Consider a combination of T and D flip-flops connected as shown below. The…
2017
Consider a combination of T and D flip-flops connected as shown below. The output of the D flip-flop is connected to the input of the T flip-flop and the output of the T flip-flop is connected to the input of the D flip-flop.
Initially, both Q0 and Q1 are set to 1 (before the 1st clock cycle). The outputs
- A.
Q1Q0 after the 3rd cycle are 11 and after the 4th cycle are 00 respectively.
- B.
Q1Q0 after the 3rd cycle are 11 and after the 4th cycle are 01 respectively.
- C.
Q1Q0 after the 3rd cycle are 00 and after the 4th cycle are 11 respectively.
- D.
Q1Q0 after the 3rd cycle are 01 and after the 4th cycle are 01 respectively.
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Correct answer: B
State update rules: Q1_next = Q1 XOR Q0; Q0_next = Q1.
Initial state (before 1st clock): Q1 Q0 = 11.
After 1st clock: Q1_next = 1 XOR 1 = 0; Q0_next = 1. State = 01.
After 2nd clock: Q1_next = 0 XOR 1 = 1; Q0_next = 0. State = 10.
After 3rd clock: Q1_next = 1 XOR 0 = 1; Q0_next = 1. State = 11.
After 4th clock: Q1_next = 1 XOR 1 = 0; Q0_next = 1. State = 01.
Therefore after the 3rd cycle Q1 Q0 = 11, and after the 4th cycle Q1 Q0 = 01.
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