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

7-14 Status Readback Commands EN
ECHO Command
The ECHO command prompts the printer to return a specified
message to the host computer. Use the ECHO command to
synchronize the printer with the host computer to ensure that the
status received is the requested status information.
Syntax:
@PJL ECHO [<words>] [<CR>]<LF>
Response Syntax:
@PJL ECHO [<words>] <CR><LF>
<FF>
Parameters:
• <words> — The <words> parameter must begin with a
printable character, and can contain any Roman-8 character
from 33 through 255, in addition to space characters and
horizontal tabs. The <words> parameter is not a string
variable, and therefore need not be enclosed in quotation
marks. The parameter should be unique, such as the time
indicated by the real time clock at the moment the ECHO
command is issued. A unique message eliminates the
possibility of duplicate messages being echoed by different
applications. The maximum length for <words> is 80 bytes.
Comments:
In a multi-user environment, the printer may respond to many different
status requests. Since the status messages are buffered in the printer
until they are received, the current application may receive status
messages that were requested by a previous application. (This
happens in situations where the application requests information, or
unsolicited status is enabled, and the application closes before
receiving the status messages.)
Parameter Functional Range Default
<words> Roman-8 characters 33 – 255, <SP>,
<HT>
N/A