Printer Status - TransAct POSjet 1500 Programmer's Manual

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Programmer' s Guide POSjet 1500 Codes and Commands

Printer Status

Status Inquire
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The POSjet 1500 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. For example, a normal computer printer
does not have cash drawers, such additional features require that the standard printer protocol be extended to deal
with the added features of a point-of-sale (POS) printer.
All inquire commands are processed as they are received (preprocessed or real time) and require a response from the
printer. Consequently, parallel, IEEE 1284 bidirectional communications, USB or bidirectional serial operation is
required.
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The POSjet 1500 Printer looks at and evaluates all commands as they are received and does not respond to Inquire
commands that happen to be embedded in graphics or other commands. (Refer to the buffer and preprocessor
descriptions in later sections.
In all cases, inquire commands are responded to by an acknowledged (ACK) or a not acknowledged (NAK) and then
the command ID, which allows the host application to make multiple requests and receive identifiable responses. If
the printer is configured for serial or USB operation the status is automatically returned to the host. If the printer is
configured for parallel, IEEE 1284 operation, the HOST must initiate a reverse channel request to return the status.
Serial and USB Mode Inquire
All inquire (ENQ) commands require a response from the printer. During serial operation, all inquire commands are
responded to by an acknowledged (ACK) or not acknowledged (NAK), the command ID, and in some cases status.
Most status responses sequences contain a length field to help decode and separate responses.
In general the printer should be configured for "Buffer Full Only" Off Line operation if Inquire commands are used.
This prevents the printer from using flow control for anything but buffer full. The programmer must take on the
responsibility for assuring that Inquire commands are used to maintain status of the printer.
The printer always accepts serial data even when it is off line. The printer has reserve buffer space that allows
additional information to be received even if the printer is signaling buffer full or off line. Because inquire
commands are processed before they go into the buffer, the printer responds even when it is busy printing.
In serial mode, it is desirable that the response to an inquiry be received by the host before another inquire command
is issued to the printer. When the printer receives an inquiry, it generates a response. If inquiries are sent to the
printer too quickly, the printer spends all of its time responding and does not have time to print.
Nov-07 Rev M Page 179