HP 5100tn Printer Job Language - Technical Reference Manual - Page 205

print jobs the printer may process before processing the application's query. When processing a job, I/O switching paces off all I/O interfaces except for the one which is providing the current print job. However, it is possible for an application to get a few bytes of data into the inactive I/O interface before the printer paces off that I/O interface. If the application times out while trying to send the initial UEL command after one or more bytes of the command are sent, but before the entire UEL command is sent, then the application can proceed using one of the following choices: 1) continue attempting to send the data to the printer, 2) remember how much of the initial UEL command has been sent to the printer and attempt to send the rest of the command at a later time, or 3) stop trying to send the command, making sure the next command the application sends to the printer is the UEL command. This is done so the parser inside the printer properly recognizes all commands following the previously sent partial UEL command. The printer will properly recognize the UEL command, even if the command appears after a partial UEL command. For example, assume the initial query is : %-12345X@PJL ECHO 08/27/92 09:53:46.5 ~033288925 If the printer only accepts "%-12", and if the application later sends: %-12345X@PJL ECHO 08/27/92 09:57:46.5 ~6202323802 The printer accepts the query and responds with: @PJL ECHO 08/27/92 09:57:46.5 6202323802 One of the conditions I/O-switching printers use to determine when to switch to another I/O interface is the idle time of the I/O interface supplying the current print job. Idle time is defined as the time elapsed since the I/O interface Programming Tips 10-25