Convert a D flip flop into JK

Discussion in 'Homework Help' started by wind_blast942, Nov 19, 2010.

  1. wind_blast942

    wind_blast942 Thread Starter New Member

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    I am confused on how to systematically convert a D flip flop into a JK flip flop
    J K Q Q+ D
    0 0 0 0
    0 0 1 1
    0 1 0 0
    0 1 1 0
    1 0 0 1
    1 0 1 1
    1 1 0 1
    1 1 1 0

    I am able to merge the characteristic and excitation table together, but since there are some values where Q to Q+ changes from 1 to 0, and there is no excitation
    possible for a d flip flop to effect this change.

    In this case what should i do?
  2. Georacer

    Georacer Moderator Staff Member

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    A FF is always excited by its input. As long as the clock is pulsing it will change its state according to the J K and Q (or D and Q) data.

    What you need to do is extract the Boolean function Q+=F(J,K,Q) and drive its output in the D input of your FF. Since a D FF will drive its next state where its D input is, you will be able to control the FF by changing that input.
  3. wind_blast942

    wind_blast942 Thread Starter New Member

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    By solving Q+ = f(J,K,Q), i get J AND (NOT Q); so does it mean i connect this expression into the D ff?

    But in this case wouldn't K not affect the flip flop at all?

    [​IMG]
  4. Georacer

    Georacer Moderator Staff Member

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    Maybe you need to check again your Karnaugh map solution. Try it once more.
  5. wind_blast942

    wind_blast942 Thread Starter New Member

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    My mistake it should be Q+ = (J . |Q) + (|K . Q)

    So to confirm will the circuit look like this? With Q as the output and J,K as the input?

    [​IMG]
  6. Georacer

    Georacer Moderator Staff Member

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    Still no...

    Are you sure you 're making this K-map?
    [​IMG]
    I suggest a revision on your K-maps.

    Attached Files:

  7. wind_blast942

    wind_blast942 Thread Starter New Member

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    But doesn't this K-Map give: (J . |Q) + (|K . Q) ?
  8. Georacer

    Georacer Moderator Staff Member

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    Yes, it does. My bad.
    F=JQ'+K'Q is the correct answer.
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