GATE 2026 IN – Question 47
The initial state $Q_3Q_2Q_1Q_0$ in the digital circuit shown below is 1011. The new value of $Q_3Q_2Q_1Q_0$ after two rising edges of the clock (CLK) will be ________.
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Correct answer: (C) 1010
Explanation
The wiring gives the simultaneous update rule $(Q_3,Q_2,Q_1,Q_0)_{new}=(Q_1\oplus Q_0,Q_3,Q_2,Q_1)$.
From 1011, the XOR output is $1\oplus1=0$, and the first new state is 0101. Using that state, the next XOR output is $0\oplus1=1$, and the second new state is 1010.
All flip-flops update together at each clock edge. After two edges the state is **1010 (C)**.