IBM AT 5170 Technical Reference page 89

The keyboard connector, J22, is as-pin, 90-degree Printed
Circuit Board (PCB) mounting, DIN connector. For pin
numbering, see the "Keyboard" Section. The pin assignments are
as follows:
Pin Assignments
1
Keyboard Clock
2
Keyboard Data
3
Reserved
4
Ground
5
+5
Vdc
Keyboard Connector (J22)
System Board 1-73