CognitiveTPG A760 - Manual (Page 90)

A760 User Guide: Programming Supplement
Chapter 4: Programming commands 90 Revision F January 2010
Real-time commands
The real time commands provide an application interface to the printer even when the printer is not
handling other commands:
• Real-time status transmission: GS (Hex 1D) sequence and DLE (Hex 10) sequence
• Real-time request to printer: GS (Hex 1D) sequence and DLE (Hex 10) sequence
• Real-time printer status transmission
The batch mode printer status commands are placed in the printer’s data buffer as they are
received and handled by the firmware in the order in which they were received. If the paper
exhausts while printing data that was in the buffer ahead of the status command, the printer
goes busy at the RS-232C interface and suspends processing the data in the buffer until paper
is reloaded. This is true for all error conditions: knife home error, thermal printhead overheat,
etc. In addition, there is no way to restart the printer after a paper jam or to cancel a slip waiting
condition when using the wait for slip command.
The real-time commands are implemented in two ways in order to overcome the limitations of
batch mode status commands. Both implementations offer the same functionality; which one you
choose depends on the current usage of your application.
Preferred implementation
For a new application the GS (1D) sequences are
recommended to avoid possible misinterpretation of a
DLE (0x10) sequence as a clear printer (0x10 0, ASCII
DLE NUL) command.
An application using these GS (1D) sequences, does not
need to distinguish for the printer between the new real
time commands and the clear printer command. This
implementation is ideal for an existing A756 application
that already uses the clear printer command or for a new
application being developed.
Alternate implementation
The alternate implementation uses the DLE (0x10)
sequences as implemented on other printers. An
application using these DLE (0x10) sequences and
the original A756 clear printer command (0x10) must
distinguish for the printer between the new real time
commands and the clear printer command by adding a
NUL (0x00) to the clear printer command.
An application using these DLE (0x10) sequences must
also send the second byte of the sequence within 100
milliseconds of the first, to prevent the first byte being
mistaken for a clear printer command.