Connecting Multiple Modbus Slaves to a Single Modbus Master I/O Server

Updated Jan 11, 2019

Reported In

Software

  • LabVIEW Real-Time Module
  • LabVIEW Datalogging and Supervisory Control Module

Issue Details

Is it possible to connect a single Modbus Master I/O Server to multiple Modbus Slave devices?

Solution

When configuring a Modbus I/O Server in LabVIEW, each master server is configured to communicate with a single COM port for Modbus Serial or a single slave IP address for Modbus Ethernet.
  • For Modbus Serial, up to 247 slave devices can be connected on a single serial network. It is important to that each slave device have a unique Unit ID.
  • For Modbus Ethernet, a Modbus Master I/O Server can only connect to a single slave device. to communicate with multiple Modbus Ethernet slave devices, you must define a separate Master I/O Server for each device.
This behavior is documented in theĀ LabVIEW Help for Modbus I/O Servers.