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

EN PJL Command Summary B-5
STMSG Response
@PJL STMSG DISPLAY="message" <CR><LF>
key <CR><LF>
<FF>
UEL
<ESC>%-12345X
USTATUS
@PJL USTATUS variable = value [<CR>]<LF>
Unsolicited Status Message (not a response, but
returned when printer events occur)
@PJL USTATUS variable <CR><LF>
[1 or more lines of printable characters or <WS>
followed by <CR><LF>]
<FF>
USTATUSOFF
@PJL USTATUSOFF [<CR>]<LF>