Mitsubishi MELSEC LJ71C24, User Manual

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6 SETTING AND WIRING
6.2 External Wiring with RS-232 Interface
This section explains the specifications of RS-232 and how to connect with external
devices.
6.2.1 RS-232 connector specifications
The following shows the specifications of the RS-232 connector that connects the 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 C24 operates according to the setting of the CD terminal check.
CD terminal check enabled CD terminal check disabled
Full-duplex
communication
• The 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 C24 initializes the
transmission sequence.
• The 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
User's Manual (Application) Setting impossible.
The CD terminal check can be set in GX Works2 as follows.
"Various_Control_Specification" screen "For designation of communication
control" "CD terminal check designation (for RS-232)"
2) RD(RXD) signal (2)
This is a signal to receive data.
3) SD(TXD) signal (3)
This is a signal to send data.
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