Realization of One Flip-Flop using Other Flip-Flop

Realization of One Flip-Flop using Other Flip-Flop

AU : May-05, 07, 12,15, Dec.-08, 10, 15, 16

• It is possible to convert one flip-flop into another flip-flop with some additional gates or simply doing some extra connection. Let us see few conversions among flip-flops.

 

1. SR Flip-Flop to D Flip-Flop

The excitation table for above conversion is as shown in Table 4.9.1.

 

2. SR Flip-Flop to JK Flip-Flop

The excitation table for above conversion is as shown in Table 4.9.2.

K-map simplification

Logic diagram

 

3. SR Flip-Flop to T Flip-Flop

The excitation table for above conversion is as shown in the Table 4.9.3.

• If we apply clock pulses to the circuit, the circuit output will toggle from 0 to 1 and 1 to 0. Thus, we can build 1-bit counter using SR flip-flop by converting it to T flip-flop.

Ex. 4.9.1 Prepare the truth table for the circuit of Fig. 4.9.7  and show that it acts as a T-type flip-flop.

Sol. :

For SR flip-flop,

Looking at column 1 and column 5 of the Table 4.9.4 we can conclude that when T = 0, the output does not change and when T = 1, the output toggles. Thus, the given circuit acts as a T flip-flop. This is another way of implementing T flip-flop using SR flip-flop.

 

4. JK Flip-Flop to T Flip-Flop

The excitation table for above conversion is as shown in Table 4.9.5.

 

5. JK Flip-Flop to D Flip-Flop

• The excitation table for above conversion is as shown in the Table 4.9.6.

 

6. D Flip-Flop to T Flip-Flop

• The excitation table for above conversion is as shown in the Table 4.9.7.

Ex. 4.9.2 Analyze the circuit and prove that it is equivalent to T flip-flop.

Sol. : To analyze the circuit means to derive the truth table for it.

We have, D = Input ⊕ Q_n

In the above circuit, output does not change when input is 0 and it toggles when input is 1. This is the characteristics of T flip-flop. Hence, the given circuit is T flip-flop constructed using D flip-flop.

 

7. T Flip-Flop to D Flip-Flop

The excitation table for above conversion is as shown in the Table 4.9.9.

 

8. JK Flip-Flop to SR Flip-Flop

The excitation table for above conversion is as shown in Table 4.9.10.

 

9. D Flip-Flop to SR Flip-Flop

The excitation table for above conversion is as shown in the Table 4.9.11.

 

Ex 4.9.3 Explain the realization of JK flip flop from T flip flop.

AU : Dec.-16, Marks 7

Sol . :

Review Questions

1. Convert a SR flip-flop into JK flip-flop.

AU : May-12, Marks 8

2. Convert a SR flip-flop into a D flip-flop.

AU : Dec.-08, Marks 8

3. Convert SR flip-flop into T flip-flop.

4. Convert JK flip-flop to T flip-flop.

5. Convert JK flip-flop to D flip-flop.

AU : May-05, 07, Marks 2

6. Convert D flip-flop into T flip-flop.

7. Convert T flip-flop into D flip-flop.

AU : May-15, Marks 2

8. Convert D flip-flop into SR flip-flop.

9. Convert JK flip-flop into SR flip-flop.