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Control Codes
Printer Status
Printer Status Set/Inquire
The PcOS Series 80PLUS Printer is designed for use as part of an automated system, where the host
computer makes every attempt to correct problems with the printer. In addition, the host application
requires that it be able to obtain more information from the printer than is typical of normal computer
printers. The normal computer printer does not have cash drawers and slip stations. As a result, the
standard printer protocol must be extended to deal with the additional features of a PcOS printer.
The PcOS Series 80PLUS Printer has defined a set of status inquiry commands that will allow the
host to obtain information about the printer and devices connected to it. The method chosen to
interact with the computer is designed to allow a reasonable approach to the host application. It will
not always be possible for an existing application to use the ENQ commands unless the
communication drivers are available to the programmer.
Serial Mode Inquire
All ENQ commands require a response from the printer. In serial operation, all ENQ commands
are responded to by ACK or NAK, the command ID, and in some cases status.
The serial ACK or NAK responses are always uniform and followed with a command ID. This
makes the design of the host application easier because the response can be identified and always
follows the same format.
The printer will always accept serial data even if the printer is off-line. It is possible to send
inquire commands to the printer even if it is off-line. Because ENQ commands are processed
before they go in the buffer, the printer will respond even if the printer is busy printing.
In serial mode, it is desirable that the response to an ENQ be received by the host before another
ENQ command is issued to the printer. When the printer receives an ENQ, it must generate a
response. If ENQ's are sent to the printer too fast, the printer will spend all of its time responding
to ENQ's and have no time to print.
IEEE 1284 Mode Inquire
In parallel IEEE 1284 mode, there is a way to return status information to the host. After the host
makes an ENQ request, the host can activate IEEE 1284 Mode 0 reverse channel and wait for a
response from the printer. The response to the ENQ is identical to serial mode.
The printer will always accept IEEE 1284 reverse channel requests but will not accept ENQ
commands when off-line. It is possible to obtain status when off-line by placing the printer in
dynamic response mode before the printer goes off-line. The IEEE 1284 reverse channel will
then respond to status changes even if the printer is off-line. It is also possible to configure the
printer, so it will not go off-line in most cases. Power off, paper out, and faults will always
generate off-line status.
Page 48
PcOS Series 80PLUS
Rev B 4/13/99
Programmer's Guide
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