JK Flip flop skizze

Discussion in 'Homework Help' started by thexy, Dec 14, 2015.

  1. thexy

    Thread Starter Member

    Dec 13, 2015
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    JKff.jpg
    It's given time course of the inputs. I need to circle is Q 1,0 or not known (unbekannt). Can someone help me with this example?

    Mod edit: reduced image size (after WBahn did it below) to reduce loading times.
     
    Last edited by a moderator: Dec 14, 2015
  2. WBahn

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    Mar 31, 2012
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    Let's first see about getting your image to a reasonable size and orientation:

    image.jpeg

    Next, you need to show YOUR best attempt to solve YOUR problem.

    Take it one step at a time.

    For slot 1, do you know what the state of the flip flop is?
     
  3. thexy

    Thread Starter Member

    Dec 13, 2015
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    No :/
     
  4. WBahn

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    I think I misread your intent. I thought you were refusing to answer the question, when in fact I think you WERE answering the question.

    That is correct, you do not know what the initial state of the flip flop is.

    That's fine -- that's one of the three options available to you. So now go on to step #2.
     
  5. thexy

    Thread Starter Member

    Dec 13, 2015
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    What is step 2?
     
  6. WBahn

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    The step after step 1. :D

    I'm referring to time slot #2 (you already have #1 done and there are a total of 12).
     
  7. WBahn

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    Mar 31, 2012
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    BTW: What does "Zeitabschnitt" translate to? Time slot? Time period?
     
  8. thexy

    Thread Starter Member

    Dec 13, 2015
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    But I don't know where should go 0,1 or not known
     
  9. thexy

    Thread Starter Member

    Dec 13, 2015
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    Time course/period
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    Hint: A flip-flop changes it's state ONLY on the rising edge of the clock (CLK).
     
  11. thexy

    Thread Starter Member

    Dec 13, 2015
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    Is Q 001unknown001001unknown0
     
  12. Papabravo

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    Feb 24, 2006
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    Q is unknown until the first rising clock edge which occurs in period #5. The value of Q in period #5 depends on the values of J, K, and possibly Q in period #4 according to the work you did on understanding the state machine diagram.
     
  13. thexy

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    Dec 13, 2015
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    Still don't understand
     
  14. Papabravo

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    1. When the clock signal (CLK) is HIGH, the output Q cannot change.
    2. When the clock signal (CLK) is LOW, the output Q cannot change.
    3. When the clock signal (CLK) has a falling edge (a transition from HIGH to LOW), the output Q cannot change.
    The clock signal has it's first rising edge (a transition from LOW to HIGH), at the beginning of period #5

    Therefore Q must be unknown in periods #1, #2, #3, and #4 because it was unknown in time period #1, and it has not changed.
    Just before the rising edge at the beginning of time period #5, J=K=1 which means that when the rising clock edge arrives the flip-flop will do what?
    Choose one of the following:
    1. Clear to 0
    2. Set to 1
    3. Do nothing
    4. Toggle
    If your answer is 1 or 2 then you know the value of Q. If your answer is 3 or 4, then you still don't know and you must proceed to the next step. which time period has the next rising edge of the clock (CLK)?
     
  15. thexy

    Thread Starter Member

    Dec 13, 2015
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    How I know that in period 5 J and K=1
     
  16. Papabravo

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    You look at the diagram.
    1. In time period #5, J is clearly higher than it is in time period #6
    2. In time period #5, K is clearly higher than it is in time period #3
    To me the diagram is showing quite clearly the values 0 and 1, true and false, high and low. What did you think the diagram was showing?
     
  17. thexy

    Thread Starter Member

    Dec 13, 2015
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    Same, but i just started learning flip flops so it's still unclear to me. So J is 1 until period 6 or?
     
  18. Papabravo

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    Yes.
    1. J=1 for periods 1 through 5
    2. J=0 for periods 6 through 8
    3. J=1 for periods 9 through 12
    Similarly for K and CLK.
     
  19. thexy

    Thread Starter Member

    Dec 13, 2015
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    Ok I understand that. Can you explain me how to get value ofQ?
     
  20. Papabravo

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    See post #14 in this thread. The values of J and K just before the rising clock edge determine the value of Q according to the state machine that you analyzed in your previous thread on the JK state machine. I wrote out the behavioral description of what happens when J and K assume certain values. Go back to that previous thread
    http://forum.allaboutcircuits.com/threads/jk-flip-flops.118483/page-2
    reread what I wrote in post #26, and this time pay attention so I don't have to keep repeating myself.
     
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