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Gigabit MII (GMII)

Issues and Recommendations

Robert Grow

XLNT Designs, Inc.
15050 Avenue of Science
San Diego, CA  92128
619-487-9320
bob@xlnt.com



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Overview

o  Base GMII on MII

   - Widen data path to 8 bits

   - Use reserved signal combinations for extensions

o  Multiplex GMII and FC 10 bit



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GMII Signals

TXD<<7:0>     CRS     RXD<<7:0>

TX_EN         COL     RX_DV

TX_ER                 RX_ER

TX_CLK                RX_CLK



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Transmit Encodings

TX_EN    TX_ER      TXD<<7:0>     REQUEST

  0        0     00 through FF    Normal inter-frame

  0        1     00 through 0E    Reserved

  0        1           0F         Carrier Extension

  0        1     10 through FF    Reserved

  1        0     00 through FF    Normal data transmission

  1        1     00 through FF    Transmit error propagation



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Receive Encodings

RX_EN    RX_ER      RXD<<7:0>     INDICATION

  0        0     00 through FF    Normal inter-frame

  0        1           00         Normal inter-frame

  0        1     00 through 0D    Reserved

  0        1          0E          False Carrier indication

  0        1          0F          Carrier Extension

  0        1     10 through FF    Reserved

  1        0     00 through FF    Normal data transmission

  1        1     00 through FF    Data reception with errors



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PLS Changes

o  PLS_DATA.request(OUTPUT_UNIT)

   - ZERO, ONE, DATA_COMPLETE, CARRIER_EXTENSION

o  PLS_DATA.indicate(INPUT_UNIT)

   - ZERO, ONE, CARRIER_EXTENSION