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TMS570LS3137: About "xx Auto-coverage"

Arriy
Expert 1720 points
Part Number: TMS570LS3137

Hello everyone.

I'm reading Safety Manual(SPNU511D).

I foud safety mechanism of "xx Auto-coverage". (i.g:RAM15)

Are those mechanism is can't not run from user ?

Is it a mechanism that must be operated by software? Auto run from hardware ?

Best Regerds

  • 0
    TI__Guru 59540 points

    Hello Arriy,

    The Auto-coverage diagnostic measures are based on the probability of a random failure causing the mechanism such as CRC or BIST to falsely pass a test. In other words, if there is a random fault during the execution of the hardware CRC test/algorithm, the probability of the fault occurring in such a way that a failing CRC check would now pass due to this random fault is very, very small.

    As noted in the safety manual description for CRC Auto-Coverage:

    "7.14 CRC Auto-coverage

    The CRC diagnostic is based on a 64-bit polynomial. For a given test, only one code is valid out of 2^64 possibilities. Therefore, if there is a fault in the CRC logic, it is extremely unlikely that the correct passing code will be generated via the fault."

    So, to summarize, this is a built-in safety measure that is based on the algorithm robustness and is included anytime the given algorithm (CRC, LBIST, PBIST) is used based solely on the probability of a false pass.

  • 0 in reply to Chuck Davenport
    Expert 1720 points

    Hello Chuck.

    Thank you for your answer.

    You said this mechanism is a built-in safety mechanism it is used when algorithm(CRC, LBIST, PBIST) has false pass.


    In case of  fault detect by the algorithm, what is action ?
    CRC, LBIST, PBIST error flag is set ?(e.g:Fail Status Fail Register (FSRF0))

    Best Regards.

  • 0 in reply to Arriy
    TI__Guru 59540 points
    Arriy,

    No, your understanding of what I said is not correct.

    The safety mechanism is based on the probability that there is a false pass. Given all the combinations of the results of the PBIST, CRC, or LBIST tests, it is unlikely that there is a false pass. This is based solely on probability of a random failure causing the results to falsely pass.

    There is no fault detection of the auto-coverage mechanism. Auto-Coverage is simply used as a test for diagnostic so it would be a secondary mechanism not a primary. Secondary diagnostics (latent fault detection mechanisms) do not require additional latent fault detection per IEC61508.
  • 0 in reply to Chuck Davenport
    Expert 1720 points

    Hello Chuck.

    Thank you reply.

    At last I understood.

     "xx Auto-coverage" is not a safety function that needs operation by software and no fault detection.

    This mechanism is fault probability with those algorithm(CRC LBIST PBIST).

    Best Regards

  • 0 in reply to Chuck Davenport
    Expert 1720 points
    Hello Chuck

    Thanks to your answer my question was solved.
    I understood "xx Auto-coverage" is indicate fault probability, but not safety mechanism operate by software.

    Best Regards