Path: utzoo!utgpu!attcan!uunet!tektronix!percival!bucket!leonard
From: leonard@bucket.UUCP (Leonard Erickson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: PC's Limited AT Serial Port Problem
Keywords: PC's Limited, serial port, modem
Message-ID: <1183@bucket.UUCP>
Date: 30 Dec 88 00:54:09 GMT
References: <464@blake.acs.washington.edu>
Reply-To: leonard@bucket.UUCP (Leonard Erickson)
Organization: Rick's Home Grown Unix; Portland, OR
Lines: 29

In article <464@blake.acs.washington.edu> djo7613@blake.acs.washington.edu (Dick O'Connor) writes:
<He's using the above computer with an AST TurboLaser printer connected
<to COM1 and a Prometheus 1200 baud external modem connected to COM2.
<The software is Procomm 2.4.2, and he has the protocol correct (1200N81).
<In response to the dialing command, the modem goes offhook, dials the
<number, gets the response, carrier detect comes on with all the right
<tone noises, and then nothing appears on the screen (where a Please
<Log In message should appear).  In response to <RETURN>s, the RD 
<(Read Data) light on the modem blinks long enough to indicate characters
<are being sent down the line, but there is no display.  I replaced the
<modem (which we tested at work on Zenith Z248 machines; no problems!)
<with a Tandy internal similar to the one I use at home, and got similar
<results.

I ran into a similar problem a few months back. In my case, the machine had
a mainframe terminal emulator board in it that used INT 3 *and* INT 4. 
This made use of a serial board impossible at anything over 1200 bps. But
the *real* kicker was that the TSR *program* for talking to the mainframe
caused the exact problem you describe. Characters being sent, but nothing
displayed.

I'd check his software and see what he has that has latched onto the 
COM interrupts. The sysmptoms fit perfectly. Some sort of TSR is grabbing
the incoming characters for itself.
-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I used to be a hacker. Now I'm a 'microcomputer specialist'.
You know... I'd rather be a hacker."