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Path: utzoo!watmath!clyde!cbosgd!ihnp4!inuxc!inuxd!gat
From: gat@inuxd.UUCP (G Taylor)
Newsgroups: net.micro.mac
Subject: Serial Cable for Mac+ (Updated Information)
Message-ID: <871@inuxd.UUCP>
Date: Fri, 4-Apr-86 09:19:07 EST
Article-I.D.: inuxd.871
Posted: Fri Apr  4 09:19:07 1986
Date-Received: Wed, 9-Apr-86 09:51:14 EST
Distribution: net
Organization: AT&T Consumer Products, Indianapolis
Lines: 53

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