KSZ8041NL

10Base-T/100Base-TX
Physical Layer Transceiver

General Description
The KSZ8041NL represents a new level of features and
The KSZ8041NL is a single supply 10Base-T/100Base-TX
performance and is an ideal choice of physical layer
Physical Layer Transceiver, which provides MII/RMII
transceiver for 10Base-T/100Base-TX applications.
interfaces to transmit and receive data. An unique mixed
signal design extends signaling distance while reducing The KSZ8041NL comes in a 32-pin, lead-free MLF® (QFN
power consumption. per JDEC) package (See Ordering Information).
HP Auto MDI/MDI-X provides the most robust solution for Data sheets and support documentation can be found on
eliminating the need to differentiate between crossover Micrel’s web site at: www.micrel.com.
and straight-through cables.

Functional Diagram

MicroLeadFrame and MLF are registered trademarks of Amkor Technology, Inc.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

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Features Applications
• Single-chip 10Base-T/100Base-TX physical layer • Printer
solution • LOM
• Fully compliant to IEEE 802.3u Standard • Game Console
• Low power CMOS design, power consumption of • IPTV
<180mW
• IP Phone
• HP auto MDI/MDI-X for reliable detection and
• IP Set-top Box
correction for straight-through and crossover cables
with disable and enable option
• Robust operation over standard cables Ordering Information
• Power down and power saving modes
Part Number Temp. Range Package Lead Finish
• MII interface support ®
KSZ8041NL 0°C to 70°C 32-Pin MLF Pb-Free
• RMII interface support with external 50MHz system
®
clock KSZ8041NLI -40°C to 85°C 32-Pin MLF Pb-Free
• MIIM (MDC/MDIO) management bus for PHY register
configuration
• Interrupt pin option
• Programmable LED outputs for link, activity and
speed
• ESD rating (6kV)
• Single power supply (3.3V)
• Built-in 1.8V regulator for core
• Available in 32-pin (5mm x 5mm) MLF® package

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Revision History
Revision Date Summary of Changes
1.0 10/13/06 Data sheet created

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Contents
Pin Configuration .................................................................................................................................................................. 8
Pin Description ...................................................................................................................................................................... 9
Strapping Options............................................................................................................................................................... 12
Functional Description ....................................................................................................................................................... 13
100Base-TX Transmit....................................................................................................................................................... 13
100Base-TX Receive........................................................................................................................................................ 13
PLL Clock Synthesizer...................................................................................................................................................... 13
Scrambler/De-scrambler (100Base-TX only).................................................................................................................... 13
10Base-T Transmit ........................................................................................................................................................... 13
10Base-T Receive ............................................................................................................................................................ 13
SQE and Jabber Function (10Base-T only)...................................................................................................................... 14
Auto-Negotiation ............................................................................................................................................................... 14
MII Management (MIIM) Interface .................................................................................................................................... 16
Interrupt (INTRP) .............................................................................................................................................................. 16
MII Data Interface ............................................................................................................................................................. 16
MII Signal Definition.......................................................................................................................................................... 17
Transmit Clock (TXC) ...................................................................................................................................................................17
Transmit Enable (TXEN)..............................................................................................................................................................17
Transmit Data [3:0] (TXD[3:0]) ...................................................................................................................................................17
Receive Clock (RXC) .....................................................................................................................................................................17
Receive Data Valid (RXDV) ..........................................................................................................................................................18
Receive Data [3:0] (RXD[3:0])......................................................................................................................................................18
Receive Error (RXER)...................................................................................................................................................................18
Carrier Sense (CRS) ......................................................................................................................................................................18
Collision (COL) .............................................................................................................................................................................18
Reduced MII (RMII) Data Interface................................................................................................................................... 18
RMII Signal Definition ....................................................................................................................................................... 19
Reference Clock (REF_CLK) .......................................................................................................................................................19
Transmit Enable (TX_EN)............................................................................................................................................................19
Transmit Data [1:0] (TXD[1:0]) ...................................................................................................................................................19
Carrier Sense/Receive Data Valid (CRS_DV) ..............................................................................................................................19
Receive Data [1:0] (RXD[1:0])......................................................................................................................................................19
Receive Error (RX_ER).................................................................................................................................................................19
Collision Detection ........................................................................................................................................................................20
HP Auto MDI/MDI-X.......................................................................................................................................................... 20
Straight Cable ................................................................................................................................................................................20
Crossover Cable .............................................................................................................................................................................21
Power Management.......................................................................................................................................................... 22
Power Saving Mode.......................................................................................................................................................................22
Power Down Mode ........................................................................................................................................................................22
Reference Clock Connection Options............................................................................................................................... 22

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Reference Circuit for Power and Ground Connections .................................................................................................... 23

Register Map........................................................................................................................................................................ 24
Register Description ........................................................................................................................................................... 24
Absolute Maximum Ratings(1) ............................................................................................................................................ 31
Operating Ratings(2) ............................................................................................................................................................ 31
Electrical Characteristics(4) ................................................................................................................................................ 31
Timing Diagrams ................................................................................................................................................................. 33
MII SQE Timing (10Base-T) ............................................................................................................................................. 33
MII Transmit Timing (10Base-T) ....................................................................................................................................... 34
MII Receive Timing (10Base-T) ........................................................................................................................................ 35
MII Transmit Timing (100Base-TX)................................................................................................................................... 36
MII Receive Timing (100Base-TX).................................................................................................................................... 37
RMII Timing....................................................................................................................................................................... 38
Auto-Negotiation Timing ................................................................................................................................................... 39
MDC/MDIO Timing............................................................................................................................................................ 40
Reset Timing..................................................................................................................................................................... 41
Reset Circuit ........................................................................................................................................................................ 42
Reference Circuits for LED Strapping Pins...................................................................................................................... 43
Selection of Isolation Transformer.................................................................................................................................... 44
Selection of Reference Crystal .......................................................................................................................................... 44
Package Information........................................................................................................................................................... 45

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List of Figures
Figure 1. Auto-Negotiation Flow Chart................................................................................................................................. 15
Figure 2. Typical Straight Cable Connection ....................................................................................................................... 20
Figure 3. Typical Crossover Cable Connection ................................................................................................................... 21
Figure 4. 25MHz Crystal / Oscillator Reference Clock for MII Mode ................................................................................... 22
Figure 5. 50MHz Oscillator Reference Clock for RMII Mode............................................................................................... 22
Figure 6. KSZ8041NL Power and Ground Connections...................................................................................................... 23
Figure 7. MII SQE Timing (10Base-T) ................................................................................................................................. 33
Figure 8. MII Transmit Timing (10Base-T) ........................................................................................................................... 34
Figure 9. MII Receive Timing (10Base-T) ............................................................................................................................ 35
Figure 10. MII Transmit Timing (100Base-TX)..................................................................................................................... 36
Figure 11. MII Receive Timing (100Base-TX)...................................................................................................................... 37
Figure 12. RMII Timing – Data Received from RMII ............................................................................................................ 38
Figure 13. RMII Timing – Data Input to RMII ....................................................................................................................... 38
Figure 14. Auto-Negotiation Fast Link Pulse (FLP) Timing ................................................................................................. 39
Figure 15. MDC/MDIO Timing.............................................................................................................................................. 40
Figure 16. Reset Timing....................................................................................................................................................... 41
Figure 17. Recommended Reset Circuit.............................................................................................................................. 42
Figure 18. Recommended Reset Circuit for interfacing with CPU/FPGA Reset Output...................................................... 42
Figure 19. Reference Circuits for LED Strapping Pins......................................................................................................... 43

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List of Tables
Table 1. MII Management Frame Format ............................................................................................................................ 16
Table 2. MII Signal Definition ............................................................................................................................................... 17
Table 3. RMII Signal Description.......................................................................................................................................... 19
Table 4. MDI/MDI-X Pin Definition ....................................................................................................................................... 20
Table 5. KSZ8041NL Power Pin Description ....................................................................................................................... 23
Table 6. MII SQE Timing (10Base-T) Parameters ............................................................................................................... 33
Table 7. MII Transmit Timing (10Base-T) Parameters ........................................................................................................ 34
Table 8. MII Receive Timing (10Base-T) Parameters ......................................................................................................... 35
Table 9. MII Transmit Timing (100Base-TX) Parameters .................................................................................................... 36
Table 10. MII Receive Timing (100Base-TX) Parameters ................................................................................................... 37
Table 11. RMII Timing Parameters ...................................................................................................................................... 38
Table 12. Auto-Negotiation Fast Link Pulse (FLP) Timing Parameters ............................................................................... 39
Table 13. MDC/MDIO Timing Parameters ........................................................................................................................... 40
Table 14. Reset Timing Parameters .................................................................................................................................... 41
Table 15. Transformer Selection Criteria ............................................................................................................................. 44
Table 16. Qualified Single Port Magnetics........................................................................................................................... 44
Table 17. Typical Reference Crystal Characteristics ........................................................................................................... 44

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Pin Configuration

®
32-Pin (5mm x 5mm) MLF

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Pin Description
(1)
Pin Number Pin Name Type Pin Function
1 GND Gnd Ground
2 VDDPLL_1.8 P 1.8V analog VDD
3 VDDA_3.3 P 3.3V analog VDD
4 RX- I/O Physical receive or transmit signal (- differential)
5 RX+ I/O Physical receive or transmit signal (+ differential)
6 TX- I/O Physical transmit or receive signal (- differential)
7 TX+ I/O Physical transmit or receive signal (+ differential)
8 XO O Crystal feedback
This pin is used only in MII mode when a 25 MHz crystal is used.
This pin is a no connect if oscillator or external clock source is used, or if RMII
mode is selected.
9 XI / I Crystal / Oscillator / External Clock Input
REFCLK MII Mode: 25MHz +/-50ppm (crystal, oscillator, or external clock)
RMII Mode: 50MHz +/-50ppm (oscillator, or external clock only)
10 REXT I/O Set physical transmit output current
Pull-down this pin with a 6.49KΩ resistor to ground.
11 MDIO I/O Management Interface (MII) Data I/O
This pin requires an external 4.7KΩ pull-up resistor.
12 MDC I Management Interface (MII) Clock Input
This pin is synchronous to the MDIO data interface.
(2)
13 RXD3 / Ipu/O MII Mode: Receive Data Output[3] /
PHYAD0 Config Mode: The pull-up/pull-down value is latched as PHYADDR[0] during
power-up / reset. See “Strapping Options” section for details.
(2)
14 RXD2 / Ipd/O MII Mode: Receive Data Output[2] /
PHYAD1 Config Mode: The pull-up/pull-down value is latched as PHYADDR[1] during
power-up / reset. See “Strapping Options” section for details.
(2)
15 RXD1 / Ipd/O MII Mode: Receive Data Output[1] /
RXD[1] / (3)
RMII Mode: Receive Data Output[1] /
PHYAD2 Config Mode: The pull-up/pull-down value is latched as PHYADDR[2] during
power-up / reset. See “Strapping Options” section for details.
(2)
16 RXD0 / Ipu/O MII Mode: Receive Data Output[0] /
RXD[0] / (3)
RMII Mode: Receive Data Output[0] /
DUPLEX Config Mode: Latched as DUPLEX (register 0h, bit 8) during power-up /
reset. See “Strapping Options” section for details.
17 VDDIO_3.3 P 3.3V digital VDD
18 RXDV / Ipd/O MII Mode: Receive Data Valid Output /
CRSDV / RMII Mode: Carrier Sense/Receive Data Valid Output /
CONFIG2 Config Mode: The pull-up/pull-down value is latched as CONFIG2 during
power-up / reset. See “Strapping Options” section for details.
19 RXC O MII Mode: Receive Clock Output

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20 RXER / Ipd/O MII Mode: Receive Error Output /

RX_ER / RMII Mode: Receive Error Output /
ISO Config Mode: The pull-up/pull-down value is latched as ISOLATE during
power-up / reset. See “Strapping Options” section for details.
21 INTRP Opu Interrupt Output: Programmable Interrupt Output
Register 1Bh is the Interrupt Control/Status Register for programming the interrupt
conditions and reading the interrupt status. Register 1Fh bit 9 sets the interrupt
output to active low (default) or active high.
22 TXC O MII Mode: Transmit Clock Output
23 TXEN / I MII Mode: Transmit Enable Input /
TX_EN RMII Mode: Transmit Enable Input
(4)
24 TXD0 / I MII Mode: Transmit Data Input[0] /
TXD[0] (5)
RMII Mode: Transmit Data Input[0]
(4)
25 TXD1 / I MII Mode: Transmit Data Input[1] /
TXD[1] (5)
RMII Mode: Transmit Data Input[1]
(4)
26 TXD2 I MII Mode: Transmit Data Input[2] /
(4)
27 TXD3 I MII Mode: Transmit Data Input[3] /
28 COL / Ipd/O MII Mode: Collision Detect Output /
CONFIG0 Config Mode: The pull-up/pull-down value is latched as CONFIG0 during
power-up / reset. See “Strapping Options” section for details.
29 CRS / Ipd/O MII Mode: Carrier Sense Output /
CONFIG1 Config Mode: The pull-up/pull-down value is latched as CONFIG1 during
power-up / reset. See “Strapping Options” section for details.
30 LED0 / Ipu/O LED Output: Programmable LED0 Output /
NWAYEN Config Mode: Latched as Auto-Negotiation Enable (register 0h, bit 12) during
power-up / reset. See “Strapping Options” section for details.
The LED0 pin is programmable via register 1Eh bits [15:14], and is defined as
follows.

LED mode = [00]

Link/Activity Pin State LED Definition
No Link H OFF
Link L ON
Activity Toggle Blinking

LED mode = [01]

Link Pin State LED Definition
No Link H OFF
Link L ON

LED mode = [10]

Reserved

LED mode = [11]

Reserved

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31 LED1 / Ipu/O LED Output: Programmable LED1 Output /

SPEED Config Mode: Latched as SPEED (register 0h, bit 13) during power-up / reset.
See “Strapping Options” section for details.
The LED1 pin is programmable via register 1Eh bits [15:14], and is defined as
follows.

LED mode = [00]

Speed Pin State LED Definition
10BT H OFF
100BT L ON

LED mode = [01]

Activity Pin State LED Definition
No Activity H OFF
Activity L ON

LED mode = [10]

Reserved

LED mode = [11]

Reserved
32 RST# I Chip Reset (active low)
PADDLE GND Gnd Ground
Notes:
1. P = Power supply.
Gnd = Ground.
I = Input.
O = Output.
I/O = Bi-directional.
Ipd = Input with internal pull-down.
Ipu = Input with internal pull-up.
Opu = Output with internal pull-up.
Ipu/O = Input with internal pull-up during power-up/reset; output pin otherwise.
Ipd/O = Input with internal pull-down during power-up/reset; output pin otherwise.
2. MII Rx Mode: The RXD[3..0] bits are synchronous with RXCLK. When RXDV is asserted, RXD[3..0] presents valid data to MAC through the MII.
RXD[3..0] is invalid when RXDV is de-asserted.
3. RMII Rx Mode: The RXD[1:0] bits are synchronous with REF_CLK. For each clock period in which CRS_DV is asserted, two bits of recovered
data are sent from the PHY.
4. MII Tx Mode: The TXD[3..0] bits are synchronous with TXCLK. When TXEN is asserted, TXD[3..0] presents valid data from the MAC through
the MII. TXD[3..0] has no effect when TXEN is de-asserted.
5. RMII Tx Mode: The TXD[1:0] bits are synchronous with REF_CLK. For each clock period in which TX_EN is asserted, two bits of data are
received by the PHY from the MAC.

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Strapping Options
(1)
Pin Number Pin Name Type Pin Function
15 PHYAD2 Ipd/O The PHY Address is latched at power-up / reset and is configurable to any value from
14 PHYAD1 Ipd/O 1 to 7.

13 PHYAD0 Ipu/O The default PHY Address is 00001.

PHY Address bits [4:3] are always set to ‘00’.
18 CONFIG2 Ipd/O The CONFIG[2:0] strap-in pins are latched at power-up / reset and are defined as
29 CONFIG1 Ipd/O follows:

28 CONFIG0 Ipd/O
CONFIG[2:0] Mode
000 MII (default)
001 RMII
010 Reserved – not used
011 Reserved – not used
100 PCS Loopback
101 Reserved – not used
110 Reserved – not used
111 Reserved – not used
20 ISO Ipd/O ISOLATE mode
Pull-up = Enable
Pull-down (default) = Disable
During power-up / reset, this pin value is latched into register 0h bit 10.
31 SPEED Ipu/O SPEED mode
Pull-up (default) = 100Mbps
Pull-down = 10Mbps
During power-up / reset, this pin value is latched into register 0h bit 13 as the Speed
Select, and also is latched into register 4h (Auto-Negotiation Advertisement) as the
Speed capability support.
16 DUPLEX Ipu/O DUPLEX mode
Pull-up (default) = Full Duplex
Pull-down = Half Duplex
During power-up / reset, this pin value is latched into register 0h bit 8 as the Duplex
Mode, and also is latched into register 4h (Auto-Negotiation Advertisement) as the
Duplex capability support.
30 NWAYEN Ipu/O Nway Auto-Negotiation Enable
Pull-up (default) = Enable Auto-Negotiation
Pull-down = Disable Auto-Negotiation
During power-up / reset, this pin value is latched into register 0h bit 12.
Note:
1. Ipu/O = Input with internal pull-up during power-up/reset; output pin otherwise.
Ipd/O = Input with internal pull-down during power-up/reset; output pin otherwise.

Pin strap-ins are latched during power-up or reset. In some systems, the MAC receive input pins may drive high during
power-up or reset, and consequently cause the PHY strap-in pins on the MII/RMII signals to be latched high. In this case,
it is recommended to add 1K pull-downs on these PHY strap-in pins to ensure the PHY does not strap-in to ISOLATE or
PCS Loopback mode, or is not configured with an incorrect PHY Address.

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Functional Description
The KSZ8041NL is a single 3.3V supply Fast Ethernet transceiver. It is fully compliant with the IEEE 802.3u Specification.
On the media side, the KSZ8041NL supports 10Base-T and 100Base-TX with HP auto MDI/MDI-X for reliable detection of
and correction for straight-through and crossover cables.
The KSZ8041NL offers a choice of MII or RMII data interface connection with the MAC processor. The MII management
bus option gives the MAC processor complete access to the KSZ8041NL control and status registers. Additionally, an
interrupt pin eliminates the need for the processor to poll for PHY status change.
Physical signal transmission and reception are enhanced through the use of patented analog circuitries that make the
design more efficient and allow for lower power consumption and smaller chip die size.

100Base-TX Transmit
The 100Base-TX transmit function performs parallel-to-serial conversion, 4B/5B coding, scrambling, NRZ-to-NRZI
conversion, and MLT3 encoding and transmission.
The circuitry starts with a parallel-to-serial conversion, which converts the MII data from the MAC into a 125MHz serial bit
stream. The data and control stream is then converted into 4B/5B coding, followed by a scrambler. The serialized data is
further converted from NRZ-to-NRZI format, and then transmitted in MLT3 current output.
The output current is set by an external 6.49kΩ 1% resistor for the 1:1 transformer ratio. It has typical rise/fall times of 4
ns and complies with the ANSI TP-PMD standard regarding amplitude balance, overshoot and timing jitter. The wave-
shaped 10Base-T output drivers are also incorporated into the 100Base-TX drivers.

100Base-TX Receive
The 100Base-TX receiver function performs adaptive equalization, DC restoration, MLT3-to-NRZI conversion, data and
clock recovery, NRZI-to-NRZ conversion, de-scrambling, 4B/5B decoding, and serial-to-parallel conversion.
The receiving side starts with the equalization filter to compensate for inter-symbol interference (ISI) over the twisted pair
cable. Since the amplitude loss and phase distortion is a function of the cable length, the equalizer must adjust its
characteristics to optimize performance. In this design, the variable equalizer makes an initial estimation based on
comparisons of incoming signal strength against some known cable characteristics, and then tunes itself for optimization.
This is an ongoing process and self-adjusts against environmental changes such as temperature variations.
Next, the equalized signal goes through a DC restoration and data conversion block. The DC restoration circuit is used to
compensate for the effect of baseline wander and to improve the dynamic range. The differential data conversion circuit
converts the MLT3 format back to NRZI. The slicing threshold is also adaptive.
The clock recovery circuit extracts the 125MHz clock from the edges of the NRZI signal. This recovered clock is then used
to convert the NRZI signal into the NRZ format. This signal is sent through the de-scrambler followed by the 4B/5B
decoder. Finally, the NRZ serial data is converted to the MII format and provided as the input data to the MAC.

PLL Clock Synthesizer

The KSZ8041NL generates 125MΗz, 25MΗz and 20MΗz clocks for system timing. Internal clocks are generated from an
external 25MHz crystal or oscillator. In RMII mode, these internal clocks are generated from an external 50MHz oscillator
or system clock.

Scrambler/De-scrambler (100Base-TX only)

The purpose of the scrambler is to spread the power spectrum of the signal in order to reduce EMI and baseline wander.

10Base-T Transmit
The 10Base-T drivers are incorporated with the 100Base-TX drivers to allow for transmission using the same magnetic.
The drivers also perform internal wave-shaping and pre-emphasize, and output 10Base-T signals with a typical amplitude
of 2.5V peak. The 10Base-T signals have harmonic contents that are at least 27dB below the fundamental frequency
when driven by an all-ones Manchester-encoded signal.

10Base-T Receive
On the receive side, input buffer and level detecting squelch circuits are employed. A differential input receiver circuit and
a PLL performs the decoding function. The Manchester-encoded data stream is separated into clock signal and NRZ data.
A squelch circuit rejects signals with levels less than 400 mV or with short pulse widths to prevent noise at the RX+ and

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RX- inputs from falsely trigger the decoder. When the input exceeds the squelch limit, the PLL locks onto the incoming
signal and the KSZ8041NL decodes a data frame. The receive clock is kept active during idle periods in between data
reception.

SQE and Jabber Function (10Base-T only)

In 10Base-T operation, a short pulse is put out on the COL pin after each frame is transmitted. This SQE Test is required
as a test of the 10Base-T transmit/receive path. If transmit enable (TXEN) is high for more than 20 ms (jabbering), the
10Base-T transmitter is disabled and COL is asserted high. If TXEN is then driven low for more than 250 ms, the 10Base-
T transmitter is re-enabled and COL is de-asserted (returns to low).

Auto-Negotiation
The KSZ8041NL conforms to the auto-negotiation protocol, defined in Clause 28 of the IEEE 802.3u specification. Auto-
negotiation is enabled by either hardware pin strapping (pin 30) or software (register 0h bit 12).
Auto-negotiation allows unshielded twisted pair (UTP) link partners to select the highest common mode of operation. Link
partners advertise their capabilities to each other, and then compare their own capabilities with those they received from
their link partners. The highest speed and duplex setting that is common to the two link partners is selected as the mode
of operation.
The following list shows the speed and duplex operation mode from highest to lowest.
• Priority 1: 100Base-TX, full-duplex
• Priority 2: 100Base-TX, half-duplex
• Priority 3: 10Base-T, full-duplex
• Priority 4: 10Base-T, half-duplex
If auto-negotiation is not supported or the KSZ8041NL link partner is forced to bypass auto-negotiation, the KSZ8041NL
sets its operating mode by observing the signal at its receiver. This is known as parallel detection, and allows the
KSZ8041NL to establish link by listening for a fixed signal protocol in the absence of auto-negotiation advertisement
protocol.
The auto-negotiation link up process is shown in the following flow chart.

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Start Auto Negotiation

N Parallel
Force Link Setting Operation
o

Yes

Listen for 10BASE-T

Bypass Auto Negotiation Attempt Auto Listen for 100BASE-TX
and Set Link Mode Negotiation Idles Link Pulses

No

Join
Flow

Link Mode Set ?

Yes

Link Mode Set

Figure 1. Auto-Negotiation Flow Chart

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MII Management (MIIM) Interface

The KSZ8041NL supports the IEEE 802.3 MII Management Interface, also known as the Management Data Input / Output
(MDIO) Interface. This interface allows upper-layer devices to monitor and control the state of the KSZ8041NL. An
external device with MIIM capability is used to read the PHY status and/or configure the PHY settings. Additional details
on the MIIM interface can be found in Clause 22.2.4.5 of the IEEE 802.3u Specification.
The MIIM interface consists of the following:
• A physical connection that incorporates the clock line (MDC) and the data line (MDIO).
• A specific protocol that operates across the aforementioned physical connection that allows an external controller
to communicate with one or more KSZ8041NL devices. Each KSZ8041NL device is assigned a PHY address
between 1 and 7 by the PHYAD[2:0] strapping pins.
• An internal addressable set of thirteen 16-bit MDIO registers. Register [0:6] are required, and their functions are
defined by the IEEE 802.3u Specification. The additional registers are provided for expanded functionality.
The KSZ8041NL supports MIIM in both MII mode and RMII mode.
The following table shows the MII Management frame format for the KSZ8041NL.

Preamble Start of Read/Write PHY REG TA Data Idle

Frame OP Code Address Address Bits [15:0]
Bits [4:0] Bits [4:0]
Read 32 1’s 01 10 00AAA RRRRR Z0 DDDDDDDD_DDDDDDDD Z
Write 32 1’s 01 01 00AAA RRRRR 10 DDDDDDDD_DDDDDDDD Z

Table 1. MII Management Frame Format

Interrupt (INTRP)
INTRP (pin 21) is an optional interrupt signal that is used to inform the external controller that there has been a status
update in the KSZ8041NL PHY register. Bits[15:8] of register 1Bh are the interrupt control bits, and are used to enable
and disable the conditions for asserting the INTRP signal. Bits[7:0] of register 1Bh are the interrupt status bits, and are
used to indicate which interrupt conditions have occurred. The interrupt status bits are cleared after reading register 1Bh.
Bit 9 of register 1Fh sets the interrupt level to active high or active low.

MII Data Interface

The Media Independent Interface (MII) is specified in Clause 22 of the IEEE 802.3u Specification. It provides a common
interface between physical layer and MAC layer devices, and has the following key characteristics:
• Supports 10Mbps and 100Mbps data rates.
• Uses a 25MHz reference clock, sourced by the PHY.
• Provides independent 4-bit wide (nibble) transmit and receive data paths.
• Contains two distinct groups of signals: one for transmission and the other for reception.

By default, the KSZ8041NL is configured in MII mode after it is power-up or reset with the following:
• A 25MHz crystal connected to XI, XO (pins 9, 8), or an external 25MHz clock source (oscillator) connected to XI.
• CONFIG[2:0] (pins 18, 29, 28) set to ‘000’ (default setting).

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MII Signal Definition

The following table describes the MII signals. Refer to Clause 22 of the IEEE 802.3u Specification for detailed information.

Direction
MII Direction
(with respect to PHY, Description
Signal Name (with respect to MAC)
KSZ8041NL signal)
TXC Output Input Transmit Clock
(2.5MHz for 10Mbps; 25MHz for 100Mbps)
TXEN Input Output Transmit Enable
TXD[3:0] Input Output Transmit Data [3:0]
RXC Output Input Receive Clock
(2.5MHz for 10Mbps; 25MHz for 100Mbps)
RXDV Output Input Receive Data Valid
RXD[3:0] Output Input Receive Data [3:0]
RXER Output Input, or (not required) Receive Error
CRS Output Input Carrier Sense
COL Output Input Collision Detection

Table 2. MII Signal Definition

Transmit Clock (TXC)

TXC is sourced by the PHY. It is a continuous clock that provides the timing reference for TXEN and TXD[3:0].
TXC is 2.5MHz for 10Mbps operation and 25MHz for 100Mbps operation.

Transmit Enable (TXEN)

TXEN indicates the MAC is presenting nibbles on TXD[3:0] for transmission. It is asserted synchronously with the first
nibble of the preamble and remains asserted while all nibbles to be transmitted are presented on the MII, and is negated
prior to the first TXC following the final nibble of a frame.
TXEN transitions synchronously with respect to TXC.

Transmit Data [3:0] (TXD[3:0])

TXD[3:0] transitions synchronously with respect to TXC. When TXEN is asserted, TXD[3:0] are accepted for transmission
by the PHY. TXD[3:0] is ”00” to indicate idle when TXEN is de-asserted. Values other than “00” on TXD[3:0] while TXEN
is de-asserted are ignored by the PHY.

Receive Clock (RXC)

RXC provides the timing reference for RXDV, RXD[3:0], and RXER.
• In 10Mbps mode, RXC is recovered from the line while carrier is active. RXC is derived from the PHY’s reference
clock when the line is idle, or link is down.
• In 100Mbps mode, RXC is continuously recovered from the line. If link is down, RXC is derived from the PHY’s
reference clock.
RXC is 2.5MHz for 10Mbps operation and 25MHz for 100Mbps operation.

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Receive Data Valid (RXDV)

RXDV is driven by the PHY to indicate that the PHY is presenting recovered and decoded nibbles on RXD[3:0].
• In 10Mbps mode, RXDV is asserted with the first nibble of the SFD (Start of Frame Delimiter), “5D”, and remains
asserted until the end of the frame.
• In 100Mbps mode, RXDV is asserted from the first nibble of the preamble to the last nibble of the frame.
RXDV transitions synchronously with respect to RXC.

Receive Data [3:0] (RXD[3:0])

RXD[3:0] transitions synchronously with respect to RXC. For each clock period in which RXDV is asserted, RXD[3:0]
transfers a nibble of recovered data from the PHY.

Receive Error (RXER)

RXER is asserted for one or more RXC periods to indicate that an error (e.g. a coding error or any error that a PHY is
capable of detecting, and that may otherwise be undetectable by the MAC sub-layer) was detected somewhere in the
frame presently being transferred from the PHY.
RXER transitions synchronously with respect to RXC. While RXDV is de-asserted, RXER has no effect on the MAC.

Carrier Sense (CRS)

CRS is asserted and de-asserted as follows:
• In 10Mbps mode, CRS assertion is based on the reception of valid preambles. CRS de-assertion is based on the
reception of an end-of-frame (EOF) marker.
• In 100Mbps mode, CRS is asserted when a start-of-stream delimiter, or /J/K symbol pair is detected. CRS is de-
asserted when an end-of-stream delimiter, or /T/R symbol pair is detected. Additionally, the PMA layer de-asserts
CRS if IDLE symbols are received without /T/R.

Collision (COL)
COL is asserted in half-duplex mode whenever the transmitter and receiver are simultaneously active on the line. This is
used to inform the MAC that a collision has occurred during its transmission to the PHY.
COL transitions asynchronously with respect to TXC and RXC.

Reduced MII (RMII) Data Interface

The Reduced Media Independent Interface (RMII) specifies a low pin count Media Independent Interface (MII). It provides
a common interface between physical layer and MAC layer devices, and has the following key characteristics:
• Supports 10Mbps and 100Mbps data rates.
• Uses a single 50MHz reference clock provided by the MAC or the system board.
• Provides independent 2-bit wide (di-bit) transmit and receive data paths.
• Contains two distinct groups of signals: one for transmission and the other for reception.

The KSZ8041NL is configured in RMII mode after it is power-up or reset with the following:
• A 50MHz reference clock connected to REFCLK (pin 9).
• CONFIG[2:0] (pins 18, 29, 28) set to ‘001’.

In RMII mode, unused MII signals, TXD[3:2] (pins 27, 26), are tied to ground.

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RMII Signal Definition

The following table describes the RMII signals. Refer to RMII Specification for detailed information.

Direction
RMII Direction
(with respect to PHY, Description
Signal Name (with respect to MAC)
KSZ8041NL signal)
REF_CLK Input Input, or Output Synchronous 50 MHz clock reference for
receive, transmit and control interface
TX_EN Input Output Transmit Enable
TXD[1:0] Input Output Transmit Data [1:0]
CRS_DV Output Input Carrier Sense/Receive Data Valid
RXD[1:0] Output Input Receive Data [1:0]
RX_ER Output Input, or (not required) Receive Error

Table 3. RMII Signal Description

Reference Clock (REF_CLK)

REF_CLK is sourced by the MAC or system board. It is a continuous 50MHz clock that provides the timing reference for
TX_EN, TXD[1:0], CRS_DV, RXD[1:0], and RX_ER.

Transmit Enable (TX_EN)

TX_EN indicates that the MAC is presenting di-bits on TXD[1:0] for transmission. It is asserted synchronously with the first
nibble of the preamble and remains asserted while all di-bits to be transmitted are presented on the RMII, and is negated
prior to the first REF_CLK following the final di-bit of a frame.
TX_EN transitions synchronously with respect to REF_CLK.

Transmit Data [1:0] (TXD[1:0])

TXD[1:0] transitions synchronously with respect to REF_CLK. When TX_EN is asserted, TXD[1:0] are accepted for
transmission by the PHY. TXD[1:0] is ”00” to indicate idle when TX_EN is de-asserted. Values other than “00” on TXD[1:0]
while TX_EN is de-asserted are ignored by the PHY.

Carrier Sense/Receive Data Valid (CRS_DV)

CRS_DV is asserted by the PHY when the receive medium is non-idle. It is asserted asynchronously on detection of
carrier. This is when squelch is passed in 10Mbps mode, and when 2 non-contiguous zeroes in 10 bits are detected in
100Mbps mode. Loss of carrier results in the de-assertion of CRS_DV.
So long as carrier detection criteria are met, CRS_DV remains asserted continuously from the first recovered di-bit of the
frame through the final recovered di-bit, and it is negated prior to the first REF_CLK that follows the final di-bit. The data
on RXD[1:0] is considered valid once CRS_DV is asserted. However, since the assertion of CRS_DV is asynchronous
relative to REF_CLK, the data on RXD[1:0] is "00" until proper receive signal decoding takes place.

Receive Data [1:0] (RXD[1:0])

RXD[1:0] transitions synchronously to REF_CLK. For each clock period in which CRS_DV is asserted, RXD[1:0] transfers
two bits of recovered data from the PHY. RXD[1:0] is "00" to indicate idle when CRS_DV is de-asserted. Values other
than “00” on RXD[1:0] while CRS_DV is de-asserted are ignored by the MAC.

Receive Error (RX_ER)

RX_ER is asserted for one or more REF_CLK periods to indicate that an error (e.g. a coding error or any error that a PHY
is capable of detecting, and that may otherwise be undetectable by the MAC sub-layer) was detected somewhere in the
frame presently being transferred from the PHY.
RX_ER transitions synchronously with respect to REF_CLK. While CRS_DV is de-asserted, RX_ER has no effect on the
MAC.

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Collision Detection
The MAC regenerates the COL signal of the MII from TX_EN and CRS_DV.

HP Auto MDI/MDI-X
HP Auto MDI/MDI-X configuration eliminates the confusion of whether to use a straight cable or a crossover cable
between the KSZ8041NL and its link partner. This feature allows the KSZ8041NL to use either type of cable to connect
with a link partner that is in either MDI or MDI-X mode. The auto-sense function detects transmit and receive pairs from
the link partner, and then assigns transmit and receive pairs of the KSZ8041NL accordingly.
HP Auto MDI/MDI-X is enabled by default. It is disabled by writing a one to register 1F bit 13. MDI and MDI-X mode is
selected by register 1F bit 14 if HP Auto MDI/MDI-X is disabled.
An isolation transformer with symmetrical transmit and receive data paths is recommended to support auto MDI/MDI-X.
The IEEE 802.3u Standard defines MDI and MDI-X as follow:

MDI MDI-X
RJ-45 Pin Signal RJ-45 Pin Signal
1 TD+ 1 RD+
2 TD- 2 RD-
3 RD+ 3 TD+
6 RD- 6 TD-

Table 4. MDI/MDI-X Pin Definition

Straight Cable
A straight cable connects a MDI device to a MDI-X device, or a MDI-X device to a MDI device. The following diagram
depicts a typical straight cable connection between a NIC card (MDI) and a switch, or hub (MDI-X).

10/100 Ethernet 10/100 Ethernet

Media Dependent Interface Media Dependent Interface

1 1
Transmit Pair Receive Pair
2 2
Straight
3 3
Cable
4 4
Receive Pair Transmit Pair
5 5

6 6

7 7

8 8

Modular Connector Modular Connector

(RJ-45) (RJ-45)
NIC HUB
(Repeater or Switch)

Figure 2. Typical Straight Cable Connection

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Crossover Cable
A crossover cable connects a MDI device to another MDI device, or a MDI-X device to another MDI-X device. The
following diagram depicts a typical crossover cable connection between two switches or hubs (two MDI-X devices).

10/100 Ethernet 10/100 Ethernet

Media Dependent Interface Media Dependent Interface

1 Crossover 1
Receive Pair Cable Receive Pair
2 2

3 3

4 4
Transmit Pair Transmit Pair
5 5

6 6

7 7

8 8

Modular Connector (RJ-45) Modular Connector (RJ-45)

HUB HUB
(Repeater or Switch) (Repeater or Switch)

Figure 3. Typical Crossover Cable Connection

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Power Management
The KSZ8041NL offers the following power management modes:

Power Saving Mode

This mode is used to reduce power consumption when the cable is unplugged. It is in effect when auto-negotiation mode
is enabled, cable is disconnected, and register 1F bit 10 is set to 1 (default setting). Under power saving mode, the
KSZ8041NL shuts down all transceiver blocks, except for energy detect and PLL circuits. Additionally, in MII mode, the
RXC clock output is disabled. RXC clock is enabled after the cable is connected and link is established.
Power saving mode is disabled by writing a zero to register 1F bit 10.

Power Down Mode

This mode is used to power down the entire KSZ8041NL device when it is not in use. Power down mode is enabled by
writing a one to register 0 bit 11. In the power down state, the KSZ8041NL disables all internal functions, except for the
MII management interface.

Reference Clock Connection Options

A crystal or clock source, such as an oscillator, is used to provide the reference clock for the KSZ8041NL. The reference
clock is 25MHz for MII mode and 50MHz for RMII mode. The following two figures illustrate how to connect the reference
clock to XI / REFCLK (pin 9) and XO (pin 8) of the KSZ8041NL.

Figure 4. 25MHz Crystal / Oscillator Reference Clock for MII Mode

Figure 5. 50MHz Oscillator Reference Clock for RMII Mode

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Reference Circuit for Power and Ground Connections

The KSZ8041NL is a single 3.3V supply device with a built-in 1.8V low noise regulator. The power and ground
connections are shown in the following figure and table.

Figure 6. KSZ8041NL Power and Ground Connections

Power Pin Pin Number Description

VDDPLL_1.8 2 Decouple with 10uF and 0.1uF capacitors-to-ground.
VDDA_3.3 3 Connect to board’s 3.3V supply through ferrite bead.
VDDIO_3.3 17 Connect to board’s 3.3V supply.

Table 5. KSZ8041NL Power Pin Description

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Register Map
Register Number (Hex) Description
0h Basic Control
1h Basic Status
2h PHY Identifier 1
3h PHY Identifier 2
4h Auto-Negotiation Advertisement
5h Auto-Negotiation Link Partner Ability
6h Auto-Negotiation Expansion
7h Auto-Negotiation Next Page
8h Link Partner Next Page Ability
9h – 14h Reserved
15h RXER Counter
16h – 1Ah Reserved
1Bh Interrupt Control/Status
1Ch – 1Dh Reserved
1Eh PHY Control 1
1Fh PHY Control 2

Register Description
(1)
Address Name Description Mode Default

Register 0h – Basic Control

0.15 Reset 1 = Software reset RW/SC 0
0 = Normal operation
This bit is self-cleared after a ‘1’ is written to it.
0.14 Loop-back 1 = Loop-back mode RW 0
0 = Normal operation
0.13 Speed Select 1 = 100Mbps RW Set by SPEED strapping pin.
(LSB) 0 = 10Mbps See “Strapping Options” section
This bit is ignored if auto-negotiation is enabled for details.
(register 0.12 = 1).
0.12 Auto- 1 = Enable auto-negotiation process RW Set by NWAYEN strapping pin.
Negotiation 0 = Disable auto-negotiation process See “Strapping Options” section
Enable for details.
If enabled, auto-negotiation result overrides
settings in register 0.13 and 0.8.
0.11 Power Down 1 = Power down mode RW 0
0 = Normal operation

0.10 Isolate 1 = Electrical isolation of PHY from MII and RW Set by ISO strapping pin.
TX+/TX- See “Strapping Options” section
0 = Normal operation for details.
0.9 Restart Auto- 1 = Restart auto-negotiation process RW/SC 0
Negotiation 0 = Normal operation.
This bit is self-cleared after a ‘1’ is written to it.

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(1)
Address Name Description Mode Default
0.8 Duplex Mode 1 = Full-duplex RW Set by DUPLEX strapping pin.
0 = Half-duplex See “Strapping Options” section
for details.
0.7 Collision Test 1 = Enable COL test RW 0
0 = Disable COL test
0.6:1 Reserved RO 000_000
0.0 Disable 0 = Enable transmitter RW 0
Transmitter 1 = Disable transmitter

Register 1h – Basic Status

1.15 100Base-T4 1 = T4 capable RO 0
0 = Not T4 capable
1.14 100Base-TX 1 = Capable of 100Mbps full-duplex RO 1
Full Duplex 0 = Not capable of 100Mbps full-duplex
1.13 100Base-TX 1 = Capable of 100Mbps half-duplex RO 1
Half Duplex 0 = Not capable of 100Mbps half-duplex
1.12 10Base-T Full 1 = Capable of 10Mbps full-duplex RO 1
Duplex 0 = Not capable of 10Mbps full-duplex
1.11 10Base-T Half 1 = Capable of 10Mbps half-duplex RO 1
Duplex 0 = Not capable of 10Mbps half-duplex
1.10:7 Reserved RO 0000
1.6 No Preamble 1 = Preamble suppression RO 1
0 = Normal preamble
1.5 Auto- 1 = Auto-negotiation process completed RO 0
Negotiation 0 = Auto-negotiation process not completed
Complete
1.4 Remote Fault 1 = Remote fault RO/LH 0
0 = No remote fault
1.3 Auto- 1 = Capable to perform auto-negotiation RO 1
Negotiation 0 = Not capable to perform auto-negotiation
Ability
1.2 Link Status 1 = Link is up RO/LL 0
0 = Link is down
1.1 Jabber Detect 1 = Jabber detected RO/LH 0
0 = Jabber not detected (default is low)
1.0 Extended 1 = Supports extended capabilities registers RO 1
Capability

Register 2h – PHY Identifier 1

2.15:0 PHY ID Assigned to the 3rd through 18th bits of the RO 0022h
Number Organizationally Unique Identifier (OUI).
Kendin Communication’s OUI is 0010A1 (hex)

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Register 3h – PHY Identifier 2

3.15:10 PHY ID Assigned to the 19th through 24th bits of the RO 0001_01
Number Organizationally Unique Identifier (OUI).
Kendin Communication’s OUI is 0010A1 (hex)
3.9:4 Model Number Six bit manufacturer’s model number RO 00_0000
3.3:0 Revision Four bit manufacturer’s model number RO -
Number

Register 4h – Auto-Negotiation Advertisement

4.15 Next Page 1 = Next page capable RW 0
0 = No next page capability.
4.14 Reserved RO 0
4.13 Remote Fault 1 = Remote fault supported RW 0
0 = No remote fault
4.12:11 Reserved RO 00
4.10 Pause 1 = PAUSE function supported RW 0
0 = No PAUSE function supported
4.9 100Base-T4 1 = T4 capable RO 0
0 = No T4 capability
4.8 100Base-TX 1 = 100Mbps full-duplex capable RW Set by SPEED & DUPLEX
Full-Duplex 0 = No 100Mbps full-duplex capability strapping pins.
See “Strapping Options” section
for details.
4.7 100Base-TX 1 = 100Mbps half-duplex capable RW Set by SPEED strapping pin.
Half-Duplex 0 = No 100Mbps half-duplex capability See “Strapping Options” section
for details.
4.6 10Base-T 1 = 10Mbps full-duplex capable RW Set by DUPLEX strapping pin.
Full-Duplex 0 = No 10Mbps full-duplex capability See “Strapping Options” section
for details.
4.5 10Base-T 1 = 10Mbps half-duplex capable RW 1
Half-Duplex 0 = No 10Mbps half-duplex capability
4.4:0 Selector Field [00001] = IEEE 802.3 RW 0_0001

Register 5h – Auto-Negotiation Link Partner Ability

5.15 Next Page 1 = Next page capable RO 0
0 = No next page capability
5.14 Acknowledge 1 = Link code word received from partner RO 0
0 = Link code word not yet received
5.13 Remote Fault 1 = Remote fault detected RO 0
0 = No remote fault
5.12 Reserved RO 0
5.11:10 Pause [00] = No PAUSE RO 00
[10] = Asymmetric PAUSE
[01] = Symmetric PAUSE
[11] = Asymmetric & Symmetric PAUSE
5.9 100Base-T4 1 = T4 capable RO 0
0 = No T4 capability

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5.8 100Base-TX 1 = 100Mbps full-duplex capable RO 0

Full-Duplex 0 = No 100Mbps full-duplex capability
5.7 100Base-TX 1 = 100Mbps half-duplex capable RO 0
Half-Duplex 0 = No 100Mbps half-duplex capability
5.6 10Base-T 1 = 10Mbps full-duplex capable RO 0
Full-Duplex 0 = No 10Mbps full-duplex capability
5.5 10Base-T 1 = 10Mbps half-duplex capable RO 0
Half-Duplex 0 = No 10Mbps half-duplex capability
5.4:0 Selector Field [00001] = IEEE 802.3 RO 0_0001

Register 6h – Auto-Negotiation Expansion

6.15:5 Reserved RO 0000_0000_000
6.4 Parallel 1 = Fault detected by parallel detection RO/LH 0
Detection Fault 0 = No fault detected by parallel detection.
6.3 Link Partner 1 = Link partner has next page capability RO 0
Next Page 0 = Link partner does not have next page
Able capability
6.2 Next Page 1 = Local device has next page capability RO 1
Able 0 = Local device does not have next page
capability
6.1 Page Received 1 = New page received RO/LH 0
0 = New page not received yet
6.0 Link Partner 1 = Link partner has auto-negotiation capability RO 0
Auto- 0 = Link partner does not have auto-negotiation
Negotiation capability
Able

Register 7h – Auto-Negotiation Next Page

7.15 Next Page 1 = Additional next page(s) will follow RW 0
0 = Last page
7.14 Reserved RO 0

7.13 Message Page 1 = Message page RW 1

0 = Unformatted page
7.12 Acknowledge2 1 = Will comply with message RW 0
0 = Cannot comply with message
7.11 Toggle 1 = Previous value of the transmitted link code RO 0
word equaled logic one
0 = Logic zero
7.10:0 Message Field 11-bit wide field to encode 2048 messages RW 000_0000_0001

Register 8h – Link Partner Next Page Ability

8.15 Next Page 1 = Additional Next Page(s) will follow RO 0
0 = Last page
8.14 Acknowledge 1 = Successful receipt of link word RO 0
0 = No successful receipt of link word
8.13 Message Page 1 = Message page RO 0
0 = Unformatted page

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8.12 Acknowledge2 1 = Able to act on the information RO 0

0 = Not able to act on the information
8.11 Toggle 1 = Previous value of transmitted link code RO 0
word equal to logic zero
0 = Previous value of transmitted link code
word equal to logic one
8.10:0 Message Field RO 000_0000_0000

Register 15h – RXER Counter

15.15:0 RXER Counter RX error counter for RX_ER frames RO/SC 0000h

Register 1Bh – Interrupt Control/Status

1b.15 Jabber 1 = Enable Jabber Interrupt RW 0
Interrupt 0 = Disable Jabber Interrupt
Enable
1b.14 Receive Error 1 = Enable Receive Error Interrupt RW 0
Interrupt 0 = Disable Receive Error Interrupt
Enable
1b.13 Page Received 1 = Enable Page Received Interrupt RW 0
Interrupt 0 = Disable Page Received Interrupt
Enable
1b.12 Parallel Detect 1 = Enable Parallel Detect Fault Interrupt RW 0
Fault Interrupt 0 = Disable Parallel Detect Fault Interrupt
Enable
1b.11 Link Partner 1 = Enable Link Partner Acknowledge Interrupt RW 0
Acknowledge 0 = Disable Link Partner Acknowledge
Interrupt Interrupt
Enable
1b.10 Link Down 1= Enable Link Down Interrupt RW 0
Interrupt 0 = Disable Link Down Interrupt
Enable
1b.9 Remote Fault 1 = Enable Remote Fault Interrupt RW 0
Interrupt 0 = Disable Remote Fault Interrupt
Enable
1b.8 Link Up 1 = Enable Link Up Interrupt RW 0
Interrupt 0 = Disable Link Up Interrupt
Enable
1b.7 Jabber 1 = Jabber occurred RO/SC 0
Interrupt 0 = Jabber did not occurred
1b.6 Receive Error 1 = Receive Error occurred RO/SC 0
Interrupt 0 = Receive Error did not occurred
1b.5 Page Receive 1 = Page Receive occurred RO/SC 0
Interrupt 0 = Page Receive did not occurred
1b.4 Parallel Detect 1 = Parallel Detect Fault occurred RO/SC 0
Fault Interrupt 0 = Parallel Detect Fault did not occurred
1b.3 Link Partner 1= Link Partner Acknowledge occurred RO/SC 0
Acknowledge 0= Link Partner Acknowledge did not occurred
Interrupt
1b.2 Link Down 1= Link Down occurred RO/SC 0
Interrupt 0= Link Down did not occurred
1b.1 Remote Fault 1= Remote Fault occurred RO/SC 0
Interrupt 0= Remote Fault did not occurred

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1b.0 Link Up 1= Link Up occurred RO/SC 0

Interrupt 0= Link Up did not occurred

Register 1Eh – PHY Control 1

1e:15:14 LED mode [00] = RW 00
LED1 : Speed
LED0 : Link/Activity

[01] =
LED1 : Activity
LED0 : Link

[10] =
Reserved

[11] =
Reserved
1e.13 Polarity 0 = Polarity is not reversed RO
1 = Polarity is reversed
1e.12 Reserved RO 0
1e.11 MDI/MDI-X 0 = MDI RO
State 1 = MDI-X
1e:10:8 Reserved
1e:7 Remote 0 = Normal mode RW 0
loopback 1 = Remote (analog) loop back is enable
1e:6:0 Reserved

Register 1Fh – PHY Control 2

1f:15 HP_MDIX 0 = Micrel Auto MDI/MDI-X mode RW 1
1 = HP Auto MDI/MDI-X mode
1f:14 MDI/MDI-X When Auto MDI/MDI-X is disabled, RW 0
Select 0 = MDI Mode
Transmit on TX+/- (pins 7,6) and
Receive on RX+/- (pins 5,4)
1 = MDI-X Mode
Transmit on RX+/- (pins 5,4) and
Receive on TX+/- (pins 7,6)
1f:13 Pairswap 1 = Disable auto MDI/MDI-X RW 0
Disable 0 = Enable auto MDI/MDI-X
1f.12 Energy Detect 1 = Presence of signal on RX+/- analog wire RO 0
pair
0 = No signal detected on RX+/-
1f.11 Force Link 1 = Force link pass RW 0
0 = Normal link operation
This bit bypasses the control logic and allow
transmitter to send pattern even if there is no
link.

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1f.10 Power Saving 1 = Enable power saving RW 1

0 = Disable power saving
If power saving mode is enabled and the cable
is disconnected, the RXC clock output (in MII
mode) is disabled. RXC clock is enabled after
the cable is connected and link is established.
1f.9 Interrupt Level 1 = Interrupt pin active high RW 0
0 = Interrupt pin active low
1f.8 Enable Jabber 1 = Enable jabber counter RW 1
0 = Disable jabber counter
1f.7 Auto- 1 = Auto-negotiation process completed RW 0
Negotiation 0 = Auto-negotiation process not completed
Complete
1f.6 Enable Pause 1 = Flow control capable RO 0
(Flow Control) 0 = No flow control capability
1f.5 PHY Isolate 1 = PHY in isolate mode RO 0
0 = PHY in normal operation
1f.4:2 Operation [000] = still in auto-negotiation RO 000
Mode [001] = 10Base-T half-duplex
Indication
[010] = 100Base-TX half-duplex
[011] = reserved
[101] = 10Base-T full-duplex
[110] = 100Base-TX full-duplex
[111] = reserved
1f.1 Enable SQE 1 = Enable SQE test RW 0
test 0 = Disable SQE test
1f.0 Disable Data 1 = Disable scrambler RW 0
Scrambling 0 = Enable scrambler
Note:
1. RW = Read/Write.
RO = Read only.
SC = Self-cleared.
LH = Latch high.
LL = Latch low.

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Absolute Maximum Ratings(1) Operating Ratings(2)

Supply Voltage Supply Voltage
(VDDPLL_1.8) ............................................... -0.5V to +2.4V (VDDIO_3.3, VDDA_3.3) .......................... +3.135V to +3.465V
(VDDIO_3.3, VDDA_3.3) ................................... -0.5V to +4.0V Ambient Temperature (TA) .............................. 0°C to +70°C
Input Voltage (all inputs) ............................... -0.5V to +4.0V Maximum Junction Temperature (TJ Max) ................. 125°C
Output Voltage (all outputs) .......................... -0.5V to +4.0V Thermal Resistance (θJA) .........................................34°C/W
Lead Temperature (soldering, 10sec.)....................... 260°C
Storage Temperature (Ts) ..........................-55°C to +150°C
ESD Rating(3) .................................................................. 6kV

Electrical Characteristics(4)
Symbol Parameter Condition Min Typ Max Units
(5)
Supply Current
IDD1 100Base-TX Chip only (no transformer); 53 mA
Full-duplex traffic @ 100% utilization
IDD2 10Base-T Chip only (no transformer); 38 mA
Full-duplex traffic @ 100% utilization
IDD3 Power Saving Mode Ethernet cable disconnected (reg. 1F.10 = 1) 32 mA
IDD4 Power Down Mode Software power down (reg. 0.11 = 1) 4 mA
TTL Inputs
VIH Input High Voltage 2.0 V
VIL Input Low Voltage 0.8 V
IIN Input Current VIN = GND ~ VDDIO -10 10 µA
TTL Outputs
VOH Output High Voltage IOH = -4mA 2.4 V
VOL Output Low Voltage IOL = 4mA 0.4 V
|Ioz| Output Tri-State Leakage 10 µA
100Base-TX Transmit (measured differentially after 1:1 transformer)
VO Peak Differential Output Voltage 100Ω termination across differential output 0.95 1.05 V
VIMB Output Voltage Imbalance 100Ω termination across differential output 2 %
tr, tf Rise/Fall Time 3 5 ns
Rise/Fall Time Imbalance 0 0.5 ns
Duty Cycle Distortion + 0.25 ns
Overshoot 5 %
VSET Reference Voltage of ISET 0.65 V
Output Jitter Peak-to-peak 0.7 1.4 ns
Notes:
1. Exceeding the absolute maximum rating may damage the device. Stresses greater than the absolute maximum rating may cause permanent
damage to the device. Operation of the device at these or any other conditions above those specified in the operating sections of this specification
is not implied. Maximum conditions for extended periods may affect reliability.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
4. TA = 25°C. Specification for packaged product only.
5. Current consumption is for the single 3.3V supply KSZ8041NL device only, and includes the 1.8V supply voltage (VDDPLL_1.8) that is provided by the
KSZ8041NL. The PHY port’s transformer consumes an additional 45mA @ 3.3V for 100Base-TX and 70mA @ 3.3V for 10Base-T.

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Electrical Characteristics(6)
10Base-T Transmit (measured differentially after 1:1 transformer)
VP Peak Differential Output Voltage 100Ω termination across differential output 2.2 2.8 V
Jitter Added Peak-to-peak 3.5 ns
tr, tf Rise/Fall Time 25 ns
10Base-T Receive
VSQ Squelch Threshold 5MHz square wave 400 mV
Notes:
6. TA = 25°C. Specification for packaged product only.

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Timing Diagrams
MII SQE Timing (10Base-T)

Figure 7. MII SQE Timing (10Base-T)

Timing Parameter Description Min Typ Max Unit

tP TXC period 400 ns
tWL TXC pulse width low 200 ns
tWH TXC pulse width high 200 ns
tSQE COL (SQE) delay after TXEN de-asserted 2.5 us
tSQEP COL (SQE) pulse duration 1.0 us

Table 6. MII SQE Timing (10Base-T) Parameters

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MII Transmit Timing (10Base-T)

Figure 8. MII Transmit Timing (10Base-T)

Timing Parameter Description Min Typ Max Unit

tP TXC period 400 ns
tWL TXC pulse width low 200 ns
tWH TXC pulse width high 200 ns
tSU1 TXD[3:0] setup to rising edge of TXC 10 ns
tSU2 TXEN setup to rising edge of TXC 10 ns
tHD1 TXD[3:0] hold from rising edge of TXC 0 ns
tHD2 TXEN hold from rising edge of TXC 0 ns
tCRS1 TXEN high to CRS asserted latency 4 Bit
Time
tCRS2 TXEN low to CRS de-asserted latency 8 Bit
Time

Table 7. MII Transmit Timing (10Base-T) Parameters

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MII Receive Timing (10Base-T)

Figure 9. MII Receive Timing (10Base-T)

Timing Parameter Description Min Typ Max Unit

tP RXC period 400 ns
tWL RXC pulse width low 200 ns
tWH RXC pulse width high 200 ns
tOD (RXD[3:0], RXER, RXDV) output 182 225 ns
delay from rising edge of RXC
tRLAT CRS to (RXD[3:0], RXER, RXDV) 6.5 us
latency

Table 8. MII Receive Timing (10Base-T) Parameters

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MII Transmit Timing (100Base-TX)

Figure 10. MII Transmit Timing (100Base-TX)

Timing Parameter Description Min Typ Max Unit

tP TXC period 40 ns
tWL TXC pulse width low 20 ns
tWH TXC pulse width high 20 ns
tSU1 TXD[3:0] setup to rising edge of TXC 10 ns
tSU2 TXEN setup to rising edge of TXC 10 ns
tHD1 TXD[3:0] hold from rising edge of TXC 0 ns
tHD2 TXEN hold from rising edge of TXC 0 ns
tCRS1 TXEN high to CRS asserted latency 4 Bit
Time
tCRS2 TXEN low to CRS de-asserted latency 4 Bit
Time

Table 9. MII Transmit Timing (100Base-TX) Parameters

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MII Receive Timing (100Base-TX)

Figure 11. MII Receive Timing (100Base-TX)

Timing Parameter Description Min Typ Max Unit

tP RXC period 40 ns
tWL RXC pulse width low 20 ns
tWH RXC pulse width high 20 ns
tOD (RXD[3:0], RXER, RXDV) output 19 25 ns
delay from rising edge of RXC
tRLAT CRS to (RXD[3:0], RXER, RXDV) 1 2 3 Bit
latency Time

Table 10. MII Receive Timing (100Base-TX) Parameters

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RMII Timing

Figure 12. RMII Timing – Data Received from RMII

Figure 13. RMII Timing – Data Input to RMII

Timing Parameter Description Min Typ Max Unit

tcyc Clock cycle 20 ns
t1 Setup time 4 ns
t2 Hold time 2 ns
tod Output delay 2.8 10 ns

Table 11. RMII Timing Parameters

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Auto-Negotiation Timing

Figure 14. Auto-Negotiation Fast Link Pulse (FLP) Timing

Timing Parameter Description Min Typ Max Units

tBTB FLP Burst to FLP Burst 8 16 24 ms
tFLPW FLP Burst width 2 ms
tPW Clock/Data Pulse width 100 ns
tCTD Clock Pulse to Data Pulse 55.5 64 69.5 µs
tCTC Clock Pulse to Clock Pulse 111 128 139 µs
Number of Clock/Data Pulse per 17 33
FLP Burst

Table 12. Auto-Negotiation Fast Link Pulse (FLP) Timing Parameters

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MDC/MDIO Timing

Figure 15. MDC/MDIO Timing

Timing Parameter Description Min Typ Max Unit

tP MDC period 400 ns
t1MD1 MDIO (PHY input) setup to rising edge of MDC 10 ns
tMD2 MDIO (PHY input) hold from rising edge of MDC 10 ns
tMD3 MDIO (PHY output) delay from rising edge of MDC 222 ns

Table 13. MDC/MDIO Timing Parameters

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Reset Timing
The KSZ8041NL reset timing requirement is summarized in the following figure and table.

Figure 16. Reset Timing

Parameter Description Min Max Units

tsr Stable supply voltage to reset high 10 ms
tcs Configuration setup time 5 ns
tch Configuration hold time 5 ns
trc Reset to strap-in pin output 6 ns

Table 14. Reset Timing Parameters

After the de-assertion of reset, it is recommended to wait a minimum of 100 us before starting programming on the MIIM
(MDC/MDIO) Interface.

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Reset Circuit
The following reset circuit is recommended for powering up the KSZ8041NL if reset is triggered by the power supply.

Figure 17. Recommended Reset Circuit

The following reset circuit is recommended for applications where reset is driven by another device (e.g., CPU or FPGA).
At power-on-reset, R, C and D1 provide the necessary ramp rise time to reset the KSZ8041NL device. The RST_OUT_n
from CPU/FPGA provides the warm reset after power up.

Figure 18. Recommended Reset Circuit for interfacing with CPU/FPGA Reset Output.

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Reference Circuits for LED Strapping Pins

The following figure shows the reference circuits for pull-up, float and pull-down on the LED1 and LED0 strapping pins.

Figure 19. Reference Circuits for LED Strapping Pins

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Selection of Isolation Transformer

A 1:1 isolation transformer is required at the line interface. An isolation transformer with integrated common-mode chokes
is recommended for exceeding FCC requirements.
The following table gives recommended transformer characteristics.

Parameter Value Test Condition

Turns ratio 1 CT : 1 CT
Open-circuit inductance (min.) 350µH 100mV, 100kHz, 8mA
Leakage inductance (max.) 0.4µH 1MHz (min.)
Inter-winding capacitance (max.) 12pF
D.C. resistance (max.) 0.9Ω
Insertion loss (max.) 1.0dB 0MHz – 65MHz
HIPOT (min.) 1500Vrms

Table 15. Transformer Selection Criteria

Magnetic Manufacturer Part Number Auto MDI-X Number of Port

Bel Fuse S558-5999-U7 Yes 1
Bel Fuse (Mag Jack) SI-46001 Yes 1
Bel Fuse (Mag Jack) SI-50170 Yes 1
Delta LF8505 Yes 1
LanKom LF-H41S Yes 1
Pulse H1102 Yes 1
Pulse (low cost) H1260 Yes 1
Transpower HB726 Yes 1
TDK (Mag Jack) TLA-6T718 Yes 1

Table 16. Qualified Single Port Magnetics

Selection of Reference Crystal

Characteristics Value Units

Frequency 25 MHz
Frequency tolerance (max) ±50 ppm
Load capacitance (max) 20 pF
Series resistance 40 Ω

Table 17. Typical Reference Crystal Characteristics

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Package Information

32-Pin (5mm x 5mm) MLF® Package

MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical
implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user.
A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to
fully indemnify Micrel for any damages resulting from such use or sale.

© 2006 Micrel, Incorporated.

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