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Homework Help: Generaly when designing mealy or moore ckts when to pick which?

  1. Mar 26, 2007 #1
    1. The problem statement, all variables and given/known data

    Not really a HW question but say we follow the steps in converting a state diagram down to its excitation table - how do we determine whether the best ckt implementation would be best implemented with either a mealy or a moore system

    2. Relevant equations

    mealy :
    state equation : Q = f(present state, current inputs)
    output equation: Z = h(present state, current inputs)

    Moore :
    state eqaution : Q = f(present state, current inputs)
    output equation: Z = h(present state)


    3. The attempt at a solution

    1) granted we 're given a function for a truth table
    f(A,B,C,D...,etc) = logic function

    2) we convert it into a state / excitation table depending on the kind of flip flops we want to use

    Code (Text):

    D flip flop:

    q  Q | D
    0..0    0  
    0  1    1
    1  0    0
    1  1    1

    not Q = C' . d + Q.D
    or Q = D

    T flip flops

    q  Q | T
    0  0    0
    0  1    1
    1  0    1
    1  1    0

    Q = Tq' + T'q

    J/K flip flops

    q Q | J  K
    0 0    0 x
    0 1    1 x
    1 0    x 1
    1 1    x 0

    let x = don't care values

    Q = Jq' + K'q
     
     
    Last edited: Mar 26, 2007
  2. jcsd
  3. Mar 27, 2007 #2

    berkeman

    User Avatar

    Staff: Mentor

    I generally use the Moore structure, and I think it is the more commonly used. I think you would only use the Mealy structure if you needed to propagate input changes through the structure a clock earlier than you get with the Moore.
     
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