HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

EN Introduction 16-5
Status Response
When the printer receives a status request (command), it processes
that request and forms the response data. This data is then stored in
an I/O status buffer. The response is saved in this buffer until it is
either read (by any user) or the printer is turned off.
In addition to clearing the status buffer by reading the status response
or by turning off the printer, status responses are cleared if one the
following settings are changed:
z Printer resolution (600/300)
z Page protection
z Language personality
Status requests and their associated response are processed in the
order in which they are received.
The number of responses the printer can buffer varies, depending on
internal printer operations. When requesting status, especially in the
case where multiple applications or users are sharing one printer, HP
recommends that you request one item, and then read its response
prior to making another request.
Note Since the printer may contain a status response requested by a
previous application’s operation, it is important to use the Echo
command (described later in this chapter) to synchronize your
application’s request with the printer’s responses. Refer to the
Echo command description and to the “Programming Hints”
section at the back of this chapter for additional information.
Note The number of status responses a printer can buffer varies from
printer to printer. The HP LaserJet 4 printer can store 5 responses.
Refer to the PCL 5 Comparison Guide for printer specific information.
A status response is returned to the printer I/O port from which it was
requested.