# Waveforms in D flip flop

Discussion in 'Homework Help' started by katerina22, Feb 8, 2009.

1. ### katerina22 Thread Starter New Member

Feb 6, 2009
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0
Hi everybody!Could someone tell me how to design output waveforms for D flip flop, when I know the CLK waveform and the input waveform? I have attached an example of an exercise.I am having an exam on Tuesday and I would appreciate any help!!

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2. ### beenthere Retired Moderator

Apr 20, 2004
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The Q output follows the clock AND the D input. If D is high and there is a clock, then Q will go high.

3. ### katerina22 Thread Starter New Member

Feb 6, 2009
6
0
I created the waveform Y1 but how can I create Y2? Y2 is the AND between Y1 and CLK?

4. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
Y2 will follow its D input, which is the Y1 output.

5. ### tuborggg Active Member

Jan 3, 2009
37
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No, Y2 is a copy of D of FF2 when there's a clk positive event.
What you should do is draw Y1, meaning, check every clk positive event check what is the wave in the D1 input, and copy it out.
Than, Y2 is actually the same as Y1 - just 1 clock later...
Y3 is checking each clock positive event, what's the Y1 NOR Y2....
Enjoy

Jan 3, 2009
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7. ### katerina22 Thread Starter New Member

Feb 6, 2009
6
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Thank you both!!

8. ### katerina22 Thread Starter New Member

Feb 6, 2009
6
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In my exercise there is an xor gate between Y1 and Y2. The result connects with the D input of the last FF. Y3 is D, isn't it?

9. ### katerina22 Thread Starter New Member

Feb 6, 2009
6
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Can I ask something else?How can I export the truth table from a MUX? I have attached an example of an exercise.

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10. ### tuborggg Active Member

Jan 3, 2009
37
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Enjoy, a short expl. inside.

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