KS8721BL/SL
3.3V Single Power Supply 10/100BASE-TX/FX
MII Physical Layer Transceiver
Rev. 1.3
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 2009 M9999-062509-1.3
General Description
Operating with a 2.5V core to meet low-voltage and low-
power requirements, the KS8721BL and KS8721SL are
10BASE-T/100BASE-TX/FX Physical Layer Transceivers
that use MII and RMII interfaces to transmit and receive
data. They contain 10BASE-T Physical Medium
Attachment (PMA), Physical Medium Dependent (PMD),
and Physical Coding Sub-layer (PCS) functions. The
KS8721BL/SL also have on-chip 10BASE-T output
ltering. This eliminates the need for external lters and
allows a single set of line magnetics to be used to meet
requirements for both 100BASE-TX and 10BASE-T.
The KS8721BL/SL automatically configure themselves
for 100 or 10Mbps and full- or half-duplex operation,
using an on-chip auto-negotiation algorithm. They are the
ideal physical layer transceiver for 100BASE-TX/
10BASE-T applications.
Features
Single chip 100BASE-TX/100BASE-FX/10BASE-T
physical layer solution
2.5V CMOS design; 2.5/3.3V tolerance on I/O
3.3V single power supply with built-in voltage
regulator; Power consumption <340mW (including
output driver current)
Fully compliant to IEEE 802.3u standard
Supports MII and Reduced MII (RMII)
Supports 10BASE-T, 100BASE-TX, and 100BASE-FX
with Far_End_Fault Detection
Supports power-down and power-saving modes
Congurable through MII serial management ports or
via external control pins
Functional Diagram
Micrel, Inc. KS8721BL/SL
June 2009 2 M9999-062509-1.3
Features (continued)
Supports auto-negotiation and manual selection for
10/100Mbps speed and full-/half-duplex modes
On-chip, built-in, analog front-end ltering for both
100BASE-TX and 10BASE-T
LED outputs for link, activity, full-/half-duplex, collision,
and speed
Supports back-to-back, FX to TX for media converter
applications
Supports MDI/MDI-X auto-crossover
KS8721BL is a drop-in replacement for the KS8721BT
in the same footprint
KS8721SL is a drop-in replacement for the KS8721B
in the same footprint
Commercial Temperature Range: 0oC to +70oC
Industrial Temperature Range: –40oC to +85oC
Available in 48-pin SSOP and LQFP
Ordering Information
Part Number Temp. Range Package Lead Finish
KS8721BL 0oC to 70oC 48-Pin LQFP Standard
KS8721SL 0oC to 70oC 48-Pin SSOP Standard
KS8721BLI –40oC to +85oC 48-Pin LQFP Standard
KSZ8721BL 0oC to 70oC 48-Pin LQFP Lead-Free
KSZ8721SL 0oC to 70oC 48-Pin SSOP Lead-Free
KSZ8721BLI –40oC to +85oC 48-Pin LQFP Lead-Free
KSZ8721SLI –40oC to +85oC 48-Pin SSOP Lead-Free
Micrel, Inc. KS8721BL/SL
June 2009 3 M9999-062509-1.3
Revision History
Revision Date Summary of Changes
0.9 01/12/04 Data sheet created.
1.0 03/06/04
Initial release. Change to new format. Added part-ordering information. Editorial changes on pin
description, RMII, and media converter operation. Update circuit design, reset timing, thermal
resistance, electrical characteristics, and strapping option circuit.
1.1 05/17/04 Added BLI product information.
1.2 01/21/05
MDIO Pull-up resistor value changed to 4.7k. Added note on strapping option pins. Updated
bits 1b.0 - 1b.7 to self clearing. Updated electrical characteristics. Updated reference schematic
for strapping option conguration to 3.3V. Crystal spec updated to 40 series resistance. Added
additional magnetics to qualied transformer table. Added 2 lead-free part options. Added
recommended reset circuit.
1.3 06/25/09 Update ordering information.
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June 2009 4 M9999-062509-1.3
Contents
Pin Configuration..............................................................................................................................................................6
Pin Description..................................................................................................................................................................7
Strapping Options(1) ........................................................................................................................................................10
Functional Description ...................................................................................................................................................11
100BASE-TX Transmit.................................................................................................................................................. 11
100BASE-TX Receive................................................................................................................................................... 11
PLL Clock Synthesizer.................................................................................................................................................. 11
Scrambler/De-scrambler (100BASE-TX only) .............................................................................................................. 11
10BASE-T Transmit ...................................................................................................................................................... 11
10BASE-T Receive ....................................................................................................................................................... 11
SQE and Jabber Function (10BASE-T only) ................................................................................................................ 12
Auto-Negotiation ........................................................................................................................................................... 12
MII Management Interface............................................................................................................................................ 12
MII Data Interface ......................................................................................................................................................... 12
Transmit Clock (TXC)........................................................................................................... ................................12
Receive Clock (RXC) ...........................................................................................................................................12
Transmit Enable...................................................................................................................................................13
Receive Data Valid............................................................................................................. ..................................13
Error Signals.........................................................................................................................................................13
Carrier Sense (CRS)............................................................................................................ ................................13
Collision................................................................................................................................................................13
RMII (Reduced MII) Data Interface............................................................................................................................... 13
RMII Signal Denition ................................................................................................................................................... 13
Reference Clock (REF_CLK)........................................................................................................................................ 14
Carrier Sense/Receive Data Valid (CRS_DV) .............................................................................................................. 14
Receive Data [1:0] (RXD[1:0]) ...................................................................................................................................... 14
Transmit Enable (TX_EN)............................................................................................................................................. 14
Transmit Data [1:0] (TXD[1:0])...................................................................................................................................... 14
Collision Detection ........................................................................................................................................................ 14
RX_ER .......................................................................................................................................................................... 14
RMII AC Characteristics................................................................................................................................................ 15
Unused RMII Pins ......................................................................................................................................................... 15
Auto-Crossover (Auto-MDI/MDI-X) ............................................................................................................................... 15
Power Management...................................................................................................................................................... 16
100BT FX Mode............................................................................................................................................................ 16
Media Converter Operation........................................................................................................................................... 17
Circuit Design Reference for Power Supply ................................................................................................................. 18
Register Map....................................................................................................................................................................19
Register 0h - Basic Control........................................................................................................................................... 19
Register 1h - Basic Status ............................................................................................................................................ 19
Register 2h - PHY Identier 1 ....................................................................................................................................... 20
Register 3h - PHY Identier 2 ....................................................................................................................................... 20
Register 4h - Auto-Negotiation Advertisement ............................................................................................................. 20
Register 5h - Auto-Negotiation Link Partner Ability ...................................................................................................... 21
Register 6h - Auto-Negotiation Expansion.................................................................................................................... 21
Register 7h - Auto-Negotiation Next Page.................................................................................................................... 21
Register 8h - Link Partner Next Page Ability ................................................................................................................ 22
Register 15h - RXER Counter....................................................................................................................................... 22
Register 1bh - Interrupt Control/Status Register .......................................................................................................... 22
Register 1fh - 100BASE-TX PHY Controller................................................................................................................. 23
Absolute Maximum Ratings(1) ........................................................................................................................................24
Operating Ratings(2) ........................................................................................................................................................24
Electrical Characteristics(4) ............................................................................................................................................24
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June 2009 5 M9999-062509-1.3
Timing Diagrams.............................................................................................................................................................26
Selection of Isolation Transformers(1)...........................................................................................................................33
Selection of Reference Crystal......................................................................................................................................33
Package Information.......................................................................................................................................................34
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June 2009 6 M9999-062509-1.3
Pin Configuration
VDDIO INT#/PHYAD02524
GND LED0/TEST2623
13VDDC
TXER
TXC/REF_CLK
TXEN
TXD0
TXD1
TXD2
TXD3
COL/RMII
CRS/RMII_BTB
36 GND
GND
FXSD/FXEN
RX+
RX-
VDDRX
PD#
LED3/NWAYEN
LED2/DUPLEX
LED1/SPD100
35
34
33
32
31
30
29
28
27
14
15
16
17
18
19
20
21
22
GND REXT3712
RXER/ISO VDDRCV3811
1MDIO
MDC
R3D3/PHYAD1
RXD2/PHYAD2
RXD1/PHYAD3
RXD0/PHYAD4
VDDIO
GND
RXDV/PCS_LPBK
RXC
48 RST#
VDDPLL
XI
XO
GND
GND
VDDTX
TX+
TX-
GND
47
46
45
44
43
42
41
40
39
2
3
4
5
6
7
8
9
10
TXD0
TXEN
TXC/REF_CLK
TXER
VDDC
TXD1
TXD2
TXD3
MDIO
MDC
RXD1/PHYAD1
RXD2/PHYAD2
RXD1/PHYAD3
RXD0/PHYAD4
VDDIO
GND
RXDV/PCS_LPBK
RXC
RXER/ISO
GND
COL/RMII
CRS/RMII_BTB
GND
VDDIO
GND
GND
FXSD/FXEN
RX+
RX–
VDDRX
PD#
LED3/NWAYEN
LED2/DUPLEX
LED1/SPD100
LED0/TEST
INT#/PHYAD0
GND
X0
X1
VDDPLL
RST#
GND
VDDTX
TX+
Tx–
GND
VDDRC
V
REXT
48-Pin SSOP (SM)
48-Pin LQFP (LQ)
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June 2009 7 M9999-062509-1.3
Pin Description
Pin Number Pin Name Type(1) Pin Function
1 MDIO I/O
Management Independent Interface (MII) Data I/O. This pin requires an external 4.7K
pull-up resistor.
2 MDC I MII Clock Input. This pin is synchronous to the MDIO.
3 RXD3/
PHYAD
Ipd/O MII Receive Data Output. RXD [3..0], these 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.
During reset, the pull-up/pull-down value is latched as PHYADDR [1]. See “Strapping
Options” section for details.
4 RXD2/
PHYAD2
Ipd/O MII Receive Data Output.
During reset, the pull-up/pull-down value is latched as PHYADDR[2]. See “Strapping
Options” section for details.
5 RXD1/
PHYAD3
Ipd/O MII Receive Data Output.
During reset, the pull-up/pull-down value is latched as PHYADDR[3]. See “Strapping
Options” section for details.
6 RXD0/
PHYAD4
Ipd/O MII Receive Data Output.
During reset, the pull-up/pull-down value is latched as PHYADDR[4]. See “Strapping
Options” section for details.
7 VDDIO P
Digital IO 2.5 /3.3V tolerant power supply. 3.3V power Input of voltage regulator. See
“Circuit Design Ref. for Power Supply" section for details.
8 GND Gnd Ground.
9 RXDV/
CRSDV/
PCS_LPBK
Ipd/O MII Receive Data Valid Output.
During reset, the pull-up/pull-down value is latched as PCS_LPBK. See “Strapping
Options” section for details.
10 RXC O MII Receive Clock Output. Operating at 25MHz = 100Mbps, 2.5MHz = 10Mbps.
11 RXER/ISO Ipd/O
MII Receive Error Output.
During reset, the pull-up/pull-down value is latched as ISOLATE during reset. See
“Strapping Options” section for details.
12 GND Gnd Ground.
13 VDDC P Digital core 2.5V only power supply. See “Circuit Design Ref. for Power Supply" section
for details.
14 TXER Ipd MII Transmit Error Input.
15 TXC/
REFCLK
I/O MII Transmit Clock Output.
Input for crystal or an external 50MHz clock. When REFCLK pin is used for REF clock
interface, pull up XI to VDDPLL 2.5V via 10k resistor and leave XO pin unconnected.
16 TXEN Ipd MII Transmit Enable Input.
17 TXD0 Ipd MII Transmit Data Input.
18 TXD1 Ipd MII Transmit Data Input.
19 TXD2 Ipd MII Transmit Data Input.
20 TXD3 Ipd MII Transmit Data Input.
21 COL/
RMII
Ipd/O MII Collision Detect Output.
During reset, the pull-up/pull-down value is latched as RMII select. See “Strapping
Options” section for details.
22 CRS/
RMII_BTB
Ipd/O MII Carrier Sense Output.
During reset, the pull-up/pull-down value is latched as RMII back-to-back mode when
RMII mode is selected. See “Strapping Options” section for details.
23 GND Gnd Ground.
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June 2009 8 M9999-062509-1.3
Pin Number Pin Name Type(1) Pin Function
24 VDDIO P Digital IO 2.5/3.3V tolerant power supply. 3.3V power input of voltage regulator.
See “Circuit Design Ref. for Power Supply” section for details.
25 INT#/
PHYAD0
Ipu/O Management Interface (MII) Interrupt Out. Interrupt level set by Register 1f, bit 9.
During reset, latched as PHYAD[0]. See “Strapping Options” section for details.
26 LED0/
TEST
Ipu/O Link/Activity LED Output. The external pull-down enable test mode and only used for
the factory test. Active low.
Link/Act Pin State LED Definition PHYAD0
No Link H “Off”
Link L “On”
Act – “Toggle”
27 LED1/
SPD100/
nFEF
Ipu/O Speed LED Output. Latched as SPEED (Register 0, bit 13) during power-up/ reset. See
“Strapping Options” section for details. Active low.
Speed Pin State LED Definition
10BT H “Off”
100BT L “On”
28 LED2 Ipu/O Full-duplex LED Output. Latched as DUPLEX (register 0h, bit 8) during power-up/ reset.
See “Strapping DUPLEX Options” section for details. Active low.
Duplex Pin State LED Definition
Half H “Off”
Full L “On”
29 LED3/
NWAYEN
Ipu/O Collision LED Output. Latched as ANEG_EN (register 0h, bit 12) during power-up/
reset. See “Strapping Options” section for details.
Collision Pin State LED Definition
No Collision H “Off”
Collision L “On”
30 PD# Ipu Power Down. 1 = Normal operation, 0 = Power-down. Active low.
31 VDDRX P Analog 2.5V power supply. See “Circuit Design Ref. for Power Supply” section for
details.
32 RX- I Receive Input. Differential receive input pins for 100FX, 100BASE-TX, or 10BASE-T.
33 RX+ I Receive Input: Differential receive input pin for 100FX, 100BASE-TX, or 10BASE-T.
34 FXSD/
FXEN
Ipd/O Fiber Mode Enable / Signal Detect in Fiber Mode. If FXEN = 0, FX mode is disable. The
default is “0”. See “100BT FX Mode” section for more details.
35 GND Gnd Ground.
36 GND Gnd Ground.
37 REXT I External resistor (6.49kW ) connects to REXT and GND.
38 VDDRCV P
Analog 2.5V power supply. 2.5V power output of voltage regulator. See “Circuit Design
Ref. for Power Supply” section for details.
39 GND Gnd Ground.
40 TX- O Transmit Outputs: Differential transmit output for 100FX, 100BASE-TX, or 10BASE-T.
41 TX+ O Transmit Outputs: Differential transmit output for 100FX, 100BASE-TX, or 10BASE-T.
42 VDDTX P
Transmitter 2.5V power supply. See “Circuit Design Ref. for Power Supply” section for
details.
43 GND Gnd Ground.
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June 2009 9 M9999-062509-1.3
Pin Number Pin Name Type(1) Pin Function
44 GND Gnd Ground.
45 XO O XTAL feedback: Used with XI for Xtal application.
46 XI I
Crystal Oscillator Input: Input for a crystal or an external 25MHz clock.
If an oscillator is used, XI connects to a 3.3V tolerant oscillator, and X2 is a no-connect.
47 VDDPLL P
Analog PLL 2.5V power supply. See “Circuit Design Ref. for Power Supply” section for
details.
48 RST# Ipu Chip Reset. Active low, minimum of 50µs pulse is required.
Note:
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.
Ipd/O = Input with internal pull-down during reset; output pin otherwise.
Ipu/O = Input with internal pull-up during reset; output pin otherwise.
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June 2009 10 M9999-062509-1.3
Strapping Options(1)
Pin Number Pin Name Type(2) Pin Function
6, 5,
4, 3
PHYAD[4:1]/
RXD[0:3]
Ipd/O
25 PHYAD0/
INT#
Ipu/O
PHY Address latched at power-up/reset. The default PHY address is 00001.
9(3) PCS_LPBK/
RXDV
Ipd/O Enables PCS_LPBK mode at power-up/reset. PD (default) = Disable, PU = Enable.
11(3) ISO/RXER Ipd/O Enables ISOLATE mode at power-up/reset. PD (default) = Disable, PU = Enable.
21(3) RMII/COL Ipd/O Enables RMII mode at power-up/reset. PD (default) = Disable, PU = Enable.
22(3) RMII_BTB
CRS
Ipd/O Enable RMII back-to-back mode at power-up/reset. PD (default) = Disable,
PU = Enable.
27 SPD100/
No FEF/
Ipu/O Latched into Register 0h bit 13 during power-up/reset. PD = 10Mbps, PU (default) =
100Mbps. If SPD100 is asserted during power-up/reset, this pin is also latched as
LED1 the Speed Support in register 4h. (If FXEN is pulled up, the latched value 0
means no Far_End _Fault.)
28 DUPLEX/
LED2
Ipu/O Latched into Register 0h bit 8 during power-up/reset. PD = Half-duplex, PU (default) =
Full-duplex. If Duplex is pulled up during reset, this pin is also latched as the Duplex
support in register 4h.
29 NWAYEN/
LED3
Ipu/O Nway (auto-negotiation) Enable. Latched into Register 0h bit 12 during power-up/reset.
PD = Disable Auto-Negotiation, PU (default) = Enable Auto-Negotiation.
30 PD# Ipu Power-Down Enable. PU (default) = Normal operation, PD = Power-Down mode.
Notes:
1. Strap-in is latched during power-up or reset.
2. Ipu = Input with internal pull-up.
Ipd/O = Input with internal pull-down during reset; output pin otherwise.
Ipu/O = Input with internal pull-up during reset; output pin otherwise.
See “Reference Circuit” section for pull-up/pull-down and oat information.
3. Some devices may drive MII pins that are designated as output (PHY) on power-up, resulting in incorrect strapping values latched at reset.
It is recommended that an external pull-down via 1k resistor be used in these applications to augment the 8721’s internal pull-down.
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June 2009 11 M9999-062509-1.3
Functional Description
100BASE-TX Transmit
The 100BASE-TX transmit function performs parallel to serial conversion, NRZ-to-NRZI conversion, and MLT-3
encoding and transmission. The circuitry starts with a parallel to serial conversion that converts the 25MHz, 4-bit
nibbles into a 125MHz serial bit stream. The incoming data is clocked in at the positive edge of the TXC signal. 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 1% 6.49k resistor for the 1:1 transformer ratio. Its typical rise/fall time of 4ns complies
with the ANSI TP-PMD standard regarding amplitude balance, overshoot, and timing jitter. The wave-shaped 10BASE-
T output driver is also incorporated into the 100BASE-TX driver.
100BASE-TX Receive
The 100BASE-TX receive function performs adaptive equalization, DC restoration, MLT-3 to NRZI conversion, data and
clock recovery, NRZI-to-NRZ conversion, and serial-to-parallel conversion. The receiving side starts with the
equalization lter to compensate inter-symbol interference (ISI) over the twisted pair cable. Since the amplitude loss
and phase distortion are a function of the length of the cable, the equalizer has to adjust its characteristic to optimize
performance. In this design, the variable equalizer will make an initial estimation based on comparisons of incoming
signal strength against some known cable characteristics, then tunes itself for optimization. This is an ongoing process
and can self-adjust for environmental changes such as temperature variations.
The equalized signal then goes through a DC restoration and data conversion block. The DC restoration circuit is used
to compensate for the effects of base line wander and improve 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. Finally, the NRZ serial data is converted to 4-bit parallel 4B
nibbles. A synchronized 25MHz RXC is generated so that the 4B nibbles are clocked out at the negative edge of
RCK25 and is valid for the receiver at the positive edge. When no valid data is present, the clock recovery circuit is
locked to the 25MHz reference clock and both TXC and RXC clocks continue to run.
PLL Clock Synthesizer
The KS8721BL/SL generates 125MHz, 25MHz, and 20MHz clocks for system timing. An internal crystal oscillator circuit
provides the reference clock for the synthesizer.
Scrambler/De-scrambler (100BASE-TX only)
The purpose of the scrambler is to spread the power spectrum of the signal in order to reduce electromagnetic
interference (EMI) and baseline wander.
10BASE-T Transmit
When TXEN (transmit enable) goes high, data encoding and transmission begins. The KS8721BL/SL continues to
encode and transmit data as long as TXEN remains high. The data transmission ends when TXEN goes low. The last
transition occurs at the boundary of the bit cell if the last bit is zero, or at the center of the bit cell if the last bit is one.
The output driver is incorporated into the 100BASE-T driver to allow transmission with the same magnetics. They are
internally wave-shaped and pre-emphasized into outputs with typical 2.5V amplitude. The harmonic contents are at
least 27dB below the fundamental when driven by 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 300mV or with short pulse widths in order to prevent
noise at the RX+ or RX- input from falsely triggering the decoder. When the input exceeds the squelch limit, the PLL
locks onto the incoming signal and the KS8721BL/SL decodes a data frame. This activates the carrier sense (CRS) and
RXDV signals and makes the receive data (RXD) available. The receive clock is maintained active during idle periods in
between data reception.
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June 2009 12 M9999-062509-1.3
SQE and Jabber Function (10BASE-T only)
In 10BASE-T operation, a short pulse is put out on the COL pin after each packet is transmitted. This is required as a
test of the 10BASE-T transmit/receive path and is called an SQE test. The 10BASE-T transmitter is disabled and COL
goes high if TXEN is high for more than 20ms (Jabbering). If TXEN then goes low for more than 250ms, the 10BASE-T
transmitter is re-enabled and COL goes low.
Auto-Negotiation
The KS8721BL/SL performs auto-negotiation by hardware strapping option (pin 29) or software (Register 0.12). It
automatically chooses its mode of operation by advertising its abilities and comparing them with those received from its
link partner whenever auto-negotiation is enabled. It can also be congured to advertise 100BASE-TX or 10BASE-T in
either full- or half-duplex mode (please refer to “Auto-Negotiation”). Auto-negotiation is disabled in the FX mode.
During auto-negotiation, the contents of Register 4, coded in fast link pulse (FLP), are sent to its link partner under the
conditions of power-on, link-loss, or restart. At the same time, the KS8721BL/SL monitors incoming data to determine
its mode of operation. The parallel detection circuit is enabled as soon as either 10BASE-T normal link pulse (NLP) or
100BASE-TX idle is detected. The operation mode is congured based on the following priority:
Priority 1: 100BASE-TX, full-duplex
Priority 2: 100BASE-TX, half-duplex
Priority 3: 10BASE-T, full-duplex
Priority 4: 10BASE-T, half-duplex
When the KS8721BL/SL receives a burst of FLP from its link partner with three identical link code words (ignoring
acknowledge bit), it will store these code words in Register 5 and wait for the next three identical code words. Once the
KS8721BL/SL detects the second code words, it then congures itself according to the above-mentioned priority. In
addition, the KS8721BL/SL also checks for 100BASE-TX idle or 10BASE-T NLP symbols. If either is detected, the
KS8721BL/SL automatically congures to match the detected operating speed.
MII Management Interface
The KS8721BL/SL 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
KS8721BL/SL. The MDIO interface consists of the following:
A physical connection including a data line (MDIO), a clock line (MDC), and an optional interrupt line (INTRPT).
A specic protocol that runs across the above-mentioned physical connection that allows one controller to
communicate with multiple KS8721BL/SL devices. Each KS8721BL/SL is assigned an MII address between 0
and 31 by the PHYAD inputs.
An internal addressable set of fourteen 16-bit MDIO registers. Registers [0:6] are required and their functions
are specied by the IEEE 802.3 specications. Additional registers are provided for expanded functionality.
The INTPRT pin functions as a management data interrupt in the MII. An active Low or High in this pin indicates a
status change on the KS8721BL/SL based on 1fh.9 level control. Register bits at 1bh[15:8] are the interrupt enable bits.
Register bits at 1bh[7:0] are the interrupt condition bits. This interrupt is cleared by reading Register 1bh.
MII Data Interface
The data interface consists of separate channels for transmitting data from a 10/100 802.3 compliant Media Access
Controller (MAC) to the KS8721BL/SL, and for receiving data from the line. Normal data transmission is implemented in
4B nibble mode (4-bit wide nibbles).
Transmit Clock (TXC)
The transmit clock is normally generated by the KS8721BL/SL from an external 25MHz reference source at the X1
input. The transmit data and control signals must always be synchronized to the TXC by the MAC. The KS8721BL/SL
normally samples these signals on the rising edge of the TXC.
Receive Cloc k (RXC)
For 100BASE-TX links, the receive clock is continuously recovered from the line. If the link goes down, and auto-
negotiation is disabled, the receive clock operates off the master input clock (X1 or TXC). For 10BASE-T links, the
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June 2009 13 M9999-062509-1.3
receive clock is recovered from the line while carrier is active, and operates from the master input clock when the line is
idle. The KS8721BL/SL synchronizes the receive data and control signals on the falling edge of RXC in order to
stabilize the signals at the rising edge of the clock with 10ns setup and hold times.
Transmit Enable
The MAC must assert TXEN at the same time as the rst nibble of the preamble, and de-assert TXEN after the last bit
of the packet.
Receive Data Valid
The KS8721BL/SL asserts RXDV when it receives a valid packet. Line operating speed and MII mode will determine
timing changes in the following way:
For 100BASE-TX links with the MII in 4B mode, RXDV is asserted from the rst nibble of the preamble to the
last nibble of the data packet.
For 10BASE-T links, the entire preamble is truncated. RXDV is asserted with the rst nibble of the SFD “5D”
and remains asserted until the end of the packet.
Error Signals
Whenever the KS8721BL/SL receives an error symbol from the network, it asserts RXER and drives “1110” (4B) on the
RXD pins. When the MAC asserts TXER, the KS8721BL/SL will drive “H” symbols (a Transmit Error dened in the IEEE
802.3 4B/5B code group) out on the line to force signaling errors.
Carrier Sense (CRS)
For 100BASE-TX links, a start-of-stream delimiter, or /J/K symbol pair causes assertion of Carrier Sense (CRS). An
end-of-stream delimiter, or /T/R symbol pair, causes de-assertion of CRS. The PMA layer will also de-assert CRS if
IDLE symbols are received without /T/R, yet in this case RXER will be asserted for one clock cycle when CRS is de-
asserted. For 10BASE-T links, CRS assertion is based on reception of valid preamble, and de-assertion on reception of
an end-of-frame (EOF) marker.
Collision
Whenever the line state is half-duplex and the transmitter and receiver are active at the same time, the KS8721BL/SL
asserts its collision signal, which is asynchronous to any clock.
RMII (Reduced MII) Data Interface
RMII interface species a low-pin count, Reduced Media Independent Interface (RMII) intended for use between
Ethernet PHYs and Switch or Repeater ASICs. It is fully compliant with IEEE 802.3u [2].
This interface has the following characteristics:
It is capable of supporting 10Mbps and 100Mbps data rates.
A single clock reference is sourced from the MAC to PHY (or from an external source).
It provides independent 2-bit wide (di-bit) transmit and receive data paths.
It uses TTL signal levels compatible with common digital CMOS ASIC processes.
RMII Signal Denition
Signal Name Direction
(w/respect to the PHY) Direction
(w/respect to the MAC)
Use
REF_CLK Input Input or Output Synchronous clock reference for receive, transmit and
control interface
CRS_DV Output Input Carrier Sense/Receive Data Valid
RXD[1:0] Output Input Receive Data
TX_EN Input Output Transmit Enable
TXD[1:0] Input Output Transmit Data
RX_ER Output Input (Not Required) Receive Error
Micrel, Inc. KS8721BL/SL
June 2009 14 M9999-062509-1.3
Reference Clock (REF_C LK)
REF_CLK is a continuous 50MHz clock that provides the timing reference for CRS_DV, RXD[1:0], TX_EN, TXD[1:0],
and RX_E. REF_CLK is sourced by the MAC or an external source. Switch implementations may choose to provide
REF_CLK as an input or an output depending on whether they provide a REF_CLK output or rely on an external clock
distribution device. Each PHY device must have an input corresponding to this clock but may use a single clock input
for multiple PHYs implemented on a single IC.
Carrier Sense/Receive Data Valid (CRS_DV)
CRS_DV is asserted asynchronously on detection of carrier due to the criteria relevant to the operating mode. That is,
in 10BASE-T mode, when squelch is passed or in 100BASE-X mode when 2 noncontiguous zeroes in 10 bits are
detected, the carrier is detected.
Loss-of-carrier results in the de-assertion of CRS_DV synchronous to REF_CLK. As carrier criteria are met, CRS_DV
remains continuously asserted from the rst recovered di-bit of the frame through the nal recovered di-bit and is
negated prior to the rst REF_CLK that follows the nal 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] remains as “00” until proper receive signal decoding takes
place (see “Denition of RXD[1:0] Behavior”).
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. In some cases (e.g., before data recovery or during error conditions),
a predetermined value for RXD[1:0] is transferred instead of recovered data. RXD[1:0] remains as “00” to indicate idle
when CRS_DV is de-asserted. Values of RXD[1:0] other than “00” when CRS_DV is de-asserted are reserved for out-
of-band signaling (to be dened). Values other than “00” on RXD[1:0] while CRS_DV is de-asserted are ignored by the
MAC/repeater. Upon assertion of CRS_DV, the PHY ensures that RXD[1:0]=00 until proper receive decoding takes
place.
Transmit Enable (TX_EN)
Transmit Enable TX_EN indicates that the MAC is presenting di-bits on TXD[1:0] on the RMII for transmission. TX_EN
is asserted synchronously with the rst nibble of the preamble and remains asserted while all transmitted di-bits are
presented to the RMII. TX_EN is negated prior to the rst REF_CLK following the nal di-bit of a frame. TX_EN
transitions synchronously with respect to REF_CLK.
Transmit Data [1:0] (TXD[1:0])
Transmit Data 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] remains as “00” to indicate idle when TX_EN is de-asserted. Values of
TXD[1:0] other than “00” when TX_EN is de-asserted are reserved for out-of-band signaling (to be dened). Values
other than “00” on TXD[1:0] while TX_EN is de-asserted are ignored by the PHY.
Collision Detection
Since the denition of CRS_DV and TX_EN both contain an accurate indication of the start of frame, the MAC reliably
re-generates the COL signal of the MII by ANDing TX_EN and CRS_DV.
During the IPG time following the successful transmission of a frame, the COL signal is asserted by some transceivers
as a self-test. The Signal Quality Error (SQE) function is not supported by the reduced MII due to the lack of the COL
signal. Historically, SQE was present to indicate that a transceiver located physically remote from the MAC was
functioning. Since the reduced MII only supports chip-to-chip connections on a PCB, SQE functionality is not required.
RX_ER
The PHY provides RX_ER as an output according to the rules specied in IEEE 802.3u [2] (see Clause 24, Figure 24-
11– Receive State Diagram). 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) is 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.
Micrel, Inc. KS8721BL/SL
June 2009 15 M9999-062509-1.3
RMII AC Characteristics
Symbol Parameter Min Typ Max Units
REF_CLK Frequency 50 MHz
REF_CLK Duty Cycle 35 65 %
tSU TXD[1:0], TX_EN, RXD[1:0], CRS_DV, RXER 4 ns
tH TXD[1:0], TX_EN, RXD[1:0], CRS_DV, RXER
Data Hold from REF_CLK
Rising Edge
2 ns
Unused RMII Pins
Input Pins TXD[2:3] and TXER are pull-down to GND.
Output Pins RXD[2:3] and RXC are no connect.
Note that the RMII pin needs to be pulled up to enable RMII mode.
Auto-Crossover (Auto-MDI/MDI-X)
Automatic MDI/MDI-X conguration is intended to eliminate the need for crossover cables between similar devices. The
assignment of pinouts for a 10/100 BASE-T crossover function cable is shown below.
This feature eliminates the confusion in applications by allowing the use of both straight and crossover cables. This
feature is controlled by register 1f:13. See “Register 1fh–100BASE-TX PHY Controller” section for details.
10/100 BASE-T
Media Dependent Interface
10/10
0
BASE-T
Media Dependent Interface
Transmit Pair
Receive Pair Transmit Pair
Receive Pair
Modular Connector (RJ45)
NIC
Modular Connector (RJ45)
HUB
(Repeater or Switch)
Figure 1. Straight Through Cable
Micrel, Inc. KS8721BL/SL
June 2009 16 M9999-062509-1.3
10/100 BASE-T
Media Dependent Interface
10/10
0
BASE-T
Media Dependent Interface
Transmit Pair
Receive Pair
Transmit Pair
Receive Pair
Modular Connector (RJ45)
HUB
(Repeater or Switch)
Modular Connector (RJ45)
HUB
(Repeater or Switch)
Figure 2. Crossover Cable
Power Management
The KS8721BL/SL offers the following modes for power management:
Power-Down Mode: This mode can be achieved by writing to Register 0.11 or pulling pin 30 PD# low.
Power-Saving Mode: This mode can be disabled by writing to Register 1fh.10. The KS8721BL/SL turns off
everything except for the Energy Detect and PLL circuits when the cable is not installed. In other words, the
KS8721BL/SL shuts down most of the internal circuits to save power if there is no link. Power-saving mode is in
the most effective state when auto-negotiation mode is enabled.
100BT FX Mode
Please contact your local eld application engineer (FAE) for a reference schematic on ber connection.
100BT FX mode is activated when FXSD/FXEN is higher than 0.6V (this pin has a default pull down). Under this mode,
the auto-negotiation and auto-MDI-X features are disabled.
In ber operation, the FXSD pin should connect to the signal detect (SD) output of the ber module. The internal
threshold of FXSD is around 1/2 VDD ±50mV (1.25V ±0.05V). Above this level, the ber signal is considered detected.
The operation is summarized in the following table:
FXSD/FXEN Condition
Less than 0.6V 100TX mode
Less than 1.25V,
but greater than 0.6V
FX mode
No signal detected
FEF generated
Greater than 1.25 FX mode
Signal detected
Table 1. 100BT FX Mode
To ensure proper operation, the swing of ber module SD should cover the threshold variation. A resistive voltage
divider is recommended to adjust the SD voltage range.
Far End Fault (FEF), repetition of a special pattern which consists of 84-one and 1-zero, is generated under “FX mode
with no signal detected.” The purpose of FEF is to notify the sender of a faulty link. When receiving an FEF, the LINK
will go down to indicate a fault, even with ber signal detected. The transmitter is not affected by receiving an FEF and
Micrel, Inc. KS8721BL/SL
June 2009 17 M9999-062509-1.3
still sends out its normal transmit pattern from MAC. FEF can be disabled by strapping pin 27 low. Refer to the
“Strapping Options” section.
Media Converter Operation
The KS8721BL/SL is capable of performing media conversion with two parts in a back-to-back RMII loop-back mode as
indicated in the diagram. Both parts are in RMII mode and with RMII BTB asserted (pins 21 and 22 strapped high). One
part is operating in TX mode and the other is operating in FX mode. Both parts can share a common 50MHz oscillator.
Under this operation, auto-negotiation on the TX side prohibits 10BASE-T link-up. Additional options can be
implemented under this operation. Disable the transmitter and set it at tri-state by controlling the high TXD2 pin. In order
to do this, RXD2 and TXD2 pins need to be connected via inverter. When TXD2 pin is high in both the copper and ber
operation, it is disabled transmit. Meanwhile, the RXD2 pin on the copper side serves as the energy detect and can
indicate if a line signal is detected. TXD3 should be tied low and RXD3 let oat. Please contact your Micrel FAE for a
media converter reference design.
Rx +/-
Tx +/-
FTx
FRx
Pin
34
TxD
(Fiber Mode)
21 22
Pin
Pin
21 22
50MHz
VCC
OSC
TxC/
Ref_CLK
TxC/
Ref_CLK
RxD
RxD
VCC
KS8721BL/SL
KS8721BL/SL
To the SD pin of the
Fiber Module
TxD
Figure 3. Fiber Module
Micrel, Inc. KS8721BL/SL
June 2009 18 M9999-062509-1.3
Circuit Design Refere nce for Power Supply
Micrel’s integrated built-in, voltage regulator technology and thoughtful implementation allows the user to save BOM
cost on both existing and future designs with the use of the new KS8721BL/SL single supply, single port 10/100
Ethernet PHY.
7
24
+3.3V
KS8721BL/SL
8 12233536394344
VDDI/O
VDDI/O
VDDC VDDPLL
Voltage
Regulator
10F
+2.5V +2.5VPLL
Ferrite Bead
10F 10F 10F
13 47
+2.5VA
Ferrite Bead
VDDTX
OUTIN
GND
42 31 38
10F 10F
VDDRX
VDDRCV
Figure 4. Circuit Design
The circuit design in Figure 4 shows the power connections for the power supply: the 3.3V to VDDI/O is the only input
power source and the 2.5V at VDDRCV, pin 38, is the output of the voltage regulator that needs to supply through the
rest of the 2.5V VDD pins via the 2.5V power plane.
The 2.5V VDD pins make the drop-in replacement with the existing KS8721B/BT part. Table 2 shows the drop-in
replacement from the existing KS8721B/BT to the KS8721SL/BL. Please contact your local Micrel FAE for Application
Note AN-117, “Drop-in Replacement with KS8721BT.”
2.5V/3.3V Supply 3.3V Supply with Built-in Regulator
Part Number Package Part Number Package
KS8721B 48-SSOP KS8721SL 48-SSOP
KS8721BT 48-TQFP KS8721BL 48-LQFP
KS8721BI 48-SSOP KS8721SLI 48-SSOP
Table 2. Drop-In Replacemen t
Micrel, Inc. KS8721BL/SL
June 2009 19 M9999-062509-1.3
Register Map
Register No. Description
0h Basic Control Register
1h Basic Status Register
2h PHY Identier I
3h PHY Identier II
4h Auto-Negotiation Advertisement Register
5h Auto-Negotiation Link Partner Ability Register
6h Auto-Negotiation Expansion Register
7h Auto-Negotiation Next Page Register
8h Link Partner Next Page Ability
15h RXER Counter Register
1bh Interrupt Control/Status Register
1fh 100BASE-TX PHY Control Register
Address Name Description Default(1) Mode
Register 0h - Basic Control
0.15 Reset 1 = software reset. Bit is self-clearing RW/SC 0
0.14 Loop-Back 1 = loop-back mode
0 = normal operation
RW 0
0.13 Speed Select (LSB) 1 = 100Mbps
0 = 10Mbps
Ignored if Auto-Negotiation is enabled (0.12 = 1)
RW Set by
SPD100
0.12 Auto-Negotiation Enable
1 = enable auto-negotiation process (override 0.13 and 0.8)
0 = disable auto-negotiation process
RW Set by
NWAYEN
0.11 Power Down 1 = power-down mode
0 = normal operation
RW 0
0.10 Isolate 1 = electrical isolation of PHY from MII and TX+/TX-
0 = normal operation
RW Set by ISO
0.9 Restart Auto-Negotiation
1 = restart auto-negotiation process
0 = normal operation. Bit is self-clearing
RW/SC 0
0.8 Duplex Mode 1 = full-duplex
0 = half-duplex
RW Set by
DUPLEX
0.7 Collision Test 1 = enable COL test
0 = disable COL test
RW 0
0.6:1 Reserved RO 0
0.0 Disable
Transmitter
0 = enable transmitter
1 = disable transmitter
RW 0
Register 1h - Basic Status
1.15 100BASE-T4 1 = T4 capable
0 = not T4 capable
RO 0
1.14 100BASE-TX Full-Duplex
1 = capable of 100BASE-X full-duplex
0 = not capable of 100BASE-X full-duplex
RO 1
Micrel, Inc. KS8721BL/SL
June 2009 20 M9999-062509-1.3
Address Name Description Default(1) Mode
1.13 100BASE-TX Half-Duplex
1 = capable of 100BASE-X half-duplex
0 = not capable of 100BASE-X half-duplex
RO 1
1.12 10BASE-T Full-Duplex
1 = 10Mbps with full-duplex
0 = no 10Mbps with full-duplex capability
RO 1
1.11 10BASE-T Half-Duplex
1 = 10Mbps with half-duplex
0 = no 10Mbps with half-duplex capability
RO 1
1.10:7 Reserved RO 0
1.6 No Preamble 1 = preamble suppression
0 = normal preamble
RO 1
1.5 Auto-Negotiation Complete
1 = auto-negotiation process completed
0 = auto-negotiation process not completed
RO 0
1.4 Remote Fault 1 = remote fault
0 = no remote fault
RO/LH 0
1.3 Auto-Negotiation Ability
1 = capable to perform auto-negotiation
0 = unable to perform auto-negotiation
RO 1
1.2 Link Status 1 = link is up
0 = link is down
RO/LL 0
1.1 Jabber Detect 1 = jabber detected
0 = jabber not detected. Default is low
RO/LH 0
1.0 Extended Capability 1 = supports extended capabilities registers RO 1
Register 2h - PHY Identier 1
2.15:0 PHY ID Number Assigned to the 3rd through 18th bits of the organizationally
unique identier (OUI). Micrel’s OUI is 0010A1 (hex).
RO 0022h
Register 3h - PHY Identier 2
3.15:0 PHY ID Number Assigned to the 19th through 24th bits of the
organizationally unique identier (OUI). Micrel’s OUI is
0010A1 (hex).
RO 000101
3.9:4 Model Number Six bit manufacturer’s model number RO 100001
3.3:0 Revision Number Four bit manufacturer’s model number RO 1001
Register 4h - Auto-Negotiation Advertisement
4.15 Next Page 1 = next page capable
0 = no next page capability
RW 0
4.14 Reserved RO 0
4.13 Remote Fault 1 = remote fault supported
0 = no remote fault
RW 0
4.12:11 Reserved RO 0
4.10 Pause 1 = pause function supported
0 = no pause function
RW 0
4.9 100BASE-T4 1 = T4 capable
0 = no T4 capability
RO 0
4.8 100BASE-TX Full-Duplex
1 = TX with full-duplex
0 = no TX full-duplex capability
RW Set by
SPD100 &
DUPLEX
4.7 100BASE-TX 1 = TX capable
0 = no TX capability
RW Set by
SPD100
4.6 10BASE-T Full-Duplex
1 = 10Mbps with full-duplex
0 = no 10Mbps full-duplex capability
RW Set by
DUPLEX
Micrel, Inc. KS8721BL/SL
June 2009 21 M9999-062509-1.3
Address Name Description Default(1) Mode
4.5 10BASE-T 1 = 10Mbps capable
0 = no 10Mbps capability
RW 1
4.4:0 Selector Field [00001] = IEEE 802.3 RW 00001
Register 5h - Auto-Negotiation Link Partner Ability
5.15 Next Page 1 = next page capable
0 = no next page capability
RO 0
5.14 Acknowledge 1 = link code word received from partner
0 = link code word not yet received
RO 0
5.13 Remote Fault 1 = remote fault detected; 0 = no remote fault RO 0
5.12 Reserved RO 0
5.11:10 Pause 5.10 5 .11
0 0
No PAUSE
0 1
Asymmetric PAUSE (link partner)
1 0
Symmetric PAUSE
1 1
Symmetric & Asymmetric PAUSE (local device)
RO 0
5.9 100 BASE-T4 1 = T4 capable
0 = no T4 capability
RO 0
5.8 100BASE-TX Full-Duplex
1 = TX with full-duplex
0 = no TX full-duplex capability
RO 0
5.7 100BASE-TX 1 = TX capable
0 = no TX capability
RO 0
5.6 10BASE-T Full-Duplex
1 = 10Mbps with full-duplex
0 = no 10Mbps full-duplex capability
RO 0
5.5 10BASE-T 1 = 10Mbps capable
0 = no 10Mbps capability
RO 0
5.4:0 Selector Field [00001] = IEEE 802.3 RO 00001
Register 6h - Auto-Negotiation Expansion
6.15:5 Reserved RO 0
6.4 Parallel Detection Fault 1 = fault detected by parallel detection
0 = no fault detected by parallel detection
RO/LH 0
6.3 Link Partner Next Page
Able
1 = link partner has next page capability
0 = link partner does not have next page capability
RO 0
6.2 Next Page Able 1 = local device has next page capability
0 = local device does not have next page capability
RO 1
6.1 Page Received 1 = new page received
0 = new page not yet received
RO/LH 0
6.0 Link Partner
Auto-Negotiation Able
1 = link partner has auto-negotiation capability
0 = link partner does not have auto-negotiation capability
RO 0
Register 7h - Auto-Negotiation Next Page
7.15 Next Page 1 = additional next page(s) will follow
0 = last page
RW 0
7.14 Reserved RO 0
7.13 Message Page 1 = message page
0 = unformatted page
RW 1
Micrel, Inc. KS8721BL/SL
June 2009 22 M9999-062509-1.3
Address Name Description Default(1) Mode
7.12 Acknowledge 2 1 = will comply with message
0 = cannot comply with message
RW 0
7.11 Toggle 1 = previous value of the transmitted link code word equaled
logic One
0 = logic Zero
RO 0
7.10:0 Message Field 11-bit wide eld to encode 2048 messages RW 001
Register 8h - Link Partner Next Page Ability
8.15 Next Page 1 = additional next page(s) will follow
0 = last page
RO 0
8.14 Acknowledge 1 = successful receipt of link word
0 = no successful receipt of link word
RO 0
8.13 Message Page 1 = Message Page
0 = unformatted page
RO 0
8.12 Acknowledge 2 1 = able to act on the information
0 = not able to act on the information
RO 0
8.11 Toggle 1 = previous value of transmitted link code word equal to
logic zero
0 = previous value of transmitted link code word equal to
logic one
RO 0
8.10:0 Message Field RO 0
Register 15h - RXER Counter
15.15:0 RXER Counter RX Error counter for the RX_ER in each package RO 000
Register 1bh - Interrupt Co ntrol/Status Register
1b.15 Jabber Interrupt Enable 1 = Enable jabber interrupt
0 = Disable jabber interrupt
RW 0
1b.14 Receive Error
Interrupt Enable
1 = Enable receive error interrupt
0 = Disable receive error interrupt
RW 0
1b.13 Page Received
Interrupt Enable
1 = Enable page received interrupt
0 = Disable page received interrupt
RW 0
1b.12 Parallel Detect Fault
Interrupt Enable
1 = Enable parallel detect fault interrupt
0 = Disable parallel detect fault interrupt
RW 0
1b.11 Link Partner Acknowledge
Interrupt Enable
1 = Enable link partner acknowledge interrupt
0 = Disable link partner acknowledge interrupt
RW 0
1b.10 Link Down
Interrupt Enable
1 = Enable link down interrupt
0 = Disable link down interrupt
RW 0
1b.9 Remote Fault
Interrupt Enable
1 = Enable remote fault interrupt
0 = Disable remote fault interrupt
RW 0
1b.8 Link Up Interrupt Enable 1 = Enable link up interrupt
0 = Disable link up interrupt
RW 0
1b.7 Jabber Interrupt 1 = Jabber interrupt occurred
0 = Jabber interrupt has not occurred
RO/SC 0
1b.6 Receive Error Interrupt 1 = Receive error occurred
0 = Receive error has not occurred
RO/SC 0
1b.5 Page Receive Interrupt 1 = Page receive occurred
0 = Page receive has not occurred
RO/SC 0
1b.4 Parallel Detect
Fault Interrupt
1 = Parallel detect fault occurred
0 = Parallel detect fault has not occurred
RO/SC 0
Micrel, Inc. KS8721BL/SL
June 2009 23 M9999-062509-1.3
Address Name Description Default(1) Mode
1b.3 Link Partner
Acknowledge Interrupt
1 = Link partner acknowledge occurred
0 = Link partner acknowledge has not occurred
RO/SC 0
1b.2 Link Down Interrupt 1 = Link down occurred
0 = Link down has not occurred
RO/SC 0
1b.1 Remote Fault Interrupt 1 = Remote fault occurred
0 = Remote fault has not occurred
RO/SC 0
1b.0 Link Up Interrupt 1 = Link up interrupt occurred
0 = Link up interrupt has not occurred
RO/SC 0
Register 1fh - 100BASE-TX PHY Contro ller
1f.15:14 Reserved RO 0
1f.13 Pairswap Disable 1 = Disable MDI/MDI-X
0 = Enable MDI/MDI-X
RW 0
1f.12 Energy Detect 1 = Presence of signal on RX+/RX- analog wire pair
0 = No signal detected on RX+/RX-
RO 0
1f.11 Force Link 1 = Force link pass
0 = Normal link operation
This bit bypasses the control logic and allow transmitter to
send pattern even if there is no link.
RW 0
1f.10 Power-Saving 1 = Enable power-saving
0 = Disable
RW 1
1f.9 Interrupt Level 1 = Interrupt pin active high
0 = Active low
RW 0
1f.8 Enable Jabber 1 = Enable jabber counter
0 = Disable
RW 1
1f.7 Auto-Negotiation Complete 1 = Auto-negotiation complete
0 = Not complete
RW 0
1f.6 Enable Pause
(Flow-Control Result)
1 = Flow control capable
0 = No ow control
RO 0
1f.5 PHY Isolate 1 = PHY in isolate mode
0 = Not isolated
RO 0
1f.4:2 Operation Mode Indication [000] = Still in auto-negotiation
[001] = 10BASE-T half-duplex
[010] = 100BASE-TX half-duplex
[011] = Reserved
[101] = 10BASE-T full-duplex
[110] = 100BASE-TX full-duplex
[111] = PHY/MII isolate
RO 0
1f.1 Enable SQE Test 1 = Enable SQE test
0 = Disable
RW 0
1f.0 Disable Data Scrambling 1 = Disable scrambler
0 = Enable
RW 0
Note:
1. RW = Read/Write.
RO = Read Only.
SC = Self Clear.
LH = Latch High.
LL = Latch Low.
Some of the default values are set by strap-in. See “Strapping Options.”
Micrel, Inc. KS8721BL/SL
June 2009 24 M9999-062509-1.3
Absolute Maximum Ratings(1)
Storage Temperature (Ts) .........................–55°C to +150°C
Supply Referenced to GND.......................... –0.5V to +4.0V
All Pins ......................................................... –0.5V to +4.0V
Operating Ratings(2)
Supply Voltage
(VDD_PLL, VDD_TX, VDD_RXC, VDD_RCV, VDDC) ......... +2.5V
(VDDIO)..............................................................+3.3V
Ambient Temperature (TA)
Commercial ......................................... 0°C to +70°C
Industrial.......................................... –40°C to +85°C
Package Thermal Resistance(3)
LQFP(θJA)
No Airflow ........................................... 83.56°C/W
SSOP(θJA)
No Airflow ........................................... 75.19°C/W
Electrical Characteristics(4)
VDD = 3.3V ±10%
Symbol Parameter Condition Min Typ Max Units
Total Supply Current (including TX output driver current)(5)
IDD1 Normal 100BASE-TX Including 43mA output current 116 mA
IDD2 Normal 100BASE-TX
(Independent of utilization)
Including 103mA output current 151 mA
IDD3 Power Saving Mode 1 Auto-negotiation is Enable 47 mA
IDD5 Power Down Mode 4 mA
TTL Inputs
VIH Input High Voltage 1/2VDD(I/O)
+0.2
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 1/2VDD(I/O)
+0.6
V
VOL Output Low Voltage IOL = 4mA 0.4 V
IOZ Output Tri-state Leakage 10 µA
100Base-TX Receive
RX+/RX– Differential Input
Resistance
8 k
RIN
Propagation Delay from magnetics to RDTX 50 110 ns
10Base-TX Transmit (mea sured differentially after 1:1 t ran sformer)
VO Peak Differential Output Voltage 50Ω from each output to VDD 0.95 1.05 V
VIMB Output Voltage Imbalance 50Ω from each output to VDD 2 %
Rise/Fall Time 3 5 ns
Rise/Fall Time Imbalance 0 0.5 ns
Duty Cycle Distortion ±0.5 ns
tr, tf
Overshoot 5 %
Reference Voltage of ISET 0.75 V
Propagation Delay from TDTX to magentics 45 60 ns
VSET
Jitters 0.7 1.4 ns(pp)
Micrel, Inc. KS8721BL/SL
June 2009 25 M9999-062509-1.3
10Base-TX Receive
RIN RX+/RX– Differential Input
Resistance
8 kW
VSQ Squelch Threshold 5MHz square wave 400 mV
10Base-TX Transmit (mea sured differentially after 1:1 t ran sformer)
Peak Differential Output Voltage 50W from each output to VDD 2.2 2.8 V VP
Jitters Added 50W from each output to VDD ±3.5 ns
tr, tf Rise/Fall Time 25 ns
Clock Outputs
X1, X2 Crystal Oscillator 25 MHz
RXC100 Receive Clock, 100TX 25 MHz
Receive Clock, 10T 2.5 MHz RXC10
Receive Clock Jitters 3.0 ns(pp)
TXC100 Transmit Clock, 100TX 25 MHz
Transmit Clock, 10T 2.5 MHz TXC10
Transmit Clock Jitters 1.8 ns(pp)
Notes:
1. Exceeding the absolute maximum rating may damage the device. Operating at maximum conditions for extended periods may affect device reliability.
2. The device is not guaranteed to function outside its operating rating. Unused inputs must always be tied to an appropriate logic voltage level
(Ground to VDD)
3. No (HS) heat spreader in this package.
4. Specification for packaged product only.
5. There is 100% data transmission in full-duplex mode and a minimum IPG with a 130-meter cable.
Micrel, Inc. KS8721BL/SL
June 2009 26 M9999-062509-1.3
Timing Diagrams
Figure 4. 10BASE-T MII Transmit Timing
Symbol Parameter Min Typ Max Units
tSU1 TXD [3:0] Set-Up to TXC High 10 ns
tSU2 TXEN Set-Up to TXC High 10 ns
tHD1 TXD [3:0] Hold After TXC High 0 ns
tHD2 TXEN Hold After TXC High 0 ns
tCRS1 TXEN High to CRS Asserted Latency 4 BT(1)
tCRS2 TXEN Low to CRS De-Asserted Latency 8 BT
tLAT TXEN High to TXP/TXM Output (TX Latency) 4 BT
tSQE COL (SQE) Delay After TXEN De-Asserted 2.5 µs
tSQEP COL (SQE) Pulse Duration 1.0 µs
Table 3. 10BASE-T MII Transmit Timing Parameters
Note:
1. 1BT = 10ns at 10BASE-TX
Micrel, Inc. KS8721BL/SL
June 2009 27 M9999-062509-1.3
Figure 5. 100BASE-T MII Transmit Timing
Symbol Parameter Min Typ Max Units
tSU1 TXD [3:0] Set-Up to TXC High 10 ns
tSU2 TXEN Set-Up to TXC High 10 ns
tHD1 TXD [3:0] Hold After TXC High 0 ns
tHD2 TXER Hold After TXC High 0 ns
tHD3 TXEN Hold After TXC High 0 ns
tCRS1 TXEN High to CRS Asserted Latency 4 BT(1)
tCRS2 TXEN Low to CRS De-Asserted Latency 4 BT
tLAT TXEN High to TXP/TXM Output (TX Latency) 9 BT
Table 4. 100BASE-T MII Transmit Timing Parameters
Note:
1. 1BT = 10ns at 100BASE-TX
Micrel, Inc. KS8721BL/SL
June 2009 28 M9999-062509-1.3
End of
Stream
Start of
Stream
Figure 6. 100BASE-T MII Receive Timing
Symbol Parameter Min Typ Max Units
tP RXC Period 40 ns
tWL RXC Pulse Width 20 ns
tWH RXC Pulse Width 20 ns
tSU RXD [3:0], RXER, RXDV Set-Up to Rising Edge of RXC 20 ns
tHD RXD [3:0], RXER, RXDV Hold from Rising Edge of RXC 20 ns
tRLAT CRS to RXD Latency, 4B or 5B Aligned 6 BT
tCRS1 “Start of Stream” to CSR Asserted 106 138 ns
t CRS2 “End of Stream” to CSR De-Asserted 154 186 ns
Table 5. 100BASE-T MII Receive Timing Parameters
Micrel, Inc. KS8721BL/SL
June 2009 29 M9999-062509-1.3
Figure 7. Auto-Negotiation/Fast Link Pulse Timing
Symbol Parameter 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 69 µs
tCTC Clock Pulse to Clock Pulse
Number of Clock/Data Pulses per Burst
17
136
33
µs
µs
Table 6. Auto-Negotiation/Fast Link Pulse Timing Parameters
Micrel, Inc. KS8721BL/SL
June 2009 30 M9999-062509-1.3
Figure 8. Serial Management Interface Timing
Symbol Parameter Min Typ Max Units
tP MDC Period 400 ns
tMD1 MDIO Set-Up to MDC (MDIO as Input) 10 ns
tMD2 MDIO Hold After MDC (MDIO as Input) 10 ns
tMD3 MDC to MDIO Valid (MDIO as Output) 222 ns
Table 7. Serial Management Interface Timin g Parameters
Micrel, Inc. KS8721BL/SL
June 2009 31 M9999-062509-1.3
Figure 9. Reset Timing
Symbol Parameter Min Typ Max Units
tsr Stable Supply Voltages to Reset High 50 µs
Table 8. Reset Timing Parameters
Reset Circuit Diagram
Micrel recommends the following discrete reset circuit as shown in Figure 10 when powering up the KS8721BL/SL device.
For the application where the reset circuit signal comes from another device (e.g., CPU, FPGA, etc), we recommend the
reset circuit as shown in Figure 11.
VCC
R
10k
D2
C
10µF
D1 CPU/FPGA
RST_OUT_n
KS8721BL/SL
RST
D1, D2: 1N4148
Figure 10. Recommended Reset Circuit
Micrel, Inc. KS8721BL/SL
June 2009 32 M9999-062509-1.3
VCC
R
10k
C
10µF
D1
KS8721BL/SL
RST
D1: 1N4148
Figure 11. Recommended Circuit for Interfacing with CPU/FPGA Reset
At power-on-reset, R, C, and D1 provide the necessary ramp rise time to reset the Micrel device. The reset out from
CPU/FPGA provides warm reset after power up. It is also recommended to power up the VDD core voltage earlier than
VDDIO voltage. At worst case, the both VDD core and VDDIO voltages should come up at the same time.
Reference Circuit for Strapping Optio n Con guration
Figure 12 shows the reference circuit for strapping option pins.
KS8721BL/SL
LED pin
3.3V
Reference circuits for unmanaged programming through LED ports.
KS8721BL/SL
LED pin
3.3V
Pull-Up
Pull-down
Figure 12. Reference Circuit, Strapping Option Pins
Micrel, Inc. KS8721BL/SL
June 2009 33 M9999-062509-1.3
Selection of Isolation Transformers(1)
One simple 1:1 isolation transformer is needed at the line interface. An isolation transformer with integrated common-
mode choke 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
Note:
1. The IEEE 802.3u standard for 100BASE-TX assumes a transformer loss of 0.5dB. For the transmit line transformer, insertion loss of up to 1.3dB
can be compensated or by increasing the line drive current by means of reducing the ISET resistor value. Please select the transformer that
supports auto-MDI/MDI-X.
Selection of Reference Crystal
An oscillator or crystal with the following typical characteristics is recommended.
Characteristics Value Units
Frequency 25 MHz
Frequency tolerance (max) ±100 ppm
Load capacitance (max) 20 pF
Series resistance (max) 40 Ω
Single Port Magnetic Manu facturer Part Number Auto MDIX Number of Ports
Pulse H1102 Yes 1
Bel Fuse S558-5999-U7 Yes 1
YCL PT163020 Yes 1
Transpower HB726 Yes 1
Delta LF8505 Yes 1
LanKom LF-H41S Yes 1
Integrated Transformers
Pulse J0011D21 Yes 1
Pulse J00-0061 Yes 1
Table 9. Qualified Transformer Lists
Micrel, Inc. KS8721BL/SL
June 2009 34 M9999-062509-1.3
Package Information
48-Pin SSOP (SM)
Micrel, Inc. KS8721BL/SL
June 2009 35 M9999-062509-1.3
48-Pin LQFP (LQ)
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.
© 2004 Micrel, Incorporated.