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Re: Null modem cable
In article <C051295020205.302@ocean-side>,
<Psion@ocean-side.ecaetc.ohio-state.edu> wrote:
> Could someone PLEASE tell me the PROPER PIN CONFIGURATION for a IIgs
> to IBM NULL MODEM CABLE!!!
PC IIgs
DB-9 DB-25 Mini-Din-8
3 2 TxD 5 RxD-
2 3 RxD 3 TxD-
7 4 RTS 2 Hshk In
8 5 CTS 1 Hshk Out
6 6 DSR -
5 7 Gnd 4 Ground
1 8 DCD -
4 20 DTR -
- - 6 TxD+ (no connection)
- - 7 DCD (no connection)
5 7 Gnd 8 RxD+ (connect to ground at IIgs or PC end)
It is debatable what should happen with the other flow control lines
at the PC end. The above could be described as a null-modem cable
with hardware handshaking. Whether this is exactly right depends on
the software being used to transfer data.
You should probably connect the PC's DTR pin to its DSR and DCD pins.
If hardware handshaking is not to be used, it may be more useful to
connect the IIgs handshaking signals to DSR and DTR instead of CTS and
RTS.
> On the other hand it may be that the cable is just to long for the
> IIgs' serial port to handle. I've heard conflicting informnation on what
> lengths certain cables can be.
The official maximum length for RS-232 cables is 50 feet. However,
the IIgs is not RS-232: it is RS-423, has lower voltages, and may
therefore be limited to shorter cables. I doubt this is the problem,
though.
> Besides, I prefer "My IIgs" as far away from "my ibm" as possible.
A wise choice. :-)
--
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand