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Consider the sequential circuit shown in the figure,  where both flip-flops used are positive edge-triggered $\text{D}$ flip-flops.

The number of states in the state transition diagram of this circuit that have a transition back to the same state on some value of "in" is ____

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Best answer
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70 votes

Answer Is 2.

Here 00 on input 0 and 11 on input 1 have transition back to itself. So, answer is 2.

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151 votes

Right answer is $2.$

The transition back to the same state means self-loop, they are asking the number of self-loop states.
The number of self-loop states is $2\:\text{(which are}\: 00\: \text{and}\: 11).$

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17 votes
17 votes

Correct answer is 2.

D(left) flip-flop's output depends on value of D. It is given that D (left) takes input as "in" which can be either 1 or 0 so,

we can see that 00 on input 0 have transition back to itself. and 11 on input 1 have transition back to itself.

7 votes
7 votes

 

 

 

 

 

 

State Table of counter can be constructed as:

Q1 Q0 in D1 D0 Q1N Q0N
0 0 0 0 0 0 0
0 0 1 0 1 0 1
0 1 0 1 0 1 0
0 1 1 1 1 1 1
1 0 0 0 0 0 0
1 0 1 0 1 0 1
1 1 0 1 0 1 0
1 1 1 1 1 1 1

Only two states as highlighted have transitions back to themselves.

Answer:

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