MITSUBISHI ELECTRIC FX0N-485ADP - Manual (Page 7)

Classification of terminating resistances
In this product, two sets of terminal end resistances (330
Ω ✕ 2, 110
Ω ✕ 1) are packaged, and the terminating
resistances to be connected differ as shown below depending on the circuit being used.
● When communicating with the RS-422 circuit, connect the resistances of “330
Ω
1/4W ” as the terminating
resistances.
● When communicating with the RS-485 circuit, connect the resistances of “110
Ω
1/2W ” as the terminating
resistances.
The terminating resistances are resistances connected between terminals SDA and SDB, and between terminals
RDA and RDB at both end stations of the circuit (or the interface when an interface such as 485PC-IF is used
at both end stations), when connecting with the RS-485 or RS-422 circuit. For connection examples, see
section 2.1 and 2.2.
〈
330
Ω〉
Brown Orange Brown Orange
〈
110
Ω〉
One-pair wiring
Terminating resistance
(110
Ω )
SDA
SDB
RDA
RDB SDA
SDB
RDA
RDB Terminating resistance
(330
Ω )
Terminating resistance
(330
Ω )
Two-pair wiring
M3
threads M3
threads
(3) Tightening torque of terminals is 0.5 to 0.8 N·m (5 to 8 kgf·cm). Screw terminals must be secure enough to
prevent a loose connection from causing a malfunction.
6.2 mm
(0.24 inches)
or less 6.2 mm
(0.24 inches)
or less
2.3 Terminating resistances
2.4 Cautions for wiring
As one of the conditions for exhibiting the function of the 485ADP sufficiently and building up a reliable system,
external wiring resistant to noise is essential. Cautions for external wiring are given below.
(1) In this system, the data is read or written (turned on or off by force) while the PC is operating. Accordingly,
if abnormal data is written into the PC due to effect of noise, the PC may malfunction, leading to machine
trouble or accident, and therefore the following cautions should be strictly observed.
● Never lay near or bundle together with the main circuit, high voltage line or load line. Or effects of noise or
surge induction may be serious. Keep at least a safe distance of over 100 mm from these lines.
● Ground the shield wire or shield of shield cable at one point at the PC side. Never ground commonly with
high voltage line.
(2) Terminals screws of terminal block for RS-485 are M3 threaded. Therefore, connect wiring by fitting a
crimped terminal suited to the terminal screws (see below) to the cable.