BUS-OFF state of system bus (CAN)

¿Qué significa CE4 ?

The controller has received too many faulty telegrams via the system bus (CAN) and has disconnected from the bus. This indicates a severe communication issue on the CAN network, preventing data exchange.

• Incorrect CAN bus termination resistor values (e.g., 60 Ohm or 180 Ohm instead of 120 Ohm) at bus ends.
• Severed or shorted CAN_H and CAN_L wires in the bus cable, often due to mechanical stress or sharp bends.
• Excessive network length (beyond 40m without repeaters) causing signal degradation and reflection issues.
• Electromagnetic interference (EMI) ingress on unshielded or improperly grounded CAN bus cables, leading to corrupt telegrams.
• Faulty CAN transceiver chip on one of the connected devices, transmitting corrupted data or failing to acknowledge.

Haga clic en los pasos para seguir su progreso.

1. 1

   Measure the resistance across CAN_H and CAN_L terminals at each end of the bus (with power off) to verify 120 Ohm termination.

2. 2

   Inspect the entire CAN bus cable length for visible damage, sharp bends, or loose connections at each node's terminal block.

3. 3

   Using an oscilloscope, monitor CAN_H and CAN_L signal integrity at several points on the bus for proper differential signaling and absence of reflections.

4. 4

   Disconnect devices one by one to isolate a potential faulty node that is flooding the bus with error frames.

5. 5

   Verify ground connection integrity for all CAN bus nodes, ensuring a low impedance path to the common ground plane.

6. 6

   Check parameter C0004 (CAN baud rate) consistency across all connected devices and adjust if mismatched.