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Why Cannot detect BUSOFF？

wang bo
Prodigy 40 points
Part Number: TCAN4551-Q1


Tool/software:

Will a short circuit between CAN_H and CAN_L cause this CAN chip to detect a BUSOFF? Currently, we are encountering such an issue:
  • When one product using TCAN4551 is mounted on a bus, and CANoe is used to monitor the data reported by the product, after CAN_H and CAN_L are shorted, the product fails to report data and a BUSOFF fault occurs.
  • When two products using TCAN4551 are mounted on the same bus, and CANoe is used to monitor the data reported by the products, after CAN_H and CAN_L are shorted, the products will report that a BUSOFF fault has occurred.
How does this chip determine whether a BUSOFF fault has occurred? Why can’t BUSOFF be detected when there is only one product?
  • 0
    TI__Mastermind 33770 points

    Hello Wang,

    As stated in the datasheet, the TCAN4551-Q1 follows the ISO 11898-1:2015, ISO 11898-2:2016, and Bosch M_CAN Revision 3.2.1.1 specifications.

    The ISO 11898-1 Standard defines the error counting and there are a couple of exceptions that would prevent the TEC error counter from causing a Bus Off condition, particularly when there is not another device to send an ACK which would occur when there is only one device used during testing.  Two devices are needed.

    Because the TCAN4551 uses the Bosch M_CAN IP for the CAN FD Controller, you may also want to reference the M_CAN User's Manual (Link) for more detailed information. 

    Regards,

    Jonathan