Real-Time Commands; Preferred Implementation; Alternate Implementation - CognitiveTPG A776 ColorPOS Programming Manual

82 Chapter 5: Programming commands
Send printer software version
ASCII
US V
Hexadecimal 1F 56
Decimal
31 86
The printer returns 8 bytes containing the boot and flash software version. The first 4 bytes returned are an ASCII string
for the boot version.
The second 4 bytes are an ASCII string for the flash version. Example: For 1.234.56 (8 bytes), the boot version is 1.23 and
the flash version is 4.56.

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.
Rules for using real-time commands
Three situations must be understood when using real time commands.
First, the printer executes the real time command within a few msec of detecting it in the input buffer and will transmit
status regardless of the condition of the DSR signal.
Second, the printer transmits status whenever it recognizes a real time status transmission command sequence, even if
that sequence happens to occur naturally within the data of another command, such as graphics data.
In this case the sequence will also be handled correctly as the graphics data it is intended to be when the graphics
command is executed from the buffer.
A776 (B780) Programming Guide A776-PG00001 D 07/13