This adapter connects an IBM PC AT keyboard — fitted with a 5-pin DIN 180° (DIN41524) connector, as specified in the IBM PC AT Technical Reference of 1984 — to a computer with a 6-pin mini-DIN PS/2 port introduced with the IBM Personal System/2 range in 1987. Both connectors carry the same four active signals (Clock, Data, Ground, and +5 Vdc) over an identical open-collector, bidirectional serial interface; the adapter is entirely passive, requiring only a straight pin-to-pin rewire with no signal conversion. AT pin 3 is designated Spare and carries no signal in either AT or PS/2 designs.
5 PIN DIN 180° (DIN41524) FEMALE to the keyboard.
6 PIN MINI-DIN MALE (PS/2 STYLE) to the computer.
| DIN | Mini-DIN | |
|---|---|---|
| Shield | Shield | Shield |
| Clock | 1 | 5 |
| Data | 2 | 1 |
| Ground | 4 | 3 |
| +5 VDC | 5 | 4 |
Signals
- Clock — bidirectional open-collector clock line; keyboard generates clock during host-to-keyboard transfers; host may inhibit transmission by holding clock low.
- Data — bidirectional open-collector data line; serial frames are 11 bits: start bit, 8 data bits, odd parity, stop bit.
- Ground — signal and power return.
- +5 VDC — +5 V power supply from the host; open-collector pull-up reference; maximum sink current 20 mA, low-level output maximum 0.5 V.
Notes
- The adapter is passive — no active components are required. The four active signals map directly across the two connectors.
- AT 5-pin DIN pin 3 (Spare) has no connection in this adapter; it carried an active-low keyboard reset on the earlier IBM PC XT but was not carried forward to the AT or PS/2 designs.
- PS/2 mini-DIN pins 2 and 6 are Reserved and not connected.
- Both connectors use TTL-compatible, open-collector signal levels pulled to approximately +5 Vdc.
- The DIN41524 5-pin 180° circular connector standard is equivalent to IEC 60130-9.
References
- IBM PC AT Technical Reference (5170), Document 1502494, March 1984
- IBM PC AT Technical Reference (5170), Document 6139362, September 1985
- IBM Personal System/2 Hardware Interface Technical Reference, May 1988
- IBM PS/2 Hardware Interface Technical Reference — Common Interfaces, Document 84F9735, October 1990