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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. $011$
asked in Digital Logic by Veteran (101k points)
edited by | 1.9k views

3 Answers

+18 votes
Best answer

Answer - D
As in D-flip-flop , next output is $Q^+=D$ 

$P_{i+1} = R_i$

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

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

answered by Loyal (9k points)
selected
+4 votes

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.

answered by (411 points)
edited by
+2 votes

As simple as possible

answered by Junior (573 points)


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