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Parallel adder SOP Expression

  1. Feb 19, 2015 #1

    My working:
    S3 = A
    S2 = B
    S1 = C'
    S0 = D'

    F = Sum-Minterm(0, 1, 2, 4, 5, 8) (Basically i find when is X smaller then Y)
    Used Kmap to arrive at
    A'C' + B'C'D' + A'B'D'

    Am i correct?
  2. jcsd
  3. Feb 19, 2015 #2


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    Did you check your result? If ABCD = 1111, what should F be?
  4. Feb 19, 2015 #3
    Ok my formula was Si = Xi XOR Yi XOR C

    That was wrong. Should be Ci. hmmmm

    I need clue bro lol
  5. Feb 19, 2015 #4


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    Focus on the relationship between the output F and the inputs ABCD. In other words: treat the whole thing as a black box with inputs ABCD and output F.
  6. Feb 19, 2015 #5
    So must i like do the excess-3 table and compare ab < cd values
  7. Feb 19, 2015 #6


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    "Excess-3", strictly speaking, operates on BCD (binary coded decimal) values. Since the input is not constrained to BCD, it's better to say "So must I like just add 3 to the input..."

    Not making fun, just trying to make a fine point. And yes, then do the comparison.
  8. Feb 19, 2015 #7
    yeayea! thank you man solved it lol. I was thinking it too complicatedly.
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