Setting The Terminal Resistance For Rs-422A/485 Communications - Omron NT31 Setup Manual

Connecting to the Host's RS-232C Port

5-1-5 Setting the Terminal Resistance for RS-422A/485 Communications

Name Model
1.25-N3A
(fork type)
Crimp Crimp
terminals
Y1.25-3.5L
(fork type)
The terminal screws of the NT-AL001 are M3 specification. When wiring,
use crimp terminals for M3 use. Tighten terminal screws with a tightening
torque of 0.5 N@m.
Note Always use crimp terminals for wiring.
Examples of applicable terminals
6.2 mm or less
The serial port B connector of the NT31/NT31C has a terminal resistance setting
terminal (TRM).
In RS-422A/485 communications, a terminal resistor must be set at the device at
the end of the communication cable, but not at any other device.
The NT31/NT31C has a built-in terminal resistor, and whether or not the terminal
resistance is applied is set by the wiring at the terminal resistance setting termi-
nals (pins No. 9 and 10 of serial port B). The terminal resistance is 120 Ω. When
carrying out RS-422A/485 communications using serial port B, short between
terminals No. 9 and 10 at the NT31/NT31C at the end of the RS-422A/485 cable.
Leave terminals No. 9 and 10 open at NT31/NT31C units other than the one at
the end of the cable.
When not using RS-422A/485 communications, the terminal resistance setting
is ineffective.
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.
Pin Nos. 9 and 10
Shorted
Open
Note Before connecting or disconnecting cables between devices, make sure that the
power supply to all of the connected devices (NT31/NT31C, PLC, etc.) is OFF.
Maker
Japan Solderless
Terminal MFG
Molex Inc.
Fork type
6.2 mm or less
Abbreviation Pin number
Connector
FG
hood
-
Terminal resistor setting
- -
9
TRM
RDB (+) 10
11
SDB (+)
- 12
-
-
- 25
Terminal resistance is applied.
Short only at the NT31/NT31C connected to the end of an
RS-422A/485 cable.
Terminal resistance is not applied.
Leave the terminals open when connecting an NT31/NT31C
anywhere other than at the end of the RS-422A/485 cable.
Section
Remarks
Recommended cable size:
AWG22 to 18 AWG22 t 18
2
(0.3 to 0.75 mm )
Round type
Function
5-1
97