Detection of short circuits in the CAN bus – Error patterns

The robustness of the CAN bus also based on its tolerance to occurring short circuits. In the following, we summarize the possibilities and show how the CANtouch detects these errors.

Case	Description	Communication	CANtouch Bus Status	CANtouch  CAN Levels Absolute	CANtouch Node Measurement	CANtouch Bus Wiring
OK	CAN-Bus without errors	yes
			Remark I Bus Status: valid CAN messages available
	CAN_H shorted to CAN_V+	no			Test setup without communication
		Remark Vdepends on the CAN transceiver type, some types can still communicate with this error Remark VIdepending on the voltage level and the duration of the error (overheating of the CAN transceiver)	Remark IIBus Status: statically recessive		Remark IVMeasurement not possible without communication	Remark IIIfinds errors when supply voltages are measured too
	CAN_L shorted to CAN_V+	no			Test setup without communication
		Remark Vdepends on the CAN transceiver type, some types can still communicate with this error	Remark IIBus Status: statically recessive		Remark IVMeasurement not possible without communication	Remark IIIfinds errors when supply voltages are measured too
	CAN_H shorted to Vcc	yes
			Remark I Bus Status: valid CAN messages available		Remark VII Error in differential signal not detectable	Remark VIIIA wiring test with connected participants remains not recommended. It provides undefined errors whose statements are difficult to judge. The displayed results depend strongly on the internal wiring of the participants.
	CAN_L shorted to Vcc	no
			Remark IIBus Status: statically recessive		Remark IVMeasurement not possible without communication	Remark VIIIA wiring test with connected participants remains not recommended. It provides undefined errors whose statements are difficult to judge. The displayed results depend strongly on the internal wiring of the participants.
	CAN_H shorted to CAN_V-	no
			Remark IIBus Status: statically recessive		Remark IVMeasurement not possible without communication	Remark IIIfinds errors when supply voltages are measured too
	CAN_L shorted to CAN_V-	yes
					Remark VII Error in differential signal not detectable	Remark IIIfinds errors when supply voltages are measured too
	CAN_H shorted to CAN_L	no
			Remark IIBus Status: statically recessive		Remark IVMeasurement not possible without communication

Legend:

Vcc: Supply voltage of the CAN transceiver

I) Bus Status: valid CAN messages available

II) Bus Status: statically recessive

III) finds errors when supply voltages are measured too

IV) Measurement not possible without communication

V) depends on the CAN transceiver type, some types can still communicate with this error

VI) depending on the voltage level and the duration of the error (overheating of the CAN transceiver)

VII) Error in differential signal not detectable

VIII) A wiring test with connected participants remains not recommended. It provides undefined errors whose statements are difficult to judge. The displayed results depend strongly on the internal wiring of the participants.