User`s manual

11
(3) Example of one-to-n connection between external devices and the module
(RS-485)
Terminal registor
R
SDA
SDB
RDA
RDB
SG
FG
RS-422/485
cable
RS-422/485
cable
SDA
SDB
RDA
RDB
SG
FG
R
SDA
SDB
RDA
RDB
SG
FG
SDA
SDB
RDA
RDB
SG
FG
RS-422/485
cable
R
External device 1)
C24 1)
External device 2) External device n
(4) Example of m-to-n connection between external devices and the modules
(RS-485)
Terminal resistor
R
SDA
SDB
RDA
RDB
SG
FG
External device 1) External device 2)
C24 1)
C24n
SDA
SDB
RDA
RDB
SG
FG
R
SDA
SDB
RDA
RDB
SG
FG
SDA
SDB
RDA
RDB
SG
FG
RS-422/485
cable
R
RS-422/485
cable
RS-422/485
cable
(5) Countermeasure for data reception error at the external device during
RS-422/485 connection
If it is suspected that erroneous data may be received by the external
devices while communicating data with the module through the RS-
422/485 interface, connect pull-up and pull-down resistors (reference
resistance: approx. 4.7 k
1/4 W) to the external device.
These resistors will prevent data reception error.
Reception data
4.7 k 1/4 W
4.7 k 1/4 W
Terminal resistor
RDA
RDB
+
-
External device
POINT
Data reception error will never occur if pull-up and pull-down resistors are connected to
the external device.