HP 5100tn Printer Job Language - Technical Reference Manual - Page 207

There is also a chance the PJL ECHO response will never by sent by the printer, due to overflowing of the printer's response data buffer as discussed in the following section. Response Data Buffer Overflow The printer contains a limited amount of memory. It is possible for an application to fill all available printer memory with printer status readback responses that have not yet been sent to the host computer, simply by sending many queries and never accepting the responses from the printer. Also, if an application enables unsolicited status and never accepts responses, the printer's response data buffer can overflow. The printer limits the amount of memory allotted to hold responses, and when that memory is full (and the host has not recently accepted any responses), the printer discards all future responses until the host accepts the currently queued responses in the printer. When the printer discards responses, the printer inserts the PJL unsolicited "printer to host data buffer overflow" message: CE CODE=10010 DISPLAY="00 READY" Note Refer to the "HP LaserJet 4 and 5 Family Comments" section in Appendix A under "Printer Status Readback" for the exact "printer to host buffer overflow" message sent by HP LaserJet 4 and 5 printer families. The PJL unsolicited "printer to host data buffer overflow" message is always inserted when the printer discards one or more responses, even if unsolicited status is turned off. I/O-switching printers set aside memory for each I/O interface. A response data buffer overflow on one I/O interface does not mean another I/O interface will also experience the overflow condition. To keep the printer's response data buffer from overflowing, applications should not send more than five queries without accepting the printer's response to those queries. Programming Tips 10-27