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Attachment Unit Interface

 

 
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Attachment Unit Interface
 
 
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An Attachment Unit Interface (AUI) is a 15 pin connection that provides a path between a node's EthernetEthernet

Ethernet is a large and diverse family of frame-based computer networking technologies for local area networks ....
 interface and the Medium Attachment UnitMedium Attachment Unit

MAU is an acronym for Medium Attachment Unit which converts signals on an Ethernet cable to and from AUI signals....
 (MAU), sometimes known as a transceiverTransceiver

A transceiver is a device that has a transmitter and a receiver which are combined....
. It is the part of the IEEEInstitute of Electrical and Electronics Engineers

The Institute of Electrical and Electronics Engineers or IEEE is an international non-profit, professional organizati...
 Ethernet standard located between the MACMedia Access Control

The Media Access Control sublayer is the part of the OSI network model data link layer that determines who is allowed to acc...
, and the MAU. An AUI cable may be up to 50 metres long, although frequently the cable is omitted altogether and the MAU and MAC are directly attached to one another.

An AUI connector is a DA-15. 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.

AUI connectors became rarer beginning in the early 1990s. This was because it became more common for computers and hubs to incorporate the MAU, particularly as the 10BASET standard became more common and use of 10BASE-5 (thicknet) and 10BASE-2 (thinnet) declined. The electrical AUI connection was still present inside the equipment. By the mid-1990s AUI had all but disappeared as fast EthernetFast Ethernet

In computer networking, Fast Ethernet is a collective term for a number of Ethernet standards that carry traffic at the nomi...
 became more common (fast Ethernet has an equivalent known as MIIMedia Independent Interface Summary

The Media Independent Interface is a standard interface used to connect a Fast Ethernet MAC-block to a PHY....
). Gigabit Ethernet and 10 gigabit Ethernet have respectively the GBICGBIC

A GBIC is a standard for transceivers, commonly used with Gigabit Ethernet and fibre channel....
 and XAUIXAUI

XAUI is a standard for connecting 10 Gigabit Ethernet ports to each other and to other electronic devices on a printed circu...
 standards which are equivalent to AUI.

A modified form using a smaller connector called the AAUIApple Attachment Unit Interface

Apple Attachment Unit Interface is a mechanical re-design of the standard Attachment Unit Interface used to connect Etherne...
 was used on Apple Macintosh computers in the early 1990s.

The pinout of the AUI is as follows:
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
13 VP Voltage Plus (+12V)
14 VS Voltage Shield (not used)
Shell PG Protective Ground

See also

  • Thicknet10BASE5 Overview

    10BASE5 is the original "full spec" variant of Ethernet cable, using special cable similar to RG-8X coaxial cable....
  • Apple Attachment Unit InterfaceApple Attachment Unit Interface

    Apple Attachment Unit Interface is a mechanical re-design of the standard Attachment Unit Interface used to connect Etherne...
  • XAUIXAUI

    XAUI is a standard for connecting 10 Gigabit Ethernet ports to each other and to other electronic devices on a printed circu...