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The SR flip flop state diagram
Figure 50: The SR flip flop state diagram
The JK state diagram
The JK flip flop state diagram is like the SR flip flop state diagram, but the only difference is that the JK
state diagram includes the toggling combination, C = 1, J = K = 1. This combination is a prohibited
combination in the SR flip flop.
Figure 51: The JK flip flop state diagram
The toggling combination is when J = 1 and K =1, transition can go either way depending on the present
state, for example when in state Q = 0 and the inputs J =1, K = 1 is applied to the flip flop, it will transit
into the next state Q =1. When in state Q = 1, and the inputs J =1, K = 1 are applied to the flip flop, it
will move to state Q = 0 (see figure 51).
14.5 SR and JK flip flops Excitation Tables
Excitation tables are derived from the state tables of flip flops. The state tables specify the next state
when the inputs and present states are known. During designing, the designer usually knows the required
transition from present state to next state but wishes to find out the flip flop input conditions that will
cause the required transition. So, an excitation table lists the required input combinations for a given
change of state. The excitation tables can be produced from flip-flop state tables or from state diagrams.
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