### Flip-flop Conversion – D flip-flop to SR flip-flop

Here you would see how to design SR flip-flop using D flip-flop step by step – Flip-flop Conversion: D flip-flop to SR flip-flop

## Flip-flop Conversion – D flip-flop to SR flip-flop

### Step 1: Write the truth table of the required flip-flop

Here the required flip-flop is SR flip-flop

Hence you need to write the truth table of SR flip-flop which is

 S R QN QN+1 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 1 1 1 1 0 X 1 1 1 X

### Step 2: Write the excitation table of the given flip-flop

In this case the given flip-flop is D flip-flop

Therefore you need to write the excitation table of D flip-flop which is

 QN QN+1 D 0 0 0 0 1 1 1 0 0 1 1 1

### Step 3: Write the conversion table

The conversion table, which is a combination of truth table and excitation table, to implement a SR flip-flop using D flip-flop is as follows

 S R QN QN+1 D 0 0 0 0 0 0 0 1 1 1 0 1 0 0 0 0 1 1 0 0 1 0 0 1 1 1 0 1 1 1 1 1 0 X X 1 1 1 X X

### Step 4: Find the Boolean expressions for the inputs of the given flip-flop

In this case the given flip-flop is

Therefore, write the Boolean expressions for D from the conversion table using K-Map.

K-Map for D:

Expression for D would be

D = S + R/QN

### Step 5: Draw the circuit for implementing SR flip-flop from D flip-flop

For this, connect the D input of the D flip-flop to the circuit of the Boolean expression for D.

Therefore, the circuit would be:

In this way a SR flip-flop can be realized using a D flip-flop. Hope this post on “Flip-flop Conversion – D flip-flop to SR flip-flop” would help in clearing many doubts in flip-flop conversions.