Xref: utzoo comp.unix.sysv386:1016 comp.unix.internals:521
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!bu.edu!snorkelwacker!bloom-beacon!eru!hagbard!sunic!kullmar!pkmab!ske
From: ske@pkmab.se (Kristoffer Eriksson)
Newsgroups: comp.unix.sysv386,comp.unix.internals
Subject: Re: HP Laserjet not working under SCO Unix
Message-ID: <4189@pkmab.se>
Date: 5 Oct 90 20:35:56 GMT
References: <4@pcssc.UUCP> <14574@hydra.gatech.EDU>
Organization: Peridot Konsult i Mellansverige AB, Oerebro, Sweden
Lines: 34

In article <14574@hydra.gatech.EDU> gt0178a@prism.gatech.EDU (Jim Burns) writes:
>in article <4@pcssc.UUCP>, dma@pcssc.UUCP (Dave Armbrust) says:
>		Also a parallel port does not have the problem
>> of print jobs going off into 'never-never' land when the
>> printer is not turned on.
>
>True enough. I have the same problem on an HP 9000/800. HP said the
>hardware protocol used w/ their mux interface doesn't support hardware
>handshaking, so we're always losing files till someone turns the printer
>on.

You shouldn't need hardware handshaking for that, just a power-on indication
(often DTR will do, but unfortunately it doesn't on the old Laserjet I have)
going from the printer to the DCD input on the computer port, and I don't
expect that the DCD input would be missing on many systems.

On my system the lp spooler automatically disables the printer if the
printer is off too long (and DCD therefore is inactive), which maybe is
not exactly what you want, but it does prevent loss of print jobs.

I think hardware handshaking will let the spooler wait indefinitely for
the printer to come online and accept input, if you make DCD permanently
active, which I suppose is what you really want. However, hardware
handshaking is a murky area, and has not been available in the tty
drivers from AT&T (don't know about the very latest versions, though).
There are unix systems that have added this to their drivers, but they
often use incompatible ways to control it. Also, since unix has not
required the hardware to be able to handle hardware handshaking, there
have been many pieces of hardware constructed for unix without that
ability, like the mux interface you have.
-- 
Kristoffer Eriksson, Peridot Konsult AB, Hagagatan 6, S-703 40 Oerebro, Sweden
Phone: +46 19-13 03 60  !  e-mail: ske@pkmab.se
Fax:   +46 19-11 51 03  !  or ...!{uunet,mcsun}!sunic.sunet.se!kullmar!pkmab!ske