Realization of One Flip-Flop using Other Flip-Flop

Realization of One Flip-Flop using Other Flip-Flop

AU: May-03,05,11,14,17, Dec.-03,04,08,09,10,11,16

• It is possible to convert one flip-flop into another flip-flop with some additional gates or simply doing some extra connection.

SR Flip-Flop to D Flip-Flop

• The excitation table for above conversion is as shown in Table 2.6.1.

SR Flip-Flop to JK Flip-Flop

• The excitation table for above conversion is as shown in Table 2.6.2.

SR Flip-Flop to T Flip-Flop

• The excitation table for above conversion is as shown in the Table 2.6.3.

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.

Example 2.6.1 Prepare the truth table for the circuit of Fig. 2.6.7 and show that it acts as a T-type flip-flop.

Solution: For SR flip-flop,

Q_n+1 = S + Ȓ Q_n                                 …Characteristics equation R = Ŝ

= S + S Q_n

= S(1 + Q_n) = S

• Looking at column 1 and column 5 of the Table 2.6.4 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.

JK Flip-Flop to T Flip-Flop

• The excitation table for above conversion is as shown in Table 2.6.5.

JK Flip-Flop to D Flip-Flop

• The excitation table for above conversion is as shown in the Table 2.6.6.

D Flip-Flop to T Flip-Flop

The excitation table for above conversion is as shown in the Table 2.6.7.

Example 2.6.2 Analyze the circuit and prove that it is equivalent to T flip-flop.

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

• 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.

T Flip-Flop to D Flip-Flop

The excitation table for above conversion is as shown in the Table 2.6.9.

JK Flip-Flop to SR Flip-Flop

The excitation table for above conversion is as shown in Table 2.6.10.

D Flip-Flop to SR Flip-Flop

The excitation table for above conversion is as shown in the Table 2.6.11.

T Flip-Flop to SR Flip-Flop

The excitation table for conversion of T FF into an SR FF is as shown in the Table 2.6.12.

D Flip-Flop to JK Flip-Flop

The excitation table for conversion of D flip-flop to JK flip-flop.

Example 2.6.3 Construct a JK flip-flop using a D flip-flop, a 2 x 1 multiplexer and an inverter.AU: Dec.-08, Marks 4

Solution: The excitation table for above conversion is as shown in the Table 2.6.13.

Review Questions

1. Convert JK flip-flop to D flip-flop.  AU: May-03, 05, Dec.-03, Marks 2

2. Convert D flip-flop into T flip-flop.  AU: Dec.-03, May-11,14, Marks 6

3. Convert JK flip-flop to T flip-flop.  AU: Dec.-04, 10, Marks 2

4. Convert a SR flip-flop into a D flip-flop.  AU: Dec.-08, Marks 8

5. Convert a T-FF into an S-R FF. Draw the circuit.  AU: Dec.-08, Marks 2

6. How will you convert a D flip-flop into JK flip-flop?  AU: Dec.-09, 11, May-14, Marks 8

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

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

9. Implement T-flip flop and JK flip flop using D flip flop.  AU: Dec.-16, May-17, Marks 16

10. Implement JK flip flop using D flip flop.  AU: Dec.-16, Marks 8