Ripple counter using d flip flops

Discussion in 'Homework Help' started by vead, Aug 18, 2016.

  1. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    Hello
    I need help to understand logic of ripple counter. I understand the operation of d flip flops
    . _20160818_103858.JPG
    _20160818_112252.JPG
    I understand the operation of first flip flop but I don't understand what will output of second and third flip flop
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi vead,
    The 'D' inputs must be connected to the /Q output in order for the F/F to toggle.
    Look at this example image.
    Post your explanation of the operation.
    E
     
    • A07.gif
      A07.gif
      File size:
      30.2 KB
      Views:
      17
  3. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    Have you even tried?

    Draw a square wave for the clock signal into the first DFF. Since you understand the operation of D flip flops, you should have no trouble drawing the output of the first flip flop.

    Well, that IS the clock signal for the second flip flop. Since you understand the operation of D flip flops, you should have no trouble drawing the output of the second flip flop.

    Well, that IS the clock signal for the third flip flop. Since you understand the operation of D flip flops, you should have no trouble drawing the output of the third flip flop.

    Now look at the results. Do they correspond to a counter? Which bit is the msb and which bit is the lsb? Is it running forward or backward?
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    How do you manage to produce those very hard to read images?
    I have used GIMP to correct the white balance and scaled them down:

    VEAD_20160818_103858.JPG
    VEAD_20160818_112252.JPG
    Bertus
     
  5. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    I think the response of counter should be below
    At first raising clock
    Input I2,I1,I0=000
    Output q2,q1,q0=000
    At second raising clock
    Input=010
    Output=010
    At third raising clock
    Input=011
    Output =011
    ....... So on
    Counter count number 01234567
    Am I correct?
     
  6. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    What do you use for the input signal at the D inputs of the flip-flops?
    When D does not change, the output will not change.

    Bertus
     
  7. vead

    Thread Starter Active Member

    Nov 24, 2011
    621
    8
    I am stuck here. If there is no input data then how to know behavior of counter. I have seen in book. D input should be connected to /Q.
    raising edge - output of flip flop will be same as input
    Falling edge - output does not change
    Clock high- no change
    Clock low- no change
     
  8. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
    Hello,

    Have a look at chapter 7.6 of the attached PDF.

    Bertus
     
  9. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    You don't have an input to any of the flip flops, so how can you say what the input is?
     
Loading...