordable price point using the powerful graphical
Microchip Flash DSC and MCU devices. It debugs and user interface of the MPLAB Integrated Development
programs PIC ® Flash MCUs and ds PIC® Flash D SCs Environment (IDE). The MPLAB PICkit 3 is connected
with the easy-to-use, powerful graphical user interface of to the de sign en gineer's PC us ing a full speed U SB
the MPLAB Integrated Development Environment (IDE), interface a nd can b e connected t o t he target via a n
included with each kit. Microchip de bug (R J-11) co nnector (c ompatible w ith
The emulator is connected to the design engineer’s PC MPLAB ICD 3 and MPLAB REAL ICE). The connector
using a high-speed USB 2.0 interface and is connected uses tw o device I/O pins and the reset line to im ple-
to the target with either a connector compatible with in- ment i n-circuit d ebugging a nd In-Circuit Se rial Pro-
circuit debugger systems (RJ11) or with the new high- gramming™.
speed, noise tolerant, Low -Voltage D ifferential S ignal The PICkit 3 Debug Express include the PICkit 3, demo
(LVDS) interconnection (CAT5). board and microcontroller, hookup cables and CDROM
The emulator is field upgradable through future firmware with user’s g uide, lessons, t utorial, c ompiler and
downloads in MPLAB ID E. In upc oming rele ases of MPLAB IDE software.
MPLAB I DE, new devices will be supported, and new
features will be added. MPLAB REAL ICE offers signifi-
cant adva ntages o ver com petitive emula tors incl uding
low-cost, fu ll-speed em ulation, run-tim e v ariable
watches, trace analysis, complex breakpoints, a rugge-
dized probe interface and long (up tothree meters) inter-
connection cables.

 2010 Microchip Technology Inc. DS41303G-page 367

PIC18F2XK20/4XK20
25.11 PICkit 2 Development 25.13 Demonstration/Development
Programmer/Debugger and Boards, Evaluation Kits, and
PICkit 2 Debug Express Starter Kits
The PICkit™ 2 Development Programmer/Debugger is A w ide v ariety of d emonstration, de velopment and
a low-cost development tool with an easy to use inter- evaluation bo ards f or va rious P IC MC Us a nd dsP IC
face for programming and debugging Microchip’s Flash DSCs allows quick application development on fully func-
families of mi crocontrollers. T he f ull f eatured tional systems. Most boards include prototyping areas for
Windows® prog ramming in terface supports baseline adding custom circuitry and provide application firmware
(PIC10F, P IC12F5xx, P IC16F5xx), mi drange and source code for examination and modification.
(PIC12F6xx, P IC16F), P IC18F, PIC24, ds PIC30, The boards support a variety of features, including LEDs,
dsPIC33, and PIC32 families of 8-bit, 16-bit, and 32-bit temperature se nsors, sw itches, s peakers, R S-232
microcontrollers, and many Microchip Serial EEPROM interfaces, LCD displays, potentiometers and additional
products. With Microchip’s powerful MPLAB Integrated EEPROM memory.
Development En vironment (I DE) the PIC kit™ 2
enables in-circuit debugging on most PIC® m icrocon- The de monstration and dev elopment bo ards c an b e
trollers. In -Circuit-Debugging runs, h alts a nd si ngle used in teaching environments, for prototyping custom
steps th e pro gram w hile t he PIC m icrocontroller i s circuits and for le arning about various microcontroller
embedded in the application. When halted at a break- applications.
point, the file registers can be examined and modified. In addition to the PICDEM™ and dsPICDEM™ demon-
The PICkit 2 Debug Express include the PICkit 2, demo stration/development board series of circuits, Microchip
board and microcontroller, hookup cables and CDROM has a line of evaluation kits and demonstration software
with user’s gui de, lessons, tut orial, co mpiler and for ana log f ilter de sign, K EELOQ® security I Cs, CAN,
MPLAB IDE software. IrDA®, P owerSmart b attery management, S EEVAL®
evaluation system, Sigma-Delta A DC, fl ow ra te
sensing, plus many more.
25.12 MPLAB PM3 Device Programmer
Also a vailable are st arter k its th at c ontain eve rything
The MPLAB PM3 D evice Programmer is a universal, needed to experience the specified device. This usually
CE compliant device programmer with programmable includes a single application and debug capability, all
voltage ve rification at V DDMIN an d V DDMAX for on one board.
maximum rel iability. It fea tures a l arge LC D d isplay
(128 x 64) for menus and error messages and a modu- Check th e M icrochip w eb p age (www.microchip.com)
lar, de tachable socket assembly to su pport var ious for th e c omplete l ist o f de monstration, de velopment
package types. The ICSP™ cable assembly is included and evaluation kits.
as a standard item. In Stand-Alone mode, the MPLAB
PM3 Device Programmer can read, verify and program
PIC devices without a PC connection. It c an also set
code p rotection in th is mode. Th e MPLAB PM 3
connects to the host PC via an RS-232 or USB cable.
The MPLAB PM3 has high-speed communications and
optimized al gorithms fo r qu ick programming of large
memory devices and incorporates an MMC card for file
storage and data applications.

DS41303G-page 368  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
26.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings (†)

Ambient temperature under bias.............................................................................................................-40°C to +125°C
Storage temperature .............................................................................................................................. -65°C to +150°C
Voltage on any pin with respect to VSS (except VDD, and MCLR) .................................................. -0.3V to (VDD + 0.3V)
Voltage on VDD with respect to VSS ......................................................................................................... -0.3V to +4.5V
Voltage on MCLR with respect to VSS (Note 2) ............................................................................................0V to +11.0V
Total power dissipation (Note 1) ...............................................................................................................................1.0W
Maximum current out of VSS pin (-40°C to +85°C) .............................................................................................. 300 mA
Maximum current out of VSS pin (+85°C to +125°C)............................................................................................ 125 mA
Maximum current into VDD pin (-40°C to +85°C) ................................................................................................ 200 mA
Maximum current into VDD pin (+85°C to +125°C) ................................................................................................85 mA
Input clamp current, IIK (VI < 0 or VI > VDD) 20 mA
Output clamp current, IOK (VO < 0 or VO > VDD)  20 mA
Maximum output current sunk by any I/O pin..........................................................................................................25 mA
Maximum output current sourced by any I/O pin ....................................................................................................25 mA
Maximum current sunk byall ports (-40°C to +85°C)........................................................................................... 200 mA
Maximum current sunk byall ports (+85°C to +125°C)......................................................................................... 110 mA
Maximum current sourced by all ports (-40°C to +85°C) ......................................................................................185 mA
Maximum current sourced by all ports (+85°C to +125°C) .....................................................................................70 mA

Note 1: Power dissipation is calculated as follows:

Pdis = VDD x {IDD –  IOH} +  {(VDD – VOH) x IOH} + (VOL x IOL)
2: Voltage spikes be low V SS a t t he M CLR/VPP/RE3 pin, inducing currents greater than 80 mA, may cause
latch-up. Th us, a se ries resistor of 50 -100 sh ould be used when applying a “lo w” le vel to th e
MCLR/VPP/RE3 pin, rather than pulling this pin directly to VSS.

† NOTICE: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress rating only and functional operation of the device at those or any other conditions above those
indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for
extended periods may affect device reliability.

 2010 Microchip Technology Inc. DS41303G-page 369

PIC18F2XK20/4XK20
FIGURE 26-1: PIC18F2XK20/4XK20 VOLTAGE-FREQUENCY GRAPH (EXTENDED)

3.5V

3.0V

2.7V
Voltage

2.0V

1.8V

10 16 20 30 32 40 48 50 60 64

Frequency (MHz)

Note: Maximum Frequency 16 MHz, 1.8V to 2.0V, -40°C to +125°C

Maximum Frequency 20 MHz, 2.0V to 3.0V, -40°C to +125°C
Maximum Frequency 48 MHz, 3.0V to 3.6V, -40°C to +125°C

FIGURE 26-2: PIC18F2XK20/4XK20 VOLTAGE-FREQUENCY GRAPH (INDUSTRIAL)

3.5V

3.0V

2.7V
Voltage

2.0V

1.8V

10 16 20 30 32 40 50 60 64

Frequency (MHz)

Note: Maximum Frequency 16 MHz, 1.8V to 2.0V, -40°C to +85°C

Maximum Frequency 20 MHz, 2.0V to 3.0V, -40°C to +85°C
Maximum Frequency 64 MHz, 3.0V to 3.6V, -40°C to +85°C

DS41303G-page 370  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

26.1 DC Characteristics: Supply Voltage, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C

Param
Symbol Characteristic Min Typ Max Units Conditions
No.
D001 VDD Supply Voltage 1.8 — 3.6 V
D002 VDR RAM Data Retention 1.5 — — V
Voltage(1)
D003 VPOR VDD Start Voltage — — 0.7 V See section on Power-on Reset for details
to ensure internal
Power-on Reset signal
D004 SVDD VDD Rise Rate 0.05 — — V/ms See section on Power-on Reset for details
to ensure internal
Power-on Reset signal
D005 VBOR Brown-out Reset Voltage
BORV<1:0> = 11(2) 1.72 1.82 1.95 V
BORV<1:0> = 10 2.15 2.27 2.40 V
BORV<1:0> = 01 2.65 2.75 2.90 V
BORV<1:0> = 00(3) 2.98 3.08 3.25 V
Note 1: This is the limit to which VDD can be lowered in Sleep mode, or during a device Reset, without losing RAM
data.
2: With BOR enabled, operation is supported until a BOR occurs. This is valid although VDD may be below the
minimum rated supply voltage.
3: With BOR enabled, full-speed operation (FOSC = 64 MHZ) is supported until a BOR occurs. This is valid
although VDD may be below the minimum voltage for this frequency.

26.2 DC Characteristics: Power-Down Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C

Param
Device Characteristics Typ Max Units Conditions
No.
D006 Power-down Current (IPD)(1) 0.05 1.0 A 40°C -
0.05 1.0 A +25°C
VDD = 1.8V, (Sleep mode)
0.6 3.0 A +85°C
4 20 A +125°C
D007 0.1 1.0 A -40°C
0.1 1.0 A +25°C
VDD = 3.0V, (Sleep mode)
0.7 3.0 A +85°C
5 20 A +125°C
Note 1: The power-down current in Sleep mode does not depend on the oscillator type. Power-down current is
measured with the part in Sleep mode, with all I/O pins in high-impedance state and tied to VDD or VSS and
all features that add delta current disabled (such as WDT, Timer1 Oscillator, BOR, etc.).

 2010 Microchip Technology Inc. DS41303G-page 371

PIC18F2XK20/4XK20

26.3 DC Characteristics: RC Run Supply Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param
Device Characteristics Typ Max Units Conditions
No.
D008 Supply Current (IDD)(1, 2) 5.5 9 A -40°C
6.0 10 A +25°C
VDD = 1.8V
6.5 14 A +85°C
9.0 30 A +125°C FOSC = 31 kHz
(RC_RUN mode,
D008A 10.0 15 A -40°C LFINTOSC source)
10.5 16 A +25°C
VDD = 3.0V
11.0 20 A +85°C
14.0 40 A +125°C
D009 0.40 0.50 mA -40°C TO +125°C VDD = 1.8V FOSC = 1 MHz
(RC_RUN mode,
D009A 0.60 0.80 mA -40°C TO +125°C VDD = 3.0V HF-INTOSC source)
D010 2.2 3.0 mA -40°C TO +125°C VDD = 1.8V FOSC = 16 MHz
(RC_RUN mode,
D010A 3.8 4.4 mA -40°C TO +125°C VDD = 3.0V HF-INTOSC source)
Note 1: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as
I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and
temperature, also have an impact on the current consumption.
2: The test conditions for all IDD measurements in active operation mode are:
All I/O pins set as outputs driven to Vss;
MCLR = VDD;
OSC1 = external square wave, from rail-to-rail (PRI_RUN and PRI_IDLE only).

DS41303G-page 372  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

26.4 DC Characteristics: RC Idle Supply Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param
Device Characteristics Typ Max Units Conditions
No.
D011 Supply Current (IDD)(1, 2) 2.0 5 A -40°C
2.0 5 A +25°C
VDD = 1.8V
2.5 9 A +85°C
5.0 25 A +125°C FOSC = 31 kHz
(RC_IDLE mode,
D011A 3.5 8 A -40°C LFINTOSC source)
3.5 8 A +25°C
VDD = 3.0V
4.0 12 A +85°C
7.0 30 A +125°C
D012 0.30 0.40 mA -40°C to +125°C VDD = 1.8V FOSC = 1 MHz
(RC_IDLE mode,
D012A 0.40 0.60 mA -40°C to +125°C VDD = 3.0V HF-INTOSC source)
D013 1.0 1.2 mA -40°C to +125°C VDD = 1.8V FOSC = 16 MHz
(RC_IDLE mode,
D013A 1.6 2.0 mA -40°C to +125°C VDD = 3.0V HF-INTOSC source)
Note 1: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as
I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and
temperature, also have an impact on the current consumption.
2: The test conditions for all IDD measurements in active operation mode are:
All I/O pins set as outputs driven to Vss;
MCLR = VDD;
OSC1 = external square wave, from rail-to-rail (PRI_RUN and PRI_IDLE only).

 2010 Microchip Technology Inc. DS41303G-page 373

PIC18F2XK20/4XK20

26.5 DC Characteristics: Primary Run Supply Current, PIC18F2XK20/4XK20

PIC18F2XK20/4XK20 Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C  TA  +125°C
Param
Device Characteristics Typ Max Units Conditions
No.
D014 Supply Current (IDD)(1, 2) 0.25 0.45 mA -40°C to +125°C VDD = 1.8V FOSC = 1 MHz
D014A (PRI_RUN,
0.50 0.75 mA -40°C to +125°C VDD = 3.0V EC oscillator)
D015 2.7 3.2 mA -40°C to +125°C VDD = 2V FOSC = 20 MHz
D015A (PRI_RUN,
4.3 5.0 mA -40°C to +125°C VDD = 3.0V EC oscillator)
D016 FOSC = 64 MHz
12.2 14.0 mA -40°C to +85°C VDD = 3.0V (PRI_RUN,
EC oscillator)
D017 2.1 2.9 mA -40°C to +125°C VDD = 1.8V FOSC = 4 MHz
D017A 16 MHz Internal
4.2 5.0 mA -40°C to +125°C VDD = 3.0V (PRI_RUN HS+PLL)
D018 FOSC = 16 MHz
12.2 15.0 mA -40°C to +85°C VDD = 3.0V 64 MHz Internal
(PRI_RUN HS+PLL)
Note 1: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as
I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and
temperature, also have an impact on the current consumption.
2: The test conditions for all IDD measurements in active operation mode are:
All I/O pins set as outputs driven to Vss;
MCLR = VDD;
OSC1 = external square wave, from rail-to-rail (PRI_RUN and PRI_IDLE only).

26.6 DC Characteristics: Primary Idle Supply Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param
Device Characteristics Typ Max Units Conditions
No.
D019 Supply Current (IDD)(1, 2) 0.05 0.07 mA -40°C to +125°C VDD = 1.8V FOSC = 1 MHz
D019A (PRI_IDLE mode,
0.09 0.15 mA -40°C to +125°C VDD = 3.0V EC oscillator)
D020 1.2 1.6 mA -40°C to +125°C VDD = 2.0V FOSC = 20 MHz
D020A (PRI_IDLEmode,
1.8 2.5 mA -40°C to +125°C VDD = 3.0V EC oscillator)
D021 FOSC = 64 MHz
5.6 7.0 mA -40°C to +85°C VDD = 3.0V (PRI_IDLEmode,
EC oscillator)
Note 1: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as
I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and
temperature, also have an impact on the current consumption.
2: The test conditions for all IDD measurements in active operation mode are:
All I/O pins set as outputs driven to Vss;
MCLR = VDD;
OSC1 = external square wave, from rail-to-rail (PRI_RUN and PRI_IDLE only).

DS41303G-page 374  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

26.7 DC Characteristics: Secondary Oscillator Supply Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param
Device Characteristics Typ Max Units Conditions
No.
D022 Supply Current (IDD)(1, 2) 5.5 9 A -40°C
5.5 10 A +25°C VDD = 1.8V
6.5 14 A +85°C FOSC = 32 kHz(3)
(SEC_RUN mode,
D022A 10.0 15 A -40°C Timer1 as clock)
10.0 16 A +25°C VDD = 3.0V
11.0 20 A +85°C
D023 2.0 5 A -40°C
2.0 5 A +25°C VDD = 1.8V
2.5 9 A +85°C FOSC = 32 kHz(3)
(SEC_IDLE mode,
D023A 3.5 8 A -40°C Timer1 as clock)
3.5 8 A +25°C VDD = 3.0V
4.0 12 A +85°C
Note 1: The supply current is mainly a function of operating voltage, frequency and mode. Other factors, such as
I/O pin loading and switching rate, oscillator type and circuit, internal code execution pattern and
temperature, also have an impact on the current consumption.
2: The test conditions for all IDD measurements in active operation mode are:
All I/O pins set as outputs driven to Vss;
MCLR = VDD;
OSC1 = external square wave, from rail-to-rail (PRI_RUN and PRI_IDLE only).
3: Low-Power mode on T1 osc. Low-Power mode is limited to 85°C.

 2010 Microchip Technology Inc. DS41303G-page 375

PIC18F2XK20/4XK20

26.8 DC Characteristics: Peripheral Supply Current, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param Unit
Device Characteristics Typ Max Conditions
No. s
Module Differential Currents
D024 Watchdog Timer 0.7 2.0 A -40°C to +125°C VDD = 1.8V
(IWDT) 1.1 3.0 A -40°C to +125°C VDD = 3.0V
D024A Brown-out Reset(2) 21 50 A -40C to +125C VDD = 2.0V
(IBOR) 25 60 A -40C to +125C VDD = 3.3V
— Sleep mode,
0 A -40C to +125C VDD = 3.3V
BOREN<1:0> = 10
D024B High/Low-Voltage Detect(2)
13 30 A -40C to +125C VDD = 1.8-3.0V
(IHLVD)
D025 Timer1 Oscillator 0.5 2.0 A -40C
(IOSCB) 0.5 2.0 A +25C VDD = 1.8V 32 kHz on Timer1(1)
LP
0.7 2.0 A +85C
0.7 3.0 A -40C
0.7 3.0 A +25C VDD = 3.0V 32 kHz on Timer1(1)
0.9 3.0 A +85C
D025A Timer1 Oscillator 11 30 A -40C
(IOSCB) 13 33 A +25C VDD = 1.8V 32 kHz on Timer1(3)
HP
15 35 A +85C
14 33 A -40C
17 37 A +25C VDD = 3.0V 32 kHz on Timer1(3)
19 40 A +85C
D026 A/D Converter(4) 200 290 A -40C to +125C VDD = 1.8V
(IAD) A/D on, not converting
260 425 A -40C to +125C VDD = 3.0V
IFRC 2 5 A -40C to +125C VDD = 1.8V Adder for FRC
11 18 A -40C to +125C VDD = 3.0V
D027 Comparators 5 15 A -40C to +125C VDD = 1.8-3.0V LP mode
(ICOMP) 40 90 A -40C to +125C VDD = 1.8-3.0V HP mode
D028 CVREF 18 40 A -40C to +125C VDD = 1.8V
(ICVREF) 32 60 A -40C to +125C VDD = 3.0V
Note 1: Low-Power mode on T1 osc. Low-Power mode is limited to 85°C.
2: BOR and HLVD enable internal band gap reference. With both modules enabled, current consumption will be
less than the sum of both specifications.
3: High-Power mode in T1 osc.
4: A/D converter differential currents apply only in RUN mode. In SLEEP or IDLE mode both the ADC and the FRC
turn off as soon as conversion (if any) is complete.

DS41303G-page 376  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

26.9 DC Characteristics: Input/Output Characteristics, PIC18F2XK20/4XK20

Standard Operating Conditions (unless otherwise stated)
DC CHARACTERISTICS
Operating temperature -40°C TA  +125°C
Param
Symbol Characteristic Min Typ† Max Units Conditions
No.
VIL Input Low Voltage
I/O ports:
D030 with TTL buffer VSS — 0.15 DD VV
D031 with Schmitt Trigger VSS — 0.2 DD VV
D032 MCLR VSS — 0.2 DD VV
D033 OSC1 VSS — 0.3 DD VV HS, HSPLL modes
D033A OSC1 VSS — 0.2 VDD V RC, EC modes(1)
D033B OSC1 VSS — 0.3 VDD V XT, LP modes
D034 T13CKI VSS — 0.3 VDD V
VIH Input High Voltage
I/O ports:
D040 with TTL buffer 0.25 VDD + 0.8V — VDD V
D041 VIH with Schmitt Trigger: 0.8 VDD — VDD V 2.4V < VDD < 3.6V
0.9 VDD — VDD V VDD < 2.4V
D042 VIH MCLR 0.8 VDD — VDD V 2.4V < VDD < 3.6V
0.9 VDD — VDD V VDD < 2.4V
D043 OSC1 0.7 VDD — VDD V HS, HSPLL modes
D043A OSC1 0.8 VDD — VDD V EC mode
D043B OSC1 0.9 VDD — VDD V RC mode(1)
D043C OSC1 1.6 — VDD V XT, LP modes
D044 T13CKI 1.6 — VDD V
IIL Input Leakage I/O and VSS VPIN VDD,
MCLR(2,3) Pin at
high-impedance
D060 I/O ports — 5 50 nA +25°C
— 10 100 nA +60°C
— 30 200 nA +85°C
— 100 1000 nA +125°C
Input Leakage RA2
D061 IIL — 10 100 nA +25°C
— 35 250 nA +60°C
— 200 750 nA +85°C
— 400 2000 nA +125°C
Input Leakage RA3
D062 IIL — 10 80 nA +25°C
— 25 200 nA +60°C
— 70 500 nA +85°C
— 300 1500 nA +125°C
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that
the PIC® device be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified
levels represent normal operating conditions. Higher leakage current may be measured at different input
voltages.
3: Negative current is defined as current sourced by the pin.
4: Parameter is characterized but not tested.

 2010 Microchip Technology Inc. DS41303G-page 377

PIC18F2XK20/4XK20
26.9 DC Characteristics: Input/Output Characteristics, PIC18F2XK20/4XK20 (Continued)
Standard Operating Conditions (unless otherwise stated)
DC CHARACTERISTICS
Operating temperature -40°C TA  +125°C

Param
Symbol Characteristic Min Typ† Max Units Conditions
No.
IPU Weak Pull-up Current
D070 IPURB PORTB weak pull-up 50 90 400 A VDD = 3.0V, VPIN =
current VSS
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that
the PIC® device be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified
levels represent normal operating conditions. Higher leakage current may be measured at different input
voltages.
3: Negative current is defined as current sourced by the pin.
4: Parameter is characterized but not tested.

DS41303G-page 378  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
26.9 DC Characteristics: Input/Output Characteristics, PIC18F2XK20/4XK20 (Continued)
Standard Operating Conditions (unless otherwise stated)
DC CHARACTERISTICS
Operating temperature -40°C TA  +125°C

Param
Symbol Characteristic Min Typ† Max Units Conditions
No.
VOL Output Low Voltage
D080 I/O ports — — 0.6 V IOL = 8.5 mA, VDD
= 3.0V,
-40C to +85C
D083 OSC2/CLKOUT — — 0.6 V IOL = 1.6 mA, VDD
(RC, RCIO, EC, ECIO = 3.0V,
modes) -40C to +85C
VOH Output High Voltage(3)
D090 I/O ports VDD – 0.7 — — V IOH = -3.0 mA, VDD
= 3.0V,
-40C to +85C
D092 OSC2/CLKOUT VDD – 0.7 — — V IOH = -1.3 mA, VDD
(RC, RCIO, EC, ECIO = 3.0V,
modes) -40C to +85C
Capacitive Loading
Specs
on Output Pins
D100(4) COSC2 OSC2 pin — — 15 pF In XT, HS and LP
modes when exter-
nal clock is used to
drive OSC1
D101 CIO All I/O pins and OSC2 — — 50 pF To meet the AC
(in RC mode) Timing
Specifications
D102 CB SCL, SDA — — 400 pF I2C™ Specification
Note 1: In RC oscillator configuration, the OSC1/CLKIN pin is a Schmitt Trigger input. It is not recommended that
the PIC® device be driven with an external clock while in RC mode.
2: The leakage current on the MCLR pin is strongly dependent on the applied voltage level. The specified
levels represent normal operating conditions. Higher leakage current may be measured at different input
voltages.
3: Negative current is defined as current sourced by the pin.
4: Parameter is characterized but not tested.

 2010 Microchip Technology Inc. DS41303G-page 379

PIC18F2XK20/4XK20

26.10 Memory Programming Requirements

Standard Operating Conditions (unless otherwise stated)
DC CHARACTERISTICS
Operating temperature -40°C  TA  +125°C
Param
Sym Characteristic Min Typ† Max Units Conditions
No.
Internal Program Memory
Programming Specifications(1)
D110 VPP Voltage on MCLR/VPP/RE3 pin VDD + 4.5 — 9 V (Note 3, Note 4)
D113 IDDP Supply Current during — — 10 mA
Programming
Data EEPROM Memory
D120 ED Byte Endurance 100K — — E/W -40C to +85C
D121 VDRW VDD for Read/Write 1.8 — 3.6 V Using EECON to
read/write
D122 TDEW Erase/Write Cycle Time — 4 — ms
D123 TRETD Characteristic Retention 40 — — Year Provided no other
specifications are violated
D124 TREF Number of Total Erase/Write 1M 10M — E/W -40°C to +85°C
Cycles before Refresh(2)
Program Flash Memory
D130 EP Cell Endurance 10K — — E/W -40C to +85C (NOTE 5)
D131 VPR VDD for Read 1.8 — 3.6 V
D132 VIW VDD for Row Erase or Write 2.2 — 3.6 V
D133 TIW Self-timed Write Cycle Time — 2 — ms
D134 TRETD Characteristic Retention 40 — — Year Provided no other
specifications are violated
† Data in “Typ” column is at 3.0V, 25°C unless otherwise stated. These parameters are for design guidance
only and are not tested.
Note 1: These specifications are for programming the on-chip program memory through the use of table write
instructions.
2: Refer to Section 7.8 “Using the Data EEPROM” for a more detailed discussion on data EEPROM
endurance.
3: Required only if single-supply programming is disabled.
4: The MPLAB ICD 2 does not support variable VPP output. Circuitry to limit the ICD 2 VPP voltage must be
placed between the ICD 2 and target system when programming or debugging with the ICD 2.
5: Self-write and Block Erase.

DS41303G-page 380  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
26.11 Analog Characteristics

TABLE 26-1: COMPARATOR SPECIFICATIONS

Operating Conditions: 1.8V < VDD < 3.6V, -40°C < TA < +125°C (unless otherwise stated).

Param
Sym Characteristics Min Typ Max Units Comments
No.
CM01 VIOFF Input Offset Voltage — 10 50 mV VREF = VDD/2,
High Power Mode
— 12 80 mV VREF = VDD/2,
Low Power Mode
CM02 VICM Input Common-mode Voltage VSS — VDD V
CM04 TRESP Response Time — 200 400 ns High Power Mode
— 300 600 ns Low Power Mode
CM05 TMC2OV Comparator Mode Change to — — 10 s
Output Valid*
* These parameters are characterized but not tested.
Note 1: Response time measured with one comparator input at VDD/2, while the other input transitions
from VSS to VDD.

TABLE 26-2: CVREF VOLTAGE REFERENCE SPECIFICATIONS

Operating Conditions: 1.8V < VDD < 3.6V, -40°C < TA < +125°C (unless otherwise stated).

Param
Sym Characteristics Min Typ Max Units Comments
No.
CV01* CLSB Step Size(2) — VDD/24 — V Low Range (VRR = 1)
— VDD/32 — V High Range (VRR = 0)
CV02* CACC Absolute Accuracy — — 1/2 LSb
CV03* CR Unit Resistor Value (R) — 3k — 
CV04* CST Settling Time(1) — 7.5 10 s
* These parameters are characterized but not tested.
Note 1: Settling time measured while CVRR = 1 and CVR3:CVR0 transitions from ‘0000’ to ‘1111’.
2: See Section 21.1 “Comparator Voltage Reference” for more information.

TABLE 26-3: FIXED VOLTAGE REFERENCE (FVR) SPECIFICATIONS

Operating Conditions: 1.8V < VDD < 3.6V, -40°C < TA < +125°C (unless otherwise stated).

Standard Operating Conditions (unless otherwise stated)

VR Voltage Reference Specifications
Operating temperature -40°C  TA  +125°C

Param
Sym Characteristics Min Typ Max Units Comments
No.
VR01 VROUT VR voltage output 1.15 1.20 1.25 V -40°C to +85°C
1.10 1.20 1.30 V +85°C to +125°C
VR02* TCVOUT Voltage drift temperature — <50 — ppm/C -40°C to +40°C (See
coefficient Figure 27-34)
VR03* VROUT/ Voltage drift with respect to — <2000 — V/V 25°C, 2.0 to 3.3V (See
VDD VDD regulation Figure 27-33)
VR04* TSTABLE Settling Time — 25 100 s 0 to 125°C
* These parameters are characterized but not tested.

 2010 Microchip Technology Inc. DS41303G-page 381

PIC18F2XK20/4XK20
FIGURE 26-3: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS

VDD

(HLVDIF can be
VHLVD cleared by software)
(HLVDIF set by hardware)

HLVDIF

TABLE 26-4: HIGH/LOW-VOLTAGE DETECT CHARACTERISTICS

Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C  TA  +125°C

Param
Symbol Characteristic Min Typ† Max Units Conditions
No.
D420 HLVD Voltage on HLVDL<3:0> = 0000 1.70 1.85 2.00 V
VDD Transition HLVDL<3:0> = 0001 1.80 1.95 2.10 V
High-to-Low
HLVDL<3:0> = 0010 1.91 2.06 2.21 V
HLVDL<3:0> = 0011 2.02 2.17 2.32 V
HLVDL<3:0> = 0100 2.15 2.30 2.45 V
HLVDL<3:0> = 0101 2.22 2.37 2.52 V
HLVDL<3:0> = 0110 2.38 2.53 2.68 V
HLVDL<3:0> = 0111 2.46 2.61 2.76 V
HLVDL<3:0> = 1000 2.55 2.70 2.85 V
HLVDL<3:0> = 1001 2.65 2.80 2.95 V
HLVDL<3:0> = 1010 2.75 2.90 3.05 V
HLVDL<3:0> = 1011 2.87 3.02 3.17 V
HLVDL<3:0> = 1100 2.98 3.13 3.28 V
HLVDL<3:0> = 1101 3.26 3.41 3.56 V
HLVDL<3:0> = 1110 3.42 3.57 3.72 V
† Production tested at TAMB = 25°C. Specifications over temperature limits ensured by characterization.

DS41303G-page 382  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
26.12 AC (Timing) Characteristics
26.12.1 TIMING PARAMETER SYMBOLOGY
The tim ing p arameter symbols have bee n cr eated
using one of the following formats:

1. TppS2ppS 3. TCC:ST (I 2
C™ specifications only)
2. TppS 4. Ts (I2C specifications only)
T
F Frequency T Time
Lowercase letters (pp) and their meanings:
pp
cc CCP1 osc OSC1
ck CLKOUT rd RD
cs CS rw RD or WR
di SDI sc SCK
do SDO ss SS
dt Data in t0 T0CKI
io I/O port t1 T13CKI
mc MCLR wr WR
Uppercase letters and their meanings:
S
F Fall P Period
H High R Rise
I Invalid (High-impedance) V Valid
L Low Z High-impedance
I2C only
AA output access High High
BUF Bus free Low Low
TCC:ST (I2C specifications only)
CC
HD Hold SU Setup
ST
DAT DATA input hold STO Stop condition
STA Start condition

 2010 Microchip Technology Inc. DS41303G-page 383

PIC18F2XK20/4XK20
26.12.2 TIMING CONDITIONS
The temperature and voltages specified in Table 26-5
apply to all timing sp ecifications unl ess oth erwise
noted. Figure 26-4 specifies the load conditions for the
timing specifications.

TABLE 26-5: TEMPERATURE AND VOLTAGE SPECIFICATIONS – AC

Standard Operating Conditions (unless otherwise stated)
Operating temperature -40°C  TA +125°C
AC CHARACTERISTICS
Operating voltage VDD range as described in DC spec Section 26.1 and
Section 26.9.

FIGURE 26-4: LOAD CONDITIONS FOR DEVICE TIMING SPECIFICATIONS

Load Condition 1 Load Condition 2

VDD/2

RL Pin CL

VSS
CL
Pin
RL = 464
VSS CL = 50 pF for all pins except OSC2/CLKOUT
and including D and E outputs as ports

26.12.3 TIMING DIAGRAMS AND SPECIFICATIONS

FIGURE 26-5: EXTERNAL CLOCK TIMING (ALL MODES EXCEPT PLL)

Q4 Q1 Q2 Q3 Q4 Q1

OSC1
1 3 3 4 4
2
CLKOUT

DS41303G-page 384  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 26-6: EXTERNAL CLOCK TIMING REQUIREMENTS
Param.
Symbol Characteristic Min Max Units Conditions
No.
1A FOSC External CLKIN DC 48 MHz EC, ECIO Oscillator mode,
Frequency(1) (Extended Range Devices)
DC 64 MHz EC, ECIO Oscillator mode,
(Industrial Range Devices)
Oscillator Frequency(1) DC 4 MHz RC Oscillator mode
0.1 4 MHz XT Oscillator mode
4 25 MHz HS Oscillator mode
4 16 MHz HS + PLL Oscillator mode,
(Industrial Range Devices)
4 12 MHz HS + PLL Oscillator mode,
(Extended Range Devices)
5 200 kHz LP Oscillator mode
1 TOSC External CLKIN Period(1) 20.8 — ns EC, ECIO, Oscillator mode
(Extended Range Devices)
15.6 — ns EC, ECIO, Oscillator mode,
(Industrial Range Devices)
Oscillator Period(1) 250 — ns RC Oscillator mode
250 10,000 ns XT Oscillator mode
40 250 ns HS Oscillator mode
62.5 250 ns HS + PLL Oscillator mode,
(Industrial range devices)
83.3 250 ns HS + PLL Oscillator mode,
(Extended Range Devices)
5 200 s LP Oscillator mode
2 TCY Instruction Cycle Time(1) 62.5 — ns TCY = 4/FOSC
3 TOSL, External Clock in (OSC1) 30 — ns XT Oscillator mode
TOSH High or Low Time 2.5 — s LP Oscillator mode
10 — ns HS Oscillator mode
4 TOSR, External Clock in (OSC1) — 20 ns XT Oscillator mode
TOSF Rise or Fall Time — 50 ns LP Oscillator mode
— 7.5 ns HS Oscillator mode
Note 1: Instruction cycle period (TCY) equals four times the input oscillator time base period for all configurations
except PLL. All specified values are based on characterization data for that particular oscillator type under
standard operating conditions with the device executing code. Exceeding these specified limits may result
in an unstable oscillator operation and/or higher than expected current consumption. All devices are tested
to operate at “min.” values with an external clock applied to the OSC1/CLKIN pin. When an external clock
input is used, the “max.” cycle time limit is “DC” (no clock) for all devices.

 2010 Microchip Technology Inc. DS41303G-page 385

PIC18F2XK20/4XK20
TABLE 26-7: PLL CLOCK TIMING SPECIFICATIONS (VDD = 1.8V TO 3.6V)
Param
Sym Characteristic Min Typ† Max Units Conditions
No.
F10 FOSC Oscillator Frequency Range 4 — 4 MHz VDD = 1.8-2.0V
4 — 5 MHz VDD = 2.0-3.0V
4 — 16 MHz VDD = 3.0-3.6V,
Industrial Range Devices
4 — 12 MHz VDD = 3.0-3.6V,
Extended Range Devices
F11 FSYS On-Chip VCO System Frequency 16 — 16 MHz VDD = 1.8-2.0V
16 — 20 MHz VDD = 2.0-3.0V
16 — 64 MHz VDD = 3.0-3.6V,
Industrial Range Devices
16 — 48 MHz VDD = 3.0-3.6V,
Extended Range Devices
F12 trc PLL Start-up Time (Lock Time) — — 2 ms
F13 CLK CLKOUT Stability (Jitter) -2 — +2 %

TABLE 26-8: AC CHARACTERISTICS: INTERNAL OSCILLATORS ACCURACY

PIC18F2XK20/4XK20
Standard Operating Conditions (unless otherwise stated)
PIC18F2XK20/4XK20
Operating temperature -40°C  TA  +125°C
Param
Min Typ Max Units Conditions
No.
OA1 HFINTOSC Accuracy @ Freq = 16 MHz, 8 MHz, 4 MHz, 2 MHz, 1 MHz, 500 kHz, 250 kHz(1)
-2 0 +2 % +0°C to +70°C VDD = 1.8-3.6V
-3 — +2 % +70°C to +85°C VDD = 1.8-3.6V
-5 — +5 % -40°C to 0°C and VDD = 1.8-3.6V
+85°C to 125°C
OA2 LFINTOSC Accuracy @ Freq = 31.25 kHz
-15 — +15 % -40°C to +125°C VDD = 1.8-3.6V
Note 1: Frequency calibrated at 25°C. OSCTUNE register can be used to compensate for temperature drift.

DS41303G-page 386  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 26-6: CLKOUT AND I/O TIMING
Q4 Q1 Q2 Q3

OSC1

10 11

CLKOUT

13 12
14 19 18
16

I/O pin
(Input)

17 15

I/O pin Old Value New Value

(Output)

20, 21
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-9: CLKOUT AND I/O TIMING REQUIREMENTS

Param
Symbol Characteristic Min Typ Max Units Conditions
No.

10 TosH2ckL OSC1  to CLKOUT  — 75 200 ns (Note 1)

11 TosH2ckH OSC1  to CLKOUT  — 75 200 ns (Note 1)
12 TckR CLKOUT Rise Time — 35 100 ns (Note 1)
13 TckF CLKOUT Fall Time — 35 100 ns (Note 1)
14 TckL2ioV CLKOUT  to Port Out Valid — — 0.5 TCY + 20 ns (Note 1)
15 TioV2ckH Port In Valid before CLKOUT  0. 25 TCY + 25 — — ns (Note 1)
16 TckH2ioI Port In Hold after CLKOUT  0 — — ns (Note 1)
17 TosH2ioV OSC1  (Q1 cycle) to Port Out Valid — 50 150 ns
18 TosH2ioI OSC1  (Q2 cycle) to Port Input Invalid 100 — — ns
(I/O in hold time)
19 TioV2osH Port Input Valid to OSC1 (I/O in setup 0 — — ns
time)
20 TioR Port Output Rise Time — 10 25 ns
21 TioF Port Output Fall Time — 10 25 ns
22† TINP INTx pin High or Low Time 20 — — ns
23† TRBP RB<7:4> Change KBIx High or Low Time TCY — — ns
† These parameters are asynchronous events not related to any internal clock edges.
Note 1: Measurements are taken in RC mode, where CLKOUT output is 4 x TOSC.

 2010 Microchip Technology Inc. DS41303G-page 387

PIC18F2XK20/4XK20
FIGURE 26-7: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER AND
POWER-UP TIMER TIMING

VDD

MCLR

30
Internal
POR

33
PWRT
Time-out 32
OSC
Time-out

Internal
Reset

Watchdog
Timer
Reset 31
34 34

I/O pins

Note: Refer to Figure 26-4 for load conditions.

FIGURE 26-8: BROWN-OUT RESET TIMING

VDD BVDD
35
VBGAP = 1.2V
VIVRST

Enable Internal
Reference Voltage
Internal Reference
Voltage Stable 36

TABLE 26-10: RESET, WATCHDOG TIMER, OSCILLATOR START-UP TIMER, POWER-UP TIMER
AND BROWN-OUT RESET REQUIREMENTS
Param.
Symbol Characteristic Min Typ Max Units Conditions
No.
30 TmcL MCLR Pulse Width (low) 2 — — s
31 TWDT Watchdog Timer Time-out Period 3.5 4.1 4.7 ms 1:1 prescaler
(no postscaler)
32 TOST Oscillation Start-up Timer Period 1024 TOSC — 1024 TOSC — TOSC = OSC1 period
33 TPWRT Power-up Timer Period 54.8 64.4 74.1 ms
34 TIOZ I/O High-Impedance from MCLR — 2 — s
Low or Watchdog Timer Reset
35 TBOR Brown-out Reset Pulse Width 200 — — s VDD  BVDD (see D005)
36 TIVRST Internal Reference Voltage Stable — 25 35 s
37 THLVD High/Low-Voltage Detect Pulse Width 200 — — s VDD  VHLVD
38 TCSD CPU Start-up Time 5 — 10 s
39 TIOBST Time for HF-INTOSC to Stabilize — 0.25 1 ms

DS41303G-page 388  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 26-9: TIMER0 AND TIMER1 EXTERNAL CLOCK TIMINGS

T0CKI

40 41

42

T1OSO/T13CKI

45 46

47 48

TMR0 or
TMR1
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-11: TIMER0 AND TIMER1 EXTERNAL CLOCK REQUIREMENTS

Param
Symbol Characteristic Min Max Units Conditions
No.
40 Tt0H T0CKI High Pulse Width No prescaler 0.5 TCY + 20 — ns
With prescaler 10 — ns
41 Tt0L T0CKI Low Pulse Width No prescaler 0.5 TCY + 20 — ns
With prescaler 10 — ns
42 Tt0P T0CKI Period No prescaler TCY + 10 — ns
With prescaler Greater of: — ns N = prescale
20 ns or value
(TCY + 40)/N (1, 2, 4,..., 256)
45 Tt1H T13CKI Synchronous, no prescaler 0.5 TCY + 20 — ns
High Time Synchronous, 10 — ns
with prescaler
Asynchronous 30 — ns
46 Tt1L T13CKI Low Synchronous, no prescaler 0.5 TCY + 5 — ns
Time Synchronous, 10 — ns
with prescaler
Asynchronous 30 — ns
47 Tt1P T13CKI Synchronous Greater of: — ns N = prescale
Input Period 20 ns or value (1, 2, 4, 8)
(TCY + 40)/N
Asynchronous 60 — ns
Ft1 T13CKI Clock Input Frequency Range DC 50 kHz
48 Tcke2tmrI Delay from External T13CKI Clock Edge to 2 TOSC 7 TOSC —
Timer Increment

 2010 Microchip Technology Inc. DS41303G-page 389

PIC18F2XK20/4XK20
FIGURE 26-10: CAPTURE/COMPARE/PWM TIMINGS (ALL CCP MODULES)

CCPx
(Capture Mode)

50 51

52

CCPx
(Compare or PWM Mode)
53 54

Note: Refer to Figure 26-4 for load conditions.

TABLE 26-12: CAPTURE/COMPARE/PWM REQUIREMENTS (ALL CCP MODULES)

Param
Symbol Characteristic Min Max Units Conditions
No.
50 TccL CCPx Input Low No prescaler 0.5 TCY + 20 — ns
Time With 10 — ns
prescaler
51 TccH CCPx Input No prescaler 0.5 TCY + 20 — ns
High Time With 10 — ns
prescaler
52 TccP CCPx Input Period 3 TCY + 40 — ns N rescale
= p
N value (1, 4 or 16)
53 TccR CCPx Output Fall Time — 25 ns
54 TccF CCPx Output Fall Time — 25 ns

DS41303G-page 390  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 26-11: PARALLEL SLAVE PORT TIMING (PIC18F4XK20)

RE2/CS

RE0/RD

RE1/WR

65

RD7:RD0

62
64

63
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-13: PARALLEL SLAVE PORT REQUIREMENTS (PIC18F4XK20)

Param.
Symbol Characteristic Min Max Units Conditions
No.

62 TdtV2wrH Data In Valid before WR  or CS  20 — ns

(setup time)
63 TwrH2dtI WR  or CS  to Data–In Invalid (hold time) 20 — ns
64 TrdL2dtV RD  and CS  to Data–Out Valid — 80 ns
65 TrdH2dtI RD  or CS  to Data–Out Invalid 10 30 ns
66 TibfINH Inhibit of the IBF Flag bit being Cleared from — 3 CY T
WR  or CS 

 2010 Microchip Technology Inc. DS41303G-page 391

PIC18F2XK20/4XK20
FIGURE 26-12: EXAMPLE SPI MASTER MODE TIMING (CKE = 0)

SS

70
SCK
(CKP = 0)

71 72
78 79

SCK
(CKP = 1)

79 78
80

SDO MSb bit 6 - - - - - -1 LSb

75, 76

SDI MSb In bit 6 - - - -1 LSb In

74
73
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-14: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 0)

Param
Symbol Characteristic Min Max Units Conditions
No.

70 TssL2scH, SS  to SCK  or SCK  Input TCY — ns

TssL2scL
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns
71A (Slave mode) Single Byte 40 — ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns
72A (Slave mode) Single Byte 40 — ns (Note 1)
73 TdiV2scH, Setup Time of SDI Data Input to SCK Edge 100 — ns
TdiV2scL
73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge 1.5 TCY + 40 — ns (Note 2)
of Byte 2
74 TscH2diL, Hold Time of SDI Data Input to SCK Edge 100 — ns
TscL2diL
75 TdoR SDO Data Output Rise Time — 25 ns
76 TdoF SDO Data Output Fall Time — 25 ns
78 TscR SCK Output Rise Time — 25 ns
(Master mode)
79 TscF SCK Output Fall Time (Master mode) — 25 ns
80 TscH2doV, SDO Data Output Valid after SCK Edge — 50 ns
TscL2doV
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.

DS41303G-page 392  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 26-13: EXAMPLE SPI MASTER MODE TIMING (CKE = 1)

SS
81
SCK
(CKP = 0)

71 72
79
73
SCK
(CKP = 1)
80
78

SDO MSb bit 6 - - - - - -1 LSb

75, 76

SDI MSb In bit 6 - - - -1 LSb In

74
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-15: EXAMPLE SPI MODE REQUIREMENTS (MASTER MODE, CKE = 1)

Param.
Symbol Characteristic Min Max Units Conditions
No.
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns
71A (Slave mode) Single Byte 40 — ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns
72A (Slave mode) Single Byte 40 — ns (Note 1)
73 TdiV2scH, Setup Time of SDI Data Input to SCK Edge 100 — ns
TdiV2scL
73A Tb2b Last Clock Edge of Byte 1 to the 1st Clock Edge 1.5 TCY + 40 — ns (Note 2)
of Byte 2
74 TscH2diL, Hold Time of SDI Data Input to SCK Edge 100 — ns
TscL2diL
75 TdoR SDO Data Output Rise Time — 25 ns
76 TdoF SDO Data Output Fall Time — 25 ns
78 TscR SCK Output Rise Time — 25 ns
(Master mode)
79 TscF SCK Output Fall Time (Master mode) — 25 ns
80 TscH2doV, SDO Data Output Valid after SCK Edge — 50 ns
TscL2doV
81 TdoV2scH, SDO Data Output Setup to SCK Edge TCY — ns
TdoV2scL
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.

 2010 Microchip Technology Inc. DS41303G-page 393

PIC18F2XK20/4XK20
FIGURE 26-14: EXAMPLE SPI SLAVE MODE TIMING (CKE = 0)

SS

70
SCK
(CKP = 0) 83

71 72
78 79

SCK
(CKP = 1)

79 78
80

SDO MSb bit 6 - - - - - -1 LSb

75, 76 77

SDI MSb In bit 6 - - - -1 LSb In

74
73

Note: Refer to Figure 26-4 for load conditions.

TABLE 26-16: EXAMPLE SPI MODE REQUIREMENTS (SLAVE MODE TIMING, CKE = 0)
Param
Symbol Characteristic Min Max Units Conditions
No.

70 TssL2scH, SS  to SCK  or SCK  Input TCY — ns

TssL2scL
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns
71A (Slave mode) Single Byte 40 — ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns
72A (Slave mode) Single Byte 40 — ns (Note 1)
73 TdiV2scH, Setup Time of SDI Data Input to SCK Edge 100 — ns
TdiV2scL
73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2)
74 TscH2diL, Hold Time of SDI Data Input to SCK Edge 100 — ns
TscL2diL
75 TdoR SDO Data Output Rise Time — 25 ns
76 TdoF SDO Data Output Fall Time — 25 ns
77 TssH2doZ SS to SDO Output High-Impedance 10 50 ns
78 TscR SCK Output Rise Time (Master mode) — 25 ns
79 TscF SCK Output Fall Time (Master mode) — 25 ns
80 TscH2doV SDO Data Output Valid after SCK Edge — 50 ns
,
TscL2doV
83 TscH2ssH SS  after SCK edge 1.5 TCY + 40 — ns
,
TscL2ssH
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.

DS41303G-page 394  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 26-15: EXAMPLE SPI SLAVE MODE TIMING (CKE = 1)
82
SS

70
SCK 83
(CKP = 0)

71 72

SCK
(CKP = 1)
80

SDO MSb bit 6 - - - - - -1 LSb

75, 76 77

SDI
MSb In bit 6 - - - -1 LSb In

74
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-17: EXAMPLE SPI SLAVE MODE REQUIREMENTS (CKE = 1)

Param
Symbol Characteristic Min Max Units Conditions
No.

70 TssL2scH, SS  to SCK  or SCK  Input TCY — ns

TssL2scL
71 TscH SCK Input High Time Continuous 1.25 TCY + 30 — ns
71A (Slave mode) Single Byte 40 — ns (Note 1)
72 TscL SCK Input Low Time Continuous 1.25 TCY + 30 — ns
72A (Slave mode) Single Byte 40 — ns (Note 1)
73A Tb2b Last Clock Edge of Byte 1 to the First Clock Edge of Byte 2 1.5 TCY + 40 — ns (Note 2)
74 TscH2diL, Hold Time of SDI Data Input to SCK Edge 100 — ns
TscL2diL
75 TdoR SDO Data Output Rise Time — 25 ns
76 TdoF SDO Data Output Fall Time — 25 ns
77 TssH2doZ SS to SDO Output High-Impedance 10 50 ns
78 TscR SCK Output Rise Time — 25 ns
(Master mode)
79 TscF SCK Output Fall Time (Master mode) — 25 ns
80 TscH2doV, SDO Data Output Valid after SCK Edge — 50 ns
TscL2doV
82 TssL2doV SDO Data Output Valid after SS  Edge — 50 ns
83 TscH2ssH SS  after SCK Edge 1.5 TCY + 40 — ns
,
TscL2ssH
Note 1: Requires the use of Parameter #73A.
2: Only if Parameter #71A and #72A are used.

 2010 Microchip Technology Inc. DS41303G-page 395

PIC18F2XK20/4XK20
FIGURE 26-16: I2C™ BUS START/STOP BITS TIMING

SCL
91 93
90 92

SDA

Start Stop
Condition Condition

Note: Refer to Figure 26-4 for load conditions.

TABLE 26-18: I2C™ BUS START/STOP BITS REQUIREMENTS (SLAVE MODE)

Param.
Symbol Characteristic Min Max Units Conditions
No.
90 TSU:STA Start Condition 100 kHz mode 4700 — ns Only relevant for Repeated
Setup Time 400 kHz mode 600 — Start condition
91 THD:STA Start Condition 100 kHz mode 4000 — ns After this period, the first
Hold Time 400 kHz mode 600 — clock pulse is generated
92 TSU:STO Stop Condition 100 kHz mode 4700 — ns
Setup Time 400 kHz mode 600 —
93 THD:STO Stop Condition 100 kHz mode 4000 — ns
Hold Time 400 kHz mode 600 —

FIGURE 26-17: I2C™ BUS DATA TIMING

103 100 102

101
SCL
90
106 107

91 92
SDA
In
110
109 109

SDA
Out

Note: Refer to Figure 26-4 for load conditions.

DS41303G-page 396  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 26-19: I2C™ BUS DATA REQUIREMENTS (SLAVE MODE)
Param.
Symbol Characteristic Min Max Units Conditions
No.
100 THIGH Clock High Time 100 kHz mode 4.0 — s PIC18FXXXX must operate
at a minimum of 1.5 MHz
400 kHz mode 0.6 — s PIC18FXXXX must operate
at a minimum of 10 MHz
SSP Module 1.5 TCY —
101 TLOW Clock Low Time 100 kHz mode 4.7 — s PIC18FXXXX must operate
at a minimum of 1.5 MHz
400 kHz mode 1.3 — s PIC18FXXXX must operate
at a minimum of 10 MHz
SSP Module 1.5 TCY —
102 TR SDA and SCL Rise 100 kHz mode — 1000 ns
Time 400 kHz mode 20 + 0.1 CB 300 ns CB is specified to be from
10 to 400 pF
103 TF SDA and SCL Fall 100 kHz mode — 300 ns
Time 400 kHz mode 20 + 0.1 CB 300 ns CB is specified to be from
10 to 400 pF
90 TSU:STA Start Condition 100 kHz mode 4.7 — s Only relevant for Repeated
Setup Time 400 kHz mode 0.6 — s Start condition
91 THD:STA Start Condition 100 kHz mode 4.0 — s After this period, the first
Hold Time 400 kHz mode 0.6 — s clock pulse is generated
106 THD:DAT Data Input Hold 100 kHz mode 0 — ns
Time 400 kHz mode 0 0.9 s
107 TSU:DAT Data Input Setup 100 kHz mode 250 — ns (Note 2)
Time 400 kHz mode 100 — ns
92 TSU:STO Stop Condition 100 kHz mode 4.7 — s
Setup Time 400 kHz mode 0.6 — s
109 TAA Output Valid from 100 kHz mode — 3500 ns (Note 1)
Clock 400 kHz mode — — ns
110 TBUF Bus Free Time 100 kHz mode 4.7 — s Time the bus must be free
400 kHz mode 1.3 — s before a new transmission
can start
D102 CB Bus Capacitive Loading — 400 pF
Note 1: As a transmitter, the device must provide this internal minimum delay time to bridge the undefined region
(min. 300 ns) of the falling edge of SCL to avoid unintended generation of Start or Stop conditions.
2: A fast mode I2C bus device can be used in a standard mode I2C bus system but the requirement,
TSU:DAT  250 ns, must then be met. This will automatically be the case if the device does not stretch the
LOW period of the SCL signal. If such a device does stretch the LOW period of the SCL signal, it must
output the next data bit to the SDA line, TR max. + TSU:DAT = 1000 + 250 = 1250 ns (according to the
standard mode I2C bus specification), before the SCL line is released.

 2010 Microchip Technology Inc. DS41303G-page 397

PIC18F2XK20/4XK20
FIGURE 26-18: MASTER SSP I2C™ BUS START/STOP BITS TIMING WAVEFORMS

SCL
91 93
90 92

SDA

Start Stop
Condition Condition

Note: Refer to Figure 26-4 for load conditions.

TABLE 26-20: MASTER SSP I2C™ BUS START/STOP BITS REQUIREMENTS

Param.
Symbol Characteristic Min Max Units Conditions
No.
90 TSU:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns Only relevant for
Setup Time 400 kHz mode 2(TOSC)(BRG + 1) — Repeated Start
condition
1 MHz mode(1) 2(TOSC)(BRG + 1) —
91 THD:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns After this period, the
Hold Time 400 kHz mode 2(TOSC)(BRG + 1) — first clock pulse is
generated
1 MHz mode(1) 2(TOSC)(BRG + 1) —
92 TSU:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns
Setup Time 400 kHz mode 2(TOSC)(BRG + 1) —
1 MHz mode(1) 2(TOSC)(BRG + 1) —
93 THD:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ns
Hold Time 400 kHz mode 2(TOSC)(BRG + 1) —
1 MHz mode(1) 2(TOSC)(BRG + 1) —
Note 1: Maximum pin capacitance = 10 pF for all I2C pins.

FIGURE 26-19: MASTER SSP I2C™ BUS DATA TIMING

103 100 102
101
SCL
90 106
91 107 92
SDA
In
109 109 110

SDA
Out

Note: Refer to Figure 26-4 for load conditions.

DS41303G-page 398  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 26-21: MASTER SSP I2C™ BUS DATA REQUIREMENTS
Param.
Symbol Characteristic Min Max Units Conditions
No.
100 THIGH Clock High Time 100 kHz mode 2(TOSC)(BRG + 1) — ms
400 kHz mode 2(TOSC)(BRG + 1) — ms
1 MHz mode(1) 2(TOSC)(BRG + 1) — ms
101 TLOW Clock Low Time 100 kHz mode 2(TOSC)(BRG + 1) — ms
400 kHz mode 2(TOSC)(BRG + 1) — ms
1 MHz mode(1) 2(TOSC)(BRG + 1) — ms
102 TR SDA and SCL 100 kHz mode — 1000 ns CB is specified to be from
Rise Time 400 kHz mode 20 + 0.1 CB 300 ns 10 to 400 pF
1 MHz mode(1) — 300 ns
103 TF SDA and SCL 100 kHz mode — 300 ns CB is specified to be from
Fall Time 400 kHz mode 20 + 0.1 CB 30 0 ns 10 to 400 pF
1 MHz mode(1) — 100 ns
90 TSU:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ms Only relevant for
Setup Time 400 kHz mode 2(TOSC)(BRG + 1) — ms Repeated Start
condition
1 MHz mode(1) 2(T OSC)(BRG + 1) — ms
91 THD:STA Start Condition 100 kHz mode 2(TOSC)(BRG + 1) — ms After this period, the first
Hold Time 400 kHz mode 2(TOSC)(BRG + 1) — ms clock pulse is generated
1 MHz mode(1) 2(T OSC)(BRG + 1) — ms
106 THD:DAT Data Input 100 kHz mode 0 — ns
Hold Time 400 kHz mode 0 0.9 ms
107 TSU:DAT Data Input 100 kHz mode 250 — ns (Note 2)
Setup Time 400 kHz mode 100 — ns
92 TSU:STO Stop Condition 100 kHz mode 2(TOSC)(BRG + 1) — ms
Setup Time 400 kHz mode 2(TOSC)(BRG + 1) — ms
1 MHz mode(1) 2(T OSC)(BRG + 1) — ms
109 TAA Output Valid 100 kHz mode — 3500 ns
from Clock 400 kHz mode — 1000 ns
1 MHz mode(1) — — ns
110 TBUF Bus Free Time 100 kHz mode 4.7 — ms Time the bus must be free
400 kHz mode 1.3 — ms before a new transmission
can start
D102 CB Bus Capacitive Loading — 400 pF
Note 1: Maximum pin capacitance = 10 pF for all I2C pins.
2: A fast mode I2C bus device can be used in a standard mode I2C bus system, but parameter 107  250 ns
must then be met. This will automatically be the case if the device does not stretch the LOW period of the
SCL signal. If such a device does stretch the LOW period of the SCL signal, it must output the next data bit
to the SDA line, parameter 102 + parameter 107 = 1000 + 250 = 1250 ns (for 100 kHz mode), before the
SCL line is released.

 2010 Microchip Technology Inc. DS41303G-page 399

PIC18F2XK20/4XK20
FIGURE 26-20: EUSART SYNCHRONOUS TRANSMISSION (MASTER/SLAVE) TIMING

RC6/TX/CK
pin 121 121
RC7/RX/DT
pin

120
122
Note: Refer to Figure 26-4 for load conditions.

TABLE 26-22: EUSART SYNCHRONOUS TRANSMISSION REQUIREMENTS

Param
Symbol Characteristic Min Max Units Conditions
No.
120 TckH2dtV SYNC XMIT (MASTER & SLAVE)
Clock High to Data Out Valid — 40 ns
121 Tckrf Clock Out Rise Time and Fall Time — 20 ns
(Master mode)
122 Tdtrf Data Out Rise Time and Fall Time — 20 ns

FIGURE 26-21: EUSART SYNCHRONOUS RECEIVE (MASTER/SLAVE) TIMING

RC6/TX/CK
pin 125
RC7/RX/DT
pin
126

Note: Refer to Figure 26-4 for load conditions.

TABLE 26-23: EUSART SYNCHRONOUS RECEIVE REQUIREMENTS

Param.
Symbol Characteristic Min Max Units Conditions
No.
125 TdtV2ckl SYNC RCV (MASTER & SLAVE)
Data Setup before CK  (DT setup time) 10 — ns
126 TckL2dtl Data Hold after CK  (DT hold time) 15 — ns

DS41303G-page 400  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
TABLE 26-24: A/D CONVERTER CHARACTERISTICS: PIC18F2XK20/4XK20
Param
Symbol Characteristic Min Typ Max Units Conditions
No.
A01 NR Resolution — — 10 bits -40°C to +85°C, VREF
 2.0V
A03 EIL Integral Linearity Error — ±0.5 ±1 LSb -40°C to +85°C, VREF
 2.0V
A04 EDL Differential Linearity Error — ±0.4 ±1 LSb -40°C to +85°C, VREF
 2.0V
A06 EOFF Offset Error — 0.4 ±2 LSb -40°C to +85°C, VREF
 2.0V
A07 EGN Gain Error — 0.3 ±2 LSb -40°C to +85°C, VREF
 2.0V
A08 ETOTL Total Error — 1 ±3 LSb -40°C to +85°C, VREF
 2.0V
A20 VREF Reference Voltage Range 1.8 — — V ABsolute Minimum
(VREFH – VREFL) 2.0 — — V Minimum for 1LSb
Accuracy
A21 VREFH Reference Voltage High VDD/2 — VDD + 0.3 V
A22 VREFL Reference Voltage Low VSS – 0.3V — VDD/2 V
A25 VAIN Analog Input Voltage VREFL — VREFH V
A30 ZAIN Recommended Impedance of — — 3 k -40°C to +85°C
Analog Voltage Source
Note 1: The A/D conversion result never decreases with an increase in the input voltage and has no missing
codes.
2: VREFH current is from RA3/AN3/VREF+ pin or VDD, whichever is selected as the VREFH source.
VREFL current is from RA2/AN2/VREF-/CVREF pin or VSS, whichever is selected as the VREFL source.

 2010 Microchip Technology Inc. DS41303G-page 401

PIC18F2XK20/4XK20
FIGURE 26-22: A/D CONVERSION TIMING

BSF ADCON0, GO
(Note 2)
131
Q4
130
A/D CLK 132

A/D DATA 9 8 7 .. . ... 2 1 0

ADRES OLD_DATA NEW_DATA

ADIF TCY

GO DONE

SAMPLING STOPPED
SAMPLE

Note 1: If the A/D clock source is selected as RC, a time of TCY is added before the A/D clock starts.
This allows the SLEEP instruction to be executed.
2: This is a minimal RC delay (typically 100 ns), which also disconnects the holding capacitor from the analog input.

TABLE 26-25: A/D CONVERSION REQUIREMENTS

Param
Symbol Characteristic Min Max Units Conditions
No.
130 TAD A/D Clock Period 0.7 25.0(1) s TOSC based,
-40C to +85C
0.7 4.0(1) s TOSC based,
+85C to +125C
1.0 4.0 s FRC mode, VDD2.0V
131 TCNV Conversion Time 12 12 TAD
(not including acquisition time) (Note 2)
132 TACQ Acquisition Time (Note 3) 1.4 — s VDD = 3V, Rs = 50
135 TSWC Switching Time from Convert  Sample — (Note 4)
136 TDIS Discharge Time 2 2 TAD
Legend: TBD = To Be Determined
Note 1: The time of the A/D clock period is dependent on the device frequency and the TAD clock divider.
2: ADRES register may be read on the following TCY cycle.
3: The time for the holding capacitor to acquire the “New” input voltage when the voltage changes full scale
after the conversion (VDD to VSS or VSS to VDD). The source impedance (RS) on the input channels is 50
.
4: On the following cycle of the device clock.

DS41303G-page 402  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
27.0 DC AND AC CHARACTERISTICS GRAPHS AND TABLES

FIGURE 27-1: PIC18F4XK20/PIC18F2XK20 TYPICAL BASE IPD

10

125°C

85°C
IPD (uA)

0.1
40°C
Limited Accuracy 25°C

-40°C

0.01
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-2: PIC184XK20/PIC18F2XK20 MAXIMUM BASE IPD

100

125°C
IPD (uA)

10

85°C

40°C

1 25°C

1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 403

PIC18F2XK20/4XK20
FIGURE 27-3: PIC18F4XK20/PIC18F2XK20 TYPICAL RC_RUN 31 KHZ IDD

16

14 125°C

12

85°C
25°C
IDD (uA)

10 -40°C

4
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-4: PIC18F4XK20/PIC18F2XK20 MAXIMUM RC_RUN 31 KHZ IDD

45

125°C
40

35

30
IDD (uA)

25

20 85°C

25°C
15 -40°C

10

5
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 404  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-5: PIC18F4XK20/PIC18F2XK20 TYPICAL RC_RUN IDD

5.0

4.5

4.0 16 MHz

3.5

3.0
IDD (mA)

2.5
8 MHz

2.0

1.5
4 M Hz
1.0

1 MHz
0.5

0.0

1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-6: PIC18F4XK20/PIC18F2XK20 MAXIMUM RC_RUN IDD

16 MHz

4
IDD (mA)

3 8 MHz

4 MHz

1
1 MHz

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 405

PIC18F2XK20/4XK20
FIGURE 27-7: PIC18F4XK20/PIC18F2XK20 TYPICAL RC_IDLE 31 KHZ IDD

125°C

5
IDD (uA)

4 85°C

25°C
-40°C
3

1
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-8: PIC18F4XK20/PIC18F2XK20 MAXIMUM RC_IDLE 31 KHZ IDD

35

125°C
30

25

20
IDD (uA)

15
85°C

10
25°C
-40°C
5

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 406  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-9: PIC18F4XK20/PIC18F2XK20 TYPICAL RC_IDLE IDD

2.5

2.0

16 MHz

1.5
IDD (mA)

8 MHz
1.0

4 MHz

0.5
1 MHz

0.0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-10: PIC18F4XK20/PIC18F2XK20 MAXIMUM RC_IDLE IDD

3.0

2.5

16 MHz
2.0
IDD (mA)

1.5

8 MHz

1.0
4 MHz

1 MHz
0.5

0.0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 407

PIC18F2XK20/4XK20
FIGURE 27-11: PIC18F4XK20/PIC18F2XK20 TYPICAL PRI_RUN IDD (EC)

16

14
64 MHz
12

10

40 MHz
IDD (mA)

20 MHz
4
16 MHz

10 MHz
2
4 MHz

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-12: PIC18F4XK20/PIC18F2XK20 MAXIMUM PRI_RUN IDD (EC)

18

16

64 MHz
14

12

10 40 MHz
IDD (mA)

6
20 MHz
16 MHz
4
10 MHz
2
4 MHz

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 408  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-13: PIC18F4XK20/PIC18F2XK20 TYPICAL PRI_RUN IDD (HS + PLL)

16

14

64 MHz
12 (16 MHz Input)

10
40 MHz
(10 MHz Input)
IDD (mA)

4
16 MHz
(4 MHz Input)
2

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-14: PIC18F4XK20/PIC18F2XK20 MAXIMUM PRI_RUN IDD (HS + PLL)

20

18

16 64 MHz
(16 MHz Input)
14

12
40 MHz
IDD (mA)

10 (10 MHz Input)

16 MHz
4 (4 MHz Input)

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 409

PIC18F2XK20/4XK20
FIGURE 27-15: PIC18F4XK20/PIC18F2XK20 TYPICAL PRI_IDLE IDD (EC)

6
64 MHz

4
40 MHz
IDD (mA)

2 20 MHz
16 MHz

1 10 MHz

4 MHz
0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-16: PIC18F4XK20/PIC18F2XK20 MAXIMUM PRI_IDLE IDD (EC)

64 MHz
7

5
IDD (mA)

40 MHz
4

3
20 MHz

2 16 MHz

10 MHz
1
4 MHz
0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 410  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-17: PIC18F4XK20/PIC18F2XK20 IWDT – Delta IPD for Watchdog Timer, -40°C to
+125°C

4.0

3.5

Max.
3.0

2.5
IPD (uA)

2.0

1.5

Typ.
1.0

0.5

0.0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-18: PIC18F4XK20/PIC18F2XK20 IBOR and IHLVD – Delta IPD for Brownout Reset
and High/Low Voltage Detect, -40°C to +125°C

70

60 Max. BOR

50

40
IPD (uA)

30 Max. HLVD

Typ. BOR

20

Typ. HLVD
10

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 411

PIC18F2XK20/4XK20
FIGURE 27-19: PIC18F4XK20/PIC18F2XK20 IOCSB – Delta IPD for Low Power Timer1 Oscillator

3.5

3.0 Max.
-40°C to +85°C

2.5

2.0
IPD (uA)

1.5

1.0
Typ. 85°C
Typ. 25°C
0.5

0.0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-20: PIC18F4XK20/PIC18F2XK20 IOCSB – Typical Delta IPD for High Power Timer1
Oscillator

20

85°C

18

25°C
16
IPD (uA)

14 -40°C

12

10
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 412  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-21: PIC18F4XK20/PIC18F2XK20 IOCSB – Maximum Delta IPD for High Power Timer1
Oscillator

42

40 85°C

38

25°C
36
IPD (uA)

34
-40°C

32

30

28
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-22: PIC18F4XK20/PIC18F2XK20 ICVREF – Delta IPD for Comparator Voltage

Reference, -40°C to +125°C

80

70

Max.
60

50
(uA)

40
IPD

Typ.
30

20

10

0
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 413

PIC18F2XK20/4XK20
FIGURE 27-23: PIC18F4XK20/PIC18F2XK20 IAD – Typical Delta IDD for ADC, 25°C to +125°C
(Run Mode, ADC on, but not converting)

340

320 125°C

300 85°C

280
(uA)

25°C
260
IDD

240

220

200

180
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-24: PIC18F4XK20/PIC18F2XK20 IAD – Maximum Delta IDD for ADC, 25°C to +125°C
(Run Mode, ADC on, but not converting)

440
125°C
420
85°C
400

380
25°C
360

340
IDD (uA)

320

300

280

260

240

220
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 414  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-25: PIC18F4XK20/PIC18F2XK20 ICOMP – Typical Delta IPD for Comparator in Low
Power Mode, -40°C to +125°C

7.0

125°C
6.5

85°C
6.0

5.5
IPD (uA)

25°C

5.0

4.5
-40°C

4.0

3.5
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-26: PIC18F4XK20/PIC18F2XK20 ICOMP – Maximum Delta IPD for Comparator in

Low Power Mode, -40°C to +125°C

16

125°C
15

85°C
14
IPD (uA)

13 25°C

12

-40°C

11

10
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 415

PIC18F2XK20/4XK20
FIGURE 27-27: PIC18F4XK20/PIC18F2XK20 ICOMP – Typical Delta IPD for Comparator in High
Power Mode, -40°C to +125°C

55

50 125°C

85°C
45
IPD (uA)

25°C
40

35 -40°C

30
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-28: PIC18F4XK20/PIC18F2XK20 ICOMP – Maximum Delta IPD for Comparator in

High Power Mode, -40°C to +125°C

95

125°C
90

85 85°C

80
IPD (uA)

25°C

75

70
-40°C

65

60
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

DS41303G-page 416  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-29: PIC18F4XK20/PIC18F2XK20 COMPARATOR OFFSET (LOW POWER, VDD = 1.8V)

70

60
-40°C 3 sigma

50
25°C 3 sigma
Abs. Offset (mV)

85°C 3 sigma
40
a
sigm
C3
125
°
30

Typical
20

10

0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

VREF (V)

FIGURE 27-30: PIC18F4XK20/PIC18F2XK20 COMPARATOR OFFSET (LOW POWER, VDD = 3.6V)

70
-40°C 3 sigma

60
a
igm
3s
°C
50 25
Abs. Offset (mV)

a
m
sig
40
3
°C

a
m
85

sig
3
C
30
5°

Typical
12

20

10

0
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6

VREF (V)

 2010 Microchip Technology Inc. DS41303G-page 417

PIC18F2XK20/4XK20
FIGURE 27-31: PIC18F4XK20/PIC18F2XK20 COMPARATOR OFFSET (HIGH POWER, VDD = 1.8V)

45

40

35 -40°C 3 sigma

25°C 3 sigma
30
ma
3 sig
Abs. Offset (mV)

85°C igma
C3s
25 125°

20
Typical
15

10

0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

VREF (V)

FIGURE 27-32: PIC18F4XK20/PIC18F2XK20 COMPARATOR OFFSET (HIGH POWER, VDD = 3.6V)

45
-40°C 3 sigma
40

35 25°C 3 sigma

a
sigm
30 C3
85°
Abs. Offset (mV)

a
igm
25 3s
5°C
12
20
Typical
15

10

0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6

VREF (V)

DS41303G-page 418  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-33: PIC18F4XK20/PIC18F2XK20 TYPICAL FIXED VOLTAGE REFERENCE

1.205

1.200 25°C
-40°C

85°C
1.195
FVR (V)

1.190

1.185

125°C

1.180

1.175
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6

VDD (V)

FIGURE 27-34: PIC18F4XK20/PIC18F2XK20 TYPICAL FIXED VOLTAGE REFERENCE (MAX./

MIN. = 1.2V +/- 50MV FROM -40°C TO +85°C)

1.205

1.200 3.6V
2.0V

1.195
FVR (V)

1.190
1.8V

1.185

1.180

1.175
-40 -20 0 20 40 60 80 100 120
Temp. (°C)

 2010 Microchip Technology Inc. DS41303G-page 419

PIC18F2XK20/4XK20
FIGURE 27-35: PIC18F4XK20/PIC18F2XK20 TTL BUFFER VIH

1.8

Min.
1.6

1.4

1.2
VIH (V)

-40°C
25°C
1.0
85°C
125°C

0.8

0.6

0.4
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
VDD (V)

FIGURE 27-36: PIC18F4XK20/PIC18F2XK20 SCHMITT TRIGGER BUFFER VIH

3.0

2.8

Min.
2.6

2.4

2.2
-40°C
VIH (V)

2.0 25°C
125°C
85°C
1.8

1.6

1.4

1.2

1.0
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
VDD (V)

DS41303G-page 420  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-37: PIC18F4XK20/PIC18F2XK20 TTL BUFFER VIL

1.2

-40°C
1.0 25°C
85°C
125°C
0.8
VIL (V)

0.6

Max.

0.4

0.2

0.0
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
VDD (V)

FIGURE 27-38: PIC18F4XK20/PIC18F2XK20 SCHMITT TRIGGER BUFFER VIL

1.6

1.4 -40°C
25°C
85°C 125°C

1.2

1.0
VIL (V)

0.8

Max.
0.6

0.4

0.2
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6
VDD (V)

 2010 Microchip Technology Inc. DS41303G-page 421

PIC18F2XK20/4XK20
FIGURE 27-39: PIC18F4XK20/PIC18F2XK20 VOH VS. IOH (-40°C TO +125°C)

3.6

2.4

Typ. 3.0V
VOH (V)

1.8
Typ. 3.6V

Min. 3.0V
1.2

Typ. 1.8V
0.6
Min. 3.6V
Min. 1.8V

0
0 5 10 15 20 25

IOH (mA)

FIGURE 27-40: PIC18F4XK20/PIC18F2XK20 VOL VS. IOL (-40°C TO +125°C)

1.8
Max. 1.8V
Max. 3.0V
1.5
Max. 3.6V

1.2
VOL (V)

0.9

0.6 1.8V

3.0V
3.6V
0.3

0
0 5 10 15 20 25

IOL (mA)

DS41303G-page 422  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-41: PIC18F4XK20/PIC18F2XK20 PIN INPUT LEAKAGE

1000

RA2 Max.

RA3 Max.

I/O Ports Max.

100
RA2 Typ.
Input Leakage (nA)

RA3 Typ.

I/O Ports Typ.

10

1
25 30 35 40 45 50 55 60 65 70 75 80 85
Temp. (°C)

 2010 Microchip Technology Inc. DS41303G-page 423

PIC18F2XK20/4XK20
FIGURE 27-42: PIC18F4XK20/PIC18F2XK20 TYPICAL HF-INTOSC FREQUENCY

16.08

16.00 25°C

15.92
Frequency (MHz)

85°C

15.84 -40°C

15.76
125°C

15.68
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
VDD (V)

FIGURE 27-43: PIC18F4XK20/PIC18F2XK20 TYPICAL HF-INTOSC FREQUENCY

16.80

16.64

16.48

16.32 Max

16.16
Frequency (MHz)

16.00 3.0V

15.84

15.68 Min

15.52

15.36

15.20
-40 -20 0 20 40 60 80 100 120
Temp. (°C)

DS41303G-page 424  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
FIGURE 27-44: PIC18F4XK20/PIC18F2XK20 TYPICAL LF-INTOSC FREQUENCY (MAX./MIN. =
31.25 KHZ +/-15%)

33.25

32.25

31.25
Frequency (kHz)

25°C

-40°C

30.25 85°C

29.25
125°C

28.25
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6
VDD (V)

FIGURE 27-45: PIC18F4XK20/PIC18F2XK20 TYPICAL LF-INTOSC FREQUENCY (MAX./MIN. =

31.25 KHZ +/-15%)

33.25

32.25

1.8V

31.25
Frequency (kHz)

2.5V

3.6V 3.0V

30.25

29.25

28.25
-40 -20 0 20 40 60 80 100 120
Temp. (°C)

 2010 Microchip Technology Inc. DS41303G-page 425

PIC18F2XK20/4XK20
NOTES:

DS41303G-page 426  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
28.0 PACKAGING INFORMATION
28.1 Package Marking Information

28-Lead PDIP Example

XXXXXXXXXXXXXXXXX PIC18F25K20-E/SP
XXXXXXXXXXXXXXXXX e3
YYWWNNN 0810017

28-Lead SOIC (7.50 mm) Example

XXXXXXXXXXXXXXXXXXXX PIC18F25K20-E/SO e3
XXXXXXXXXXXXXXXXXXXX 0810017
XXXXXXXXXXXXXXXXXXXX
YYWWNNN

40-Lead PDIP Example

XXXXXXXXXXXXXXXXXX PIC18F45K20-E/P e3
XXXXXXXXXXXXXXXXXX 0810017
XXXXXXXXXXXXXXXXXX
YYWWNNN

Legend: XX...X Customer-specific information

Y Year code (last digit of calendar year)
YY Year code (last 2 digits of calendar year)
WW Week code (week of January 1 is week ‘01’)
NNN Alphanumeric traceability code
e3 Pb-free JEDEC designator for Matte Tin (Sn)
* This package is Pb-free. The Pb-free JEDEC designator ( e3 )
can be found on the outer packaging for this package.

Note: In the event the full Microchip part number cannot be marked on one line, it will
be ca rried over to the next line, thus lim iting the nu mber of av ailable
characters for customer-specific information.

 2010 Microchip Technology Inc. DS41303G-page 427

PIC18F2XK20/4XK20
Package Marking Information (Continued)

28-Lead SSOP Example

XXXXXXXXXXXXXXX PIC18F25K20-E/SS
XXXXXXXXXXXXXXX e3
XXXXXXXXXXXXXXX
YYWWNNN 0810017

28-Lead QFN Example

XXXXXXXX 18F24K20
XXXXXXXX -E/ML e3
YYWWNNN 0810017

44-Lead QFN Example

XXXXXXXXXX PIC18F45K20
XXXXXXXXXX -E/ML e3
XXXXXXXXXX 0810017
YYWWNNN

44-Lead TQFP Example

XXXXXXXXXX PIC18F44K20
XXXXXXXXXX -E/PT e3
XXXXXXXXXX 0810017
YYWWNNN

28-Lead UQFN Example

XXXXX PIC18
XXXXXX F23K20
XXXXXX -E/MV e3
YWWNNN 810017

DS41303G-page 428  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
28.2 Package Details
The following sections give the technical details of the packages.

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 2010 Microchip Technology Inc. DS41303G-page 429

PIC18F2XK20/4XK20

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DS41303G-page 430  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

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NOTE 1
E1

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A A2
L c
b1
A1
b e eB

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1XPEHURI3LQV 1 
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6KRXOGHUWR6KRXOGHU:LGWK (  ± 
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7LSWR6HDWLQJ3ODQH /  ± 
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 3LQYLVXDOLQGH[IHDWXUHPD\YDU\EXWPXVWEHORFDWHGZLWKLQWKHKDWFKHGDUHD
 †6LJQLILFDQW&KDUDFWHULVWLF
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 2010 Microchip Technology Inc. DS41303G-page 431

PIC18F2XK20/4XK20

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D
N

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E1

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c
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DS41303G-page 432  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

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D D2
EXPOSED
PAD

E
b
E2

2 2
1 1 K

N N
NOTE 1 L
TOP VIEW BOTTOM VIEW

A3 A1

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 2010 Microchip Technology Inc. DS41303G-page 433

PIC18F2XK20/4XK20

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DS41303G-page 434  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging

 2010 Microchip Technology Inc. DS41303G-page 435

PIC18F2XK20/4XK20

Note: For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging

DS41303G-page 436  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

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EXPOSED
PAD

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A3 A1

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 2010 Microchip Technology Inc. DS41303G-page 437

PIC18F2XK20/4XK20

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DS41303G-page 438  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20

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 2010 Microchip Technology Inc. DS41303G-page 439

PIC18F2XK20/4XK20

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DS41303G-page 440  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
APPENDIX A: REVISION HISTORY Revision E (04/2009)
Revised dat a s heet ti tle; R evised Power-Managed
Revision A (07/2006)
Modes, Perip heral H ighlights, and Anal og F eatures;
Original data sheet for PIC18F2XK20/4XK20 devices. Revised 26.2, DC Char. table.

Revision B (03/2007) Revision F (09/2009)

Added part n umbers PIC 18F26K20 an d Changed t he v alues i n th e “Ex treme Low-Power
PIC18F46K20; R eplaced D evelopment Support Management with nanoWatt XLP” section; Added new
Section; Replaced Package Drawings. Note 2 to Pi n D iagrams; U pdated Electrical
Characteristics section; Add ed ch arts to the DS
Characteristics se ction; Removed Prel iminary la bel;
Revision C (10/2007) Added UQFN to Pi n D iagrams; Added the 2 8-pin
Revised Table 1, DIL Pins 34 and 35; Table 2, Pins 22 UQFN to Table 3-1; Updated MSSP section (Register
and 24; Table 1-2, Pins RB1 and RB3; Table 1-3, Pins 17-3; c hanging SSP ADD<6:0> to SSP ADD<7:0>);
RB1 and RB3; Revised Sections 4.3, 4.4, 4.4.1, 4.4.2, Updated th e D evelopment Sup port sec tion d eleting
4.4.4; R evised Table 4- 3, Note 2; R evised Table 6- 1; section 25. 7; Ad ded the 2 8-Lead U QFN p ackage
Revise Section 7 .8: Rev ised S ection 9. 2; Revised marking diagrams and the 28-Lead Plastic Ultra Thin
Examples 1 0-1 a nd 1 0-2; Revised T able 10-3 , Pin s Quad Flat, No Lead Package (MV) - 4X4X0.5 mm Body
RB1 and R B3; R evised Sec tions 12. 2 thro ugh 12. 5; (UQFN) p ackage to Pac kaging In formation s ection;
Revised Register 16-1, bit 3-0; Revised Sections 16.1, Other minor corrections.
16.2, 16.4.4; R evised R egister 16-2, bit 6-4; R evised
Table 1 6-2, Note 2 ; R evised R egister 1 7-1, bit 6; Revision G (01/2010)
Revised Register 17- 3; R evised Table 17 -4; R evised Updated Fi gure 9-1 ; R eviewed Section 26 (Ele ctrical
Register 19-1, added N ote 2; R evised R egister 20-3, Characteristics); Add ed Fi gures 27 -29, 27-30, 27-3 1
bits 5 and 4; Revised Register 23-4, bit 1; Revised Reg- and 27-32 to Section 27 (D C and AC C haracteristics
ister 23-12, bit 7-5; Revised Section 23.3; Revised Sec- Graphs and Tables); R eviewed Produ ct Iden tification
tion 24 .1.1, instruction set des criptions; Rev ised System section.
Section 26.0, voltage on MCLR; Revised DC Charac-
teristics 2 6.2, 26.3 , 26 .4 26 .5, 2 6.6, 26. 7, 26 .8 an d
26.10; Revised Tables 26-1, 26-6, 26-7, 26-9, 26-23.

Revision D (08/2008)
Update to Peripher al Highlights (USART m odule);
Deleted Section 2.2.6 (Oscillator Transitions); Revised
Sections 2.5.3, 2.9; Added Section 2.9.3 (Clock Switch
Timing); Deleted Section 2.10.4 (Clock Switching Tim-
ing); Replaced BAUDCTL with BAUDCON throughout;
Revised T able 5-2 ( PLUSW0, P LUSW1, PLU SW2);
Add Note 1 to Table 7-1 (EEADRH); Revised Section
6.4.4 and Register 16-2 (FLT0 pin); Revised Registers
17-2 and 17-5 ( SSPEN); R evised R egister 17 -6
(SEN); Added new p aragraph after Figure 18- 2;
Revised Note, Section 18.1. 1; Deleted Note, S ection
18.1.2; Added new Note 2, Sections 18.1.2.9 and
18.1.2.10; R evised N ote 1, Se ction 18.3.1; A dded
Section 18.3.2; R evised Sect ion 18.3.5; Added new
Note 2, Sections 18.4. 1.5, 18.4.1. 10, 18.4.2. 2,
18.4.2.4; Revised Register 21-1 (CVR); Revised Note
1, Registers 23-6, 23.8, 23-10, Table 23-3; Added new
Figure 26-1; Revised 26.2, 26.6, 26.7 (Note 3), 26.8,
26.9, 26.10; Revised Tables 26-1, 26-2, 26-3, 26-6, 26-
7, 26-8, 26-25; Updated Package Drawings.

 2010 Microchip Technology Inc. DS41303G-page 441

PIC18F2XK20/4XK20
APPENDIX B: DEVICE
DIFFERENCES
The differences between the devices listed in this data
sheet are shown in Table B-1.

TABLE B-1: DEVICE DIFFERENCES

Features PIC18F23K20 PIC18F24K20 PIC18F25K20 PIC18F26K20 PIC18F43K20 PIC18F44K20 PIC18F45K20 PIC18F46K20

Program Memory 8192 16384 32768 65536 8192 16384 32768 65536
(Bytes)
Program Memory 4096 8192 16384 32768 4096 8192 16384 32768
(Instructions)
Interrupt ources S 19 19 19 19 20 20 20 20
I/O Ports Ports A, B, C, Ports A, B, C, Ports A, B, C, Ports A, B, C, Ports A, B, C, Ports A, B, C, Ports A, B, C, Ports A, B, C,
(E) (E) (E) (E) D, E D, E D, E D, E
Capture/Compare/PWM 1 1 1 1 1 1 1 1
Modules
Enhanced 1 1 1 1 1 1 1 1
Capture/Compare/PWM
Modules
Parallel No No No No Yes Yes Yes Yes
Communications (PSP)
10-bit Analog-to-Digital 11 input 11 input 11 input 11 input 14 input 14 input 14 input 14 input
Module channels channels channels channels channels channels channels channels
Packages 28-pin PDIP 28-pin PDIP 28-pin PDIP 28-pin PDIP 40-pin PDIP 40-pin PDIP 40-pin PDIP 40-pin PDIP
28-pin SOIC 28-pin SOIC 28-pin SOIC 28-pin SOIC 44-pin TQFP 44-pin TQFP 44-pin TQFP 44-pin TQFP
28-pin SSOP 28-pin SSOP 28-pin SSOP 28-pin SSOP 44-pin QFN 44-pin QFN 44-pin QFN 44-pin QFN
28-pin QFN 28-pin QFN 28-pin QFN 28-pin QFN
28-pin UQFN

DS41303G-page 442  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
INDEX
A B
A/D Bank Select Register (BSR) .............................................. 71
Analog Port Pins, Configuring .................................. 277 Baud Rate Generator ...................................................... 221
Associated Registers ............................................... 277 BAUDCON Register ........................................................ 248
Conversions .. ........................................................... 268 BC .................................................................................... 323
Converter Characteristics ........................................ 401 BCF .. ............................................................................... 324
Discharge ................................................................. 269 BF ... ................................................................................. 225
Selecting and Configuring Acquisition Time ............ 266 BF Status Flag ................................................................. 225
Special Event Trigger (ECCP) ................................. 174 Block Diagrams
Absolute Maximum Ratings ............................................. 369 ADC .. ....................................................................... 265
AC (Timing) Characteristics ............................................. 383 ADC Transfer Function ............................................ 276
Load Conditions for Device Timing Specifications ... 384 Analog Input Model .......................................... 276, 286
Parameter Symbology ............................................. 383 Baud Rate Generator .............................................. 221
Temperature and Voltage Specifications . ................ 384 Capture Mode Operation ......................................... 146
Timing Conditions .................................................... 384 CCP PWM ............................................................... 149
AC Characteristics Clock Source ............................................................. 27
Internal RC Accuracy ............................................... 386 Comparator 1 ........................................................... 280
Access Bank Comparator 2 ........................................................... 280
Mapping with Indexed Literal Offset Mode ................. 87 Comparator Voltage Reference ............................... 290
ACKSTAT . ....................................................................... 225 Compare Mode Operation ....................................... 147
ACKSTAT Status Flag ..................................................... 225 Crystal Operation ....................................................... 31
ADC . ................................................................................ 265 EUSART Receive .................................................... 238
Acquisition Requirements ........................................ 275 EUSART Transmit ................................................... 237
Block Diagram .......................................................... 265 External POR Circuit (Slow VDD Power-up) .............. 53
Calculating Acquisition Time .................................... 275 External RC Mode ..................................................... 32
Channel Selection .................................................... 266 Fail-Safe Clock Monitor (FSCM) ................................ 40
Configuration ............................................................ 266 Generic I/O Port ....................................................... 121
Conversion Clock ..................................................... 266 High/Low-Voltage Detect with External Input .......... 294
Conversion Procedure ............................................. 270 Interrupt Logic .......................................................... 108
Internal Sampling Switch (RSS) IMPEDANCE ... .......... 275 MSSP (I2C Master Mode) ........................................ 219
Interrupts .................................................................. 267 MSSP (I2C Mode) .................................................... 202
Operation .. ............................................................... 268 MSSP (SPI Mode) ................................................... 193
Operation During Sleep ........................................... 269 On-Chip Reset Circuit ................................................ 51
Port Configuration .................................................... 266 PIC18F2XK20 ............................................................ 14
Power Management ................................................. 269 PIC18F4XK20 ............................................................ 15
Reference Voltage (VREF) ........................................ 266 PLL (HS Mode) .......................................................... 35
Result Formatting ..................................................... 267 PORTD and PORTE (Parallel Slave Port) ............... 139
Source Impedance ................................................... 275 PWM (Enhanced) .................................................... 175
Special Event Trigger ............................................... 269 Reads from Flash Program Memory ......................... 93
Starting an A/D Conversion ..................................... 267 Resonator Operation ................................................. 31
ADCON0 Register ............................................................ 271 Table Read Operation ............................................... 89
ADCON1 Register ............................................................ 272 Table Write Operation ............................................... 90
ADCON2 Register ............................................................ 273 Table Writes to Flash Program Memory .................... 95
ADDFSR . ......................................................................... 358 Timer0 in 16-Bit Mode ............................................. 157
ADDLW ... ......................................................................... 321 Timer0 in 8-Bit Mode ............................................... 156
ADDULNK . ....................................................................... 358 Timer1 .. ................................................................... 160
ADDWF ... ......................................................................... 321 Timer1 (16-Bit Read/Write Mode) ............................ 160
ADDWFC .. ....................................................................... 322 Timer2 .. ................................................................... 168
ADRESH Register (ADFM = 0) ........................................ 274 Timer3 .. ................................................................... 170
ADRESH Register (ADFM = 1) ........................................ 274 Timer3 (16-Bit Read/Write Mode) ............................ 171
ADRESL Register (ADFM = 0) ......................................... 274 Voltage Reference Output Buffer Example ............. 291
ADRESL Register (ADFM = 1) ......................................... 274 Watchdog Timer ...................................................... 308
Analog Input Connection Considerations ......................... 286 BN .................................................................................... 324
Analog-to-Digital Converter. See ADC BNC .. ............................................................................... 325
ANDLW ... ......................................................................... 322 BNN .. ............................................................................... 325
ANDWF ... ......................................................................... 323 BNOV . ............................................................................. 326
ANSEL (PORT Analog Control) ....................................... 136 BNZ .. ............................................................................... 326
ANSEL Register ............................................................... 136 BOR. See Brown-out Reset.
ANSELH Register ............................................................ 137 BOV .. ............................................................................... 329
Assembler BRA .. ............................................................................... 327
MPASM Assembler .................................................. 366 Break Character (12-bit) Transmit and Receive .............. 256
BRG. See Baud Rate Generator.
Brown-out Reset (BOR) ..................................................... 54

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PIC18F2XK20/4XK20
Detecting . ................................................................... 54 CM1CON0 Register ......................................................... 284
Disabling in Sleep Mode ............................................ 54 CM2CON0 Register ......................................................... 285
Minimun Enable Time ................................................ 54 CM2CON1 Register ......................................................... 287
Software Enabled ....................................................... 54 Code Examples
BSF .. ................................................................................ 327 16 x 16 Signed Multiply Routine .............................. 106
BTFSC . ............................................................................ 328 16 x 16 Unsigned Multiply Routine .......................... 106
BTFSS .............................................................................. 328 8 x 8 Signed Multiply Routine .................................. 105
BTG .................................................................................. 329 8 x 8 Unsigned Multiply Routine .............................. 105
BZ ..................................................................................... 330 A/D Conversion ........................................................ 270
Changing Between Capture Prescalers ................... 145
C Clearing RAM Using Indirect Addressing .................. 83
C Compilers Computed GOTO Using an Offset Value ................... 68
MPLAB C18 ............................................................. 366 Data EEPROM Read ............................................... 101
CALL .. .............................................................................. 330 Data EEPROM Refresh Routine .............................. 102
CALLW ............................................................................. 359 Data EEPROM Write ............................................... 101
Capture (CCP Module) ..................................................... 145 Erasing a Flash Program Memory Row ..................... 94
Associated Registers ............................................... 148 Fast Register Stack ................................................... 68
CCP Pin Configuration ............................................. 145 Implementing a Timer1 Real-Time Clock ................ 164
CCPRxH:CCPRxL Registers ................................... 145 Initializing PORTA .................................................... 121
Prescaler . ................................................................. 145 Initializing PORTB .................................................... 124
Software Interrupt .................................................... 145 Initializing PORTC ................................................... 127
Timer1/Timer3 Mode Selection ................................ 145 Initializing PORTD ................................................... 130
Capture (ECCP Module) .................................................. 174 Initializing PORTE .................................................... 133
Capture/Compare/PWM (CCP) ........................................ 143 Loading the SSPBUF (SSPSR) Register ................. 196
Capture Mode. See Capture. Reading a Flash Program Memory Word .................. 93
CCP Mode and Timer Resources ............................ 144 Saving Status, WREG and BSR Registers
CCPRxH Register .................................................... 144 in RAM ............................................................. 119
CCPRxL Register ..................................................... 144 Writing to Flash Program Memory ....................... 96–97
Compare Mode. See Compare. Code Protection ............................................................... 299
Interaction of Two CCP Modules ............................. 144 COMF .. ............................................................................ 332
Module Configuration ............................................... 144 Comparator
PWM Mode .............................................................. 149 Associated Registers ............................................... 288
Duty Cycle ........................................................ 150 Operation .. ............................................................... 279
Effects of Reset ................................................ 152 Operation During Sleep ........................................... 283
Example PWM Frequencies & Resolutions Response Time ........................................................ 281
Fosc=20 MHZ .......................................... 151 Comparator Module ......................................................... 279
Fosc=40 MHZ .......................................... 151 C1 Output State Versus Input Conditions ................ 281
Fosc=8 MHZ ............................................ 151 Comparator Specifications ............................................... 381
Operation in Sleep Mode ................................. 152 Comparator Voltage Reference (CVREF)
Setup for Operation .......................................... 152 Associated Registers ............................................... 292
System Clock Frequency Changes .................. 152 Effects of a Reset ............................................ 283, 289
PWM Period ............................................................. 150 Operation During Sleep ........................................... 289
Setup for PWM Operation ........................................ 152 Overview .................................................................. 289
CCP1CON Register ......................................................... 173 Comparator Voltage Reference (CVREF)
CCP2CON Register ......................................................... 143 Response Time ........................................................ 281
Clock Accuracy with Asynchronous Operation ................ 246 Comparators
Clock Sources Effects of a Reset .................................................... 283
Associated registers ................................................... 41 Compare (CCP Module) .................................................. 147
External Modes .......................................................... 30 Associated Registers ............................................... 148
EC ... ................................................................... 30 CCPRx Register ...................................................... 147
HS ... ................................................................... 31 Pin Configuration ..................................................... 147
LP ....................................................................... 31 Software Interrupt .................................................... 147
OST .................................................................... 30 Special Event Trigger ...................................... 147, 172
RC ...................................................................... 32 Timer1/Timer3 Mode Selection ................................ 147
XT ... ................................................................... 31 Compare (ECCP Module) ................................................ 174
Internal Modes ........................................................... 32 Special Event Trigger .............................................. 174
Frequency Selection .......................................... 34 Computed GOTO ............................................................... 68
HFINTOSC ......................................................... 32 CONFIG1H Register ........................................................ 301
INTOSC .. ........................................................... 32 CONFIG2H Register ........................................................ 302
INTOSCIO .......................................................... 32 CONFIG2L Register ........................................................ 302
LFINTOSC .. ....................................................... 34 CONFIG3H Register ........................................................ 303
Selecting the 31 kHz Source ...................................... 28 CONFIG4L Register ........................................................ 303
Selection Using OSCCON Register ........................... 28 CONFIG5H Register ........................................................ 304
Clock Switching .................................................................. 37 CONFIG5L Register ........................................................ 304
CLRF ................................................................................ 331 CONFIG6H Register ........................................................ 305
CLRWDT .......................................................................... 331

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 PIC18F2XK20/4XK20
CONFIG6L Register ......................................................... 305 Device Reset Timers ......................................................... 55
CONFIG7H Register ........................................................ 306 PLL Lock Time-out .................................................... 55
CONFIG7L Register ......................................................... 306 Power-up Timer (PWRT) ........................................... 55
Configuration Bits ............................................................. 300 Time-out Sequence ................................................... 55
Configuration Register Protection .................................... 313 DEVID1 Register ............................................................. 307
Context Saving During Interrupts ..................................... 119 DEVID2 Register ............................................................. 307
CPFSEQ . ......................................................................... 332 Direct Addressing .............................................................. 84
CPFSGT . ......................................................................... 333
CPFSLT .. ......................................................................... 333 E
Customer Change Notification Service ............................ 453 ECCPAS Register ............................................................ 183
Customer Notification Service .......................................... 453 EECON1 Register ...................................................... 91, 100
Customer Support ............................................................ 453 Effect on Standard PIC Instructions ................................. 362
CVREF Voltage Reference Specifications ........................ 381 Effects of Power Managed Modes on Various
Clock Sources ........................................................... 36
D Effects of Reset
Data Addressing Modes ..................................................... 83 PWM mode .............................................................. 152
Comparing Addressing Modes with the Electrical Characteristics ................................................. 369
Extended Instruction Set Enabled ..................... 86 Enhanced Capture/Compare/PWM (ECCP) .................... 173
Direct .......................................................................... 83 Associated Registers ............................................... 191
Indexed Literal Offset ................................................. 85 Capture and Compare Modes ................................. 174
Instructions Affected .......................................... 85 Capture Mode. See Capture (ECCP Module).
Indirect .. ..................................................................... 83 Enhanced PWM Mode ............................................. 175
Inherent and Literal .................................................... 83 Auto-Restart .. .................................................. 184
Data EEPROM Auto-shutdown .. .............................................. 183
Code Protection ....................................................... 313 Direction Change in Full-Bridge
Data EEPROM Memory ..................................................... 99 Output Mode ............................................ 181
Associated Registers ............................................... 103 Full-Bridge Application ..................................... 179
EEADR and EEADRH Registers ............................... 99 Full-Bridge Mode ............................................. 179
EECON1 and EECON2 Registers ............................. 99 Half-Bridge Application .................................... 178
Operation During Code-Protect ............................... 102 Half-Bridge Application Examples ................... 185
Protection Against Spurious Write ........................... 102 Half-Bridge Mode ............................................. 178
Reading .................................................................... 101 Output Relationships (Active-High and
Using ........................................................................ 102 Active-Low) .............................................. 176
Write Verify .............................................................. 101 Output Relationships Diagram ......................... 177
Writing ...................................................................... 101 Programmable Dead Band Delay .................... 185
Data Memory ..................................................................... 71 Shoot-through Current ..................................... 185
Access Bank .............................................................. 77 Start-up Considerations ................................... 182
and the Extended Instruction Set ............................... 85 Outputs and Configuration ....................................... 174
Bank Select Register (BSR) ....................................... 71 Standard PWM Mode .............................................. 174
General Purpose Registers ........................................ 77 Timer Resources ..................................................... 174
Map for PIC18F23K20/43K20 .................................... 72 Enhanced Universal Synchronous Asynchronous
Map for PIC18F24K20/44K20 .................................... 73 Receiver Transmitter (EUSART) ............................. 237
Map for PIC18F25K20/45K20 .............................. 74, 75 Errata .. ............................................................................... 10
Special Function Registers ........................................ 77 EUSART . ......................................................................... 237
DAW ................................................................................. 334 Asynchronous Mode ................................................ 239
DC and AC Characteristics 12-bit Break Transmit and Receive ................. 256
Graphs and Tables .................................................. 403 Associated Registers, Receive ........................ 245
DC Characteristics Associated Registers, Transmit ....................... 241
Input/Output . ............................................................ 377 Auto-Wake-up on Break .................................. 254
Peripheral Supply Current ........................................ 376 Baud Rate Generator (BRG) ........................... 249
Power-Down Current ............................................... 371 Clock Accuracy ................................................ 246
Primary Idle Supply Current ..................................... 374 Receiver .. ........................................................ 242
Primary Run Supply Current .................................... 374 Setting up 9-bit Mode with Address Detect ..... 244
RC Idle Supply Current ............................................ 373 Transmitter .. .................................................... 239
RC Run Supply Current ........................................... 372 Baud Rate Generator (BRG)
Secondary Oscillator Supply Current ....................... 375 Associated Registers ....................................... 249
Supply Voltage ......................................................... 371 Auto Baud Rate Detect .................................... 253
DCFSNZ . ......................................................................... 335 Baud Rate Error, Calculating ........................... 249
DECF . .............................................................................. 334 Baud Rates, Asynchronous Modes ................. 250
DECFSZ ........................................................................... 335 Formulas .......................................................... 249
Development Support ...................................................... 365 High Baud Rate Select (BRGH Bit) ................. 249
Device Differences ........................................................... 442 Clock polarity
Device Overview ................................................................ 11 Synchronous Mode .......................................... 257
Details on Individual Family Members ....................... 12 Data polarity
New Core Features .................................................... 11 Asychronous Receive ...................................... 242
Other Special Features .............................................. 12 Asychronous Transmit ..................................... 239

 2010 Microchip Technology Inc. DS41303G-page 445

PIC18F2XK20/4XK20
Synchronous Mode .......................................... 257 Characteristics .. ....................................................... 382
Interrupts Current Consumption ............................................... 295
Asychronous Receive ...................................... 243 Effects of a Reset .................................................... 297
Asychronous Transmit ..................................... 239 Operation .. ............................................................... 294
Synchronous Master Mode .............................. 257, 262 During Sleep .................................................... 297
Associated Registers, Receive ........................ 261 Setup .. ..................................................................... 295
Associated Registers, Transmit ............... 259, 262 Start-up Time ........................................................... 295
Reception ......................................................... 260 Typical Application ................................................... 297
Transmission .................................................... 257 HLVD. See High/Low-Voltage Detect. ............................. 293
Synchronous Slave Mode HLVDCON Register ......................................................... 293
Associated Registers, Receive ........................ 263
Reception ......................................................... 263 I
Transmission .................................................... 262 I/O Ports ........................................................................... 121
Extended Instruction Set I2C
ADDFSR . ................................................................. 358 Associated Registers ............................................... 235
ADDULNK . ............................................................... 358 I2C Mode (MSSP)
and Using MPLAB Tools .......................................... 364 Acknowledge Sequence Timing .............................. 228
CALLW ..................................................................... 359 Baud Rate Generator .............................................. 221
Considerations for Use ............................................ 362 Bus Collision
MOVSF ... ................................................................. 359 During a Repeated Start Condition .................. 232
MOVSS ... ................................................................. 360 During a Stop Condition .................................. 234
PUSHL . .................................................................... 360 Clock Arbitration ...................................................... 222
SUBFSR . ................................................................. 361 Clock Stretching ....................................................... 214
SUBULNK . ............................................................... 361 10-Bit Slave Receive Mode (SEN = 1) ............ 214
Syntax .. .................................................................... 357 10-Bit Slave Transmit Mode ............................ 214
7-Bit Slave Receive Mode (SEN = 1) .............. 214
F 7-Bit Slave Transmit Mode .............................. 214
Fail-Safe Clock Monitor .............................................. 40, 299 Clock Synchronization and the CKP bit (SEN = 1) .. 215
Fail-Safe Condition Clearing ...................................... 40 Effects of a Reset .................................................... 229
Fail-Safe Detection .................................................... 40 General Call Address Support ................................. 218
Fail-Safe Operation .................................................... 40 I2C Clock Rate w/BRG ............................................. 221
Reset or Wake-up from Sleep .................................... 40 Master Mode ............................................................ 219
Fast Register Stack ............................................................ 68 Operation ......................................................... 220
Firmware Instructions ....................................................... 315 Reception . ....................................................... 225
Flash Program Memory ...................................................... 89 Repeated Start Condition Timing .................... 224
Associated Registers ................................................. 97 Start Condition Timing ..................................... 223
Control Registers ....................................................... 90 Transmission .. ................................................. 225
EECON1 and EECON2 ..................................... 90 Multi-Master Communication, Bus Collision
TABLAT (Table Latch) Register ......................... 92 and Arbitration ................................................. 229
TBLPTR (Table Pointer) Register ...................... 92 Multi-Master Mode ................................................... 229
Erase Sequence ........................................................ 94 Operation .. ............................................................... 207
Erasing ....................................................................... 94 Read/Write Bit Information (R/W Bit) ............... 207, 208
Operation During Code-Protect ................................. 97 Registers .. ............................................................... 202
Reading ...................................................................... 93 Serial Clock (RC3/SCK/SCL) ................................... 208
Table Pointer Slave Mode .............................................................. 207
Boundaries Based on Operation ........................ 92 Addressing ....................................................... 207
Table Pointer Boundaries .......................................... 92 Reception . ....................................................... 208
Table Reads and Table Writes .................................. 89 Transmission .. ................................................. 208
Write Sequence ......................................................... 95 Sleep Operation ....................................................... 229
Writing To ................................................................... 95 Stop Condition Timing ............................................. 228
Protection Against Spurious Writes ................... 97 ID Locations ............................................................. 299, 313
Unexpected Termination .................................... 97 INCF .. .............................................................................. 336
Write Verify ........................................................ 97 INCFSZ ............................................................................ 337
In-Circuit Debugger .......................................................... 313
G In-Circuit Serial Programming (ICSP) ...................... 299, 313
General Call Address Support ......................................... 218 Indexed Literal Offset Addressing
GOTO ............................................................................... 336 and Standard PIC18 Instructions ............................. 362
Indexed Literal Offset Mode ............................................. 362
H Indirect Addressing ............................................................ 84
Hardware Multiplier .......................................................... 105 INFSNZ ............................................................................ 337
Introduction . ............................................................. 105 Initialization Conditions for all Registers ...................... 59–62
Operation .. ............................................................... 105 Instruction Cycle ................................................................ 69
Performance Comparison ........................................ 105 Clocking Scheme ....................................................... 69
High/Low-Voltage Detect ................................................. 293 Instruction Flow/Pipelining ................................................. 69
Applications .............................................................. 297 Instruction Set .................................................................. 315
Associated Registers ............................................... 297 ADDLW .................................................................... 321

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 PIC18F2XK20/4XK20
ADDWF .................................................................... 321 SUBLW .................................................................... 351
ADDWF (Indexed Literal Offset Mode) .................... 363 SUBWF .................................................................... 351
ADDWFC .. ............................................................... 322 SUBWFB .. ............................................................... 352
ANDLW . ................................................................... 322 SWAPF .................................................................... 352
ANDWF .................................................................... 323 TBLRD ..................................................................... 353
BC ... ......................................................................... 323 TBLWT . ................................................................... 354
BCF .......................................................................... 324 TSTFSZ .. ................................................................. 355
BN ... ......................................................................... 324 XORLW .. ................................................................. 355
BNC .. ....................................................................... 325 XORWF .. ................................................................. 356
BNN .. ....................................................................... 325 INTCON Register ............................................................. 109
BNOV ....................................................................... 326 INTCON Registers ................................................... 109–111
BNZ .......................................................................... 326 INTCON2 Register ........................................................... 110
BOV .. ....................................................................... 329 INTCON3 Register ........................................................... 111
BRA .......................................................................... 327 Inter-Integrated Circuit. See I2C.
BSF . ......................................................................... 327 Internal Oscillator Block
BSF (Indexed Literal Offset Mode) .......................... 363 HFINTOSC Frequency Drift ....................................... 34
BTFSC .. ................................................................... 328 PLL in HFINTOSC Modes ......................................... 35
BTFSS .. ................................................................... 328 Internal RC Oscillator
BTG .......................................................................... 329 Use with WDT .......................................................... 308
BZ ... ......................................................................... 330 Internal Sampling Switch (RSS) IMPEDANCE ... .................. 275
CALL . ....................................................................... 330 Internet Address .............................................................. 453
CLRF ........................................................................ 331 Interrupt Sources ............................................................. 299
CLRWDT .................................................................. 331 ADC .. ....................................................................... 267
COMF . ..................................................................... 332 Capture Complete (CCP) ........................................ 145
CPFSEQ . ................................................................. 332 Compare Complete (CCP) ...................................... 147
CPFSGT . ................................................................. 333 Interrupt-on-Change (RB7:RB4) .............................. 124
CPFSLT .. ................................................................. 333 INTn Pin ................................................................... 119
DAW ......................................................................... 334 PORTB, Interrupt-on-Change .................................. 119
DCFSNZ . ................................................................. 335 TMR0 ....................................................................... 119
DECF .. ..................................................................... 334 TMR0 Overflow ........................................................ 157
DECFSZ ................................................................... 335 TMR1 Overflow ........................................................ 159
Extended Instruction Set .......................................... 357 TMR3 Overflow ................................................ 169, 171
General Format ........................................................ 317 Interrupts .. ....................................................................... 107
GOTO . ..................................................................... 336 IORLW .. ........................................................................... 338
INCF ......................................................................... 336 IORWF ............................................................................. 338
INCFSZ . ................................................................... 337 IPR Registers ................................................................... 116
INFSNZ . ................................................................... 337 IPR1 Register .................................................................. 116
IORLW .. ................................................................... 338 IPR2 Register .................................................................. 117
IORWF .. ................................................................... 338
LFSR ........................................................................ 339 L
MOVF ....................................................................... 339 LFSR .. ............................................................................. 339
MOVFF . ................................................................... 340 Low-Voltage ICSP Programming. See Single-Supply
MOVLB . ................................................................... 340 ICSP Programming
MOVLW .. ................................................................. 341
MOVWF .. ................................................................. 341
M
MULLW . ................................................................... 342 Master Clear (MCLR) ......................................................... 53
MULWF .................................................................... 342 Master Synchronous Serial Port (MSSP). See MSSP.
NEGF .. ..................................................................... 343 Memory Organization ........................................................ 65
NOP .. ....................................................................... 343 Data Memory ............................................................. 71
Opcode Field Descriptions ....................................... 316 Program Memory ....................................................... 65
POP .. ....................................................................... 344 Microchip Internet Web Site ............................................. 453
PUSH .. ..................................................................... 344 MOVF . ............................................................................. 339
RCALL .. ................................................................... 345 MOVFF . ........................................................................... 340
RESET .. ................................................................... 345 MOVLB . ........................................................................... 340
RETFIE . ................................................................... 346 MOVLW .. ......................................................................... 341
RETLW . ................................................................... 346 MOVSF . ........................................................................... 359
RETURN . ................................................................. 347 MOVSS ............................................................................ 360
RLCF ........................................................................ 347 MOVWF .. ......................................................................... 341
RLNCF .. ................................................................... 348 MPLAB ASM30 Assembler, Linker, Librarian .................. 366
RRCF .. ..................................................................... 348 MPLAB Integrated Development Environment
RRNCF . ................................................................... 349 Software . ................................................................. 365
SETF ........................................................................ 349 MPLAB PM3 Device Programmer ................................... 368
SETF (Indexed Literal Offset Mode) ........................ 363 MPLAB REAL ICE In-Circuit Emulator System ............... 367
SLEEP .. ................................................................... 350 MPLINK Object Linker/MPLIB Object Librarian ............... 366
SUBFWB .................................................................. 350 MSSP
ACK Pulse ....................................................... 207, 208

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PIC18F2XK20/4XK20
Control Registers (general) ...................................... 193 RB1/INT1/AN10/C12IN3- ........................................... 22
I2C Mode. See I2C Mode. RB1/INT1/AN10/P1C/C12IN3- ................................... 18
Module Overview ..................................................... 193 RB2/INT2/AN8 .. ......................................................... 22
SPI Master/Slave Connection .................................. 197 RB2/INT2/AN8/P1B .. ................................................. 18
SPI Mode. See SPI Mode. RB3/AN9/CCP2/C12IN2- ..................................... 18, 22
SSPBUF Register .................................................... 198 RB4/KBI0/AN11 ... ...................................................... 22
SSPSR Register ...................................................... 198 RB4/KBI0/AN11/P1D .. ............................................... 18
MULLW .. .......................................................................... 342 RB5/KBI1/PGM .................................................... 18, 22
MULWF .. .......................................................................... 342 RB6/KBI2/PGC . ................................................... 18, 22
RB7/KBI3/PGD . ................................................... 18, 22
N RC0/T1OSO/T13CKI . .......................................... 19, 23
NEGF . .............................................................................. 343 RC1/T1OSI/CCP2 ................................................ 19, 23
NOP . ................................................................................ 343 RC2/CCP1/P1A ... ................................................ 19, 23
RC3/SCK/SCL .. ................................................... 19, 23
O RC4/SDI/SDA . ..................................................... 19, 23
OSCCON Register ............................................................. 29 RC5/SDO ............................................................. 19, 23
Oscillator Configuration RC6/TX/CK . ......................................................... 19, 23
EC .. ............................................................................ 27 RC7/RX/DT .......................................................... 19, 23
ECIO .. ........................................................................ 27 RD0/PSP0 .. ............................................................... 24
HS .. ............................................................................ 27 RD1/PSP1 .. ............................................................... 24
HSPLL ........................................................................ 27 RD2/PSP2 .. ............................................................... 24
INTOSC .. ................................................................... 27 RD3/PSP3 .. ............................................................... 24
INTOSCIO .................................................................. 27 RD4/PSP4 .. ............................................................... 24
LP ............................................................................... 27 RD5/PSP5/P1B ... ...................................................... 24
RC .............................................................................. 27 RD6/PSP6/P1C ... ...................................................... 24
RCIO .. ........................................................................ 27 RD7/PSP7/P1D ... ...................................................... 24
XT .. ............................................................................ 27 RE0/RD/AN5 .............................................................. 25
Oscillator Module ............................................................... 27 RE1/WR/AN6 ............................................................. 25
HFINTOSC ................................................................. 27 RE2/CS/AN7 .............................................................. 25
LFINTOSC .. ............................................................... 27 VDD .. .................................................................... 19, 25
Oscillator Selection .......................................................... 299 VSS .. .................................................................... 19, 25
Oscillator Start-up Timer (OST) ................................... 36, 55 Pinout I/O Descriptions
Oscillator Switching PIC18F2XK20 ............................................................ 16
Fail-Safe Clock Monitor .............................................. 40 PIC18F4XK20 ............................................................ 20
Two-Speed Clock Start-up ......................................... 38 PIR Registers ................................................................... 112
Oscillator, Timer1 ..................................................... 159, 171 PIR1 Register .................................................................. 112
Oscillator, Timer3 ............................................................. 169 PIR2 Register .................................................................. 113
OSCTUNE Register ........................................................... 33 PLL Frequency Multiplier ................................................... 35
HSPLL Oscillator Mode ............................................. 35
P
POP . ................................................................................ 344
P1A/P1B/P1C/P1D.See Enhanced Capture/ POR. See Power-on Reset.
Compare/PWM (ECCP) ........................................... 175 PORTA
Packaging Information ..................................................... 427 Associated Registers ............................................... 123
Marking ... ................................................................. 427 LATA Register ......................................................... 121
Parallel Slave Port (PSP) ......................................... 130, 139 PORTA Register ...................................................... 121
Associated Registers ............................................... 141 TRISA Register ........................................................ 121
CS (Chip Select) ...................................................... 139 PORTB
PORTD ... ................................................................. 139 Associated Registers ............................................... 126
RD (Read Input) ....................................................... 139 LATB Register ......................................................... 124
Select (PSPMODE Bit) .................................... 130, 139 PORTB Register ...................................................... 124
WR (Write Input) ...................................................... 139 TRISB Register ........................................................ 124
PIE Registers ................................................................... 114 PORTC
PIE1 Register ................................................................... 114 Associated Registers ............................................... 129
PIE2 Register ................................................................... 115 LATC Register ......................................................... 127
Pin Functions PORTC Register ...................................................... 127
MCLR/VPP/RE3 .................................................... 16, 20 RC3/SCK/SCL Pin ................................................... 208
OSC1/CLKI/RA7 . ................................................. 16, 20 TRISC Register ........................................................ 127
OSC2/CLKO/RA6 . ............................................... 16, 20 PORTD
RA0/AN0/C12IN0- ................................................ 17, 21 Associated Registers ............................................... 132
RA1/AN1/C12IN0- ...................................................... 21 LATD Register ......................................................... 130
RA1/AN1/C12IN1- ...................................................... 17 Parallel Slave Port (PSP) Function .......................... 130
RA2/AN2/VREF-/CVREF/C2IN+ ............................. 17, 21 PORTD Register ...................................................... 130
RA3/AN3/VREF+/C1IN+ ........................................ 17, 21 TRISD Register ........................................................ 130
RA4/T0CKI/C1OUT .............................................. 17, 21 PORTE
RA5/AN4/SS/HLVDIN/C2OUT . ............................ 17, 21 Associated Registers ............................................... 135
RB0/INT0/FLT0/AN12 .......................................... 18, 22

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 PIC18F2XK20/4XK20
LATE Register .......................................................... 133 PWM1CON Register ........................................................ 186
PORTE Register ...................................................... 133
PSP Mode Select (PSPMODE Bit) .......................... 130 R
TRISE Register ........................................................ 133 RAM. See Data Memory.
Power Managed Modes ..................................................... 43 RC_IDLE Mode .................................................................. 48
and A/D Operation ................................................... 269 RCALL .. ........................................................................... 345
and PWM Operation ................................................ 190 RCON Register .......................................................... 52, 118
and SPI Operation ................................................... 201 Bit Status During Initialization .................................... 58
Clock Transitions and Status Indicators ..................... 44 RCREG ............................................................................ 244
Effects on Clock Sources ........................................... 36 RCSTA Register .............................................................. 247
Entering ...................................................................... 43 Reader Response ............................................................ 454
Exiting Idle and Sleep Modes .................................... 48 Register
by Interrupt ......................................................... 48 RCREG Register ..................................................... 253
by Reset ............................................................. 48 Register File ....................................................................... 77
by WDT Time-out ............................................... 48 Register File Summary ................................................ 79–81
Without a Start-up Delay .................................... 49 Registers
Idle Modes ................................................................. 45 ADCON0 (ADC Control 0) ....................................... 271
PRI_IDLE .. ......................................................... 47 ADCON1 (ADC Control 1) ....................................... 272
RC_IDLE ............................................................ 48 ADCON2 (ADC Control 2) ....................................... 273
SEC_IDLE ... ...................................................... 47 ADRESH (ADC Result High) with ADFM = 0) ......... 274
Multiple Sleep Functions ............................................ 44 ADRESH (ADC Result High) with ADFM = 1) ......... 274
Run Modes ................................................................. 44 ADRESL (ADC Result Low) with ADFM = 0) ........... 274
PRI_RUN .. ......................................................... 44 ADRESL (ADC Result Low) with ADFM = 1) ........... 274
SEC_RUN .......................................................... 44 ANSEL (Analog Select 1) ........................................ 136
Selecting . ................................................................... 43 ANSEL (PORT Analog Control) ............................... 136
Sleep Mode ................................................................ 45 ANSELH (Analog Select 2) ...................................... 137
Summary (table) ........................................................ 43 ANSELH (PORT Analog Control) ............................ 137
Power-on Reset (POR) ...................................................... 53 BAUDCON (Baud Rate Control) .............................. 248
Power-up Timer (PWRT) ........................................... 55 BAUDCON (EUSART Baud Rate Control) .............. 248
Time-out Sequence .................................................... 55 CCP1CON (Enhanced Capture/Compare/PWM
Power-up Delays ................................................................ 36 Control) ............................................................ 173
Power-up Timer (PWRT) ................................................... 36 CCP2CON (Standard Capture/Compare/PWM
Prescaler, Timer0 ............................................................. 157 Control) ............................................................ 143
PRI_IDLE Mode ................................................................. 47 CM1CON0 (C1 Control) .......................................... 284
PRI_RUN Mode ................................................................. 44 CM2CON0 (C2 Control) .......................................... 285
Program Counter ............................................................... 66 CM2CON1 (C2 Control) .......................................... 287
PCL, PCH and PCU Registers ................................... 66 CONFIG1H (Configuration 1 High) .......................... 301
PCLATH and PCLATU Registers .............................. 66 CONFIG2H (Configuration 2 High) .......................... 302
Program Memory CONFIG2L (Configuration 2 Low) ........................... 302
and Extended Instruction Set ..................................... 87 CONFIG3H (Configuration 3 High) .......................... 303
Code Protection ....................................................... 311 CONFIG4L (Configuration 4 Low) ........................... 303
Instructions ................................................................. 70 CONFIG5H (Configuration 5 High) .......................... 304
Two-Word . ......................................................... 70 CONFIG5L (Configuration 5 Low) ........................... 304
Interrupt Vector .......................................................... 65 CONFIG6H (Configuration 6 High) .......................... 305
Look-up Tables .......................................................... 68 CONFIG6L (Configuration 6 Low) ........................... 305
Map and Stack (diagram) ........................................... 65 CONFIG7H (Configuration 7 High) .......................... 306
Reset Vector .............................................................. 65 CONFIG7L (Configuration 7 Low) ........................... 306
Program Verification and Code Protection ....................... 310 CVRCON (Comparator Voltage Reference
Associated Registers ............................................... 310 Control CVRCON Register .............................. 291
Programming, Device Instructions ................................... 315 CVRCON2 (Comparator Voltage Reference
PSP. See Parallel Slave Port. Control 2) CVRCON2 Register ........................ 292
PSTRCON Register ......................................................... 187 DEVID1 (Device ID 1) .............................................. 307
Pulse Steering .................................................................. 187 DEVID2 (Device ID 2) .............................................. 307
PUSH . .............................................................................. 344 ECCPAS (Enhanced CCP Auto-shutdown
PUSH and POP Instructions .............................................. 67 Control) ............................................................ 183
PUSHL . ............................................................................ 360 EECON1 (Data EEPROM Control 1) ................. 91, 100
PWM (CCP Module) HLVDCON (High/Low-Voltage Detect Control) ....... 293
Associated Registers ............................................... 153 INTCON (Interrupt Control) ..................................... 109
PWM (ECCP Module) INTCON2 (Interrupt Control 2) ................................ 110
Effects of a Reset ..................................................... 190 INTCON3 (Interrupt Control 3) ................................ 111
Operation in Power Managed Modes ...................... 190 IPR1 (Peripheral Interrupt Priority 1) ....................... 116
Operation with Fail-Safe Clock Monitor ................... 190 IPR2 (Peripheral Interrupt Priority 2) ....................... 117
Pulse Steering .......................................................... 187 OSCCON (Oscillator Control) .................................... 29
Steering Synchronization ......................................... 189 OSCTUNE (Oscillator Tuning) ................................... 33
PWM Mode. See Enhanced Capture/Compare/PWM ..... 175 PIE1 (Peripheral Interrupt Enable 1) ....................... 114
PIE2 (Peripheral Interrupt Enable 2) ....................... 115

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PIC18F2XK20/4XK20
PIR1 (Peripheral Interrupt Request 1) ..................... 112 Special Event Trigger ...................................................... 269
PIR2 (Peripheral Interrupt Request 2) ..................... 113 Special Event Trigger. See Compare (ECCP Mode).
PSTRCON (Pulse Steering Control) ........................ 187 Special Event Trigger. See Compare (ECCP Module).
PWM1CON (Enhanced PWM Control) .................... 186 Special Features of the CPU ........................................... 299
RCON (Reset Control) ....................................... 52, 118 Special Function Registers ................................................ 77
RCON (Reset control) .............................................. 118 Map ............................................................................ 78
RCSTA (Receive Status and Control) ...................... 247 SPI Mode (MSSP)
SLRCON (PORT Slew Rate Control) ....................... 138 Associated Registers ............................................... 201
SSPADD (MSSP Address and Baud Rate, Bus Mode Compatibility ........................................... 201
SPI Mode) ........................................................ 203 Effects of a Reset .................................................... 201
SSPCON1 (MSSP Control 1, I2C Mode) ................. 205 Enabling SPI I/O ...................................................... 197
SSPCON1 (MSSP Control 1, SPI Mode) ................. 195 Master Mode ............................................................ 198
SSPCON2 (MSSP Control 2, I2C Mode) ................. 206 Master/Slave Connection ......................................... 197
SSPMSK (SSP Mask) .............................................. 213 Operation .. ............................................................... 196
SSPSTAT (MSSP Status, SPI Mode) .............. 194, 204 Operation in Power Managed Modes ...................... 201
STATUS ..................................................................... 82 Serial Clock .............................................................. 193
STKPTR (Stack Pointer) ............................................ 67 Serial Data In ........................................................... 193
T0CON (Timer0 Control) .......................................... 155 Serial Data Out ........................................................ 193
T1CON (Timer1 Control) .......................................... 159 Slave Mode .............................................................. 199
T2CON (Timer2 Control) .......................................... 167 Slave Select ............................................................. 193
T3CON (Timer3 Control) .......................................... 169 Slave Select Synchronization .................................. 199
TRISE (PORTE/PSP Control) .................................. 134 SPI Clock ................................................................. 198
TXSTA (Transmit Status and Control) ..................... 246 Typical Connection .................................................. 197
WDTCON (Watchdog Timer Control) ....................... 309 SS .. .................................................................................. 193
RESET . ............................................................................ 345 SSPADD Register ............................................................ 203
Reset State of Registers .................................................... 58 SSPCON1 Register ................................................. 195, 205
Resets .. ...................................................................... 51, 299 SSPCON2 Register ......................................................... 206
Brown-out Reset (BOR) ........................................... 299 SSPMSK Register ........................................................... 213
Oscillator Start-up Timer (OST) ............................... 299 SSPOV ... ......................................................................... 225
Power-on Reset (POR) ............................................ 299 SSPOV Status Flag ......................................................... 225
Power-up Timer (PWRT) ......................................... 299 SSPSTAT Register .................................................. 194, 204
RETFIE .. .......................................................................... 346 R/W Bit ............................................................ 207, 208
RETLW ............................................................................. 346 Stack Full/Underflow Resets .............................................. 68
RETURN .. ........................................................................ 347 Standard Instructions ....................................................... 315
Return Address Stack ........................................................ 66 STATUS Register .............................................................. 82
Return Stack Pointer (STKPTR) ........................................ 67 STKPTR Register .............................................................. 67
Revision History ............................................................... 441 SUBFSR .. ........................................................................ 361
RLCF ................................................................................ 347 SUBFWB .. ....................................................................... 350
RLNCF . ............................................................................ 348 SUBLW ... ......................................................................... 351
RRCF . .............................................................................. 348 SUBULNK .. ...................................................................... 361
RRNCF ............................................................................. 349 SUBWF ............................................................................ 351
SUBWFB .. ....................................................................... 352
S SWAPF ... ......................................................................... 352
SCK .................................................................................. 193
SDI . .................................................................................. 193 T
SDO . ................................................................................ 193 T0CON Register .............................................................. 155
SEC_IDLE Mode ................................................................ 47 T1CON Register .............................................................. 159
SEC_RUN Mode ................................................................ 44 T2CON Register .............................................................. 167
Serial Clock, SCK ............................................................. 193 T3CON Register .............................................................. 169
Serial Data In (SDI) .......................................................... 193 Table Pointer Operations (table) ........................................ 92
Serial Data Out (SDO) ..................................................... 193 Table Reads/Table Writes ................................................. 68
Serial Peripheral Interface. See SPI Mode. TBLRD . ............................................................................ 353
SETF .. .............................................................................. 349 TBLWT ............................................................................. 354
Shoot-through Current ..................................................... 185 Time-out in Various Situations (table) ................................ 55
Single-Supply ICSP Programming. Timer0 .............................................................................. 155
Slave Select (SS) .. ........................................................... 193 Associated Registers ............................................... 157
Slave Select Synchronization ........................................... 199 Operation .. ............................................................... 156
SLEEP .............................................................................. 350 Overflow Interrupt .................................................... 157
Sleep Prescaler .. ............................................................... 157
OSC1 and OSC2 Pin States ...................................... 36 Prescaler Assignment (PSA Bit) .............................. 157
Sleep Mode ........................................................................ 45 Prescaler Select (T0PS2:T0PS0 Bits) ..................... 157
Slew Rate ......................................................................... 138 Prescaler. See Prescaler, Timer0.
SLRCON Register ............................................................ 138 Reads and Writes in 16-Bit Mode ............................ 156
Software Simulator (MPLAB SIM) .................................... 367 Source Edge Select (T0SE Bit) ............................... 156
SPBRG ............................................................................. 249 Source Select (T0CS Bit) ......................................... 156
SPBRGH .. ........................................................................ 249 Switching Prescaler Assignment ............................. 157

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 PIC18F2XK20/4XK20
Timer1 .. ............................................................................ 159 Full-Bridge PWM Output .......................................... 180
16-Bit Read/Write Mode ........................................... 162 Half-Bridge PWM Output ................................. 178, 185
Associated Registers ............................................... 165 High/Low-Voltage Detect Characteristics ................ 382
Asynchronous Counter Mode .................................. 161 High/Low-Voltage Detect Operation
Reading and Writing ........................................ 161 (VDIRMAG = 0) ............................................... 295
Interrupt .................................................................... 163 High/Low-Voltage Detect Operation
Operation .. ............................................................... 160 (VDIRMAG = 1) ............................................... 296
Oscillator . ......................................................... 159, 162 I2C Bus Data ............................................................ 396
Oscillator Layout Considerations ............................. 163 I2C Bus Start/Stop Bits ............................................ 396
Overflow Interrupt .................................................... 159 I2C Master Mode (7 or 10-Bit Transmission) ........... 226
Prescaler .................................................................. 161 I2C Master Mode (7-Bit Reception) ......................... 227
Resetting, Using the CCP Special Event Trigger ..... 163 I2C Slave Mode (10-Bit Reception, SEN = 0) .......... 211
Special Event Trigger (ECCP) ................................. 174 I2C Slave Mode (10-Bit Reception, SEN = 1) .......... 217
TMR1H Register ...................................................... 159 I2C Slave Mode (10-Bit Transmission) .................... 212
TMR1L Register ....................................................... 159 I2C Slave Mode (7-bit Reception, SEN = 0) ............ 209
Use as a Real-Time Clock ....................................... 164 I2C Slave Mode (7-Bit Reception, SEN = 1) ............ 216
Timer2 .. ............................................................................ 167 I2C Slave Mode (7-Bit Transmission) ...................... 210
Associated Registers ............................................... 168 I2C Slave Mode General Call Address
Interrupt .................................................................... 168 Sequence (7 or 10-Bit Address Mode) ............ 218
Operation .. ............................................................... 167 I2C Stop Condition Receive or Transmit Mode ........ 228
Output . ..................................................................... 168 Internal Oscillator Switch Timing ............................... 39
Timer3 .. ............................................................................ 169 Master SSP I2C Bus Data ....................................... 398
16-Bit Read/Write Mode ........................................... 171 Master SSP I2C Bus Start/Stop Bits ........................ 398
Associated Registers ............................................... 172 Parallel Slave Port (PIC18F4XK20) ......................... 391
Operation .. ............................................................... 170 Parallel Slave Port (PSP) Read ............................... 140
Oscillator . ......................................................... 169, 171 Parallel Slave Port (PSP) Write ............................... 140
Overflow Interrupt ............................................ 169, 171 PWM Auto-shutdown
Special Event Trigger (CCP) .................................... 172 Auto-restart Enabled ........................................ 184
TMR3H Register ...................................................... 169 Firmware Restart ............................................. 184
TMR3L Register ....................................................... 169 PWM Direction Change ........................................... 181
Timing Diagrams PWM Direction Change at Near 100% Duty Cycle .. 182
A/D Conversion ........................................................ 402 PWM Output (Active-High) ...................................... 176
Acknowledge Sequence .......................................... 228 PWM Output (Active-Low) ....................................... 177
Asynchronous Reception ......................................... 245 Repeat Start Condition ............................................ 224
Asynchronous Transmission .................................... 240 Reset, Watchdog Timer (WDT), Oscillator Start-up
Asynchronous Transmission (Back to Back) ........... 241 Timer (OST), Power-up Timer (PWRT) .......... 388
Auto Wake-up Bit (WUE) During Normal Send Break Character Sequence ............................ 256
Operation .. ....................................................... 255 Slave Synchronization ............................................. 199
Auto Wake-up Bit (WUE) During Sleep ................... 255 Slow Rise Time (MCLR Tied to VDD,
Automatic Baud Rate Calculator .............................. 254 VDD Rise > TPWRT) . ........................................... 57
Baud Rate Generator with Clock Arbitration ............ 222 SPI Mode (Master Mode) ........................................ 198
BRG Reset Due to SDA Arbitration During SPI Mode (Slave Mode, CKE = 0) ........................... 200
Start Condition ................................................. 231 SPI Mode (Slave Mode, CKE = 1) ........................... 200
Brown-out Reset (BOR) ........................................... 388 Synchronous Reception (Master Mode, SREN) ...... 261
Bus Collision During a Repeated Start Condition Synchronous Transmission ..................................... 258
(Case 1) ........................................................... 232 Synchronous Transmission (Through TXEN) .......... 258
Bus Collision During a Repeated Start Condition Time-out Sequence on POR w/PLL Enabled
(Case 2) ........................................................... 233 (MCLR Tied to VDD) .. ........................................ 57
Bus Collision During a Start Condition (SCL = 0) .... 231 Time-out Sequence on Power-up (MCLR
Bus Collision During a Stop Condition (Case 1) ...... 234 Not Tied to VDD, Case 1) ................................... 56
Bus Collision During a Stop Condition (Case 2) ...... 234 Time-out Sequence on Power-up (MCLR
Bus Collision During Start Condition (SDA only) ..... 230 Not Tied to VDD, Case 2) ................................... 56
Bus Collision for Transmit and Acknowledge ........... 229 Time-out Sequence on Power-up (MCLR
Capture/Compare/PWM (CCP) ................................ 390 Tied to VDD, VDD Rise < TPWRT) ... .................... 56
CLKO and I/O .......................................................... 387 Timer0 and Timer1 External Clock .......................... 389
Clock Synchronization ............................................. 215 Timer1 Incrementing Edge ...................................... 161
Clock/Instruction Cycle .............................................. 69 Transition for Entry to Sleep Mode ............................ 46
Comparator Output .................................................. 279 Transition for Wake from Sleep (HSPLL) .................. 46
Example SPI Master Mode (CKE = 0) ..................... 392 Transition Timing for Entry to Idle Mode .................... 47
Example SPI Master Mode (CKE = 1) ..................... 393 Transition Timing for Wake from Idle to
Example SPI Slave Mode (CKE = 0) ....................... 394 Run Mode .......................................................... 47
Example SPI Slave Mode (CKE = 1) ....................... 395 USART Synchronous Receive (Master/Slave) ........ 400
External Clock (All Modes except PLL) .................... 384 USART Synchronous Transmission
Fail-Safe Clock Monitor (FSCM) ................................ 41 (Master/Slave) .. ............................................... 400
First Start Bit Timing ................................................ 223 Timing Diagrams and Specifications ............................... 384

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PIC18F2XK20/4XK20
A/D Conversion Requirements ................................ 402
Capture/Compare/PWM Requirements ................... 390
CLKO and I/O Requirements ................................... 387
Example SPI Mode Requirements
(Master Mode, CKE = 0) .................................. 392
(Master Mode, CKE = 1) .................................. 393
(Slave Mode, CKE = 0) .................................... 394
(Slave Mode, CKE = 1) .................................... 395
External Clock Requirements .................................. 385
I2C Bus Data Requirements (Slave Mode) .............. 397
I2C Bus Start/Stop Bits Requirements
(Slave Mode) .................................................... 396
Master SSP I2C Bus Data Requirements ................ 399
Master SSP I2C Bus Start/Stop Bits
Requirements ................................................... 398
Parallel Slave Port Requirements (PIC18F4X20) .... 391
PLL Clock ................................................................. 386
Reset, Watchdog Timer, Oscillator Start-up Timer,
Power-up Timer and Brown-out Reset
Requirements ................................................... 388
Timer0 and Timer1 External Clock Requirements ... 389
USART Synchronous Receive Requirements ......... 400
USART Synchronous Transmission
Requirements ................................................... 400
Top-of-Stack Access .......................................................... 66
TRISE Register ................................................................ 134
PSPMODE Bit .......................................................... 130
TSTFSZ ............................................................................ 355
Two-Speed Clock Start-up Mode ....................................... 38
Two-Speed Start-up ......................................................... 299
Two-Word Instructions
Example Cases .......................................................... 70
TXREG ............................................................................. 239
TXSTA Register ............................................................... 246
BRGH Bit ................................................................. 249

V
Voltage Reference (VR)
Specifications ........................................................... 381
Voltage Reference. See Comparator Voltage
Reference (CVREF)
Voltage References
Fixed Voltage Reference (FVR) ............................... 290
VR Stabilization ........................................................ 290
VREF. SEE ADC Reference Voltage

W
Wake-up on Break ........................................................... 254
Watchdog Timer (WDT) ........................................... 299, 308
Associated Registers ............................................... 309
Control Register ....................................................... 309
Programming Considerations .................................. 308
WCOL ...................................................... 223, 224, 225, 228
WCOL Status Flag ................................... 223, 224, 225, 228
WDTCON Register ........................................................... 309
WWW Address ................................................................. 453
WWW, On-Line Support ..................................................... 10

X
XORLW .. .......................................................................... 355
XORWF ............................................................................ 356

DS41303G-page 452  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
THE MICROCHIP WEB SITE CUSTOMER SUPPORT
Microchip provides online support via our WWW site at Users of Microchip p roducts c an rec eive as sistance
www.microchip.com. This web site is used as a means through several channels:
to m ake fi les an d i nformation e asily av ailable to • Distributor or Representative
customers. Accessible by using your favorite Internet
• Local Sales Office
browser, th e w eb si te c ontains the following
information: • Field Application Engineer (FAE)
• Technical Support
• Product Support – Data sheets and errata,
application notes and sample programs, design • Development Systems Information Line
resources, user’s guides and hardware support Customers sh ould con tact the ir dis tributor,
documents, latest software releases and archived representative o r fi eld application en gineer (FAE) f or
software support. Local sales offices are also available to help
• General Technical Support – Frequently Asked customers. A lis ting of s ales o ffices an d lo cations i s
Questions (FAQ), technical support requests, included in the back of this document.
online discussion groups, Microchip consultant Technical support is available through the web site
program member listing at: http://support.microchip.com
• Business of Microchip – Product selector and
ordering guides, latest Microchip press releases,
listing of seminars and events, listings of
Microchip sales offices, distributors and factory
representatives

CUSTOMER CHANGE NOTIFICATION

SERVICE
Microchip’s c ustomer notification s ervice h elps keep
customers current on Microchip products. Subscribers
will r eceive e-mail notification w henever t here are
changes, upd ates, rev isions or errat a related to a
specified product family or development tool of interest.
To register, access t he Microchip w eb s ite a t
www.microchip.com, c lick o n Customer C hange
Notification and follow the registration instructions.

 2010 Microchip Technology Inc. DS41303G-page 453

PIC18F2XK20/4XK20
READER RESPONSE
It is our intention to provide you with the best documentation possible to ensure successful use of your Microchip prod-
uct. If you wish to provide your comments on organization, clarity, subject matter, and ways in which our documentation
can better serve you, please FAX your comments to the Technical Publications Manager at (480) 792-4150.
Please list the following information, and use this outline to provide us with your comments about this document.

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Application (optional):
Would you like a reply? Y N

PIC18F2XK20/4XK20
Device: Lite rature Number: DS41303G

Questions:

1. What are the best features of this document?

2. How does this document meet your hardware and software development needs?

3. Do you find the organization of this document easy to follow? If not, why?

4. What additions to the document do you think would enhance the structure and subject?

5. What deletions from the document could be made without affecting the overall usefulness?

6. Is there any incorrect or misleading information (what and where)?

7. How would you improve this document?

DS41303G-page 454  2010 Microchip Technology Inc.

 PIC18F2XK20/4XK20
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.
PART NO. X /XX XXX
Examples:
Device Temperature Package Pattern a) PIC18F45K20-E/P 301 = Extended temp.,
Range PDIP package, QTP pattern #301.
b) PIC18F23K20-I/SO = Industrial temp., SOIC
package.
c) PIC18F44K20-E/P = Extended temp., PDIP
Device: PIC18F23K20(1), PIC18F24K20(1), PIC18F25K20(1), package.
PIC18F26K20(1), PIC18F43K20(1), PIC18F44K20(1),
PIC18F45K20(1), PIC18F46K20(1) d) PIC18F46K20T-I/TP = Industrial temp., TQFP
package, tape and reel.

Temperature E =40C -to +125C (Extended)

Range: I =40C to
- +85C (Industrial)

Package: ML = QFN
MV = UQFN
P = PDIP
PT = TQFP (Thin Quad Flatpack)
SO = SOIC
SP = Skinny Plastic DIP Note 1: T = Part number appended with T
SS = SSOP indicates tape and reel. P and SP
package options not available in tape
and reel.
Pattern: QTP, SQTP, Code or Special Requirements
(blank otherwise)

 2010 Microchip Technology Inc. DS41303G-page 455

 WORLDWIDE SALES AND SERVICE
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01/05/10

DS41303G-page 456  2010 Microchip Technology Inc.