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If the state machine described in figure should have a stable state, the restriction on the inputs is given by

  1. $a.b=1$
  2. $a+b=1$
  3. $\bar{a} + \bar{b} =0$
  4. $\overline{a.b}=1$
  5. $\overline{a+b} =1$
in Digital Logic by Veteran (105k points)
edited by | 1.6k views

2 Answers

+1 vote
Best answer
If $a = 0$ state changes from $S_1$ to $S_2$ and if $b = 0$ state changes from $S_2$ to $S_1.$

So, $a = 0, b = 0$ is surely not a stable state as then the states will be oscillating. So, the condition for stability is that both $a$ and $b$ should not be $0$ together which is given by $a+b = 1$ or $\overline {ab} = 0.$

Options A and C are equivalent and both ensures stable states albeit by enforcing stricter than required conditions.

Correct Answer: Option B.
by Veteran (424k points)
+1 vote

Answer is B) 

by Active (4.1k points)
0
explain please, how r u solving it?
0
explain plz.....
0
What is the meaning of stable state? And please someone add explanation.
0

@Swapnil Naik stable  state means after certain time(after all delays) it gets stable and doesn't change. For above diagram to make sure output does not change, at S1 we should apply a=1 and at S2 we should apply b=1. Any other input will make our output fluctuate between S1 and S2.

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