Modbus Slave CRC/LRC Error

What does I x .Slave.CRC_LRCError mean?

This boolean tag indicates that a CRC (Cyclic Redundancy Check) or LRC (Longitudinal Redundancy Check) error occurred during Modbus slave communication. A value of 1 (Occurrence) means that the received Modbus message failed its integrity check, suggesting data corruption during transmission. This indicates an issue with the physical layer or data format.

• Noise or electromagnetic interference (EMI) on the Modbus communication line
• Damaged or improperly shielded serial communication cable
• Mismatch in CRC/LRC calculation method or setting between the Modbus master and slave
• Incorrect communication line termination (e.g., missing or improper resistors)

Click steps to track your progress.

1. 1

   Inspect the serial communication cable for physical damage, proper shielding, and correct termination (e.g., 120 ohm resistors at ends of bus).

2. 2

   Verify the Modbus master's CRC/LRC calculation method and settings match the slave module's expected method.

3. 3

   Check for external sources of electromagnetic interference (EMI) affecting the communication line and implement mitigation measures.

4. 4

   Measure the signal integrity on the Modbus communication lines using an oscilloscope to identify noise or signal degradation.