Path: utzoo!utgpu!watmath!uunet!cbmvax!ditto
From: ditto@cbmvax.UUCP (Michael "Ford" Ditto)
Newsgroups: unix-pc.general
Subject: Re: Convert modem to serial port?
Summary: Possible
Keywords: hardware hacking
Message-ID: <5304@cbmvax.UUCP>
Date: 22 Nov 88 21:00:07 GMT
References: <378@balrog.UUCP>
Reply-To: ditto@cbmvax.UUCP (Michael "Ford" Ditto)
Distribution: unix-pc
Organization: Commodore Technology, West Chester, PA
Lines: 28

In article <378@balrog.UUCP> glg@balrog.UUCP (Gary L. Grebus) writes:
>Here's one for the hardware hackers...how hard would it be turn the 
>unix-pc 1200 baud modem into a serial port?

I agree that the OBM is less useful than a serial port for most people,
and it is quite feasible to bypass it and use its uart for a serial
port.  There are three problems that I can think of:

	1) RS-232 Line driver & receiver would be needed (one IC).

	2) There are no other RS-232 lines (DTR/CD/RTS/CTS).  Even
	   if there were, the driver would require modification to
	   use them.  I seem to remember that those pins off the
	   8274 are already used for the other port or something.

	3) The driver won't set the speed to anything other than 300
	   or 1200 bps.

I suspect, though, that the driver changes might turn out to be
trivial since the desired code is already in there.  It might be as
simple as pointing a few vectors at the tty00[0-6] routines.
-- 
					-=] Ford [=-

"The number of Unix installations	(In Real Life:  Mike Ditto)
has grown to 10, with more expected."	ford@kenobi.cts.com
- The Unix Programmer's Manual,		...!sdcsvax!crash!elgar!ford
  2nd Edition, June, 1972.		ditto@cbmvax.commodore.com