Chapter 7 Modbus/Rtu, Ascii (Slave); System Configuration; Wiring; Selection Of Cable - Mitsubishi Electric LE7-40GU Instruction Manual

7
MODBUS/RTU, ASCII (SLAVE)
LE7-40GU can be operated as a slave station for MODBUS/RTU and ASCII communication.
Data monitoring and parameter writing from a master station for up to 247 slave stations (LE7-40GU units) can be carried out.
Precautions
• For 5 seconds after turning on the power of LE7-40GU, data from master station will not be accepted.
• Initial setting of LE7-40GU can not be done only by MODBUS communication.
• Simultaneous use of MODBUS communication and CC-Link communication is not possible.
7.1

System Configuration

MODBUS/RTU, ASCII master station
(FX series PLC)
Connection equipment
MODBUS/RTU, ASCII
master device
*1 The shortest specification on the MODBUS/RTU master device side takes precedence.
7.2

Wiring

This section describes wiring.

Selection of cable

Use the following procedure to select cables.
Twisted pair cable
Use a shield twisted pair wire for connection with RS-485 communication equipment.
■RS-485 cable specification
Item
Cable type
Pairs
Conductor resistance (20)
Insulation resistance
Withstand voltage
Capacitance (1 kHz)
Characteristic impedance (100 kHz)
7 MODBUS/RTU, ASCII (SLAVE)
112
7.1 System Configuration
Connection Cable
Communication Connection cable
form
Cable type name
RS-485 User created
LE7-40GU
Tension controller
(Slave station)
Longest Optional equipment
distance
*1
 (Built-in to main unit)
1200 m
Specifications
Shielded cable
2 p, 3 p
88.0 /km or less
10000 M-km or more
500 V DC 1 minute
An average of 60 nF/km or less
11010 
Number of
connectable
devices
Main unit
LE7-40GU Up to 247 slave
stations (LE7-40GU)
from the master station