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Homework Help: What is this circuit functionality?

  1. Jan 21, 2014 #1
    1. The problem statement, all variables and given/known data
    The question asks the circuit's functionality


    FA = Full Adder
    2. Relevant equations
    3. The attempt at a solution
    I got two questions:
    1) To understand this circuit functionality should I write it output considering all input possibilities (32 lines)?
    2) If the carry out in the last full adder is input in the first full adder, how can I establish an output? What if the last carry out affects the circuit, then changes the output?
  2. jcsd
  3. Jan 22, 2014 #2
    Your diagram only shows two adders.
    Notice that the "I3" signal provides two of the adder inputs to the left adder.
    So what effect will I3 have on S?
  4. Jan 22, 2014 #3
    hey .Scott thanks for helping.

    It's a thumbnail, click to see the full image

    The carry-in will say who S is?

  5. Jan 22, 2014 #4
    And that provides one way of answering your second question.

    Nothing that happens in the two right side adders will ever affect the left side adder.
    Also, the second adder from the left is just passing signals (I3 to S1, 2nd carry to S).
  6. Jan 22, 2014 #5
    Thanks for the help .Scott!
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