gat@inuxd.UUCP (G Taylor) (04/04/86)
Last week I posted some information about making a Mac+ 8-pin to DB-25
serial cable from an Apple M0187 cable that has the 8-pin connnectors on
each end. What follows is an update and correction to that posting:
Step 1:
Cut an M0187 cable into two pieces
Step 2:
Identify whether the "red" conductor is pin 1 or pin 2
Step 3:
Wire the half or halves up according to the table below:
=================================================================
M0187 Cable
8-Pin Half-1 Half-2 25-Pin (EIA Fcn) Apple Description
------ ------ ------ ---------------- ----------------------
1 Red White 20&4 (DTR & RTS) Handshake Out (*CHANGED*)
2 White Red 8 (DCD) Handshake In (*CHANGED*)
3 Black Blue 2 (TxD) TxD-
4 Yellow Yellow 7 (GND) Ground
5 Blue Black 3 (RxD) RxD-
6 Green Grey no connection TxD+
7 Brown Brown no connection No Connection
8 Grey Green 7 (GND) RxD+
=================================================================
NOTES:
In my previous posting I noted that I had wired the Handshake In/Out leads
reversed from Apple's designations. That was a mistake I made trying
to work around a problem I didn't understand. It turns out I had two
problems unrelated to how the cable should have been wired that were
messing things up.
I didn't actually make two standard RS232 cables from the M0187. I
have several serial devices that I want to be able to select among. I
wanted to connect the Mac+ to a switch box and select devices as
needed. One of the devices on the switch box is my Imagewriter II.
Since the original cable was a "null modem" cable that has the
handshake and xmit/receive leads switched, I made up the second half
of the M0187 as a "null modem" cable. To do that you simply wire the
second half using the same color scheme as the "1st Half" in the
table above. The only exception was that I omitted the RxD+
connection, e.g. the Green/Grey wires. The resulting combination
works fine.
My thanks to those who responded with advice!
Glen A. Taylor
AT&T (Consumer Products Division)
Indianapolis, IN
(317) 845-3709 inhp4!inuxd!gat