Communication Format | DIGITAL "0" | DIGITAL "1"(BUS IDLE ) | CAN Communication Line Resistance | |||
HIGH | LOW | HIGH | LOW | Inside of ECM | Inside of In-pannel junction box | |
CAN 2.0B | 3.5V | 1.5V | 2.5V | 2.5V | 120Ω (20℃) | 120Ω (20℃) |
Fig.1) CAN communication waveform
Monitoring CAN HIGH and LOW simultaneously is important in monitoring CAN communication waveform. When CAN HIGH signal rise to 3.5V and LOW signal drops to 1.5V - voltage difference between HIGH and LOW signal is 2V - at BUS IDLE state(DIGITAL "1") whose reference voltage is 2.5V, "0" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5V, Check if current cam signal transfers correctly.
Continuous "0"signal above 6BIT means the occurence of error in CAN communication. 1BIT is easily distinguished as calculating the time when "SOF"(START OF FRAME) which notifies the start of frame occurs. Check if "0"signal above 6BIT is detected continuously when monitoring CAN communication waveform.
