Attachment Unit Interface

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AUI Connectors. The male connector (left) is on the MAU and the female connector (right) is on the MAC device (normally either a computer or an Ethernet hub)
AUI Connector with numbered pins on the DEC EtherWorks LC (DE100) ethernet controller

The Attachment Unit Interface (AUI) is a physical and logical interface defined in the original IEEE 802.3 standard for 10BASE5 Ethernet.[1] The (optional) physical interface consists of a 15 pin connection that provides a path between an Ethernet node's Physical Signaling and the Medium Attachment Unit (MAU),[2] sometimes also known as a transceiver. An AUI cable may be up to 50 metres (160 feet) long, although frequently the cable is omitted altogether and the MAU and MAC are directly attached to one another.

AUI connectors became rare beginning in the early 1990s when computers and hubs began to incorporate the MAU, particularly as the 10BASE-T standard became more common and use of 10BASE5 (thicknet) and 10BASE2 (thinnet) declined[citation needed]. The electrical AUI connection was still present inside the equipment. By the mid-1990s AUI had all but disappeared as Fast Ethernet became more common (Fast Ethernet has an equivalent known as Media Independent Interface, MII). Gigabit Ethernet and 10 Gigabit Ethernet have respectively the GMII and XGMII standards which are equivalent to AUI.

A modified form using a smaller connector called the AAUI was introduced on Apple Macintosh computers in 1991, and its use discontinued in 1998.[3]

Connector and signals[edit]

An AUI connector is a DA-15 (D-subminiature), it has a sliding clip in place of the thumbscrews normally found on a D-connector to hold two connectors together. This clip permits the MAU and MAC to be directly attached to one another even when their size and shape would preclude the use of thumbscrews, this clip is however frequently found to be awkward and/or unreliable.[by whom?]

AUI pin-out
Pin Circuit Description
3 DO-A Data Out Circuit A
10 DO-B Data Out Circuit B
11 DO-S Data Out Circuit Shield (not used)
5 DI-A Data In Circuit A
12 DI-B Data In Circuit B
4 DI-S Data In Circuit Shield
7 CO-A Control Out Circuit A (not used)
15 CO-B Control Out Circuit B (not used)
8 CO-S Control Out Circuit Shield (not used)
2 CI-A Control In Circuit A
9 CI-B Control In Circuit B
1 CI-S Control In Circuit Shield
6 VC Voltage Common (0 V)
13 VP Voltage Plus (+12 V)
14 VS Voltage Shield (not used)
Shell PG Protective Ground

See also[edit]

References[edit]

  1. ^ "IEEE Standard for Ethernet, Section 1, Clause 7". IEEE Computer Society. Retrieved 14 February 2017. 
  2. ^ IEEE 802.3 7. Physical Signaling (PLS) and Attachment Unit Interface (AUI) specifications
  3. ^ Dan, Knight. "Apple's AAUI Ethernet Connector". Apple's AAUI Ethernet Connector. Retrieved 13 February 2012.