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C.2. RS-232C/RS-422A Interface
C.2.
RS-232C/RS-422A Interface
RS-232C interface
Interface Signals
The pins of the printer's RS-232C interface connector carry the signals listed in Table C.2.
The table also indicates whether each signal is incoming or outgoing with respect to the
printer.
Table C.2. RS-232C Signal Pin Assignments
Pin
In/out
1
2
3
4
5
6
7
11
20
Brief descriptions of the signals follow.
FG - Frame Ground - (Pin 1)
This pin is connected directly to the printer frame.
TXD - Transmit Data - (Pin 2)
This output carries asynchronous data sent by the printer to the computer. It is used mainly
in handshaking protocols.
RXD - Receive Data - (Pin 3)
This input carries serial asynchronous data sent by the computer to the printer.
RTS - Request To Send - (Pin 4)
This output is always held high (above 3 volts).
CTS - Clear To Send - (Pin 5)
DSR - Data Set Ready - (Pin 6)
Unused.
SG - Signal Ground - (Pin 7)
All signals can transmit between the printer and the host computer to send each signals
with a signal ground.
C-4
Signal
–
FG
Out
TXD
In
RXD
Out
RTS
In
CTS
In
DSR
–
SG
–
+5V DC
Out
DTR
Description
Frame ground
Transmit Data
Receive Data
Request To Send
Clear To Send
Data Set Ready
Signal Ground
Reserved
Data Terminal Ready
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