AT Keyboard Connector 5pin-DIN          XT Keyboard Connector 5pin-DIN
pin     assignment                      pin     assignment
1       CLK/CTS (open-collector)        1       CLK/CTS (open-collector)
2       RxD/TxD/RTS (open-collector)    2       Keyboard Data
3       N/C                             3       Reset
4       GND                             4       GND
5       +5V                             5       +5V


PS2 Keyboard/Mouse Connector
pin     assignment
1       Data
2       N/C
3       GND
4       Vcc
5       CLK
6       N/C