how many j k flipflop needed to count the series 0..1..0..2..0..3...0..1..0..2..0..3.. and so on

Discussion in 'Homework Help' started by Debasmita Bhoumik, Feb 14, 2016.

  1. Debasmita Bhoumik

    Thread Starter New Member

    Feb 14, 2016
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    0
    i think it will be 2. cz
    q1 q0
    0 0
    0 1
    0 0
    1 0
    0 0
    1 1
    0 0
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    759
    Welcome to AAC
    2 outputs, I say 2 FF
     
  3. RBR1317

    Active Member

    Nov 13, 2010
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    Consider how many unique states of '00' there are, i.e., when the next state after '00' produces a different result. How will the logic know which '00' state in the sequence it is at if there are only 2 FF?
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,413
    3,353
    RBR is correct.

    You are trying to design a state machine. Ask yourself how many unique states there are.

    0 1 0 2 0 3 ...

    There are six unique states. How many flip-flops will you require for six states?
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    A simple AND gates with a ripple counter would do it. The clock has to be a square wave.

    2 flip flops, 2 AND gates, and the clock.

    Need a schematic?
     
  6. Debasmita Bhoumik

    Thread Starter New Member

    Feb 14, 2016
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    0
    wendy, can u plz explain a little more?
     
  7. RBR1317

    Active Member

    Nov 13, 2010
    227
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    A signal chopper on the Q outputs will certainly display the correct series of numbers, but it will not 'count' the series.
     
    Last edited: Feb 15, 2016
  8. Wendy

    Moderator

    Mar 24, 2008
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    True enough, so you add a flip flop and do it. I'll try to draw something up.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    OK this is not complete, but it should give you the idea. I suspect this is homework, so it would not hurt for you to complete it.

    ff.png
     
  10. RBR1317

    Active Member

    Nov 13, 2010
    227
    47
    The problem of designing ripple counters, with gated outputs no less, is that it is a hit or miss operation. However, there are established design procedures for creating a fully synchronous sequential state machine using JK flip-flops. I tried to get a LibreOffice spreadsheet to implement the transition mapping procedure, starting with the sequential state table to automatically produce the sequential transition table, the index transition table, and from that to automatically draw the Karnaugh transition maps. However, it is still a manual process to go from the sequential table to the index table. Also, the spreadsheet has problems with persistent formatting of Boolean results to display as simple numbers (TRUE, FALSE vs 0,1). Nevertheless, here is the result of one possible design of a state machine to count 0,1,0,2,0,3,0,1... using 4 JK FF.
    Chopper-Counter-JKdirect.png
     
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