Exam-style question
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In a SR latch, what happens when both S and R inputs are high?.
- A.The latch holds its previous state.
- B.The latch resets to 0.
- C.The latch sets to 1.
- D.The latch enters an undefined or forbidden state.
Model answer
What a good answer should say
- The latch enters an undefined or forbidden state.
Explanation
Why this works
Rule: In an SR latch, the forbidden state occurs when S=1 and R=1. Substitution: S=1, R=1.
Working: Both inputs being high forces both outputs to try to be 1 and 0 simultaneously, which is impossible. Answer: The latch enters an undefined state.
Conclusion: The SR latch cannot have both S and R high; it is a forbidden condition.
Common mistake
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