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  #1  
Old 03-18-2009, 01:05 PM
Astrokit Astrokit is offline
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Default [Urgent] Design a counter with using D Flip-Flop

The question is :
Design a counter that counts pulses on line w and displays the count in the sequence 0,2,1,3,0,2, ... Use D Flip-Flops in your circuit.

i wanna ask how to design this circuit?
What are the steps to design this circuit?
and What is the answer of this question?

the ans. of the expressions are D(input) of A = A XOR B and D(input) of B = not A??

thank a lot~ =]
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  #2  
Old 03-18-2009, 11:44 PM
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Papabravo Papabravo is offline
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Write a Truth Table
Code:
 A  B  |  P  Q
---------------
 0  0  |  1  0
 0  1  |  1  1
 1  0  |  0  1
 1  1  |  0  0
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Columns A and B represent the current Q-output state of each of the D-Flip-Flops
Columns P and Q represent the next Q-output state of D-Flip-Flops A and B respectively.
When you present the next Q-output state on the D-inputs, the sequence of states is:
Code:
0 -> 2 -> 1 -> 3 -> 0 ...
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By inspection:
Code:
P = .NOT. A   
Q = A .XOR. B = (A .AND. .NOT. B) .OR. (.NOT. A .AND. B)
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P and Q could, of course, be any functions of two boolean variables, and the sequences would change accordingly.
[Question] What sequence do you get if you swap the functions for P and Q?

It's not rocket science after all, just boolean algebra.
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  #3  
Old 03-18-2009, 11:51 PM
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wr8y wr8y is offline
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Quote:
Originally Posted by Papabravo View Post

It's not rocket science after all, just boolean algebra.
That Boolean guy was WAY ahead of his time.

But I still think Boolean Algebra is weird stuff.
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Old 03-19-2009, 02:07 AM
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Papabravo Papabravo is offline
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Quote:
Originally Posted by wr8y View Post
That Boolean guy was WAY ahead of his time.

But I still think Boolean Algebra is weird stuff.
That's George Boole,

http://en.wikipedia.org/wiki/George_Boole

and I think Tensor Algebra, Riemanian Manifolds, Fractal Geometry, and Stochastic Calculus are way more wierd and complicated. Just my opinion -- I could be wrong.

http://en.wikipedia.org/wiki/Tensor_algebra
http://en.wikipedia.org/wiki/Riemannian_manifold
http://en.wikipedia.org/wiki/Fractal
http://en.wikipedia.org/wiki/Stochastic_calculus
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Last edited by Papabravo; 03-19-2009 at 02:12 AM.
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