Answer1

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WHAT'S YOUR ENGINEERING QUOTIENT?

Problem 1—What is the output of the following digital circuit? A" is the negation of A, the flip-flops are D-type, and assume the outputs are 0 initially.

Answer:

Initially A=0, B=0. The inputs to the D-flip flops are:

Da = A" = 1
Db = A XOR B = 0

After the next clock edge, the D flip flop transfers its inputs to the output (this is the definition of a D flip-flop). The output becomes A = 1, B = 0.

Now, the inputs are

Da = A" = 0
Db = A XOR B = 1

After the next clock edge the output becomes A = 0, B = 1.

The inputs are now:

Da = A" = 1
Db = A XOR B = 1

After the next clock edge, the output becomes A = 1, B = 1.

The inputs are now Da = 0, Db = 0; after the next clock edge, the output becomes A = 0 and B = 0, which is what we started with initially. So, we can conclude that this cycle repeats and the output sequences as follows with each clock edge:

A B

0 0

1 0

0 1

1 1

This is a 2-bit binary counter.

Contributor: Naveen P N

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