> 
> I've got an old PC/XT I want to use as a dumb terminal, my girlfriend
> wants her Classic back ;-)
> 
> I'm trying to make up a cable to hook the two together but I'm not sure
> which bit is attached to which, is this correct?
> 
>         Mac mini-din                            PC/XT 25 pin
> 
>         1       Handshake Output
>         2       Handshake Input
>         3       Transmit Data -         --->    5       CTS
>         4       Ground                  --->    7       GND
>         5       Receive Data -          --->    4       RTS
>         6       Transmit Data +         --->    3       RXD
>         7       General Purpose Input
>         8       Receive Data +          --->    2       TXD
> 
> Any advice would be appreciated.

It's not correct.

Here are the pinouts for a mac modem cable lying around. To work
with the XT, you need to effectively build in a null modem.

# What		Modem		Other computer (guess)
1 HSKo		DTR		CTS
2 HSKi		CTS		RTS
3 TxD-		TXD		RXD
4 SG		Ground
5 RxD-		RXD		TXD
6 TxD+		N/C		N/C
7 GPi		DCD		DTR
8 RxD+		N/C		N/C

What's up? The Mac uses rs-422, which has differential outputs, instead
of the single-ended signals of RS-232. Also, AFAIK, a (1) in RS-422
is TxD+ > TxD- -> TxD+ = +5 (or +12?), TxD- = -5V. In RS-232, a (1)
is when the signal is <0V. So TxD- on the mac gives an output sutable
for RS-232. Likewise the input to the mac sould go on RxD-. Don't
touch TxD+. On a cable I made, I wired RxD+ to ground. My cable here
doesn't. YMMV.

GPi is used as DCD on a modem, so DTR would be the appropriate thing
for another computer. HSKi is CTS, so RTS from a computer. HSKo is
the only non-data output, so it serves various uses. For a modem, it's
used for DTR; it will make the modem hang up. For another computer,
it should be CTS, so we can do input flow control.

Note: the current driver does NOT support input flow contrl. Output
(us shutting up when asked) works. Input (asking the other to shut
up) does not. I'm working on another driver which should support it, but
it's not ready yet.

Good luck!

Bill