The Media Independent Interface [MII] is a 40 pin Miniature-D connector.
The pinout for the 40 pin D is shown below.
Pins 2 and pin 3 of the MII interface form the MDIO interface.
The MII is used to transition
between a MAC [Media Access Control] and Ethernet physical devices [PHY].
Pin Number | name Signal | Description |
---|---|---|
1 | Power | +5 Vdc/ 3.3 Vdc |
2 | MDIO | MII Data Input/Output |
3 | MDC | MII Data Clock |
4 | RxD 3 | Receive Data 3 |
5 | RxD 2 | Receive Data 2 |
6 | RxD 1 | Receive Data 1 |
7 | RxD 0 | Receive Data 0 |
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 0 | Transmit Data 0 |
15 | TxD 1 | Transmit Data 1 |
16 | TxD 2 | Transmit Data 2 |
17 | TxD 3 | Transmit Data 3 |
18 | COL | Collision |
19 | CRS | Carrier Sense |
20 | Power | +5 Vdc/ +3.3 Vdc |
21 | Power | +5 Vdc/ +3.3 Vdc |
22 | GND | Signal Ground |
23 | ||
24 | ||
25 | ||
26 | ||
27 | ||
28 | ||
29 | ||
30 | ||
31 | ||
32 | ||
33 | ||
34 | ||
35 | GND | Ground |
36 | ||
37 | ||
38 | GND | Signal Ground |
39 | ||
40 | Power | +5 Vdc/ +3.3 Vdc |
Although the MII interface uses a 40 position D-subminiature connector, it is not a standard D-type connector.
The standard D-type connector is not available in 40-position contacts, and this connector differs in other ways.
The most common number of positions for a D-type connector is 9, 15, 25 and 37 contacts;
Refer to Dsub Connector positions for more details on connector shape and dimensions.
There are also other differences in the physical shape of the connector, but manufacturers may still list them under D type connectors.
The D-shell of the connector is not as rounded as a standard D-type connector, although it still appears to be a D-sub shape.
The pin receptacles of this connector style are square, while the true D-sub receptacles are round.
Dsub Connector manufacturers for companies making D-Sub Connectors.
All other Connector types; Connector manufacturers.
Back to the 10/100 Base Ethernet page, or
1000 base Ethernet page for additional
pinout tables and interface descriptions.
Note this connector is also used with some SCSI interconnects, of course the pinout differs.
Latch bars or jackscrews are available on many connectors of this style [the graphic uses latch-bars].
The dimensions for the connector as pointed out in the attached graphic are as follows;
E: 1.580, F: 0.950, and overall length dimension G: 1.815 inches.
The MII connector is normally only found on OEM gear, or servers.
The connector is some what large, so you wouldn't expect to find it on a small NICK card.
Check the IEEE802.3 specification for additional details on the Mechanical Ethernet standard.
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