+ Post New Thread
Results 1 to 13 of 13
  1. #1
    Junior Member level 3
    Points: 200, Level: 2

    Join Date
    Apr 2019
    Posts
    27
    Helped
    0 / 0
    Points
    200
    Level
    2

    scan chain inside memory

    How can scan chains be present inside memories? What are the functionalities of these sequential cells inside a memory so that during DFT these sequential flipflops are replaced by scan flipflops.

  2. #2
    Advanced Member level 5
    Points: 8,683, Level: 22

    Join Date
    Apr 2016
    Posts
    1,823
    Helped
    320 / 320
    Points
    8,683
    Level
    22

    Re: scan chain inside memory

    Quote Originally Posted by fragnen View Post
    How can scan chains be present inside memories? What are the functionalities of these sequential cells inside a memory so that during DFT these sequential flipflops are replaced by scan flipflops.
    I think you got your terminology wrong. Memories don't have flip-flops inside. Classical SRAM memory has bit-cells.
    Really, I am not Sam.



  3. #3
    Junior Member level 3
    Points: 200, Level: 2

    Join Date
    Apr 2019
    Posts
    27
    Helped
    0 / 0
    Points
    200
    Level
    2

    Re: scan chain inside memory

    Quote Originally Posted by ThisIsNotSam View Post
    I think you got your terminology wrong. Memories don't have flip-flops inside. Classical SRAM memory has bit-cells.
    The reason I started this thread is that I also though in your way. The terminology is not wrong.



    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 5
    Points: 8,683, Level: 22

    Join Date
    Apr 2016
    Posts
    1,823
    Helped
    320 / 320
    Points
    8,683
    Level
    22

    Re: scan chain inside memory

    Quote Originally Posted by fragnen View Post
    The reason I started this thread is that I also though in your way. The terminology is not wrong.
    Then you have to explain yourself because clearly we are not talking about the same thing.
    Really, I am not Sam.



    •   AltAdvertisement

        
       

  5. #5
    Newbie level 1
    Points: 90, Level: 1

    Join Date
    Apr 2019
    Posts
    1
    Helped
    0 / 0
    Points
    90
    Level
    1

    Re: scan chain inside memory

    Are you implying that memory cells are re-used as part of the scan chain? I don't think that is the case. Scan circuitry would be added on top of the existing memory circuit. And as mentioned already, the devices used in memory and in scan chains are not the same.



    •   AltAdvertisement

        
       

  6. #6
    Junior Member level 3
    Points: 200, Level: 2

    Join Date
    Apr 2019
    Posts
    27
    Helped
    0 / 0
    Points
    200
    Level
    2

    Re: scan chain inside memory

    Quote Originally Posted by anuraagkn View Post
    Are you implying that memory cells are re-used as part of the scan chain? I don't think that is the case. Scan circuitry would be added on top of the existing memory circuit. And as mentioned already, the devices used in memory and in scan chains are not the same.
    Memories were purchased from third part and the documents of those memories show scan pins. What scan chains are there inside this memories?



  7. #7
    Advanced Member level 5
    Points: 8,683, Level: 22

    Join Date
    Apr 2016
    Posts
    1,823
    Helped
    320 / 320
    Points
    8,683
    Level
    22

    Re: scan chain inside memory

    Quote Originally Posted by fragnen View Post
    Memories were purchased from third part and the documents of those memories show scan pins. What scan chains are there inside this memories?
    ... this is a completely different question from your original question. I suggest you google MBIST, BIST, JTAG, boundary scan, etc. And after that, read the documentation of the purchased memory carefully (I am sure they tell you how to test their memories).
    Really, I am not Sam.



  8. #8
    Junior Member level 3
    Points: 200, Level: 2

    Join Date
    Apr 2019
    Posts
    27
    Helped
    0 / 0
    Points
    200
    Level
    2

    Re: scan chain inside memory

    Quote Originally Posted by ThisIsNotSam View Post
    ... this is a completely different question from your original question. I suggest you google MBIST, BIST, JTAG, boundary scan, etc. And after that, read the documentation of the purchased memory carefully (I am sure they tell you how to test their memories).
    Aware of MBIST, BIST, JTAG. Can you please state what are those scan-in pins for in the memory that are purchased. I do not have the document to read hot those memories should be tested.



  9. #9
    Advanced Member level 5
    Points: 8,683, Level: 22

    Join Date
    Apr 2016
    Posts
    1,823
    Helped
    320 / 320
    Points
    8,683
    Level
    22

    Re: scan chain inside memory

    Quote Originally Posted by fragnen View Post
    Aware of MBIST, BIST, JTAG. Can you please state what are those scan-in pins for in the memory that are purchased. I do not have the document to read hot those memories should be tested.
    I can only make an educated guess that the memory also has some controller logic or buffer that is implemented with flip-flops and that those are tested through a conventional scan chain. The memory bits themselves will NEVER be tested that way, bitcells don't have scan inputs.

    But then again, there are so many things that don't make sense in this thread that my guess is a pointless exercise.
    Really, I am not Sam.



  10. #10
    Junior Member level 3
    Points: 200, Level: 2

    Join Date
    Apr 2019
    Posts
    27
    Helped
    0 / 0
    Points
    200
    Level
    2

    Re: scan chain inside memory

    Quote Originally Posted by ThisIsNotSam View Post
    I can only make an educated guess that the memory also has some controller logic or buffer that is implemented with flip-flops and that those are tested through a conventional scan chain. The memory bits themselves will NEVER be tested that way, bitcells don't have scan inputs.

    But then again, there are so many things that don't make sense in this thread that my guess is a pointless exercise.
    That I am aware memory bit cells are not tested through scan chain.

    What can there be inside the memory that requires scan input? Why did you talk of MBIST, JTAG and BIST?



  11. #11
    Advanced Member level 5
    Points: 8,683, Level: 22

    Join Date
    Apr 2016
    Posts
    1,823
    Helped
    320 / 320
    Points
    8,683
    Level
    22

    Re: scan chain inside memory

    Quote Originally Posted by fragnen View Post
    That I am aware memory bit cells are not tested through scan chain.
    You are going in circles now. You started this thread saying exactly the opposite.
    Really, I am not Sam.



    •   AltAdvertisement

        
       

  12. #12
    Newbie level 4
    Points: 100, Level: 1

    Join Date
    Jul 2019
    Posts
    9
    Helped
    0 / 0
    Points
    100
    Level
    1

    Re: scan chain inside memory

    There will be scan cells but they are used to bypass the memory to get controllability and observability of the design



  13. #13
    Junior Member level 1
    Points: 523, Level: 4

    Join Date
    Mar 2017
    Posts
    17
    Helped
    0 / 0
    Points
    523
    Level
    4

    Re: scan chain inside memory

    Quote Originally Posted by Varun124 View Post
    There will be scan cells but they are used to bypass the memory to get controllability and observability of the design
    That's correct, in my experiment we also have ram sequential pattern to cover all logic from FLOP to D pin of memory.



--[[ ]]--