This chapter explains the setup method for using the MODBUS protocol with an FX3U PLC and MODBUS
1 Setup method for MODBUS serial communication
MODBUS communication is setup via the PLC program using GX Developer.
2 Example of communication setup
To initiate the setup, the PLC program must use the auxiliary relay M8411 for Channel 1 or Channel 2. When
the PLC program contains the "LD M8411" instruction, it is then possible to configure the MODBUS
functionality using MOV operations.
The communication parameters for MODBUS communication can be setup using the following ladder code:
Parameters for a Master using Channel 1:
Device Name Description
D8400 Communication Format
D8409 Slave Response Timeout