CE4

What does 065 mean?

The controller has entered a BUS-OFF state on the system bus (CAN) due to receiving too many faulty telegrams, leading to disconnection from the bus. This indicates a severe communication breakdown.

• Physical layer issue: Damaged CAN bus cable (e.g., cut shield, broken conductor), incorrect termination resistors (e.g., missing 120 Ohm resistor at bus ends), or poor connector contacts leading to signal reflections or attenuation.
• Interference: High electromagnetic interference (EMI) from nearby power cables, contactors, or VFDs corrupting CAN signals, often due to inadequate cable shielding or grounding.
• Device hardware fault: Malfunctioning CAN transceiver on the controller or a connected slave device sending corrupted data or failing to acknowledge.
• Incorrect bus speed: CAN bus speed (e.g., parameter P7-01) configured differently on various devices, leading to misinterpretation of telegrams.

Click steps to track your progress.

1. 1

   Measure the resistance across the CAN_H and CAN_L lines at both ends of the bus; it should be approximately 60 Ohms (due to two 120 Ohm termination resistors in parallel).

2. 2

   Inspect the CAN bus cable for visible damage, kinks, or crushing; verify continuity of each conductor and shield using a multimeter (e.g., resistance check across X3/1 to X3/1 on different nodes).

3. 3

   Check for proper shielding termination at both ends of the CAN cable (e.g., connected to ground terminal X9/GND) to minimize EMI.

4. 4

   Verify the CAN bus baud rate setting (e.g., parameter P7-01 or specific device communication parameters) is identical across all connected devices.

5. 5

   Disconnect slave devices one by one to isolate a potential faulty device injecting corrupted telegrams, observing if the controller exits BUS-OFF state.