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Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!arizona!kelvin
From: kelvin@arizona.UUCP (Kelvin Nilsen)
Newsgroups: net.dcom,net.micro.pc
Subject: Re: ibm pc and interrupt driven asynch output
Message-ID: <23122@arizona.UUCP>
Date: Mon, 1-Apr-85 18:33:25 EST
Article-I.D.: arizona.23122
Posted: Mon Apr  1 18:33:25 1985
Date-Received: Tue, 2-Apr-85 07:30:25 EST
References: <23097@arizona.UUCP> <324@bu-cs.UUCP>, <21@utastro.UUCP> <329@bu-cs.UUCP>
Organization: Dept of CS, U of Arizona, Tucson
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Xref: watmath net.dcom:923 net.micro.pc:3627

Thanks to all for an abundance of responses, comments, and suggestions.

To clarify, I want interrupt driven output because I have actually written
a small time-sharing kernel that can schedule different activities to be
going on concurrently.  One thing I like to do when transferring files
with "kermit" or "xmodem" (both are already incorporated in this program),
is read the next packet of data from the disk while the current packet is
being transmitted via the interrupt driver.

As has been pointed out, I cannot always use a protocol like kermit when
interacting with existing programs through smart function keys or ascii
file dumps.  And slowing everything down to 18 characters a second seems
a little unreasonable. 

Although it is not likely that one types faster than 1200 baud, a peculiarity
of my design (in which the keyboard is polled 18 times a second) makes it
appear to the outgoing interrupt handler that certain bursts of characters
are typed even faster.

The most helpful clue so far was for someone to point out to me that UNIX
translates framing errors into the user's interrupt character (^C in my case).
So I tried setting stop bits to two and lo and behold the problem disappears.
Now, I'll need to find out if this is a peculiarity of my system, an XPC by
XOR(?!) which has already demonstrated a few serial port anomalies, or a
problem common to all IBM PC compatibles.

Any more thoughts?
	thanks again, kelvin nilsen