Omron NT631 Operation Manuals page 150

Connecting to the Host's RS-422A/485 Port
Connecting between NT631/NT631C Units
142
NT631/NT631C
RS-485
:
RDA
TRM
RDB
SDA
SDB
RSA
RSB
24V
+DC
* Short TRM and RDA terminals of the NT631/NT631C at the end of the RS-485 cable
( marked in the above figure) using the short-circuit tool supplied with the
:
NT631/NT631C.
In order to avoid an FG ground loop, do not connect the functional ground of the
NT631/NT631C to the shielding of the RS-422A cable.
NT631/NT631C side
Short-circuit tool
Abbreviation
:
RDA (−)
TRM
RS-422A
RDB (+)
/485
SDA (−)
terminal
block SDB (+)
RSA (−)
RSB (+)
Functional
ground
Shielding wire
Section 5-2
Host
NT631/NT631C side
Abbreviation
RDA (−)
TRM
RS-422A
RDB (+)
/485
SDA (−)
terminal
SDB (+) block
RSA (−)
RSB (+)
Functional
ground
RDA
TRM
RDB
SDA
SDB
RSA
RSB
24V
+DC