Step-by-Step Guide to Modbus Communication

Step-by-Step Guide to Modbus Communication
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Step-by-Step Guide to Modbus Communication
Technical Training
This article will introduce the detailed steps for Modbus communication between the S7-1200 PLC and the V20 frequency converter.
1. Find an S7-1200 PLC with an RS485 communication module and a V20 frequency converter.
Step-by-Step Guide to Modbus Communication
2. Connect the RS485 module to the V20 frequency converter. The wiring method is to connect the red wire to P+ and the green wire to N-.
Step-by-Step Guide to Modbus Communication
3. Set the parameters of the V20 frequency converter.
Step-by-Step Guide to Modbus Communication
4. Create a TIA Portal project and upload the hardware configuration of the S7-1200 PLC.
Step-by-Step Guide to Modbus Communication
Step-by-Step Guide to Modbus Communication
Step-by-Step Guide to Modbus Communication
Step-by-Step Guide to Modbus Communication
5. Set the parameters of the RS485 module. The communication parameters of the module must match those set in the V20. Here, I set it to 9600, 8, even.
Step-by-Step Guide to Modbus Communication
6. Add Modbus communication instructions.
Step-by-Step Guide to Modbus Communication
7. Modify the mode parameter in the background DB of the initialization instruction to 4.
Step-by-Step Guide to Modbus Communication
8. Program testing: the motor starts and stops normally. The Modbus address 40101 is the command source, 047E is stop, 047F is forward, 0C7F is reverse, and address 40100 is the frequency source, with 16#0-16#4000 corresponding to 0Hz-50Hz.
Step-by-Step Guide to Modbus Communication
9. You can observe the communication status by checking the communication indicator lights on the module. If TX and RX flash alternately, communication is successful.
Step-by-Step Guide to Modbus Communication

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Step-by-Step Guide to Modbus Communication

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