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TMS570LS1114: Software test of PBIST vs PBIST autocoverage

Arshad moilingal
Prodigy 200 points
Part Number: TMS570LS1114

Hello,

I have some doubts related to safety mechanisms that decscribed in the 'Safety Manual for TMS570LS12x and 11xHercules™ ARM®-Based Safety Critical Microcontrollers'

 

Safety mechanisms the described in the document,

PBIST Auto-coverage

Definition: The PBIST diagnostic is based on a 32-bit signature capture. For a given test, only one code is valid out of 2^32 possibilities. Therefore, if there is a fault in the PBIST logic, it is extremely unlikely that the correct passing code will be generated via the fault.

Software Test of PBIST

Definition: It is possible to configure the PBIST logic by selecting an algorithm that should fail, and seeing if the PBIST Logic reports an error under this condition. For example, a read-write test could be performed on a read-only memory to ensure that a failure is reported. An alternative scheme is to run a test for memory with more bits than are actually present on the device memory.

My doubts are:

1. Is PBIST autocoverage is about the only positive test of PBIST during the initialization or running of the system?

2. Is Software test of PBIST is about the negative test of PBIST (wrong algorithm or read only memory) and positive test of PBIST test (hence, PBIST auto coverage is happened once during the initialization)?

3. What would be recommendation of PBIST execution for peripheral that rated as ASIL C and ASIL B during only initialization or during run time as well)?

Best Regards,

Arshad Ziyad

  • 0
    TI__Guru**** 197036 points

    1. The Auto-coverage diagnostic measures are based on the probability of a random failure causing PBIST to falsely pass a test. There is no fault detection of the auto-coverage mechanism. The auto-coverage is effective for all the PBIST test at boot-time or run-time. It is ok if you want to define it as positive test.

     2. The software test of PBIST is to inject a fault (wrong algorithm, read-only memory, etc) to check if the PBIST reports an error.

     3. Running PBIST on the RAM is not a suitable method if you want to do it periodically since the content of the RAM will be destroyed. Remember the stacks are located in RAM and you might run the risk of crashing the program.