Conversion of Flip Flops

Contents

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Key learnings:

Flip Flop Conversion Definition: Flip flop conversion is defined as the process by which one type of flip flop is modified to perform as another type, involving adjustments to its circuitry and logic.
Truth Table Role: Understanding the truth table of both the original and target flip flops is crucial as it dictates the necessary inputs and expected outputs.
Excitation Table Usage: The excitation table reveals the required inputs to achieve specific states, facilitating the conversion process.
Logical Simplification: Simplifying the input expressions, often using K-maps, is essential for efficiently converting flip flops.
Practical Conversion Steps: The steps include designing truth tables, creating excitation and conversion tables, simplifying logic, and finalizing the circuit design, demonstrating the methodical approach to the conversion of flip flops.

Flip-flop conversion transforms one type of flip-flop to function like another by adding specific circuitry or making new connections.

Conversion of JK Flip-Flop to SR Flip-Flop

Step 1: Write the Truth Table of the Desired Flip-Flop
To design an SR flip flop using a JK flip-flop, start by drafting the SR flip-flop truth table.

Step 2: Obtain the Excitation Table for the given Flip-Flop from its Truth Table
Excitation tables detail the inputs needed for a flip flop to transition from a current state (Q_n) to a next state (Q_n+1).

From the truth table of JK flip-flop one can see that Q_n+1 will become 0 from Q_n = 0 for both (i) J = K = 0 and (ii) J = 0 and K =1 (blue entries in first and third rows of the truth table).

This means that to obtain the next state, Q_n+1 as 0 from the current state Q_n = 0, J must be made zero while K can be either 0 or 1.

This is indicated by the first row of the excitation table (blue entries in the first row of excitation table) where the value of K is expressed as ‘X’ indicating don’t care condition. Similarly to obtain the next state as 1 from the current state 0, one has to have J equal to 1 while K can be either 0 or 1 (indicated by green entries of the truth table).

This leads to the second row of excitation table (green entries) to be filled with values Q_n = 0, Q_n+1 = 1, J = 1 and K = X. On the same grounds, the entire excitation table needs to be filled (entries in pink and dark red colors).

Step 3: Append the Excitation Table of the given Flip-Flop to the Truth Table of the Desired Flip-Flop Appropriately to obtain Conversion Table
Here the conversion table is obtained by filling-up the values of the J and K inputs for the given Q_n and Q_n+1, by referring to the excitation table.

Step 4: Simplify the Expressions for the Inputs of the given Flip-Flop
In this case, one needs to arrive at the logical expressions for the inputs J and K in terms of S, R, and Q_n using suitable simplification techniques like K-map.

Step 5: Design the Necessary Circuit and make the Connections accordingly
In this case, no new circuits or connections are needed to complete the conversion.
Using this method, you can similarly convert the specified flip flop into any other type as demonstrated.