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From: mcba@newt.phys.unsw.OZ.AU (Michael C. B. Ashley)
Newsgroups: comp.sys.hp
Subject: LaserJet III problems with XON/XOFF limitations
Keywords: LaserJetIII XON/XOFF
Message-ID: <917@usage.csd.unsw.oz.au>
Date: 31 Oct 90 23:47:05 GMT
Sender: news@usage.csd.unsw.oz.au
Lines: 33

I'm driving a LaserJet III (with HP PostScript cartridge + 2Mbytes) via
a serial line at 19200 baud from a DECstation 5000 running ULTRIX 4.0,
and I'm having a lot of trouble. The problem is that when the LaserJet's
input buffer becomes full (which appears to be after 60000 bytes) it
sends a control-S to the DECstation, but the DECstation can transmit up
to another 40 or so characters before stopping. Unfortunately, the
LaserJet only appears to be able to buffer another 30 characters before
it gives an IO CONFIG ERR. My local HP response centre have not been
particularly helpful and assure me that the problem is with the
DECstation. However, I have used the DECstation with Apple LaserWriters
and NEC LC890s without difficulty. Perhaps HP's "Robust XON/XOFF" is to
blame ...

Can someone confirm the 30 character buffering limitation? Is there a
way around this (e.g, with some obscure PostScript system call?)?

Another unfortunate feature of the LaserJet is that when you remove the
print tray, the printer immediately sends a control-S to the computer.
It would have been better to delay sending a control-S until the printer
was actually about to print a page. That's how Apple do it.

Another problem is the inability to swap between PCL and PostScript
without having to switch the printer off and remove the cartidge. I
thought I was buying a machine that would run with both PCL and PostScript
with some sensible method of software switching.

Enough problems. The JaserJet is really a very neat printer, and the
resolution enhancement technology is a vast improvement over other
300dpi printers.

Thanks for any advice on the XON/XOFF problem.
Michael Ashley  mcba@usage.csd.unsw.oz.au Astrophysics Dept. /
Uni. of NSW / Australia.