In a JK flip flop output Qn = 1 and it does not change when a clock pulse is applied. What is the possible combination of inputs (Jn, Kn) in this condition ('X' denotes don't care)

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VSSC ISRO Technical Assistant Electronics 14 July 2021 Official Paper
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  1. (X, 1)
  2. (X, 0)
  3. (0, 1)
  4. (1, 1)

Answer (Detailed Solution Below)

Option 2 : (X, 0)
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Detailed Solution

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Concept:

The excitation table for JK Flip Flop is given by,

Thus, to change the output from 0 to 1 the input combination can be either,

J = 1, K = 0

J = 1, K = 1

Combined these two conditions can be written as

J= 1 K = X

Where X represents don’t care condition

Hence (X, 0)  is the possible combination of inputs for output Qn = 1

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