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?
- A.
011,101,000
- B.
001,010,111
- C.
011,101,111
- 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:
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.
Current = 011. Compute T = (R, NOT P, NOT Q) = (1, 1, 0). Next = (0⊕1, 1⊕1, 1⊕0) = 101.
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.
A video solution is available for this question — log in and enroll to watch it.