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Homework Help: A question about flip flop

  1. Mar 16, 2008 #1

    if one of them was 0 then no problem because the other wire value doesnt matter
    but here we have both 1
    if i look on one of the NANDs gates we have one input of 1
    and the other input value is unknown because it comes from the resolt of the other gate
    which has the same problem

    how to solve it??
  2. jcsd
  3. Mar 17, 2008 #2


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    Gold Member

    When SET = RESET = 1, there are two likely outputs of our RS NAND latch. We can have Q = 0 and Q(not) = 1. In this case, the input to the lower NAND gate is 0 and 1, which gives Q(not) = 1. The inputs to the first NAND are both 1 which makes Q = 0.

    The second possibility is to have Q = 1 and Q(not) = 0. The same analysis used above can be applied for this situation.

    So which situation occurs first? This depends on what has occurred previously at the inputs.
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