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HMI configured as Modbus-TCP client and server simultaneously

 

We are going to do this tutorial with 3 devices

  • Our HMI (HM-070MW Firmware 7.2.0.47), which acts simultaneously as a Modbus-TCP Client and Server
    • its IP address is 192.168.111.26
    • LW60000 are the HMI seconds in BCD format, available via any Modbus-TCP Client (4×60000)
    • We are going to read in Modbus-TCP the temperature sensor at the 4×0 Modbus register
  • A sensor Modbus-TCP Server with a temperature available in its 4×0 register.
    • its IP address is 192.168.111.110
    • We can read the temperature in its 4×0 Modbus register
  • A PC with Modbus-Doctor software, which is a Modbus-TCP Client

Note: Some Modbus Servers have a register that starts from 0 or 1, so you can have an offset of 1. Try both. Example: Could be 4×60000 or 4×60001)

In our HMI

Set the Modbus Master Port
  • Select “Modbus Master TCP/IP”
  • Select “Extended Mode” for “Address Mode” to allow multiple Modbus-TCP devices to be added.
  • In next tab, IP must be the temperature sensor IP address, 192.168.111.110 (first slave device)
  • The port number must be the official Modbus port, I nammed 502

Set the Modbus Slave Port
  • IP must be the HMI IP address, the same as we have for all other Ethernet communication (See HMI Ethernet IP address and Modbus-TCP)
  • The port number must be the official Modbus port, I nammed 502
Modbus Master : Add the temperature display from the sensor Modbus-TCP Server with a temperature available in its 4×0 register
  • Ethernet
  • Modbus Master TCP/IP
  • 4x : Read Holding Register
  • 1 : “Station No” define in “IP Settings” of the Modbus Master TCP/IP Port
  • 0 : Sensor temperature register (4×0)
 “Station No” define in “IP Settings” of the Modbus Master TCP/IP Port

Note: Station 2 is not use in this tutorial. It is another Slave Modbus-TCP device.

 

If you have another slave device, nammed here “Station 2”, the value display (register 1) would look like this

  • Ethernet
  • Modbus Master TCP/IP
  • 4x : Read Holding Register
  • 2 : “Station No” define in “IP Settings” of the Modbus Master TCP/IP Port
  • 1 : Register value (4×1)

 

Modbus Slave: Read the LW60000 HMI register from a Modbus-Doctor software tool on the PC
  • IP addres 192.168.111.222 (Our HMI)
  • Port 502 as usual for Modbus TCP
  • Register 60000 (LW60000 = Seconds in HMI)