SR Flip Flop Conversion Techniques

SR Flip Flop Conversion Techniques

SR Flip Flop is the basis of all other Flip Flop designs. But it has a major drawback that the output becomes not defined whenever both inputs S=R=1. Here we discuss how to convert a SR Flip Flop into JK and D Flip Flops. As you may know for T Flip Flop, both the inputs are same, which is a limitation in case both inputs are 1. So T Flip Flop cannot be realised here.

The first thing that needs to be done for converting one flip flop into another is to draw the truth table for both the flip flops. The next step is to create the equivalent K-Maps for the required outputs.

JK Flip Flop using SR Flip Flop

To create a JK Flip Flop using SR, the inputs are given as JK Flip Flop inputs and the outputs are taken from the SR Flip Flop. First the conversion table is created as shown:

J K Qn Qn+1 S R

0


0

0

0

0



X

0

0

1



1

X

0

0

1

0

0

0

X

0

1

1

0

0

1

1

0

0

1

1

0

1

0

1

1

X

0

1

1

0

1

1

0

1

1

1

0

0

1

X – Don’t care

The following are the K-Maps for the required input-output relations:

JK Flip Flop using SR Flip Flop S

K-map for S

JK Flip Flop using SR Flip Flop -K-map for R

K-map for R

Logic Diagram is given below..

JK Flip Flop using SR Flip Flop - Logic Diagram

JK Flip Flop using SR Flip Flop – Logic Diagram

 

D Flip Flop using SR Flip Flop

To create a D Flip Flop using SR, the inputs are given as D Flip Flop inputs and the outputs are taken from the SR Flip Flop. First the conversion table is created as shown:

D Qn Qn+1 S R

0

0

0

0

X

0

1

0

0

1

1

0

1

1

0

1

1

1

X

0

X – Don’t care

The following are the K-Maps for the required input-output relations:

D Flip Flop using SR Flip Flop - K-map  for S

K-map for S

D Flip Flop using SR Flip Flop - K-Map for R

K-Map for R

Therefore it can be said that a SR Flip Flop acts as a D Flip Flop when inverted inputs are provided. Its logic diagram can be given as:

D Flip Flop using SR Flip Flop - Logic Diagram

D Flip Flop using SR Flip Flop – Logic Diagram

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