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How to detect and handle bus off?

Question asked by lpcware Employee on Sep 2, 2016

Bus off means that the transmit error counter (see explanation further down) has reached 256. There
are many possible causes of this but it could mean that the CAN controller is misconfigured or the
controller is not connected to the CAN bus. The root cause of the problem should be addressed to stop
it happening again. For a misconfiguration it could be that the bit rate is incorrect.
Once in bus off the CAN controller will set a flag in the status register to indicate the state has been
entered and it is common that CAN controllers also trigger an interrupt.
Bus off mode traditionally can only be exited by re-initializing the CAN controller, but some newer CAN
controllers also allow to clear that state individually or even automatically after a certain time.



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