SV0369 Data Transfer Error (CRC) fault in Fanuc drive

SV0369 Data Transfer Error (CRC) fault in Fanuc drive

Description

SV0369 (often accompanied by SV0368) is a communication error involving the built-in serial encoder. Specifically, it is a CRC (Cyclic Redundancy Check) error. The drive receives data packets from the encoder continuously. It calculates a checksum for each packet. If the calculated checksum does not match the checksum sent by the encoder, the drive rejects the data as corrupted and triggers SV0369. This implies the data arrived, but it was garbled during transmission.

Cause

This is the hallmark of electrical noise interference.

• Shielding Failure: The braided shield on the feedback cable is not clamped tightly to the ground plate, allowing EMI (Electromagnetic Interference) to penetrate the signal wires.
• Dirty Power: Noise from EDM machines, welders, or poorly grounded VFDs sharing the same electrical panel.
• Cable Degradation: The insulation on the twisted pair wires inside the cable is cracking, allowing cross-talk between the 5V power and data lines.
• Connector Moisture: Coolant inside the connector changes the capacitance of the pins, distorting the square wave signals.

Solution

1. Inspect Grounds: Ensure the feedback cable shield is grounded only at the drive end (usually) to prevent ground loops. Clean the clamp surface to bare metal.
2. Cable Separation: Are the encoder cables zip-tied to the high-voltage motor power cables? Cut the zip ties and separate them by at least 10cm.
3. Replace Cable: If the error occurs intermittently when the axis moves to a specific spot, the cable has an internal break.