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5-2SectionConnecting to the Host’s RS-422A/485 Port
101
This connection method can be used only with the NT link (1:N) method
(standard or high-speed) of type RS-485.
PT Host
RS-485 cable
(max. 500 m)
• Method in which the RS-422A ports of multiple NT31/NT31Cs and the
RS-422A port of the host are connected in a 1:N connection (page 122).
This connection method is used with the RS-422A type NT link (1:N) method
(standard or high-speed).
PT
Host
RS-422A cable
(max. total length 500 m)
• Method in which the RS-485 ports of multiple NT31/NT31Cs and the RS-485
port of the host are connected in a 1:N connection (page 125).
This connection method is used with the RS-485 type NT link (1:N) method
(standard or high-speed).
PT
Host
RS-485 cable
(max. total length 500 m)
Note One end of the wire must always be connected to the host (PC), and there must
be no branching. Branching will cause problems such as transmission delays
and communication failures.
NT31
NT31C
PC
PC
NT31
PC
NT31C NT31CNT31 NT31 NT31 NT31 NT31
(At termination)
Relay terminal block Relay terminal block
Max. 2 m
(Not at
termination)
(Not at
termination)
(Not at
termination)
(At
termination)
Example of Good Connection Examples of Bad Connections
Reference: CS1 series CPUs 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 113) or Using the High-speed NT link (1:N) Method (page 115).
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 NT31/NT31C, 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 PCs have the RS-422A/485 type host link