Consider a 3-bit counter, designed using T flip-flops, as shown below:…

2021

Consider a 3-bit counter, designed using T flip-flops, as shown below:

 Assuming the initial state of the counter given by PQR as 000, what are the next three states?

  1. A.

    011,101,000

  2. B.

    001,010,111

  3. C.

    011,101,111

  4. D.

    001,010,000

Attempted by 116 students.

Show answer & explanation

Correct answer: A

Solution: Determine T inputs and apply the T flip-flop rule (next = current XOR T).

From the wiring:

  • T_P = R

  • T_Q = NOT P

  • T_R = NOT Q

Compute the next three states starting from PQR = 000:

  1. Current = 000. Compute T = (T_P, T_Q, T_R) = (R, NOT P, NOT Q) = (0, 1, 1). Next = current XOR T = (0⊕0, 0⊕1, 0⊕1) = 011.

  2. Current = 011. Compute T = (R, NOT P, NOT Q) = (1, 1, 0). Next = (0⊕1, 1⊕1, 1⊕0) = 101.

  3. Current = 101. Compute T = (R, NOT P, NOT Q) = (1, 0, 1). Next = (1⊕1, 0⊕0, 1⊕1) = 000.

Therefore the next three states are 011, 101, 000.

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