Multiple choice

Which of the following input combinations is not allowed in a SR flip-flop?

  1. S = 0, R = 0

  2. S = 0, R = 1

  3. S = 1, R = 0

  4. S = 1, R = 1

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a standard SR flip-flop, the state S = 1, R = 1 is considered invalid or forbidden because it leads to an indeterminate state where both outputs Q and Q' attempt to go to 0.