Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!kth!enea!dkuug!dde!kbe
From: kbe@dde.uucp (Kjeld Borch Egevang)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Commodore PC-1 , serieller Port
Summary: I guess
Message-ID: <142@mother.dde.uucp>
Date: 15 Mar 89 10:38:15 GMT
References: <692@sbsvax.UUCP>
Organization: Dansk Data Elektronik A/S, Herlev, Denmark
Lines: 26

In article <692@sbsvax.UUCP>,
fs-info@sbsvax.UUCP (Fachschaft Mathe/Info) writes:

> ...
> Hier mein Problem:
>   
> Es geht um den seriellen Port meines PC-1.
> ...

I won't try writing in German though my old teacher would be disappointed.

I've had the same problem. I made an interrupt-driven TSR-program when
trying to get two PC1's to communicate. Suddenly the screen went black
and it was stone-dead. But I mostly had the problem when I turned off
the other machine, which apparently sent a lot of garbage on the line
when going down. I think the reason is the interrupts being too frequent
thus overflowing the stack. My advice is to try to disable all interrupts
from the 8250 and see if it works (I vaguely remember it did). Be free
to write me if you don'n know how to handle the 8250 (the 8259 is tricky
but you could try here too). There is an undocumented interrupt enable
bit namely one of the out-bits (I don't remember exactly which one) from
the 8250. If you study the diagram you'll find out.


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