The interface between the MAC-layer and Layer 1 is AAUI (Apple Attachment Unit Interface). This connector can was used to connect different physical interface tranceivers, like 10Base-T, 10Base-2 or 10Base-5. The electrical characteristics and functions are identical to the AUI connector defined in the IEEE 802.3. The signalling used is EIA modified RS422. With a speed of 230k bps. The signal encoding used FMO (bi-phase space). AAUI signals have the same description, function, and electrical requirements as the AUI signals of the same name, as detailed in the IEEE Standard 802.3-1990 CSMA/CD, section 7.
| Pin | Name | Description |
|---|---|---|
| 1 | FN Pwr | Power (+12V @ 2.1W or +5V @ 1.9W) |
| 2 | DI-A | Data In circuit A |
| 3 | DI-B | Data In circuit B |
| 4 | VCC | Voltage Common |
| 5 | CI-A | Control In circuit A |
| 6 | CI-B | Control In circuit B |
| 7 | +5V | +5 volts (from host) |
| 8 | +5V | Secondary +5 volts (from host) |
| 9 | DO-A | Data Out circuit A |
| 10 | DO-B | Data Out circuit B |
| 11 | VCC | Secondary Voltage Common |
| 12 | NC | Reserved |
| 13 | NC | Reserved |
| 14 | FN Pwr | Secondary +12V @ 2.1W or +5V @ 1.9W |
| Shell | Protective Gnd | Protective Ground |
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