What Is a Modbus CRC Error?
A CRC (Cyclic Redundancy Check) error indicates that a Modbus message was corrupted during transmission.
The receiving device rejects the message because the checksum does not match.
Common Causes
- Electrical noise
- Improper RS-485 termination
- Loose wiring
- Incorrect baud rate
- Grounding issues
- Long cable runs without repeaters
Troubleshooting Steps
1. Verify Termination Resistors
Ensure correct placement at both ends of the network.
2. Inspect Shield Grounding
Improper grounding increases noise susceptibility.
3. Confirm Baud Rate and Parity
All devices must match communication settings.
4. Shorten Test Cable
If possible, temporarily reduce cable length to isolate noise issues.
FAQ
Is a CRC error always wiring-related?
Most commonly yes, though configuration mismatches can also cause errors.