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Mitsubishi QJ71C24N “Modbus RTU” Omron E5CC Tutorial

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Mitsubishi Q Series PLC is a compact, high-performance PLC series, It can connect multiple PLCs together. Suitable for high-end control applications. Module QJ71C24N is Communication Module of Q-Series PLC, it has 2 channels, “CH1” is RS232 Communication Port, “CH2” is RS485 Communication Port.

Today will guide you to use Mitsubishi QJ71C24N to connect to Omron E5CC temperature controller through “Modbus RTU” communication protocol.

QJ71C24N & Omron E5CC “Connection Diagram”

+ It is necessary to choose Model Omron E5CC that supports RS485 communication port (In Project use Model E5CC-QX2ASM-802)

+ Only QJ71C24N Modules with “Product Information 101220000000 or later” support Modbus RTU Communication.

Omron E5CC Modbus Parameters Setting

In order for Omron E5CC Controller to be controlled and monitored by Modbus RTU, we need to set the following communication parameters:

Omron E5CC Modbus Registers Address

>>> Temperature Setting (SV) Address = 2103 (hex)

>>> Current Temperature (PV) Address = 2000 (hex)

Mitsubishi QJ71C24N Modbus Configuration

Below is a detailed guide on the settings of communication parameters for the Mitsubishi QJ71C24N Module, you should pay attention to carefully read all the steps:

+ Step 1: Create Project

+ Step 2: I/O Assignment

+ Step 3: QJ71C24N CH2. Parameters Settings

+ Step 4: Sent Module Parameters to PLC

+ Step 5: RS422/485 IF “Disable Echoback”

  • Echoback refers to the function in which data transmitted by RS-485 (2-wire) is returned about the local station’s RDA and RDB.
  • Echoback refers to the function in which data transmitted by RS-485 (2 wires) is returned about the local station’s RDA and RDB.
  • Set G450 = 1 (Disable Echoback) / = 0 (Enable Echoback)
QJ71C24N & Omron E5CC “Registers Address Mapping”

+ Go to “Serial Communication Module…”

+ Add Protocol, “Sent Protocols to PLC / Read Protocols form PLC”

Registers Addres Mapping in Project

+ Protocol No.1: “Read Holding Registers”

  • Slave Address = D100
  • Starting Address = D101
  • Quantity of Registers = D102
  • Registers Value Response = D110 “From D110…D235 depending on the number of Registers (D102) to read”
  • “Error Code” Save = D300

+ Protocol No.2: “Write Single Registers”

  • Slave Address = D200
  • Register Adress = D201
  • Register Value = D202
  • “Error Code” Save = D300

You can install the registers like below:

Important: Need to set “Receive Wait Time” > 0, if you set = 0, the command will wait for infinity when error and need to Reset PLC

QJ71C24N “Modbus RTU” Example

+ Disable “Echoback” & Error Reset

+ Read / Write Distribution

+ Read Data Monitoring

+ Temperature Setting Command

+ HMI Registers Address

Project Video Tutorial


+ Download Omron E5CC Manual PDF
+ Download GX Works.2 for Mitsubishi Q-Series
+ Mitsubishi Q03UDV & HMI Weintek “Connection Tutorial”

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