The program takes serial port 2 as example, so corresponding communication flag is the serial
port 2’s. About other serial port, please refer to appendix 1. Serial port, please refer to
appendix 1.
Method 2 use broadcasting function：
When master Y0 status changes, it broadcasts the status to all the slaves. The synchronization
of three PLCs is better than method 1.
6-2-8．Application
Example 1:
Following are the programs for reading and writing Modbus communication between 1
master station and 3 slave stations.
Program operation:
(1) Write master PLC Y0~Y11 status to slave PLC 2 Y0~Y11
(2) Read slave PLC 2 Y0~Y11 to master PLC M10~M19
(3) Write master PLC D10~D19 to slave PLC 2 D10~D19
(4) Read slave PLC 2 D10~D19 to master PLC D20~D29
(5) So as slave PLC 3 and 4
The following is a comparison of XC and XD series Modbus-RTU communication programs
for reference. The communication programs in XC series are as follows:
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