The GATE Grind

GATE 2020 EC – Question 49

Digital Circuits · Sequential Circuits · 2 marks · Multiple choice

The state diagram of a sequence detector is shown below. State $S_0$ is the initial state of the sequence detector. If the output is 1, then

Diagram for GATE 2020 EC question 49
  1. the sequence 01010 is detected.
  2. the sequence 01011 is detected.
  3. the sequence 01110 is detected.
  4. the sequence 01001 is detected.

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Show answer and explanation

Correct answer: (A) the sequence 01010 is detected.

Explanation

The only transition with output 1 is $S_4\to S_3$ on input 0. Reaching $S_4$ from $S_0$ requires $S_0\xrightarrow{0}S_1\xrightarrow{1}S_2\xrightarrow{0}S_3\xrightarrow{1}S_4$, and then the final 0 gives output 1. So the detected sequence is 0, 1, 0, 1, 0.