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 the
LabVIEW Help for Modbus I/O Servers.