Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site arizona.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!arizona!kelvin
From: kelvin@arizona.UUCP (Kelvin Nilsen)
Newsgroups: net.dcom,net.micro.pc
Subject: ibm pc and interrupt driven asynch output
Message-ID: <23097@arizona.UUCP>
Date: Sat, 30-Mar-85 03:35:15 EST
Article-I.D.: arizona.23097
Posted: Sat Mar 30 03:35:15 1985
Date-Received: Sun, 31-Mar-85 03:26:33 EST
Distribution: net
Organization: Dept of CS, U of Arizona, Tucson
Lines: 40
Xref: watmath net.dcom:921 net.micro.pc:3607

I have written a terminal emulator for the ibm pc to which i am attempting
to add several enhancements.  One feature i would like is to be able to
send all asynchronous port output under the direction of interrupt handlers.
I believe I have properly implemented this capability, but have observed
problems when communicating with mainframes.

The problems are:
	On a VAX running 4.2 UNIX, when I type a fast string of characters
	at 1200 baud, the command line interpreter aborts the line I am
	typing and echoes my interrupt character, ^C.  I am running the
	C-shell.  I have similar problems when running editors, etc. 

	On a DEC-10, when I type a fast string of characters to the command
	line interpreter, all or some of the characters are ignored.

	In "loop-back" testing on the pc, no matter how fast i type characters
	i am unable to drop or garbage any characters.  It is quite easy to
	reproduce the problem on a mainframe at will.
		Note that "loop-back" testing is vulnerable to timing
		problems not present in the mainframe hookup as the same
		pc will receive two interrupts almost simultaneously, one
		upon completion of the transmission, and the other on receipt
		of the character transmitted.

		i have not yet been able to test the program between two PC's.

I have hypothesized that the main-frames are not able to keep up with 1200
baud characters packed as closely together as is possible using interrupt
driven output.  Is this consistent with anyone else's knowledge/experience?
If so, what is the proper delay between characters for compatibility with
a maximum number of host computers?

Is my PC corrupting the data word before/while it's being transmitted?  It
seems possible that the PC might be garbaging data even though it can
read its own garbage in the "loop-back" test.

I would greatly appreciate any insight you might be able to offer,
	thanks in advance.

	kelvin nilsen