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When an SRAM is power - uped what state do its locations have?

  1. Dec 18, 2012 #1
    Hi PF,
    I am searching for a good entropy source for random number generation. I want to know if when an SRAM is powered will its all contents be high(1) or low (0) or do it contain random bits unpredictable.

    -Devanand T
     
  2. jcsd
  3. Dec 18, 2012 #2
    I think that is up to the manufacturer. However, I do believe that it will be either High or Low. I don't think you will find one where it is random however.
     
  4. Dec 18, 2012 #3

    nsaspook

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    The memory cells are designed to be identical during the manufacturing process but small variations in the process across even a small die will generate a small bias in most cells that will normally cause them to be a 1 or 0 during power-up but usually there is also a sizable number of cells that are close to a state balance that can randomly be a 1 or 0 due to thermal noise or other random events.

    http://www.cs.umass.edu/~kevinfu/papers/holcomb-FERNS-IEEE-Computers.pdf
     
    Last edited: Dec 18, 2012
  5. Dec 18, 2012 #4
    Thanks for the reply... :)
     
  6. Dec 18, 2012 #5

    nsaspook

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    Something you have to watch out for when looking for random bits in SRAM is the default actions of the software tools. The usual default is to zero all memory in the run-time startup module but most embedded software systems will have a option in the linker not to zero or initialize memory on power up.
     
  7. Dec 18, 2012 #6
    Thank you for the tip...:smile:
     
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