HP Color LaserJet 5500 Technical Reference Manual page 211

query and one generated because of the resent query). If the
application is using an outstanding solicited query list, then
when the first response is received, the query will be
removed from the list. When the second response is
received, the second response will be ignored because there
is no matching query in the outstanding solicited query list.
Given the above structure for sending queries and
processing responses, applications should adhere to the
following guidelines:
1. If the application sends data to the printer in blocks, fol-
lowed by long pauses between blocks (i.e. greater than
five seconds), then it should cause the printer to use a
larger I/O interface idle time value by using the PJL JOB
command as described in the "Printer Status Readback
and Printer I/O Switching" section.
2. Check status readback availability as described in the
"Determining if Printer Status Readback is Available"
section.
3. Synchronize with the printer-to-host data stream as de-
scribed in the "Old Printer Status Readback Responses"
section.
4. Do not have more than five outstanding queries before ac-
cepting printer status readback responses. This prevents
response data loss as described in the "Response Data
Buffer Overflow" section.
5. Before quitting, turn off all unsolicited status enabled by
the application. Also, accept all responses from the
printer that were generated because of actions performed
by the application.
6. Do not be dependent on the timing characteristics of a
single printer model. For example, the response time of
the HP LaserJet 4 printer's built-in Bi-Tronics I/O inter-
face will be different than the timing characteristics of a
Bi-Tronics I/O interface in an I/O card installed into the
printer.
Programming Tips 10-31