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TMS320F280049: Power up sequence of DCAN and external CAN transceiver

Sheldon He
Expert 8585 points
Part Number: TMS320F280049


Hi expert,

My customer encounter below conditon when debugging CAN module on F280049:

1. Power up external CAN transceiver first, then power up DSP. In this case CAN module will work normally

2. Power up DSP first, then power up CAN. In this case CAN module will enter a bus-off or error passive conditon

If they don't set ABO bit, they will meet above two conditions, but if they set, power up sequencing will not matter any more. Could you confirm this and explain more details on this for us?

Thanks

Sheldon

  • 0
    TI__Mastermind 38060 points

    Hi Sheldon,

    From your description, is seems that as soon as the F280049 powers up, application immediately starts to transmit data to the CAN bus.  In the first scenario where the CAN transceiver is powered up first, CANTX and CANRX transaction loop is established through the transceiver path since transceiver is already on.  In the second scenario, the loop between CANTX and CANRX cannot be established since transceiver path is not available as it is not yet powered on.  CAN will try to transmit several times until transmit error count reaches the threshold limit then will  put the CAN in bus-off mode.

    When ABO bit is set, the CAN module will attempt to automatically start the bus-off recovery sequence by clearing the init bit and waiting for.  Device will then wait for several occurences of bus idle before starting CAN transactions.  This is probably what is happening with the second scenario.

    Hope this helps with the explanation.

    Best regards,

    Joseph