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

16-6 Status Readback EN
Status Response Syntax
All status responses start with the letters “PCL” followed by a
Carriage Return control code (decimal 13; <CR>) and a Line Feed
control code (decimal 10; <LF>). In addition, each remaining line of
the response is terminated by a Carriage Return and Line Feed
control code. Finally, status responses are terminated by a Form
Feed control code (decimal 12; <FF>). The basic syntax for the
status response is shown below.
PCL<CR><LF>
INFO TITLE<CR><LF>
KEYWORDn=DATAn<CR><LF>
KEYWORDn=DATAn<CR><LF>
M
<FF>
TITLE, KEYWORDn, and DATAn are strings that vary depending on
the particular status readback command being executed. Each status
readback response has one or more keyword lines associated with it.
A slight variation of this is the Echo command response. This
response is shown below.
PCL<CR><LF>
ECHO ValueField<CR><LF>
<FF>
ValueField is the decimal number taken from the Echo command
value field.
Note Keywords may be added for future printers that are not documented
here. Applications that use status readback should be designed to
ignore lines with keywords they do not recognize.
Two example status responses are shown below.
PCL<CR><LF>
INFO MEMORY<CR><LF>
TOTAL=100000<CR><LF>
LARGEST=25000<CR><LF>
<FF>