LptInit

                               by J. Scott Sanbar

                                  8100 Glenwood
                             Oklahoma City, OK 73114

                                 CIS: 73760,3304




LPTINIT.PAS is a demonstration program, and a useful command line utility
for determining the disposition of a printer.  It is written for Turbo
Pascal 5.x, and also included is the compiled and ready to run executable
LPTINIT.EXE.  IBM PC/XT/AT/PS/2 and true compatibles only.

BIOS interrupt $17 is often used to determine whether a printer is ready
to receive output and diagnose its status.  Indeed, I used to use it
and still do.  However, I found it to be inadequate in situations where
a printer has been disconnected while on or has a bad cable.  In these
cases, Intr. $17 would report an online printer which was not really
online and which would lock up upon access.

The technique used in LptInit is to directly access the parallel port
and send a reset signal to the printer.  Based on the behaviour of the
status register after the reset is sent I can more reliably diagnose
the true status of the printer.

The drawbacks are that the printer is reset, which usually denotes activity
on the printer.  For instance, on my Panasonic KX-P1180 the printhead is
returned to the left edge of the platten.  This is generally harmless
and may actually be desirable but can take a little time.  Also, if an
offline situation is detected the program will timeout.  I have set the
timeout to a conservative level so there will be a noticeable pause,
although this can easily be altered.

Therefore, this technique is best used only sparingly, perhaps at the
beginning of a program or once before each printout.  Thereafter, repeated
checks should use Intr. $17 or rely on the critical error handler to
pass back an error condition.

This text and the program LPTINIT.PAS are both:

Copyright (C) 1990 by J. Scott Sanbar.  All rights reserved.

I hereby commit LPTINIT.PAS to the public domain, to be freely distributed,
used and altered by anyone without fee.

NOTE:  One anomaly I could not resolve.  If the printer is disconnected
while the printer is on but the printer is either offline or out of paper
this technique will fail to diagnose the cable disconnect, but will report
printer offline or out of paper, reporting the pre-disconnect status.
Although this is probably not a critical problem, it is nevertheless
an anomaly.  Every other situation I could think of is accurately
diagnosed, at least on my equipment, and it never reports printer ready
when it is not, which is the critical test.