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Homework Help: Need help with a mod-6 counter using JK flip flops w/ control bit

  1. Aug 4, 2017 #1
    1. The problem statement, all variables and given/known data

    I am currently working on an assignment in which I create a six-state up/down counter. The purpose is to understand the functionality of flip-flops within a circuit among other things.

    There are 3 input bits (Q2,Q1, Q0), and a 4th control bit (C) which determines the direction that the counter runs. Naturally I derived a design from 3 next-state function 4x4 k-maps, and I created a design utilizing D flip flops, which runs perfectly forwards and backwards.

    The second part asks me to convert from a D-ff design to using JK flip flops. I mostly understand the logic of how a JK flip flop works, but I can't for the life of me figure out how to fit that extra control bit into the translation.

    2. Relevant equations

    3. The attempt at a solution

    My trouble comes in keeping the circuit bi-directional. I am very confused about what to do with the control bit. I created an excitation table for the next states, which I believe is correct, and conversions for the six JK k-maps (K2, K1, K0, J2, J1, and J0). However, I now have two sets of J & K values, one for C=0 and one for C=1.

    In trying to work it out, I populated the 6 k-maps with the proper data (only C=0) and constructed a function/circuit, but of course it only clocks in one direction whether C is set to 0 or 1. What am I supposed to do with the control bit when I translate to the new k-maps for K2, K1 etc... which each only take the three Q input bits?

    What am I missing in the logic of utilizing JK flip flops for 3 input bits when there is the control bit as well?

    Hopefully thats clear, I'm sure it is just a conceptual problem I am having trouble figuring out. If anyone wants me to upload my excitation table or any other part I've done so far, let me know. Any help is greatly appreciated!
  2. jcsd
  3. Aug 4, 2017 #2


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    Staff: Mentor

    Welcome to the PF. :smile:

    Yes, please upload your work for the D-FF version and your work so far for the JK-FF version. That will help a lot in our efforts to help you out. :smile:
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