Path: utzoo!telly!attcan!lsuc!jimomura
From: jimomura@lsuc.on.ca (Jim Omura)
Newsgroups: comp.os.os9
Subject: CoCo3 Serial Port
Message-ID: <1990Sep3.041013.5444@lsuc.on.ca>
Date: 3 Sep 90 04:10:13 GMT
Reply-To: jimomura@lsuc.on.ca (Jim Omura)
Distribution: na
Organization: Consultant, Toronto
Lines: 30


     I've bbeen having a particularly annoying  problem for a
long time now.  I'm using a DWP-210 printer on the "bit-banger"
serial port for years.  A few months ago, after I added the diode
by-pass ffor the CART line, the  bit-banger port started to become
unreliable and then it went dead.  Now all I get is a #246 error
(the serial port not ready).  I expected this to mean that the
"printer ready" signal was not beinng detected on the CoCo3.  I
tried substituting another old CoCco and the printer and cable
were working properly.  So, not having adequate testing equipment,
I started in changing thee parts that were related to this signal.

     I've changed the jack, the SALT chip (I added a socket and
new chip) and the resister and diode between the SALT and the PIA
(in fact I changged both the diodes and resistors on the data-in
circuit and Carrier Detect  lines), and I chaanged the PIA (I added
a socket for the first PIA at that time).  None of this hhelped.
I also added a switch in the diode by-pass line for the CART signal
and that didn't help either.

     There's another PIA "downstream" from the one I changed,
and some other TTL chips.  It just doesn't seem likely to me that
these would be the problem.  Does anybodyy have any advice or should
I just keep on changing chips?

Cheers! -- Jim O.
-- 
Jim Omura, 2A King George's Drive, Toronto, (416) 652-3880
lsuc!jimomura
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