Omron NT31 NT31C manual Standard or high-speed of type RS-485

Connecting to the Host’s RS-422A/485 Port		Section 5-2
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.

PC	(At termination)
				Relay terminal block
					Max. 2 m
NT31C		NT31				NT31
			NT31
(Not at		(Not at				(At
termination)		termination)	(Not at			termination)
			termination)

PC

NT31 NT31C

NT31

PC

Relay terminal block

NT31 NT31C NT31

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

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