Real Time Commands - NCR 7167 Owner's Manual

7167 Owner's Manual

Real Time Commands

These commands provide an application interface to the printer even when the printer is
not handling other commands (RS-232C communication interface only):
1. Real Time Status Transmission (GS Sequence and DLE Sequence)
2. Real Time Request to Printer (GS Sequence and DLE Sequence)
3. 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 are 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, slip
paper jam, thermal print head 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 to correct these problems. 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 7156 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 7156 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 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.
November 2002
Chapter 6: Commands
163