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5-6 ADVANCED OPERATION GUIDE
Serial Interface (Option)
Interface Signals
The pins of the printer’s RS-232C interface connector carry the signals
listed in the table below. The table also indicates whether each signal is
incoming or outgoing with respect to the printer.
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.
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 asynchronous 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 reference 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.