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Appendix A
Communications
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
1
Received line signal
detector
2
Serial receive
3
Serial transmit
4
Data terminal ready
5
Ground
6
Data set ready
7
Request to send
8
Clear to send
9
Ring indicator
Page 112
PcOS Series 80PLUS
Signal Function
Not used
Input signal to receive data from the host
system
Output signal sending data to the host
system
Output signal to float control the host
Logic ground
Input signal to float control the printer
Output signal to float control the host
Input signal to float control the printer
Not used
Rev B 4/13/99
Programmer's Guide
PC Host 9-pin
Cross Connect
Pin #
3 Tx
2 Rx
6 DSR
5 GND
4 DTR
8 CTS
7 RTS
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