User`s manual

27
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
5 Communication Setup
5.1 Setup method for MODBUS serial communication
1
Outline
2
Specifications
3
System Configuration
4
Wiring
5
Communication Setup
6
Related Devices and Comm. Status
7
MODBUS Standard Commands
8
Master Specification
9
Slave Specification
10
Creating Programs
5. Communication Setup
This chapter explains the setup method for using the MODBUS protocol with an FX3U PLC and MODBUS
Communication ADP.
5.1 Setup method for MODBUS serial communication
MODBUS communication is setup via the PLC program using GX Developer.
5.2 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
For Descriptions, refer to Chapter 6.
D8401 Protocol
D8409 Slave Response Timeout
D8410 Turn Around Delay
D8411 Message to Message Delay
D8412 Number of Retries
D8415 Communication Status Information Setup
D8416 Communication Status Device Range Setup