From: markw@antimatr.hou.tx.us (Mark Whetzel)
Newsgroups: comp.sys.ibm.pc.rt
Subject: Re: rs232  -- here are the actual connections.
Summary: Here are the IBM specs on rs232 cables for planar on RT
Date: 23 Nov 92 03:15:53 GMT
Organization: StarTrek and Lionel trains fan, Missouri City, TX

In article <Bxr23n.KK2.2@cs.cmu.edu>, zitsky+@cs.cmu.edu (Mark Ryan Miller) writes:
> I'm trying to build an RS-232 cable for my IBM RT so I can
> hook up a modem.  I have a regular RS-232 25 pin cable,
> and an RT 10 pin connector.  Does anyone have the wiring
> info?? Like what pin on the 25 pin connector goes to what
> pin on the 10 pin connector??

The funny connector on the back of the RT is refered to in the 
hardware manuals as a MODU connector.   I know that AMP makes a mating
connector and metal hood for it, but I don't have the part numbers here
at home cuurently.. I will post the AMP part numbers when I get to the
office tommorrow.

Here is looking into the connector pins into the RT planar.

                         T = RT transmits   R = RT receives (listens)

                                 pin  abb   function
   +-----------------+        T   1   TX  = Transmited data from RT
   |                 |        T   2   DTR = Data Terminal Ready   
   |  1  2  3  4  5  |        T   3   RTS = Ready to send
    |               |         R   4   RI  = Ring Indicate
    | 6  7  8  9 10 |         -   5   -     No connection
    |               |         R   6   RX  = Received data to RT
    +---------------+         R   7   DSR = Data Set Ready
                              R   8   CTS = Clear to send
                              R   9   CD  = Carrier Detect
                              ?  10   GND = Signal Ground

The following were discovered by using a meter probe on IBM RT RS232
cables and by opening the hoods on the DB25 connector ends.
IBM part numbers and option numbers listed where known.
They are still orderable from IBM the last time I checked.. but they
would most likely want a fortune for a simple cable.
The 6000's use the same cables, mostly. 
Some RT cables will work on the 6000's depending on what is attached.

RS232 Terminal attach cable     Part# 6298526      DB25 Female connector
                                Option# 6298186

   DB25             MODU
    1   --+--------  10
          |
    7   --+
    2   -----------  6
    3   -----------  1
    4   --+
          |
    5   --+--------  9
    6   -----------  2
    8   -------+---  8
               |
               +---  3
   20   -----------  7


RS232 Serial Printer attach cable.   Part# 6298525
                                     Option#6294803
   DB25             MODU
    1   --+--------  10              Has a DB25 male connector.
          |
    7   --+
    2   -----------  6
    3   -----------  1
    4   -----------  7
    5   -------+---  9
               |
               +---  3
    6   ---+-------  2
           |
    8   ---+
   20   -----------  8

This has worked for my modem attach.. I have not actually used a meter
on a STOCK IBM RT modem cable, but it works for me.

   DB25             MODU
    2   -----------  1 
    20  -----------  2 
    4   -----------  3 
    22  -----------  4 
             N/C  -  5 
    3   -----------  6 
    6   -----------  7 
    5   -----------  8 
    8   -----------  9 
    7   ---+-------  10
           |
    1   ---+

Later,
markw
-- 
M. Whetzel 
Home: markw@antimatr.hou.tx.us        | IBM RT/125 running AIX 2.2.1 
UUCP ..!uhnix1!lobster!antimatr!markw 
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