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Media Independent Interface (MII)

40 PIN HI-DENSITY D-SUB FEMALE (at the network device).
40 PIN HI-DENSITY D-SUB MALE (at the transciever).

40 PIN HI-DENSITY D-SUB FEMALE at the network device.
40 PIN HI-DENSITY D-SUB MALE at the transciever.

Pin Name Dir Description
1 V --- +5 Vdc/ 3.3 Vdc
2 MDIO <-> MII Data Input/Output
3 MDC --> MII Data Clock
4 RxD <-- Rx Data
5 RxD <-- Rx Data
6 RxD <-- Rx Data
7 RxD <-- Rx Data
8 Rx_DV <-- Rx Data Valid
9 Rx_CLK <-- Rx Clock
10 Rx_ER <-- Rx Error
11 Tx_ER --> Tx Error
12 Tx_CLK <-- Tx Clock
13 Tx_EN --> Tx Enable
14 TxD --> Tx Data
15 TxD --> Tx Data
16 TxD --> Tx Data
17 TxD --> Tx Data
18 COL <-- Collision
19 CRS <-- Carrier Sense
20 V --- +5 Vdc/ +3.3 Vdc
21 V --- +5 Vdc/ +3.3 Vdc
22 GND --- Ground
23 GND --- Ground
24 GND --- Ground
25 GND --- Ground
26 GND --- Ground
27 GND --- Ground
28 GND --- Ground
29 GND --- Ground
30 GND --- Ground
31 GND --- Ground
32 GND --- Ground
33 GND --- Ground
34 GND --- Ground
35 GND --- Ground
36 GND --- Ground
37 GND --- Ground
38 GND --- Ground
39 GND --- Ground
40 V --- +5 Vdc/ +3.3 Vdc

Note: Direction is DTE (Network device) relative DCE (Transciever).

Contributor: Joakim Ögren, Mark S Stephenson
Source: Ethernet (IEEE802.3) page at Connectivity Knowledge Platform (Made IT)
A Tech Doc at Cisco Systems

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Document last modified: 2002-01-10