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From: slerner@sesame.UUCP (Simcha-Yitzchak Lerner)
Newsgroups: net.micro.pc
Subject: Re: Re: Does DOS listen to LaserJets?
Message-ID: <243@sesame.UUCP>
Date: Fri, 2-Aug-85 11:46:51 EDT
Article-I.D.: sesame.243
Posted: Fri Aug  2 11:46:51 1985
Date-Received: Sun, 4-Aug-85 06:26:49 EDT
References: <596@alberta.UUCP> <103700004@ima.UUCP>
Organization: Lotus Development Corp
Lines: 28

> 
> 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.  

{{HP, are you listening?}}


-- 
Opinions expressed are public domain, and do not belong to Lotus
Development Corp.
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Simcha-Yitzchak Lerner

              {genrad|ihnp4|ima}!wjh12!talcott!sesame!slerner
                      {cbosgd|harvard}!talcott!sesame!slerner
                                slerner%sesame@harvard.ARPA