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Interface Signals
B-5
B.2 Serial Interface
B.2.1 Interface Signals
Table B-2 below shows the pins and corresponding input and output signals of the RS-232C
interface connector.
B.2.2 Interface voltage levels
The voltage levels of the interface signals conform to EIA RS-232C specifications. The
voltage level of SPACE is 3 to 15 volts. The voltage level of MARK is -3 to -15 volts. Voltages
between -3 and 3 volts are undefined.
B.2.3 Serial connector
The serial interface connector (RS-232C) is a DB-25S connector. Use a cable with a DB-25P
connector or its equivalent for this connector.
Pin In or out Signal Description
1 —FG
Frame Ground.
This pin is connected directly to the
printer frame.
2 Out TXD
Transmit Data.
This pin is used to output asynchronous
data sent from the printer to the computer. This signal is
often used in handshaking.
3 In RXD
Receive Data.
This pin is used to input serial asynchro-
nous data sent from the computer to the printer.
4 Out RTS
Request To Send.
This output is always high (above 3
volts).
5 In CTS Clear To Send. Not used.
6 In DSR Data Set Ready. Not used.
7 —SG
Signal Ground.
This pin is used to establish a common ref-
erence level for the voltages of all signals other than
Frame Ground.
20 Out DTR
Data Terminal Ready .
This pin is used to notify the status
of the printer buffer (i.e., nearly full or nearly empty)
when handshaking is used. The pin goes high (above 3
volts) when the buffer is able to accept more data.
Table B-2