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Original question:

TCAN1146-Q1: Some bus faults are latched only for almost one second although the fault is physically applied on bus

TCAN1146-Q1: TCAN1146-Q1

Mohamed Assem
Prodigy 10 points

Part Number: TCAN1146-Q1

Tool/software:

Hello,

Referring to the questions: TCAN1146-Q1: Some bus faults are latched only for almost one second although the fault is physically applied on bus - Interface forum - Interface - TI E2E support forums

You asked whether the bus termination is 60 ohm. I can confirm that the CAN bus is terminated with two 120 ohm resistors in parallel, resulting in a total impedance of 60 ohm.

Let’s proceed with the discussion in this new thread.

  • 0
    TI__Guru 67837 points

    Hi Mohamed,

    It would seem INT_CANBUS bits are interrupt flags and set when a fault transition is detected I.e., the fault entered or exited. The bit is most likely cleared once acknowledged in the software (R/W1C - read/write-1-to-clear) and the device will not keep it asserted forever even with the physical condition present. As described, it seems your loop of 500 ms catches the bit twice for the 1 second window (you may increase your polling frequency as well) and the device do not seem to set it again after you read and clear it - until a new event like the fault being removed and re-applied occurs.

    The other shorts behave differently as the device interprets them as though the bus dominant is stuck, which then triggers the bus fault detection or line bias faults where the bus is actively forced to a rail and INT_CANBUS flag stays active. Hence, the device settles into the error state and typically do not continuously re-trigger the interrupt. 

    I would further recommend to treat INT-CANBUS as an interrupt / event trigger only and only clear once sampled or confirmed the condition is cleared. You may also add your own latching logic in the firmware for persistent monitoring or use a bus fault status instead. INT_CANBUS seems to be intended for only notifying the MCU that something happened and do not serve as a latched diagnostic, thanks.

    Best Regards,

    Michael.