Omron Programmable Terminals NT631C - Manual (Page 111)

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Connecting to the Host’s RS-422A/485 Port Section 5-2
This connection method is used with the RS-485 NT Link (1:N) method
(standard or high-speed).
Note One end of the wire must always be connected to the host (PLC), and there
must be no branching. Branching will cause problems such as transmission
delays and communications failures.
Reference: CS/CJ-series CPU Units cannot be connected with the 1:1 connection NT
Link method. Use the 1:N connection NT Link method (standard or high-
speed) instead to make the 1:1 connection. For details, refer to Using the NT
Link (1:N) Method (page 106) or Using the High-speed NT Link (1:N) Method
(page 108).
5-2-1 Host Types and Settings
The types of host that have an RS-422A port and can be connected to the
RS-422A/485 port of the NT631/NT631C, and the settings to be made at the
host, are described here.
When Using the Host Link
Method Compatible Host Units
Some models and series of OMRON PLCs have the RS-422A/485 host link
function built in. With the CS/CJ-series and CQM1H, the host link method can
be used by installing a Serial Communications Board/Unit. In addition, some
C200HX/HG/HE(-Z)E CPU Unit can be connected in the host link method by
installing a Communications Board.
With the CPM2A and CPM2C, an RS-422A of 1:1 NT Link can be created
through a CPM1-CIF11 RS-422A Adapter.
Check the model and series of the PLC and the type of the installed Board or
Unit before making a connection.
PT Host
RS-485 cable
(max. total length 500 m)
NT631
NT631C
PLC PLC
NT631
PLC
NT631C NT631C NT631 NT631 NT631 NT631 NT631
(At termination)
Relay terminal block Relay terminal block
Max. 2 m
Example of Good Connection Examples of Bad Connections
(Not at
termination) (Not at
termination) (Not at
termination)
(At
termination)