A customer who is spooling PostScript files from a VAX to a LaserWriter wants
to know if it's possible to suppress the LaserWriter's EOT acknowledgment or
timeout messages.
There is no way to suppress the LaserWriter's EOT acknowledgment. In the
PostScript Language Reference Manual, pages 278-279 (copyright 1985, Adobe
Systems, Inc., Addison-Wesley Publishing Co., ISBN 0-201-10174-2): "Certain
character codes serve special purposes, such as control-D to mark end-of-file.
The server performs a job by reading and executing a PostScript program from
the serial channel. When it reads the end-of-file character and the program
terminates, the server sends an end-of-file character, ends the job, and starts
a new one."
The LaserWriter's timeout and job flush message are generated in response to
the CONTROL-G from the spooler. The LaserWriter's PostScript command
interpreter does not understand the CONTROL-G and generates an error. The
spooler does not know the printer is in a timeout/flush mode and continues to
send data to the printer. Error messages from the LaserWriter are generated
spontaneously and are directed to the standard output file and
cannot be suppressed.
Note: The customer may want to consider using DTR for the handshake,
eliminating the need for two-way communications with the LaserWriter.
This way, the spooler can neither confuse nor be confused with extra
control characters. To use DTR on the LaserWriter, the ROMs in the
LaserWriter must be revision 2.0.