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Attachment Unit Interface
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<h2 id="modes">Modes</h2> <p>The AUI can operate in both <i>normal mode</i> and <i>monitor mode</i>. In normal mode, it functions as a direct connection between the DTE and the network medium. Monitor mode, an optional feature, isolates the MAU's transmitter from the medium while allowing the DTE to observe network activity. This mode is useful for diagnostic and monitoring purposes without impacting the physical medium.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="signaling-and-control">Signaling and control</h2> <p>The AUI uses <a href="/facts/Manchester_encoding/0nb5SVmP">Manchester encoding</a> for data transmission, which ensures clock synchronization without requiring a separate timing signal. The data and control circuits operate independently and are self-clocked. Control signals coordinate communication between the DTE and MAU, enabling error signaling, MAU isolation, and medium access requests.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <h2 id="connector-and-signals">Connector and signals</h2> <p>An AUI connector is a DA-15 (<a href="/facts/D-subminiature/ygqtB3CQ">D-subminiature</a>) type, where the DTE side has a female connector and the MAU side has a male connector.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p><p>The connector often uses a sliding clip instead of the typical thumbscrews found on D-connectors, allowing the DTE and MAU to be directly attached, even when their size or shape would not accommodate thumbscrews. However, the clip mechanism is sometimes considered awkward or unreliable.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>In the case of incompatible fittings, the jackposts or sliding clip can be unscrewed and replaced, or adapter dongles and cables can be used. </p><p>Electrically, the AUI's differential signals are designed for use with a 78 Ω cable and can transmit data between DTE and MAU at 10 Mbps over the standard's specified 50-meter length.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> </p><p>AUI drivers and receivers are required to tolerate wiring faults without permanent impairment of the pair. Signal jitter is controlled to within <i>1.5 nanoseconds</i> across the interface.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p> <h2 id="pinout-table">Pinout table</h2> <p>The DA-15 <a href="/facts/Pinout/AtksXTwD">pinout</a> is specified by the IEEE 802.3 standard and describes four differential pairs: </p> Attachment Unit Interface <table><tbody><tr><th>Pin</th><th>Signal</th><th>Direction</th><th>Description</th></tr><tr><td>03</td><td>DO-A</td><td>AUI→MAU</td><td>Data Out Circuit A</td></tr><tr><td>10</td><td>DO-B</td><td>AUI→MAU</td><td>Data Out Circuit B</td></tr><tr><td>11</td><td>DO-S</td><td>AUI→MAU</td><td>Data Out Circuit Shield</td></tr><tr><td>05</td><td>DI-A</td><td>MAU→AUI</td><td>Data In Circuit A</td></tr><tr><td>12</td><td>DI-B</td><td>MAU→AUI</td><td>Data In Circuit B</td></tr><tr><td>04</td><td>DI-S</td><td>MAU→AUI</td><td>Data In Circuit Shield</td></tr><tr><td>07</td><td>CO-A</td><td>AUI→MAU</td><td>Control Out Circuit A</td></tr><tr><td>15</td><td>CO-B</td><td>AUI→MAU</td><td>Control Out Circuit B</td></tr><tr><td>08</td><td>CO-S</td><td>AUI→MAU</td><td>Control Out Circuit Shield</td></tr><tr><td>02</td><td>CI-A</td><td>MAU→AUI</td><td>Control In Circuit A</td></tr><tr><td>09</td><td>CI-B</td><td>MAU→AUI</td><td>Control In Circuit B</td></tr><tr><td>01</td><td>CI-S</td><td>MAU→AUI</td><td>Control In Circuit Shield</td></tr><tr><td>06</td><td>VC</td><td>AUI→MAU</td><td>Voltage Common (0 V)</td></tr><tr><td>13</td><td>VP</td><td>AUI→MAU</td><td>Voltage Plus (+12 V)</td></tr><tr><td>14</td><td>VS</td><td>AUI→MAU</td><td>Voltage Shield</td></tr><tr><td>Shell</td><td>PG</td><td>AUI→MAU</td><td>Protective Ground</td></tr></tbody></table> <h2 id="external-links">External links</h2> <ul><li> Media related to Attachment Unit Interface at Wikimedia Commons</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>IEEE 802.3 7. Physical Signaling (PLS) and Attachment Unit Interface (AUI) specifications <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>https://www.zx.net.nz/computers/dec/networks/DELNI/ <a href="https://www.zx.net.nz/computers/dec/networks/DELNI/" target="_blank">https://www.zx.net.nz/computers/dec/networks/DELNI/</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>https://vt100.net/mirror/hcps/delnitm1.pdf <a href="https://vt100.net/mirror/hcps/delnitm1.pdf" target="_blank">https://vt100.net/mirror/hcps/delnitm1.pdf</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>https://serverfault.com/questions/375782/is-it-possible-to-cross-connect-two-aui-ports-without-transceivers <a href="https://serverfault.com/questions/375782/is-it-possible-to-cross-connect-two-aui-ports-without-transceivers" target="_blank">https://serverfault.com/questions/375782/is-it-possible-to-cross-connect-two-aui-ports-without-transceivers</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"Archived copy". Archived from the original on 2024-08-28. Retrieved 2024-10-02.{{cite web}}: CS1 maint: archived copy as title (link) <a href="https://www.mattmillman.com/projects/usbaui/" target="_blank">https://www.mattmillman.com/projects/usbaui/</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>"The Evolution of Network Port Sizes: From 10BASE-T to 100 Gigabit Ethernet". June 2022. Archived from the original on 2024-06-14. Retrieved 2024-10-02. <a href="https://servercloud.com/the-evolution-of-network-port-sizes-from-10base-t-to-100-gigabit-ethernet/" target="_blank">https://servercloud.com/the-evolution-of-network-port-sizes-from-10base-t-to-100-gigabit-ethernet/</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Overview of the XAUI, XLAUI and CAUI: Part1 Archived 2019-05-17 at the Wayback Machine, "...the existing AUI was not suitable and it was replaced by the MII interface..." <a href="https://40gethernet.wordpress.com/2009/05/08/overview-of-the-xaui-xlaui-and-caui-part1/" target="_blank">https://40gethernet.wordpress.com/2009/05/08/overview-of-the-xaui-xlaui-and-caui-part1/</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Dan, Knight. "Apple's AAUI Ethernet Connector". Archived from the original on 26 March 2009. Retrieved 13 February 2012. <a href="http://lowendmac.com/tech/aaui.html" target="_blank">http://lowendmac.com/tech/aaui.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>"Archived copy". Archived from the original on 2024-08-29. Retrieved 2024-10-02.{{cite web}}: CS1 maint: archived copy as title (link) <a href="https://www.mattmillman.com/projects/10base5/#comment-35680" target="_blank">https://www.mattmillman.com/projects/10base5/#comment-35680</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>"Federal Information Processing Standards Publication: local area networks: baseband carrier sense multiple access with collision detection access method and physical layer specifications and link layer protocol" (PDF). American National Standard (doi:10.6028/NBS.FIPS.107). Retrieved 3 October 2024. <a href="https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf" target="_blank">https://nvlpubs.nist.gov/nistpubs/Legacy/FIPS/fipspub107-Mar1985.pdf</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> </ol>