HP PCL/PJL reference - Printer Job Language Technical Reference Manual

EN Status Readback Commands 7-1
7
Status Readback
Commands
Introduction
PJL allows applications to request configuration and status
information from the printer. The printer also can be programmed to
send unsolicited status information to the application when printer
events occur. For example, the printer can send status information
indicating the printer door is open, toner is low, online/offline status,
the text displayed on the control panel, and other pertinent
information.
PJL status readback is especially useful during application
development. Status readback enables you to determine that your
application successfully changed feature settings to your
specifications.
This chapter describes the requirements for using status readback,
and explains the following status readback commands:
• INQUIRE requests the current value (PJL Current
Environment) for a specified environment variable.
• DINQUIRE requests the default value (User Default
Environment) for a specified environment variable.
• ECHO returns a comment to the host computer to synchronize
status information.
• INFO requests a specified category of printer information.
• USTATUS allows the printer to send unsolicited status
messages, including device, job, page, and timed status.
• USTATUSOFF turns off all unsolicited status.
This chapter also explains job recovery.