Finite state machines: counter
	q1	q0	x	q1+	q0+	z1	z0	D1	D0
	0	0	0	0	0	0	0	0	0
	0	0	1	0	1	0	0	0	1
	0	1	0	0	1	0	1	0	1
	0	1	1	1	0	0	1	1	0
	1	0	0	1	0	1	0	1	0
	1	0	1	1	1	1	0	1	1
	1	1	0	1	1	1	1	1	1
	1	1	1	0	0	1	1	0	0
	2. Pick flip-flops: both D
	3. Use excitation tables to get values for D
		(copy columns for next state)