I understand that in a D latch, whenever the clock signal is high, Q matches D, and while the clock signal is low, it holds the previous state of D. For a D flip-flop, Q will hold whatever value D is at the exact moment C goes high, and will hold that same state until C goes high again. I am able to draw the clock diagram and identify these circuits. But I am not understanding the purpose of these components in a high level context.

  1. What exactly does the D latch and D flip-flop do? (Differences and similarity)
  2. From my understanding, it is to be able to "store" a bit value, but if that's the case, why not use an SR latch?

Edit: I have seen the following post. However, my question is a little more specific. I am asking specifically about a D latch/flip-flop. I also want to be able to differentiate how this is different from a SR latch, since it seems that their descriptions seem to do the same thing.

  • 1
    $\begingroup$ Possible duplicate of What is the exact difference between a latch & a flipflop? $\endgroup$ – David Richerby May 12 '16 at 20:29
  • $\begingroup$ I have also noted a second part to the question, asking about the difference between the D latch and SR latch. $\endgroup$ – Jonathan May 12 '16 at 20:33
  • $\begingroup$ This is part of the reason why we prefer one question per question! Your title says the question is about latches vs flip-flops but the question itself is also about other things. Since the question about latches vs flip-flops has already been answered, I suggest you edit your question to remove that part and focus on the part that's not already been answered. Don't forget to update the title. Thanks! $\endgroup$ – David Richerby May 12 '16 at 20:36
  • $\begingroup$ I have done my best to edit, is it ok now? $\endgroup$ – Jonathan May 12 '16 at 20:38

One big difference is that while the SR flipflop has a "not-allowed" state (i.e., inputs S=1, R=1), the D flipflop has no such condition.

Another difference, is that the D flipflop just mirrors the input into the output, while SR has two inputs: one for setting the ouput to 1, and one for resetting the output into a 0.

  • $\begingroup$ As the related thread answers the flipflop/latch question, here I unser the D vs SR question. $\endgroup$ – Ran G. May 12 '16 at 21:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.