Omron NT31 NT31C manual Connecting to the Host’s RS-422A/485 Port, Pin Nos Function

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

In order to set the terminal resistance, wiring work is required at the cable’s con- nector: carry out the wiring correctly by referring to APPENDIX E Making the Cable, page 267.

Abbreviation Pin number
FG	Connector
	hood
-	Terminal resistor setting
-
	-
TRM	9
RDB (+)	10
SDB (+)	11
-	12
-
	-
-	25
Pin Nos. 9 and 10	Function

	Terminal resistance is applied.
Shorted	Short only at the NT31/NT31C connected to the end of an
	RS-422A/485 cable.
	Terminal resistance is not applied.
Open	Leave the terminals open when connecting an NT31/NT31C
	anywhere other than at the end of the RS-422A/485 cable.

Note Before connecting or disconnecting cables between devices, make sure that the power supply to all of the connected devices (NT31/NT31C, PC, etc.) is OFF.

Reference: S The internal circuit of the NT31/NT31C is shown below.

+ 10 (RDB)

−	16 (RDA)
	Terminal resistor (120 Ω)
	9 (TRM)

Making a connection here inserts a terminator between + (RDB) and − (RDA).

SFor details on setting the terminal resistance of NT-AL001-E, refer to Settings at the RS-232C/RS-422A Convertor Unit (NT-AL001-E)(page 88).

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

The methods for connecting the RS-422A/485 port of the NT31/NT31C and the RS-422A/485 port of the host are described here. There are the following meth- ods.

The following discussion is focused on the connection method to OMRON PCs (By using the memory link method, a connection can be made to any arbitrary RS-422 unit). When making a connection to a host other than OMRON PCs, re- fer to the PC Connection Manual (V042-E1-j) or Multi Vendor Connection Manual (V060-E1-j).

•Method in which the RS-422A ports of the NT31/NT31C and host are con- nected directly by an RS-422A cable (page 117).

When this method is used, the cable length can be extended up to 500 m.

PT Host

RS-422A cable

(max. 500 m)

•Method in which the RS-485 ports of the NT31/NT31C and host are connected by an RS-485 cable (page 121).

When this method is used, the cable length can be extended up to 500 m.

100