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Non-sequential counter design

  1. Apr 11, 2014 #1

    JJBladester

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    Gold Member

    1. The problem statement, all variables and given/known data

    Hello, I need to create a digital counter that follows this sequence:


    00, 10, 01, 11, 01, 00, 11, 10
    A , C, B, D, B, A, D, C


    2. Relevant equations

    N/A

    3. The attempt at a solution

    There are four states (A = 00, B = 01, C = 10, D = 11) so I believe I need two flip-flops. There are eight transitions and then the counter should wrap. I'm having a hard time drawing the state diagram for this.

    Here's what I have so far.

    non-sequential-counter-state-diagram.jpg
     
  2. jcsd
  3. Apr 11, 2014 #2

    berkeman

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    Staff: Mentor

    The sequence does not repeat in what you showed, so you will need to add another FF to tell you whether it's the first time through AC... or 2nd time through AD...
     
  4. Apr 13, 2014 #3

    LCKurtz

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    Hey Bladester, wasn't it a couple of years ago when you posted your first problem of this type? You must be about ready to graduate, eh?

    I agree with Berkeman. You need 8 states instead of 4. Otherwise, for example, when the machine is in state A, how can it know whether to proceed to C or D next? So try:$$
    y_2y_1y_0=000, 010, 001, 011, 101, 100, 111, 110, 000$$Then the output ##y_1y_0## gives you your sequence.
     
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