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Homework Help: D flip-flop, S-R master-slave flip-flop, falling edge of clock, NAND

  1. Mar 2, 2013 #1


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    1. The problem statement, all variables and given/known data
    A D flip-flop is implemented using an S-R master-slave flip-flop that changes states on the falling edge of the clock. Assume that the circuit is fabricated using NAND gates and that each gate has exactly a propagation delay Tpd = 1ns.

    a) Determine the set-up (Tsu), hold (Th), and propagation delay (Tpd) parameters for this D flip-flop.

    *Convert a master-slave S-R flip-slop into a J-K using the appropriate gates.
    *Compare the behaviour of this circuit to a falling edge-triggered J-K flip-flop. What are the fundamental differences?

    2. Relevant equations

    3. The attempt at a solution
    I watched this video ( ) and, it helped me somewhat understand the basics but, I am still not too certain as to what is going on, specifically, and I'm unsure as to how I should start this problem.

    I don't know what else to say but, if you need to me to say something, ask me.

    Any help in solving this problem would be greatly appreciated!
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Mar 4, 2013 #2


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    Draw the logic diagram for the D-Type using NAND gates. Explore what happens when you keep the clock = 1 but D changes. The change on D will propagate around inside the latch. What happens if the clock falls while that's still happening? Will the output Q end up as the old or new value of D? If you want Q to become the new value of D how long do you need to allow for the change to propagate around inside the latch before the clock can change. That's the set up time.
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