Xon/Xoff Protocol; Dtr/Dsr Protocol; Rs-232C Technical Specifications - NCR 7197 Owner's Manual

7197 Owner's Manual

XON/XOFF Protocol

The XON/XOFF characters coordinate the information transfer between the printer and
the host computer. The printer sends an XON character when it is ready to receive data
and it sends an XOFF character when it cannot accept any more data. The software on the
host computer must monitor the communication link as shown in the following flowchart
in order to send data at the appropriate times.
If XON/XOFF has been selected, the printer also toggles the DTR signal, as described in
the next section, but it does not look at the DSR signal to transmit data.

DTR/DSR Protocol

The DTR signal is used to control data transmission to the printer. It is driven low when
the printer is ready to recieve data and driven high when it cannot accept any more data.
Data is transmitted from the printer after it confirms that the DSR signal is low.

RS-232C Technical Specifications

This section describes the pin settings for the connectors and the RS-232C interface
parameters. The RS-232C parameters are selectable in the Diagnostic mode. See
"Diagnostics: Communications Interface Settings" in chapter 4 for the position of the DIP
switches. The RS-232C parameters must match those of the host.
XON character = Hex 11.
XOFF character = Hex 13.
March 2002
Chapter 5: Communication
62