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Connecting to the Host’s RS-232C Port Section 5-1
The terminal screws of the NT631/NT631C are M3.5 specification. When wir-
ing, use crimp terminals for M3.5 use. Tighten terminal screws with a tighten-
ing torque of 0.8 N
⋅m.
Note Always use crimp terminals for wiring.
Examples of applicable terminals
5-1-5 Setting the Terminal Resistance for RS-422A/485
Communications
The serial port B connector of the NT631/NT631C 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 communications cable, but not at any other device.
The NT631/NT631C has a built-in terminal resistor, and whether or not the
terminal resistance is applied is set by shorting or opening the terminal resis-
tance setting terminals (TRM). The terminal resistance is 120
Ω.
When carrying out RS-422A/485 communications using serial port B, short
between TRM and RDA terminals at the NT631/NT631C at the end of the RS-
422A/485 cable. Leave these terminals open at NT631/NT631C PTs other
than the one at the end of the cable.
When not using RS-422A/485 communications, the terminal resistance set-
ting is ineffective.
Note Before connecting or disconnecting cables between devices, make sure that
the power supply to all of the connected devices (NT631/NT631C, PLC, etc.)
is OFF.
Cable TKVVBS4P-03 Tachii Electric Wire
Co., Ltd.
Crimp ter-
minals
1.25-N3A
(fork type)
Japan Solderless
Terminal MFG
Recommended cable size:
AWG22 to 18
(0.3 to 0.75 mm
2
)
Y1.25-3.5L (fork
type)
Molex Inc.
Name Model Maker Remarks
Fork type
7 mm max.
Round type
7 mm max.
TRM-RDA terminals Function
Shorted Terminal resistance is applied.
Short only at the NT631/NT631C connected to the end of an
RS-422A/485 cable.
Open Terminal resistance is not applied.
Leave the terminals open when connecting an NT631/
NT631C anywhere other than at the end of the RS-422A/485
cable.
RDA
TRM
RDB
SDA
Short-circuit tool