Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-sdd!megatek!eta!hollen
From: hollen@eta.megatek.uucp (Dion Hollenbeck)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Interfacing serial printers to PCs
Message-ID: <578@megatek.UUCP>
Date: 14 Jun 89 14:17:57 GMT
References: <626@acheron.UUCP>
Sender: news@megatek.UUCP
Lines: 40

From article <626@acheron.UUCP>, by clarke@acheron.UUCP (Ed Clarke/10240000):
> From article <3484@i.sei.cmu.edu>, by gjp@sei.cmu.edu (George Pandelios):
> -    My AT-class computer is unable to print a file at data rates greater
> -    than 150 baud without overflowing the printer's buffer.  This is be-
> -    cause the LQP03 uses an XON/XOFF protocol, whereas DOS implements a 
> -
> -            SUPERSPL  which I believe to be a commercial product.  I
> - 		     was unable to discover who makes it, though.
> 
> Hmmm - I've been using the following to drive my LaserJet at 9600 baud.
> The LaserJet uses XON/XOFF protocol:
> 
> MODE COM1:9600,N,8,1,P
> MODE LPT1:=COM1
> 
What you have done with the above commands does not have anything to
do with XON/XOFF protocol handling.  Neither does the BIOS support
it nor the above commands turn it on.  All you are doing is setting
the serial port to the appropriate baud rate, data bits, stop, bits,
parity and retry on timeout.  The P parameter merely causes continuous
retries on timeouts to the asynchronous adapter.  I would guess that
you are able to get this to work only on a fluke.  You have done
nothing to implement XON/XOFF protocol.

If anyone is interested in a discussion of XON/XOFF protocol in
greater detail, I can supply it.  I have implemented XON/XOFF
protocol in 6 different operating systems and know what it is
supposed to do and how it actually works.  I can also supply information
about hardware handshaking and ETX/ACK protocols.  Much of what I
do for a living is implement serial device drivers on all kinds of
operating systems and proprietary hardware.  I also program at the
very lowest level extensively on the PC (I have ported MS-DOS to
several different PC hardware environments).


	Dion Hollenbeck             (619) 455-5590 x2814
	Megatek Corporation, 9645 Scranton Road, San Diego, CA  92121

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