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From: lance@helios.ucsc.edu (Lance Bresee)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Null Modem
Message-ID: <10359@saturn.ucsc.edu>
Date: 18 Jan 90 15:35:09 GMT
References: <1990Jan17.153819.12882@ncsuvx.ncsu.edu>
Sender: usenet@saturn.ucsc.edu
Reply-To: lance@helios.ucsc.edu (Lance Bresee)
Organization: UCO/Lick Observatory, Santa Cruz
Lines: 19

In article <1990Jan17.153819.12882@ncsuvx.ncsu.edu> wall-rt@cscosl.UUCP (Richard Todd Wall) writes:
>     Could someone please tell my how my null modem cable should be
>set up??  I've tried 3 different configurations so I'm open to 
>suggestions.   Thanks.
>
Basically, you need to swap pins 2 and 3.  You need to have pins 7 and 1
for signal and chassis ground respectively.  Now the fun starts!  The rest
depends on the handshake or control system your terminal requires, and the
dtr/cts system IBM uses.  It may be that your terminal uses xon/xoff protocal,
and generates NO control signals.  In such a case, you have to dummy them out
on your cable by connecting the output control lines from the PC to the input.
Also, you have to get xon/xoff for your PC.  There were a series of articles
on how to do this on the net a while back, and some assembler source.  We copied
it and have been successfully running a laser printer using xon/xoff for some
time.
Check the IBM technical reference for better data on IBM's required control
lines.  Check your monitors manual for the proper protocall to use.

lance