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D Latch and D type Flip Flop Question

  1. May 2, 2014 #1
    1. The problem statement, all variables and given/known data
    Hello,



    I am thinking about the operation of the D latches and Flip Flops. I know
    the operation of Latch :
    When clock is hi:
    -Q follows D in simple combinational behaviour
    - D/Q path is transperant ( what I think it means what is on D can be seen on Q) ?
    At the transition from hi to low
    - Q output frozen
    -Non - combinational behaviour, Q ignores D intput changes.
    D-latch_zpsd7e2cfc7.jpg

    Flip Flop :
    When clock is low:
    - the 'master' is transperant
    -slave retained memorized output

    At the transition low- hi:
    -master stores input,slave transperant
    -slave passes master stored value to the output
    -'Data in' sampled at the rising clock edge, stored and passed to 'Data out'

    Screenshotfrom2014-05-02103224_zps0431e799.png




    My question is about the graphs under the diagrams. Should I take care only on the rising and folling edges of the clock ? Does it what only matters , I mean the values of D and Q on the rising and folling edges? If so, why the output waveform is like this, I mean it is changing during the hold, setup time ?

    Thanks

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 2, 2014 #2

    donpacino

    User Avatar
    Gold Member

    In a D flip flop the output only changes on a rising clock edge.
     
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