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PBIST Triple Read Slow/Fast

Joris Gansler
Prodigy 80 points

Hello,

 

in the Technical Reference Manual (SPNA489b) on pages 188 and 189 there are explained the algorithms for RAM tests used by the PBIST controller. But what exactly is the PBIST controller doing during the PBIST/STC-ROM test with the Triple Read Slow or Fast algorithms?  How do these algorithms work? And is there a difference in quality between slow and fast mode?

 

Best regards,

 

Joris

  • 0
    TI__Mastermind 22375 points

    Joris,

     

    Your question has been forwarded to our PBIST engineer.
    I'm expecting a reply by Monday.

     

    Thanks and Regards,

    Jean-Marc

  • 0 in reply to Jean-Marc Mifsud
    Prodigy 80 points

    Jean-Marc,

     

    did you get some information from your PBIST engineer about my question?

     

    Thanks and best regards,

     

    Joris

  • 0
    TI__Intellectual 1480 points

    Joris,

    The triple read consists of 3 tests targetted towards ROM testing .

    1) A fast read which sequentially traverses through the whole ROM depth based on its max operating specification frequency . This predominantly catches most of the defects like stuck-at, updown transition, some adress decode and parametric faults(parametric).

    2) The slow read is mainly a hammer type of algorithm where the each address location  of the ROMis read multiple times before sequentially going to the next address this is mainly to stress the metal structures of the rom

    3)The Xnor read is mainly targeted towards the address decode structure of the ROM where the test starts a read  at location 0 then reads from location n(where n is the maximum address location of theROM) goes back address 1 followed by address n-1 and parses the whole ROM in this fashion.

    This PBIST controller treats the ROM's just like any RAMinfo group During the PBIST test for ex: The STC ROM would be an RAMinfo group and the PBIST ROM will be another RAMinfo group. All the above mentioned test are signature based tests.

  • 0 in reply to Hari Pendurty
    Prodigy 80 points

    Hello Hari,

     

    thank you very much for your reply. So it is recommended to run all ROM tests, not only one. But in the TRM and Datasheet there's no "Xnor read" algorithm mentioned. How can I activate this algorithm? Or did I misunderstand your answer in this point?

     

    Best regards,

    Joris

  • 0 in reply to Joris Gansler
    TI__Intellectual 1480 points

    Joris,

    To clarify on your question due to the fact that we have run out of bits(each bit correspond to a pirticular algorithm) on the ALGO ovveride register, The Xnor algorithm is not included in the PBIST ROM.

    We run for the Xnor algorithm from PBIST tester interface as a production test only  and not from the ROM interface which is used during self test. This is the reason why it is not included in the data sheet.

    If the ROM test is run as a part of the Self test my recommendation would be to run the Triple read fast test as you get the best bang for the buck i.e coverage vs run time

     

    Regards,

     Hari