Q6Digital Electronics

An excitation table is a critical reverse-engineering design tool. For an SR flip-flop transitioning from its current state ($Q_n$) to a desired next state ($Q_{n+1}$): to transition $0\to 0$, requires $S=0,R=X$ (Don't care); $0\to 1$ requires $S=1,R=0$; $1\to 0$ requires $S=0,R=1$; and $1\to 1$ requires $S=X,R=0$.