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Here At the time t0 the initial state is 00 and after first clock the state become 10 (Q1,Q0) here Q1 is clock to D

flip – flop and because of that we are getting the output of d in next state/time so currently we output should

remain 1 0 not become 1 1 at time 1 , but ans here is 1 1 , is anything i am during here is wrong?

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Best answer

Flip flops are positive edge triggered.

T = Q1’ ⊕ Q0

D = Q1’

Q0 Q1  Q0 (Next) Q1 (Next) D T
0 0 1 1 1 1
1 1 1 0 0 1
1 0 1 0 1 0
1 0 1 0 1 0

At Time 0:  Initial state (Q0 Q1) = (0, 0)

At Time 1: Since T is 1 i.e. trigger so Q1 will change its state to 0 → 1 now this change of state is given as CLK to D FF and that is +ve edge triggered so Q0 will also change its state from 0 → 1 because i/p to D FF is 1. Therefore (Q0, Q1) = (1, 1)

At time 2: Here T is 1, so state of Q1 is changed from 1 → 0 but this will act as -ve edge to D FF so Q0 will not change its state. Therefore (Q0 Q1) = (1,0)

At time 3: i/p to T FF is 0 i.e. latch so Q1 will retain its state 0 → 0, this will act as -ve level to D FF so Q0 will not change its state. Therefore (Q0 Q1) = (1,0)

Now it will stuck at (1,0)

Therefore: 00 → 11 → 10 → 10 is correct answer.

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