Flip Flops help, I have an exam this Friday! Cramming!!!!!!!

Discussion in 'Homework Help' started by jshakil, May 4, 2015.

  1. jshakil

    Thread Starter New Member

    May 4, 2015
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    Hi, I need help with this problem, (I'm going to be posting a bit more) I don't want any answers, but instead I would like help on how to solve the problem. I have been struggling with this stuff and don't know what to do. So I've decided to come here. Thank you in advance! Homework 1.png
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
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    Since are using a flip flop that is sensitive to the falling clock edge (and assuming the setup and hold times aren't violated*), Q <= D at each falling edge.

    So, at each falling edge of the clock signal, what is D? The value of D will be output on Q at the clock transition.

    *given the nature of this problem, it is probably safe to assume no setup and hold times for this flip flop.
     
  3. jshakil

    Thread Starter New Member

    May 4, 2015
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    Okay, so I know that D=Q. So at the falling edge of the clock, that's where Q will be whatever D is, right?
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
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    The falling clock edge is the point Q changes to be what D is at that point, yes - Q doesn't change at any other time.

    So, Q gets the value of D at the falling edge and holds its value until the next falling clock edge.
     
  5. jshakil

    Thread Starter New Member

    May 4, 2015
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    Okay, awesome! I'm going to put my results in paint, and upload it here for you to look at if that' alright. Thank you tshuck
     
    Last edited by a moderator: May 5, 2015
  6. jshakil

    Thread Starter New Member

    May 4, 2015
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    Homework 1 solution.png
    I came up with this...
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
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    That looks right to me, though your question is also asking for the value at t=35ms, which your diagram doesn't seem to account for...
     
  8. jshakil

    Thread Starter New Member

    May 4, 2015
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    I just submitted the answers and it says they were partially correct. (It doesn't give information on which were correct/incorrect)

    I'm going to try this again when I come back from work. I'll let you know. Thank you for your help so far tshuck.
     
  9. tshuck

    Well-Known Member

    Oct 18, 2012
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    I would suggest you examine the value of Q at t=35ms...
     
  10. jshakil

    Thread Starter New Member

    May 4, 2015
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    Ah okay, so that would be 0-->1 for the 35ms.
     
  11. tshuck

    Well-Known Member

    Oct 18, 2012
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    Thats it! :)
     
  12. jshakil

    Thread Starter New Member

    May 4, 2015
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    Thank you, awesome news. I just submitted it and it came out correct. Now on to the next one!
     
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