mdsh.com/wiki

This connector is not present on Macintosh 128K, 512K, and 512K enhanced computers. To connect DE-9 cables to the Mini DIN-8 port, use adapter cable 590-0341 (beige) or 590-0553/699-0430 (smoke).. a. On serial port A (modem), if the VIA1 SYNC signal is high, this input will be routed to the receive/transmit clock input of the SCC. This clock input supports high-speed synchronous devices. Pin 7 is not connected on the Macintosh Plus, LC, or IIsi.



8 pin Apple mini din connector at the end of the peripheral cable, from the front of the connector

Pin	Signal	Description
1	HSKo	Handshake out
2	HSKi	Handshake in/external clock
3	TxD-	Transmit data -
4	GND	Signal ground
5	RxD-	Receive data -
6	TxD+	Transmit data +
7	GPI/NC	General-purpose input or no connection
8	RxD+	Receive data +