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MELSEC-Q
3 SPECIFICATIONS
3.2 RS-232 Interface Specification
The following shows the RS-232 interface specifications.
3.2.1 RS-232 connector specifications
The following shows the specifications of the RS-232 connector that connects the Q
series C24 to an external device.
(1) The control signals are described below. (The pin numbers of the connector are
enclosed in parentheses.)
1) CD(DCD) signal (1)
• The Q series C24 operates according to the setting CD terminal check (see
Section 9.4.5) of the Q series C24.
CD terminal check enabled CD terminal check disabled
Full-duplex
communication
• The Q series C24 performs send and receive
processing when the CD(DCD) signal
(receive carrier detection) is ON.
• If the CD(DCD) signal is turned off during
data communication, the Q series C24
initializes the transmission sequence.
• The Q series C24 performs send and receive
processing regardless of the ON/OFF status
of the CD(DCD) signal.
• Data communications is possible with an
external device that cannot turn the
CD(DCD) signal ON/OFF.
Half-duplex
communication
See User's Manual (Application) Setting impossible.
2) RD(RXD) signal
This is a signal to receive data.
3) SD(TXD) signal
This is a signal to send data.
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