Chapter 6: Programming Information | A794 Owner’s Guide |
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 original Printer Status commands, Transmit Printer Status (Hex 1B 76, ASCII ESC
v)and Transmit Cash Drawer Status (Hex 1B 75 0, ASCII ESC u 0) 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
The Real Time commands are implemented in two ways to correct these problems. Both implementations offer the same functionality; which one you choose depends on the current usage of your application.
Rules for Using Real Time Commands
Three situations must be understood when using real time commands.
First, the printer executes the Real Time command upon receiving it 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.
Third, care must be taken not to insert a Real Time command into the data sequence of another command that consists of two or more bytes.
In this case the printer will use the real time command sequence bytes instead of the other command’s parameter bytes when finally executing that other command from the buffer; the other command will NOT be executed correctly.
These three situations generally preclude use of standard DOS drivers for the serial communication ports when using real time commands.
100 | March 1999 |
