HP Color LaserJet 5500 Technical Reference Manual page 147

The printer sends the unsolicited status associated with the
JOB command when the JOB command is parsed. The
printer sends the unsolicited status associated with the
EOJ command when all of the pages received before the
EOJ command have been printed. To maximize
performance, HP printers start processing the next job
before the last page of the current job has been printed.
Therefore, the printer may return unsolicited JOB and EOJ
status messages in an order different than sent by the
application or spooler. For example, when printing two
consecutive jobs, the unsolicited EOJ status message
associated with the first job may not arrive at the host until
after the JOB status message of the second job.
PAGE Variable
The USTATUS PAGE = ON command is used to notify the
application that a particular page finished printing. This is
useful for applications such as spoolers, where it is
beneficial to monitor the job on a page-by-page basis. For
job recovery, described later in this chapter, it is helpful to
know which pages are completely printed.
The number of pages is incremented by one for each
simplex page formatted, and by two for each duplex page
formatted. The page count includes all pages printed and
all pages processed in non-printing mode since the last JOB
or EOJ command. (This is different than the PAGES = page
count returned with the unsolicited JOB status, which does
not include pages processed in non-printing mode.)
Status Readback Commands 7-39