Appendix A
PcOS Series 80PLUS
Programmer’s Guide
Communications
Page 112
Rev B 4/13/99
XON/XOFF Protocol
ASCII characters coordinate the information transfer between the printer and the host system.
The printer sends an ASCII DC1 (11 Hex, XON) character when it is ready to receive data, and it
sends an ASCII DC3 (13 Hex, XOFF) character when it cannot accept any more data. The host
system must monitor the communication link in order to send data at the appropriate times.
RS-232C Technical Specification
This section describes the pin settings for the connectors and the RS-232C interface parameters.
Connectors
The following illustration shows the RS-232C communication connector and pin
assignments. The connector is a 9-pin male D-shell connector and is located in the hollow
cavity under the printer.
Pin
Signal Name
Signal Function
PC Host 9-pin
Cross Connect
Pin #
1
Received line signal
detector
Not used
2
Serial receive
Input signal to receive data from the host
system
3 Tx
3
Serial transmit
Output signal sending data to the host
system
2 Rx
4
Data terminal ready
Output signal to float control the host
6 DSR
5
Ground
Logic ground
5 GND
6
Data set ready
Input signal to float control the printer
4 DTR
7
Request to send
Output signal to float control the host
8 CTS
8
Clear to send
Input signal to float control the printer
7 RTS
9
Ring indicator
Not used