Need help to design a counter that follows a given sequence using D Flip Flops

Discussion in 'Homework Help' started by dragstang86, Nov 11, 2010.

  1. dragstang86

    Thread Starter New Member

    Nov 11, 2010
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    I need to design a counter diagram that follows a count sequence 0-2-4-1-0 using DFFs.

    The characteristic equation for the DFF is Q+ = D. I have the sequence in the present state and next state table but don't know where to go from there.

    Code ( (Unknown Language)):
    1.  
    2. Present State | Next State|Da |Db |Dc |
    3. 000           | 010       | 0 | 1 | 0
    4. 010           | 100       | 1 | 1 | 0
    5. 100           | 001       | 1 | 0 | 1
    6. 001           | 011       | 0 | 1 | 0
    7. 011           | 000       | 0 | 1 | 1
    8.  
    I appreciate any help. I have been trying to find a similar example for hours with no luck.

    I think what the main thing I need help with is how to go from the state table to the k-map. If what I have done in the state table is correct. So I guess the first question is, is my state table correct?

    Thanks for your help
     
    Last edited by a moderator: Nov 11, 2010
  2. bertus

    Administrator

    Apr 5, 2008
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  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    Be sure of your assignment. Your table shows a sequence 0-2-4-1-3-0.
     
    dragstang86 likes this.
  4. dragstang86

    Thread Starter New Member

    Nov 11, 2010
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    Thanks! The 3 shouldn't be in there. I mixed the numbers up with a state graph that I just put together that used that sequence. I couldn't figure out how to edit my post but it should read:

    Present State | Next State|Da |Db |Dc |
    000 | 010 | 0 | 1 | 0
    010 | 100 | 1 | 1 | 0
    100 | 001 | 1 | 0 | 1
    001 | 000 | 0 | 0 | 1
     
  5. dragstang86

    Thread Starter New Member

    Nov 11, 2010
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    Thanks for the suggestion. I read that thread but it is more involved than my problem and I'm not quite at that point yet in my circuit knowledge. I am just now trying to learn the basics of these flip flops.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    In the eBook at the top, there is this page on D flip-flops:
    http://www.allaboutcircuits.com/vol_4/chpt_10/4.html

    An other page with a lot of links is this one on the EDUCYPEDIA:
    http://www.educypedia.be/electronics/digitalflipflops.htm

    There are more pages like that over there on other digital subjects:

    Digital electronics:
    Arithmetic circuits D/A-A/D converters Number systems Codes and decoders Flip flops Technology Counters and registers General overview Technology-CMOS Digital logic Memories Technology-TTL Timers and oscillators

    Bertus
     
  7. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Isn't this just a 3-bit shift register,
    with outputs Q1, Q2, Q3
    ordered as q2, q1, q3
    ?
     
  8. Georacer

    Moderator

    Nov 25, 2009
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    4-bit actually; zero counts as information. It's a clever idea but usually homework assignments are very specific on the implementation methods.
     
  9. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I figured out the 4-bit requirement, but didn't edit the post because I thought I had provided enough information for the OP. :)
     
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