Micrel, Inc.

KSZ8081RNA/KSZ8081RND

February 6, 2014

4

Revision 1.1

Contents

List of Figures.......................................................................................................................................................................... 6

List of Tables ........................................................................................................................................................................... 7

Pin Configuration..................................................................................................................................................................... 8

Pin Description ........................................................................................................................................................................ 9

Strapping Options ................................................................................................................................................................. 11

Functional Description: 10Base-T/100Base-TX Transceiver ................................................................................................ 12

100Base-TX Transmit.......................................................................................................................................................................... 12

100Base-TX Receive........................................................................................................................................................................... 12

Scrambler/De-Scrambler (100Base-TX Only)...................................................................................................................................... 12

10Base-T Transmit .............................................................................................................................................................................. 12

10Base-T Receive ............................................................................................................................................................................... 13

PLL Clock Synthesizer ........................................................................................................................................................................ 13

Auto-Negotiation.................................................................................................................................................................................. 13

RMII Interface........................................................................................................................................................................ 15

RMII Signal Definition .......................................................................................................................................................................... 15

RMII Signal Diagram – 25/50MHz Clock Mode ................................................................................................................................... 16

Back-to-Back Mode – 100Mbps Copper Repeater ............................................................................................................... 18

RMII Back-to-Back Mode..................................................................................................................................................................... 18

MII Management (MIIM) Interface......................................................................................................................................... 19

Interrupt (INTRP)................................................................................................................................................................... 19

HP Auto MDI/MDI-X .............................................................................................................................................................. 19

Straight Cable...................................................................................................................................................................................... 20

Crossover Cable.................................................................................................................................................................................. 20

Loopback Mode..................................................................................................................................................................... 21

Local (Digital) Loopback ...................................................................................................................................................................... 21

Remote (Analog) Loopback ................................................................................................................................................................. 22

LinkMD

® Cable Diagnostic .................................................................................................................................................... 23

NAND Tree Support .............................................................................................................................................................. 23

NAND Tree I/O Testing ....................................................................................................................................................................... 24

Power Management .............................................................................................................................................................. 24

Power-Saving Mode ............................................................................................................................................................................ 24

Energy-Detect Power-Down Mode ...................................................................................................................................................... 24

Power-Down Mode .............................................................................................................................................................................. 24

Slow-Oscillator Mode........................................................................................................................................................................... 25

Reference Circuit for Power and Ground Connections......................................................................................................... 26

Typical Current/Power Consumption .................................................................................................................................... 27

Transceiver (3.3V), Digital I/Os (3.3V)................................................................................................................................................. 27

Transceiver (3.3V), Digital I/Os (2.5V)................................................................................................................................................. 27

Transceiver (3.3V), Digital I/Os (1.8V)................................................................................................................................................. 28