# [Urgent] Design a counter with using D Flip-Flop

Discussion in 'Homework Help' started by Astrokit, Mar 18, 2009.

1. ### Astrokit Thread Starter New Member

Mar 18, 2009
1
0
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~ =]

2. ### Papabravo Expert

Feb 24, 2006
11,783
2,496
Write a Truth Table
Code ( (Unknown Language)):
1.
2.  A  B  |  P  Q
3. ---------------
4.  0  0  |  1  0
5.  0  1  |  1  1
6.  1  0  |  0  1
7.  1  1  |  0  0
8.
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 ( (Unknown Language)):
1.
2. 0 -> 2 -> 1 -> 3 -> 0 ...
3.
By inspection:
Code ( (Unknown Language)):
1.
2. P = .NOT. A
3. Q = A .XOR. B = (A .AND. .NOT. B) .OR. (.NOT. A .AND. B)
4.
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.

3. ### wr8y Active Member

Sep 16, 2008
232
1
That Boolean guy was WAY ahead of his time.

But I still think Boolean Algebra is weird stuff.

4. ### Papabravo Expert

Feb 24, 2006
11,783
2,496
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

Last edited: Mar 18, 2009