Preliminary

CAT24WC256
256K-Bit I2C Serial CMOS EEPROM

FEATURES
■ 1MHz I2C bus compatible* ■ Write protect feature
■ 1.8 to 6 volt operation – entire array protected when WP at VIH

■ Low power CMOS technology ■ 100,000 program/erase cycles

■ 64-byte page write buffer ■ 100 year data retention

■ Self-timed write cycle with auto-clear ■ 8-pin DIP or 8-pin SOIC

■ Commercial, industrial and automotive

temperature ranges

DESCRIPTION
The CAT24WC256 is a 256K-bit Serial CMOS EEPROM features a 64-byte page write buffer. The device oper-
internally organized as 32,768 words of 8 bits each. ates via the I2C bus serial interface and is available in 8-
Catalyst’s advanced CMOS technology substantially pin DIP or 8-pin SOIC packages.
reduces device power requirements. The CAT24WC256

PIN CONFIGURATION BLOCK DIAGRAM

DIP Package (P) EXTERNAL LOAD

1 8 VCC DOUT SENSE AMPS

A0
SHIFT REGISTERS
A1 2 7 WP ACK
NC 3 6 SCL VCC
VSS 4 5 SDA
VSS WORD ADDRESS COLUMN
BUFFERS DECODERS

512
SOIC Package (K) SDA START/STOP
LOGIC
A0 1 8 VCC
A1 2 7 WP
E2PROM
NC 3 6 SCL XDEC 512 512X512
VSS 4 5 SDA CONTROL
24WC256 F01 WP LOGIC

PIN FUNCTIONS
Pin Name Function
DATA IN STORAGE
A0, A1 Address Inputs
SDA Serial Data/Address
HIGH VOLTAGE/
SCL Serial Clock TIMING CONTROL

WP Write Protect
SCL STATE COUNTERS
VCC +1.8V to +6.0V Power Supply
A0 SLAVE
VSS Ground A1 ADDRESS
COMPARATORS
NC No Connect
24WC256 F02
* Catalyst Semiconductor is licensed by Philips Corporation to carry the I2C Bus Protocol.

© 2002 by Catalyst Semiconductor, Inc. Doc. No. 1031, Rev. A

Characteristics subject to change without notice 1
CAT24WC256 Preliminary

ABSOLUTE MAXIMUM RATINGS* *COMMENT

Temperature Under Bias ................. –55°C to +125°C Stresses above those listed under “Absolute Maximum
Storage Temperature ....................... –65°C to +150°C Ratings” may cause permanent damage to the device.
These are stress ratings only, and functional operation of
Voltage on Any Pin with the device at these or any other conditions outside of those
Respect to Ground(1) ........... –2.0V to +VCC + 2.0V listed in the operational sections of this specification is not
VCC with Respect to Ground ............... –2.0V to +7.0V implied. Exposure to any absolute maximum rating for
extended periods may affect device performance and
Package Power Dissipation reliability.
Capability (Ta = 25°C) ................................... 1.0W
Lead Soldering Temperature (10 secs) ............ 300°C
Output Short Circuit Current(2) ........................ 100mA

RELIABILITY CHARACTERISTICS
Symbol Parameter Reference Test Method Min Typ Max Units
NEND (3) Endurance MIL-STD-883, Test Method 1033 100,000 Cycles/Byte
TDR (3) Data Retention MIL-STD-883, Test Method 1008 100 Years
VZAP(3) ESD Susceptibility MIL-STD-883, Test Method 3015 2000 Volts
ILTH(3)(4) Latch-up JEDEC Standard 17 100 mA

D.C. OPERATING CHARACTERISTICS

VCC = +1.8V to +6.0V, unless otherwise specified.

Symbol Parameter Test Conditions Min Typ Max Units

ICC1 Power Supply Current - Read fSCL = 100 KHz 1 mA
VCC=5V
ICC2 Power Supply Current - Write fSCL = 100KHz 3 mA
VCC=5V
ISB(5) Standby Current VIN = GND or VCC 0 µA
VCC=5V
ILI Input Leakage Current VIN = GND to VCC 1 µA
ILO Output Leakage Current VOUT = GND to VCC 1 µA
VIL Input Low Voltage –1 VCC x 0.3 V
VIH Input High Voltage VCC x 0.7 VCC + 0.5 V
VOL1 Output Low Voltage (VCC = +3.0V) IOL = 3.0 mA 0.4 V
VOL2 Output Low Voltage (VCC = +1.8V) IOL = 1.5 mA 0.5 V

CAPACITANCE TA = 25°C, f = 1.0 MHz, VCC = 5V

Symbol Test Conditions Min Typ Max Units
CI/O(3) Input/Output Capacitance (SDA) VI/O = 0V 8 pF
CIN(3) Input Capacitance (SCL, WP, A0, A1) VIN = 0V 6 pF
Note:
(1) The minimum DC input voltage is –0.5V. During transitions, inputs may undershoot to –2.0V for periods of less than 20 ns. Maximum DC
voltage on output pins is VCC +0.5V, which may overshoot to VCC + 2.0V for periods of less than 20ns.
(2) Output shorted for no more than one second. No more than one output shorted at a time.
(3) This parameter is tested initially and after a design or process change that affects the parameter.
(4) Latch-up protection is provided for stresses up to 100 mA on address and data pins from –1V to VCC +1V.
(5) Standby current (ISB ) = 0 µA (<900 nA).

Doc. No. 1031, Rev. A

2
Preliminary CAT24WC256

A.C. CHARACTERISTICS
VCC = +1.8V to +6V, unless otherwise specified
Output Load is 1 TTL Gate and 100pF
Read & Write Cycle Limits
Symbol Parameter VCC=1.8V - 6.0V VCC=2.5V - 6.0V VCC=3.0V - 5.5V
Min Max Min Max Min Max Units
FSCL Clock Frequency 100 400 1000 kHz
tAA SCL Low to SDA Data Out 0.1 3.5 0.05 0.9 0.05 0.55 µs
and ACK Out
tBUF(2) Time the Bus Must be Free Before 4.7 1.2 0.5 µs
a New Transmission Can Start
tHD:STA Start Condition Hold Time 4.0 0.6 0.25 µs
tLOW Clock Low Period 4.7 1.2 0.6 µs
tHIGH Clock High Period 4.0 0.6 0.4 µs
tSU:STA Start Condition Setup Time 4.0 0.6 0.25 µs
(for a Repeated Start Condition)
tHD:DAT Data In Hold Time 0 0 0 ns
tSU:DAT Data In Setup Time 100 100 100 ns
tR(2) SDA and SCL Rise Time 1.0 0.3 0.3 µs
tF(2) SDA and SCL Fall Time 300 300 100 ns
tSU:STO Stop Condition Setup Time 4.7 0.6 0.25 µs
tDH Data Out Hold Time 100 50 50 ns
tWR Write Cycle Time 10 10 10 ms

Power-Up Timing (2)(3)

Symbol Parameter Min Typ Max Units
tPUR Power-Up to Read Operation 1 ms
tPUW Power-Up to Write Operation 1 ms
Note:
(1) AC measurement conditions:
RL (connects to VCC): 0.3VCC to 0.7 VCC
Input rise and fall times: < 50ns
Input and output timing reference voltages: 0.5 VCC
(2) This parameter is tested initially and after a design or process change that affects the parameter.
(3) tPUR and tPUW are the delays required from the time VCC is stable until the specified operation can be initiated.

The write cycle time is the time from a valid stop interface circuits are disabled, SDA is allowed to remain
condition of a write sequence to the end of the internal high, and the device does not respond to its slave
program/erase cycle. During the write cycle, the bus address.

3 Doc. No. 1031, Rev. A

CAT24WC256 Preliminary

FUNCTIONAL DESCRIPTION SDA: Serial Data/Address

The bidirectional serial data/address pin is used to
The CAT24WC256 supports the I2C Bus data transmis- transfer all data into and out of the device. The SDA pin
sion protocol. This Inter-Integrated Circuit Bus protocol is an open drain output and can be wire-ORed with other
defines any device that sends data to the bus to be a open drain or open collector outputs.
transmitter and any device receiving data to be a re-
ceiver. The transfer is controlled by the Master device WP: Write Protect
which generates the serial clock and all START and
STOP conditions for bus access. The CAT24WC256 This input, when tied to GND, allows write operations to
operates as a Slave device. Both the Master device and the entire memory. When this pin is tied to Vcc, the
Slave device can operate as either transmitter or re- entire memory is write protected. When left floating,
ceiver, but the Master device controls which mode is memory is unprotected.
activated.
A0, A1: Device Address Inputs
PIN DESCRIPTIONS These pins are hardwired or left connected. When
hardwired, up to four CAT24WC256's may be addressed
SCL: Serial Clock on a single bus system. When the pins are left uncon-
The serial clock input clocks all data transferred into or nected, the default values are zero.
out of the device.

Figure 1. Bus Timing

tF tHIGH tR

tLOW tLOW

SCL

tSU:STA tHD:DAT
tHD:STA tSU:DAT tSU:STO

SDA IN
tBUF
tAA tDH

SDA OUT

5020 FHD F03

Figure 2. Write Cycle Timing

SCL

SDA 8TH BIT ACK

BYTE n
tWR

STOP START ADDRESS

CONDITION CONDITION
5020 FHD F04

Figure 3. Start/Stop Timing

SDA

SCL

5020 FHD F05

START BIT STOP BIT

Doc. No. 1031, Rev. A

4
Preliminary CAT24WC256

I2C BUS PROTOCOL

The features of the I2C bus protocol are defined as many as four devices on the same bus. These bits must
follows: compare to their hardwired input pins. The last bit of the
slave address specifies whether a Read or Write opera-
(1) Data transfer may be initiated only when the bus is tion is to be performed. When this bit is set to 1, a Read
not busy. operation is selected, and when set to 0, a Write opera-
tion is selected.
(2) During a data transfer, the data line must remain
stable whenever the clock line is high. Any changes After the Master sends a START condition and the slave
in the data line while the clock line is high will be address byte, the CAT24WC256 monitors the bus and
interpreted as a START or STOP condition. responds with an acknowledge (on the SDA line) when
its address matches the transmitted slave address. The
START Condition
CAT24WC256 then performs a Read or Write operation
The START Condition precedes all commands to the depending on the state of the R/W bit.
device, and is defined as a HIGH to LOW transition of
SDA when SCL is HIGH. The CAT24WC256 monitors Acknowledge
the SDA and SCL lines and will not respond until this After a successful data transfer, each receiving device is
condition is met. required to generate an acknowledge. The Acknowledg-
ing device pulls down the SDA line during the ninth clock
STOP Condition
cycle, signaling that it received the 8 bits of data.
A LOW to HIGH transition of SDA when SCL is HIGH
determines the STOP condition. All operations must end The CAT24WC256 responds with an acknowledge after
with a STOP condition. receiving a START condition and its slave address. If the
device has been selected along with a write operation,
it responds with an acknowledge after receiving each 8-
DEVICE ADDRESSING bit byte.
The bus Master begins a transmission by sending a When the CAT24WC256 begins a READ mode it trans-
START condition. The Master sends the address of the mits 8 bits of data, releases the SDA line, and monitors
particular slave device it is requesting. The five most the line for an acknowledge. Once it receives this ac-
significant bits of the 8-bit slave address are fixed as knowledge, the CAT24WC256 will continue to transmit
10100(Fig. 5). The CAT24WC256 uses the next two bits data. If no acknowledge is sent by the Master, the device
as address bits. The address bits A1 and A0 allow as

Figure 4. Acknowledge Timing

SCL FROM 1 8 9
MASTER

DATA OUTPUT
FROM TRANSMITTER

DATA OUTPUT
FROM RECEIVER

START ACKNOWLEDGE

5020 FHD F06

Figure 5. Slave Address Bits

1 0 1 0 0 A1 A0 R/W

5027 FHD F07

5 Doc. No. 1031, Rev. A

CAT24WC256 Preliminary

terminates data transmission and waits for a STOP If the Master transmits more than 64 bytes before sending
condition. the STOP condition, the address counter ‘wraps around’,
and previously transmitted data will be overwritten.
WRITE OPERATIONS
When all 64 bytes are received, and the STOP condition
Byte Write has been sent by the Master, the internal programming
In the Byte Write mode, the Master device sends the cycle begins. At this point, all received data is written to
START condition and the slave address information the CAT24WC256 in a single write cycle.
(with the R/W bit set to zero) to the Slave device. After
Acknowledge Polling
the Slave generates an acknowledge, the Master sends
two 8-bit address words that are to be written into the Disabling of the inputs can be used to take advantage of
address pointers of the CAT24WC256. After receiving the typical write cycle time. Once the stop condition is
another acknowledge from the Slave, the Master device issued to indicate the end of the host's write operation,
transmits the data to be written into the addressed CAT24WC256 initiates the internal write cycle. ACK
memory location. The CAT24WC256 acknowledges polling can be initiated immediately. This involves issu-
once more and the Master generates the STOP condi- ing the start condition followed by the slave address for
tion. At this time, the device begins an internal program- a write operation. If CAT24WC256 is still busy with the
ming cycle to nonvolatile memory. While the cycle is in write operation, no ACK will be returned. If
progress, the device will not respond to any request from CAT24WC256 has completed the write operation, an
the Master device. ACK will be returned and the host can then proceed with
the next read or write operation.
Page Write
The CAT24WC256 writes up to 64 bytes of data, in a WRITE PROTECTION
single write cycle, using the Page Write operation. The
page write operation is initiated in the same manner as The Write Protection feature allows the user to protect
the byte write operation, however instead of terminating against inadvertent programming of the memory array.
after the initial byte is transmitted, the Master is allowed If the WP pin is tied to VCC, the entire memory array is
to send up to 63 additional bytes. After each byte has protected and becomes read only. The CAT24WC256
been transmitted, CAT24WC256 will respond with an will accept both slave and byte addresses, but the
acknowledge, and internally increment the six low order memory location accessed is protected from program-
address bits by one. The high order bits remain un- ming by the device’s failure to send an acknowledge
changed. after the first byte of data is received.

Figure 6. Byte Write Timing

S
T S
BUS ACTIVITY: A SLAVE BYTE ADDRESS T
MASTER R ADDRESS A15–A8 A7–A0 DATA O
T P
SDA LINE S P
*
A A A A
C C C C
K K K K
24WC256 F08
*=Don't Care Bit
Figure 7. Page Write Timing

S
T S
BUS ACTIVITY: A SLAVE BYTE ADDRESS T
MASTER R ADDRESS A15–A8 A7–A0 DATA DATA n DATA n+63 O
T P

SDA LINE S P
*
A A A A A A A
C C C C C C C
K K K K K K K

24WC256F09
*=Don't Care Bit

Doc. No. 1031, Rev. A

6
Preliminary CAT24WC256

READ OPERATIONS wishes to read. After CAT24WC256 acknowledges, the

Master device sends the START condition and the slave
The READ operation for the CAT24WC256 is initiated in address again, this time with the R/W bit set to one. The
the same manner as the write operation with one excep- CAT24WC256 then responds with its acknowledge and
tion, that R/W bit is set to one. Three different READ sends the 8-bit byte requested. The master device does
operations are possible: Immediate/Current Address not send an acknowledge but will generate a STOP
READ, Selective/Random READ and Sequential READ. condition.
Immediate/Current Address Read Sequential Read
The CAT24WC256’s address counter contains the ad- The Sequential READ operation can be initiated by
dress of the last byte accessed, incremented by one. In either the Immediate Address READ or Selective READ
other words, if the last READ or WRITE access was to operations. After the CAT24WC256 sends the initial 8-
address N, the READ immediately following would ac- bit byte requested, the Master will respond with an
cess data from address N+1. If N=E (where E=32767), acknowledge which tells the device it requires more
then the counter will ‘wrap around’ to address 0 and data. The CAT24WC256 will continue to output an 8-bit
continue to clock out data. After the CAT24WC256 byte for each acknowledge sent by the Master. The
receives its slave address information (with the R/W bit operation will terminate when the Master fails to respond
set to one), it issues an acknowledge, then transmits the with an acknowledge, thus sending the STOP condition.
8 bit byte requested. The master device does not send
an acknowledge, but will generate a STOP condition. The data being transmitted from CAT24WC256 is out-
putted sequentially with data from address N followed by
Selective/Random Read data from address N+1. The READ operation address
Selective/Random READ operations allow the Master counter increments all of the CAT24WC256 address bits
device to select at random any memory location for a so that the entire memory array can be read during one
READ operation. The Master device first performs a operation. If more than E (where E=32767) bytes are
‘dummy’ write operation by sending the START condi- read out, the counter will ‘wrap around’ and continue to
tion, slave address and byte addresses of the location it clock out data bytes.

Figure 8. Immediate Address Read Timing

S
T S
BUS ACTIVITY: A SLAVE T
MASTER R ADDRESS DATA O
T P
SDA LINE S P

A N
C O
K A
C
K

SCL 8 9

SDA 8TH BIT

DATA OUT NO ACK STOP

24WC128 F10 24WC256 F10

7 Doc. No. 1031, Rev. A

CAT24WC256 Preliminary

Figure 9. Selective Read Timing

S S
T T S
BUS ACTIVITY: A SLAVE BYTE ADDRESS A SLAVE T
MASTER R ADDRESS A15–A8 A7–A0 R ADDRESS DATA O
T T P

SDA LINE S
* S P

A A A A N
C C C C O
K K K K A
C
K

*=Don't Care Bit

24WC256 FIG. 11

Figure 10. Sequential Read Timing

S
BUS ACTIVITY: SLAVE T
MASTER ADDRESS DATA n DATA n+1 DATA n+2 DATA n+x O
P
SDA LINE P

A A A A N
C C C C O
K K K K
A
C
K
5020 FHD F12

Doc. No. 1031, Rev. A

8
Preliminary CAT24WC256

ORDERING INFORMATION

Prefix Device # Suffix

CAT 24WC256 K I -1.8 TE13

Optional Product Temperature Range Tape & Reel

Company ID Number Blank = Commercial (0˚ - 70˚C) TE13: 2000/Reel
I = Industrial (-40˚ - 85˚C)
A = Automotive (-40˚ - 105˚C)*

Package Operating Voltage

P: PDIP Blank: 2.5 to 6.0V
K: SOIC (EIAJ) 1.8: 1.8 to 6.0V
3: 3.0V to 5.5V

* -40˚ to +125˚C is available upon request

24WC256 FIG. 13

Notes:
(1) The device used in the above example is a 24WC256KI-1.8TE13 (SOIC, Industrial Temperature, 1.8 Volt to 6 Volt Operating
Voltage, Tape & Reel)

9 Doc. No. 1031, Rev. A

CAT24WC256 Preliminary

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Catalyst Semiconductor, Inc.

Corporate Headquarters
1250 Borregas Avenue
Sunnyvale, CA 94089 Publication #: 1031
Phone: 408.542.1000 Revison: A
Fax: 408.542.1200 Issue date: 5/02/02
www.catalyst-semiconductor.com
Doc. No. 1031, Rev. A Type: Preliminary
10