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MELSEC-Q
5 SETTINGS AND PROCEDURES UP UNTIL OPERATION
5.5.1 Connecting to the RS-232 interface
Here connection precautions and an example of connection when carrying out full
duplex communications using the QD51 (-R24)'s RS-232 interface are shown.
(1) Precautions when connecting
(a) Connect the FG signal and shield of the connection cable as shown below.
Connection method Remark
Connection cable FG
signal
Connect to the connector body on the QD51 (-R24)
side.
Connection cable shield
Connect to the FG terminal of the external device
side or the connector body of the QD51 (-R24).
• Do not short circuit the connection cable FG
signal and the SG signal.
• When the FG signal in the external device side
is connected to the SG signal, do not connect
the FG signal on the QD51 (-R24) side.
(b) If data communications cannot be done normally due to external noise,
make connections as shown below.
1) Connect the external device side's FG terminal with the QD51 (-R24)
side by the connection cable's shield.
2) Connect each of the signals other than SG with the SG signal in
twisted pairs.
FG
RD
SD
DTR
DSR
SG
RD
SD
DTR
DSR
SG
To the
connector
body.
QD51 (-R24) Side
Shield
(External Device Side)
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