7167 Owner’s Manual    Chapter 5: Communication 
 November 2003 
77
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. 
 
 
XON character = Hex 11. 
XOFF character = Hex 13. 
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.