SR Latch Excitation Table and Characteristic Equation
The logical operation of the SR latch is summarized in the excitation table of Fig. 6.11a.
The excitation table is simply the state table of the latch, showing the state transitions for each combination of excitation inputs.
The information from the table can be represented as a state diagram, as shown in Fig. 6.11b, and plotted in K-map form, as shown in Fig. 6.11c, where the value of the next state Q* is plotted as a function of the inputs, S and R, and the present state Q.
From the K-map the characteristic equation of the SR latch can be derived: Q* = S + RQ.