User manual

APOS Premium Printer Series User Manual Page 91 /136 Reference: FDE 3107312 Issue A

6.13 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 Request to Printer: GS (Hex 1D) Sequence and DLE (Hex 10) Sequence

♦ Real Time Status Transmission: GS (Hex 1D) Sequence and DLE (Hex 10) Sequence

♦ Real Time Printer Status Transmission

The original Printer Status commands, Transmit Printer Status (Hex 1B 76, ASCII ESC v) 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 communication interface and suspends processing the data in the buffer until paper is

reloaded.

This is true for all error conditions: knife home error, thermal print head overheating, etc. In addition, there

is no way to restart the printer after a paper jam or other error.

The Real Time commands are provided to overcome these restrictions.

ULES FOR USING REAL TIME COMMANDS

Three situations must be understood when using real time commands:

1) The printer executes the Real Time command upon receiving it and will transmit status regardless of the

condition of the host being ready to receive or not.

2) 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 be processed both ways: as a real time command and as the graphics data it is

intended to be when the graphics command is executed from the buffer. The result is that the host might

receive status messages it has not requested.

3) If the printer is in error condition, meaning that the communication interface is likely to be busy, the host

must be able to send the real time commands regardless of this busy state at the interface. Otherwise those

commands wouldn’t be received and processed.

These three situations generally preclude use of standard DOS drivers for the serial communication ports

when using real time commands.