Mitsubishi QJ71C24N User Manual page 114

4 SETTINGS AND PROCEDURES PRIOR TO OPERATION
Incorrect insertion
Terminal
resistor
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(e) If data cannot be communicated with the external device at all, the polarity of
the external device could be wrong and should be checked again. If the
polarities of the Q series C24 and the external device do not match, reverse
the polarity of each signal on either device side and connect the devices with
the cable; this may enable the data to be communicated.
POINT
(1) For terminal resistor setting/connection described in this section, when the RS-
232 to RS-422 converters or similar device is used at the external device at
both ends of the circuit, a terminal resistor must be set, or connected, at the
converter.
(2) When using the RS-232 to RS-422 converters to connect the external devices
and the Q series C24, use a converter that is compatible with the external
device and programmable controller CPU system configuration (1:1, 1:n, m:n).
(3) Device connected to the Q series C24 RS-422/485 interface must be
standardized as RS-422 or RS-485, including 1:n, n:1 and m:n connections.
(2) Connection examples
(a) External device and Q series C24 with 1:1 system configuration
Q series C24
Signal name
SDA
SDB
RDA
R
RDB
SG
FG
FG
Inserted horizontally.
External device
Terminal
Signal name
resistor
RDA
R
RDB
SDA
SDB
RSA
RSB
CSA
CSB
SG
FG
MELSEC-Q
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