From:	neil AT robots DOT ox DOT ac DOT uk (Neil Townsend)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Dzcomm and multiple port cards
Date:	Fri, 24 Jul 1998 15:20:58 GMT
Organization:	None evident here.
Lines:	42
Message-ID:	<1998Jul24.152058.9677@catorobots.ox.ac.uk>
NNTP-Posting-Host:	cato.robots.ox.ac.uk
Originator:	neil AT cato
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

I am currently trying to get dzcomm to work with an multiple port RS-232
card which has 4 ports and is, I believe, based on the 16550D chip. I think
that there may be a problem in the dzcomm library when it comes to handling
multiple channels, although I could be wrong.

I have configured the card as follows:

ch.    irq      i/o base addr
1       3        300
2       3        308
3       3        310
4       3        318

(The card works just fine under DOS using the manufacturers drivers which
are, of course, incompatible with protected mode, and have so far not let
let me have a look at their source code.)

If I set up the dzcomm term program to read just one of the channels, it
works just fine. However, if I try to set it up to read two channels, it
fails to read either channel. (Both of these channels have a constant stream
of data coming into them).

I thought that this might be due to the interupt handler returning 0 (which
stops interupt chaining) but the behaviour was the identical when I changed
the return value to non zero.

What is interesting is that a small quantity of data is read from the first
channel which is set up, presumably the data which is acquired before the
second channel is set up. I can only conclude that the setting up of the
second channel has somehow scuppered both channels, although how is not
clear to me.

Another intertesting effect is that If I execute term, quit and then run it
again it hangs, the only solution beign ctrl-alt-delete which forces a
reboot and is not trapped by DJGPP.

Sorry to go on so long, thanks for reading this far, any ideas gratefully
received.

Neil
-- 
Neil Townsend   +44 (1865) 273121   neil AT robots DOT ox DOT ac DOT uk

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