🚀 go-pugleaf

In article <1993Jan6.150357.22690@adobe.com> zisk@adobe.com (Stephen Zisk) writes:

   In article <justin.726213640@tasman>, justin@tasman.cc.utas.edu.au
   (Justin Ridge) wrote:
   > Is it possible to cancel a job which is being processed in a PS
   > printer - specifically, in a Apple LaserWriter IINT/NTX/f/g?

   For any PostScript printer data stream there is an "interrupt" command.
   On serial and parallel streams, emit a ^C character. On Appletalk, I
   do not know the command, but you could look it up in Inside Appletalk.
   The effect of the command depends on the state of the printer job.

Actually, there is unfortunately no such command on AppleTalk.  The protocol
you talk to the printer with (PAP, Printer Access Protocol) does not have a
Cancel notion.  The "Cancel" button on your Macintosh only stops the flow of
data to the printer.  This usually works if you interrupt a job before it's
gotten too far along, because the printer will go to read data and get EOF
instead.  The EOF can be in the middle of an image, in the middle of an
operator name, or wherever, but will generally cause some sort of error, and
the job will abort.  You'll never see the error, because the Macintosh will
have already closed the connection and won't be listening for it.

However, back to your real question, how to stop the interpreter on a
LaserWriter.  Even though you can't generate the interrupt over the
communication channel itself (in the AppleTalk case), if you have physical
access you can interrupt the job by changing the switch position for a few
seconds, and then changing it back.  This can have anti-social consequences,
if you switch the printer from LocalTalk to serial mode, say, because running
serial line levels on a LocalTalk wire will freeze the network.  It's probably
safest to disconnect the communication channels before fussing with the
switch.

Finally, even using the switch may not be enough, because as mentioned
earlier, the printer may have some pages queued up via copypage, and the
interrupt will not do anything to them.
--
Joel Sacks				sacks@mv.us.adobe.com
Adobe Systems Inc.			...!decwrl!adobe!sacks