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Path: utzoo!linus!philabs!cmcl2!lanl!jp
From: jp@lanl.ARPA
Newsgroups: net.micro.pc
Subject: Re: Re: Does DOS listen to LaserJets?
Message-ID: <29231@lanl.ARPA>
Date: Mon, 5-Aug-85 19:21:24 EDT
Article-I.D.: lanl.29231
Posted: Mon Aug  5 19:21:24 1985
Date-Received: Wed, 7-Aug-85 00:57:59 EDT
References: <596@alberta.UUCP> <103700004@ima.UUCP> <243@sesame.UUCP>
Organization: Los Alamos National Laboratory
Lines: 32

> > 
> > The laser jet seems to use all known forms of flow control, simultaneously.
> > It sends xon/xoff, and also raises and lowers DTR.  The IBM BIOS doesn't
> > know anything about xon/xoff, but it slavishly follows DTR.  If you're
> > having flow control problems, most likely your cable isn't bringing the
> > flow control signals through.  The laser jet manual has a detailed picture
> > of how the cable should be wired.
> 
> DTR is not usable for handshakeing unless you are at a low baud rate.
> I can't say for sure, but from my observations, it appears that the HP LJ
> sends an xoff when the buffer is getting close to full, and drops
> DTR when it IS full.  Since even PC's have 'reaction time', a few
> chars are sent before DTR is noticed...by the way, I have had
> similar problems with HP plotters.  
> 

Something is very strange in your printer driver.  The DTR should work
"instantly" in a normal driver.  The DTR signal should be tested immediately
before attempting to send a character.  The driver will loop until the
printer is ready for a new character.  I am using a LaserJet on a CompuPro
running PCPRO (MSDOS 2.1) successfully at 9600 baud.  Never have had a problem
even when spewing large files out to the printer.  I know it is halting by
using CTRL-P to start the printer and then typing a file to the screen.  When
the printer buffer is full and waiting for a ready the screen stands still 
until the printer is ready.  I think it waits to eject a page before
proceeding.  Also DTR works satisfactorily when the printer is out of paper
or jams or whatever.

I believe that the problem is with the cable.  Check the manual for the
required connections.

Jim Potter jp@lanl.arpa