Cable - Mitsubishi MELSEC iQ-F FX5 User Manual

One-pair wiring and two-pair wiring are applicable for communication in accordance with RS-485 (RS-422). The wiring
method is determined for each application. Refer to the table below, and perform suitable wiring.
*1
MC protocol When the message waiting time should be 70 ms or less
When the message waiting time may be more than 70 ms
: Recommended wiring method, : Applicable wiring method, : Non-applicable wiring method
*1 When computer link is added to an existing system, adopt the wiring method used in the existing system.
*2 "Echo" is generated when the FX-485PC-IF is used in one-pair wiring.
Take proper countermeasures in the computer so that the echo can be ignored.

Cable

Select cables using the procedure described below.
Twisted pair cable (RS-485)
Use shielded twisted pair cables for connecting RS-485 communication equipment.
The specifications of the cables used in wiring are shown.
■RS-485 cable specifications
Items
Cable type
Number of pairs
Conductor resistance (20)
Insulation resistance
Voltage resistance
Electrostatic capacitance (1 kHz)
Characteristic impedance (100 kHz)
■Cable structural drawing (reference)
Example of two-pair cable structural drawing
Connecting cables
The table below shows applicable cables and tightening torques.
FX5U CPU module built-in RS-485 port
FX5UC CPU module built-in RS-485 port
FX5-485-BD
FX5-485ADP
Precautions
Do not tighten terminal screws exceeding the specified torque range. Failure to do so may cause equipment failures or
malfunctions.
Pair
Shield
Number of wires
connected per
terminal
One wire
Two wires
One wire
Two wires
One-pair wiring


Description
Shielded cable
2p, 3p
88.0 Ω/km or less
10000 MΩ-km or more
500 V DC, 1minute
60 nF/km or less as an average
110±10 Ω
Example of three-pair cable structural drawing
Wire size
Solid wire, Wire ferrule with
Stranded wire insulation sleeve
2
0.2 to 0.5 mm 0.2 to 0.5 mm
(AWG24 to 20) (AWG24 to 20)
2
0.2 mm (AWG24) 
2
0.3 to 0.5 mm 0.3 to 0.5 mm
(AWG22 to 20) (AWG22 to 20)
2
0.3 mm (AWG22) 
Two-pair wiring

*2

Tightening torque
2
0.22 to 0.25 N⋅m
2
4 MC PROTOCOL
4.5 Wiring
4
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