Media Independent Interface (MII) 40 pin

40-pin pinout of the Media Independent Interface (MII), the IEEE 802.3 link between an Ethernet MAC and the PHY transceiver.

Updated:

Media Independent Interface (MII) 40 pin – 40-pin D-sub female 40 pin hi-density D-SUB female connector at the network device.

Media Independent Interface (MII) 40 pin – 40-pin D-sub male 40 pin hi-density D-SUB male connector at the transceiver.

The Media Independent Interface (MII) is the standard connection between an Ethernet MAC controller and the physical-layer transceiver (PHY), defined in IEEE 802.3 (clause 22) as part of the 100BASE-T Fast Ethernet standard. It supports 10 and 100 Mbit/s operation, carrying data as 4-bit nibbles in each direction (TXD[3:0] and RXD[3:0]) clocked at 25 MHz for 100 Mbit/s (2.5 MHz for 10 Mbit/s), and includes a two-wire management interface (MDIO data and MDC clock) for configuring the PHY. The 40-pin connector shown here was defined for attaching an external transceiver; faster and reduced-pin variants include RMII, GMII and RGMII.

PinNameDirDescription
1V-+5 Vdc/ 3.3 Vdc
2MDIOIN/OUTManagement Data I/O
3MDCOUTManagement Data Clock
4RxDINRx Data
5RxDINRx Data
6RxDINRx Data
7RxDINRx Data
8Rx_DVINRx Data Valid
9Rx_CLKINRx Clock
10Rx_ERINRx Error
11Tx_EROUTTx Error
12Tx_CLKINTx Clock
13Tx_ENOUTTx Enable
14TxDOUTTx Data
15TxDOUTTx Data
16TxDOUTTx Data
17TxDOUTTx Data
18COLINCollision
19CRSINCarrier Sense
20V-+5 Vdc/ +3.3 Vdc
21V-+5 Vdc/ +3.3 Vdc
22GND-Ground
23GND-Ground
24GND-Ground
25GND-Ground
26GND-Ground
27GND-Ground
28GND-Ground
29GND-Ground
30GND-Ground
31GND-Ground
32GND-Ground
33GND-Ground
34GND-Ground
35GND-Ground
36GND-Ground
37GND-Ground
38GND-Ground
39GND-Ground
40V-+5 Vdc/ +3.3 Vdc

Notes

  • Direction is given for the DTE (network device) relative to the DCE (transceiver).

References

Category:Networking Connectors