Before dealing with the conversion let’s summarize the truth table of JK flip flop circuits.
From the truth table it’s quite evident that 4 main transitions occur between the current state and next state of JK flip-flop.
They are 0->0; 0->1; 1->0; 1->1.
0-> 0 Transition:
For both the present state and the next state to remain in 0, the J input must remain at 0 and the K input can either be 1 or 0. In simple words, irrespective of the value of K input, the present state and next state remains in 0, if the value of J input is 0.
This is the transition where the present state is 0, but the next state should change to 1. For this transition to occur the value of J input should be 1 and K input can either be 0 or 1. When K value is 0, it is called SET condition (J=1 and K=0, SET condition) and when K value is 1, it is called toggle condition. (J=1 and K=1, TOGGLE condition). So for this transition to occur J has to be high, but K can be either high or low.
1-> 0 Transition:
In this case the present state is 1 and the next state should be 0. For this transition to occur the value of K input should be 1 and the value of J input can be either 0 or 1. Irrespective of the J input, the transition occurs if the value of K remains at 1.
For this transition to occur the value of K should remain low or 0, irrespective of the value of J. J can be either 1 or 0. The value of J will not affect this transition.
From the above transitions we can form the excitation table as shown below.
The four transitions and excitation table of RS flip-flop is shown below.