1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Non-sequential counter design

  1. Apr 11, 2014 #1


    User Avatar
    Gold Member

    1. The problem statement, all variables and given/known data

    Hello, I need to create a digital counter that follows this sequence:

    00, 10, 01, 11, 01, 00, 11, 10
    A , C, B, D, B, A, D, C

    2. Relevant equations


    3. The attempt at a solution

    There are four states (A = 00, B = 01, C = 10, D = 11) so I believe I need two flip-flops. There are eight transitions and then the counter should wrap. I'm having a hard time drawing the state diagram for this.

    Here's what I have so far.

  2. jcsd
  3. Apr 11, 2014 #2


    User Avatar

    Staff: Mentor

    The sequence does not repeat in what you showed, so you will need to add another FF to tell you whether it's the first time through AC... or 2nd time through AD...
  4. Apr 13, 2014 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hey Bladester, wasn't it a couple of years ago when you posted your first problem of this type? You must be about ready to graduate, eh?

    I agree with Berkeman. You need 8 states instead of 4. Otherwise, for example, when the machine is in state A, how can it know whether to proceed to C or D next? So try:$$
    y_2y_1y_0=000, 010, 001, 011, 101, 100, 111, 110, 000$$Then the output ##y_1y_0## gives you your sequence.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted