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TCAN1167-Q1: Communication when bus fault happen

Marc Liu
Expert 4100 points

Part Number: TCAN1167-Q1

Hi Team,

When bus fault happen, customer find the TX/RX working conditions are different.

Does TX / RX can works seperately under different faults? Or does TCAN1167 not guarantee both Tx/Rx communication under any bus fault? 

Test result from customer showed as below:

Initial state: Normal.
CANL shorted to ground: Tx and Rx present; functions normal.
CANL shorted to power: No Tx or Rx.
CANH shorted to ground: Tx present but no Rx; lighting control works, but touch function does not.
CANH shorted to power: Tx and Rx present; functions normal.

Initial state: CANH shorted to ground for >10s: Tx present but no Rx.
Without power cycling, CANH shorted to power: Tx present but no Rx.
Without power cycling, CANL shorted to ground: Tx present but no Rx.
Without power cycling, CANL shorted to power: No Tx or Rx.

Thank you!

Marc

  • 0
    TI__Mastermind 31360 points

    Hi Marc,

    To answer your question, yes TXD & RXD works differently. TXD is the input from MCU to transceiver, the TCAN1167 has no control of TXD. RXD is reflecting whatever the bus is when device in normal mode, regardless of what's the input on TXD. Thus, the RXD output has not a direct relationship with TXD input.

    The CAN communication may still work (with possibility of error bits and degradation of EMC performance) in a CANH short to supply or CANL short to GND fault. However, no communication will be possible if it's CANH short to GND or CANL short to supply, the CAN receiver sees the bus as being stuck in recessive state thus there will be no output on RXD. The MCU could cut off the TXD input in such fault conditions when the controller have received too many error frames. The TCAN1167 also has an interrupt register that indicates bus fault type, so I would recommend them check their software, if their system utilize this interrupt and how does it handle those bus fault conditions. 

    Regards,

    Sean