How to troubleshoot Modbus communication problem between DCS / SCADA and third party devices.
We may see two types of major error while dealing with modbus communication.
1. No response error
2. CRC error
The causes of No response error are
- Modbus parameters of Master and Slave may be different
Modbus parameters are Baud rate,Frame Format (ASCII / RTU) ,Start Bit , Stop bit ,Parity
2.Incorrect address of slave
3.Check the physical connection (Wiring and power )
4.Check the reverse polarity of RS485 line
5.Ensure slave device is enabled for Modbus communication
1.Ensure baud rate and character format are correct
2.Check physical connection (Wiring) .Noise may be the culprit
3.Check reversed polarity on RS485 lines