Question

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

Hint:

In T flip-flop counters, always examine the toggle conditions carefully instead of assuming a standard binary count sequence.

Answer 1

The Correct Option is A

Step 1: Review T flip-flop behavior.
A T flip-flop changes (toggles) its output on every clock pulse when T = 1, and retains its current state when T = 0.

---

Step 2: Examine the given counter configuration.
From the circuit diagram, the T inputs of the flip-flops are not constant. Instead, each stage is controlled by the outputs of other flip-flops, creating a feedback-based synchronous counter.

Hence, the toggling of P, Q, and R depends on the present state of the counter.

---

Step 3: Trace the state transitions.
Starting with the initial state:

Initial state: PQR = 000

• After the first clock pulse, the toggle conditions cause the counter to move to 011.
• After the second clock pulse, the next state becomes 101.
• After the third clock pulse, the feedback again forces a transition back to 000.

---

Final Conclusion:
The sequence of the next three states of the counter is:

011 → 101 → 000