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Consider the following circuit involving three D-type flip-flops used in a certain type of counter configuration.

If at some instance prior to the occurrence of the clock edge, $P, Q$ and $R$ have a value $0$, $1$ and $0$ respectively, what shall be the value of $PQR$ after the clock edge?

1. $000$
2. $001$
3. $010$
4. $011$
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As in D-flip-flop , next output is $Q^+=D$

$P_{i+1} = R_i$

$Q_{i+1} = (P_i + R_i)'$

$R_{i+1} = R_i'Q_i$

selected

DP = QR

DQ = ( QP + QR )’

DR = QQ (QR)’

Characteristic Table:-

 Input Previous State Next State DP DQ DR QP QQ QR QPN QQN QRN 0 1 0 0 0 0 0 1 0 1 0 0 0 0 1 1 0 0 0 1 1 0 1 0 0 1 1 1 0 0 0 1 1 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0 1 1 0 0 0 0 1 1 1 0 0 0 1 1 0 0 1 1 1 1 0 0

Thus the value of PQR after 010 is 011. Option D.

edited by

As simple as possible

option d) 011

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