Finite State Machine

1. Finite State Machine Switching and Logic Lab Standard Laboratory Exercises

2. Suggestions and Warnings • Read for detail and comprehension • Should be able to complete within normal laboratory period. • Make sure you program unused pins as tri-state inputs or you may burnout EPM7128S device on PLDT-2.

3. Vending Machines • Project 1 -- Basic Vending Machine • Combinational Logic • State • Moore Outputs • Sequential Devices -- D Flip-Flops • Project 2 -- Modified Vending Machine • Provides change • Add state and modify transitions

4. State Diagram 2 State Bits

5. Vending Entity ENTITY Vending IS PORT ( Nickel, Dime, Reset, Clk : IN BIT; Dispense : OUT BIT ); END Vending;

6. Vending Architecture ARCHITECTURE Moore OF Vending IS TYPE State_Type is (ZeroCents,FiveCents,TenCents, FifteenCents); SIGNAL State : State_Type; BEGIN --FSM Logic --Moore Output logic goes here END Moore;

7. Finite State Machine Logic --FSM Logic Goes Here FSM: PROCESS BEGIN IF Reset = '1' THEN State <= ZeroCents; ELSIF (CLK'event AND Clk = '1') THEN • • • • • END PROCESS FSM; Sequential Process Statement

8. Moore Output Logic --Moore Output logic goes here Output: PROCESS(State) BEGIN CASE State IS WHEN FifteenCents => Dispense <= '1'; WHEN Others => Dispense <= '0'; END CASE; END PROCESS Output; Dispense = State_Bit_0 & State_Bit_1;1 1Technology Map Netlist Viewer

9. State Logic CASE State IS WHEN ZeroCents => IF Dime = '1' THEN State <= TenCents; ELSIF Nickel = '1' THEN State <= FiveCents; ELSE State <= ZeroCents; END IF; WHEN FiveCents => IF Dime = '1' THEN State <= FifteenCents; ELSIF Nickel = '1' THEN State <= TenCents; ELSE State <= FiveCents; END IF;

10. State Logic (Continued) WHEN TenCents => IF Dime = '1' THEN State <= FifteenCents; ELSIF Nickel = '1' THEN State <= FifteenCents; ELSE State <= TenCents; END IF; WHEN FifteenCents => IF Reset = '1' THEN State <= ZeroCents; ELSE State <= FifteenCents; END IF; END CASE;

11. State Equations1 State_Bit_1.T = Dime & !State_Bit_1 + !State_Bit_1 & State_Bit_0 &Nickel State_Bit_1.Clk = Clk State_Bit_1.Rst = Reset State_Bit_0.D = !(Dime & !State_Bit_0 & State_Bit_1 + Nickel & Dime & !State_Bit_0 & State_Bit_1 + !Nickel & !Dime & ! State_Bit_0 State_Bit_0.Clk = Clk State_Bit_0.Rst = Reset 1Technology Map Netlist Viewer

12. Simulation & Verification Scenarios • Nickel, Nickel, Nickel  Dispense • Nickel, Dime  Dispense • Dime, Dime  Dispense • Nickel, Nickel, Dime  Dispense • Do not violate setup and hold time in simulation

13. 8 Steps to Success • Create Project (tri-state as input all unused pins) • Capture Logic • Analysis and Synthesis • Pin Assignments • Full Compile • Timing Simulation • Programming • Exercise circuit

14. Revised Vending Machine • Gives nickel change from 20¢ • Does not require reset after 15¢ and 20 ¢ states. 20¢ Change, Dis 0¢ 5¢ 10¢ 15¢ Dis Reset

15. 8 Steps to Success • Create Project (tri-state as input all unused pins) • Capture Logic • Analysis and Synthesis • Pin Assignments • Full Compile • Timing Simulation • Programming • Exercise circuit

16. Unused Pins as Tri-State Inputs • Select “Assignments” • Select “Device” • Select “Device & Pin Options” • Select “Unused Pins” Tab • Select “As inputs, tri-stated” • OK