Question

Design an Moore FSM for an 8-interval stoplight system where the red light is ON (yellow and green lights are OFF) for 4 intervals, then yellow light is ON (red and green lights are OFF) for 1 interval and then green light is ON (red and yellow lights are OFF) for 3 intervals. After the green light has been ON for three intervals, we go back to the red light being ON for 4 intervals. Use binary encoding for states and use JK FFs for storing the state. You have report the state machine (using 8 states), state table, Boolean expression and a gate-level diagram (FFs + combinational logic).

Answer 1

Using binary state encoding,

S0 = Q2Q1Q0 = 000

S1 = 001

S2 = 010

S3 = 011

S4 = 100

S5 = 101

S6 = 110

S7 = 111

Moore State diagram is shown below:

Excitation Table of JK Flip Flop

PRESENT STATE Q	NEXT STATE Q+	J	K
0	0	0	X
0	1	1	X
1	0	X	1
1	1	X	0

State Table

PRESENT STATE			NEXT STATE			OUTPUT			JK EXCITATION INPUT
Q2	Q1	Q0	Q2+	Q1+	Q0+	RED	YELLOW	GREEN	J2	K2	J1	K1	J0	K0
0	0	0	0	0	1	1	0	0	0	X	0	X	1	X
0	0	1	0	1	0	1	0	0	0	X	1	X	X	1
0	1	0	0	1	1	1	0	0	0	X	X	0	1	X
0	1	1	1	0	0	1	0	0	1	X	X	1	X	1
1	0	0	1	0	1	0	1	0	X	0	0	X	1	X
1	0	1	1	1	0	0	0	1	X	0	1	X	X	1
1	1	0	1	1	1	0	0	1	X	0	X	0	1	X
1	1	1	0	0	0	0	0	1	X	1	X	1	X	1

K Map technique to derive next state boolean expression

Circuit