1. Digital Logic & Design
Dr. Waseem Ikram
Lecture 38

2. Recap

3. Equation definition for the Traffic Light Controller
Equations
TRSTATE.CLK = clk;
TMRST := (TRSTATE = = NSY2) # (TRSTATE = = EWY2);

4. The circuit diagram of the Traffic Light Controller

5. Pin declarations for the turning on/off traffic lamps
FLASHCLK, MANUAL pin 1, 2;
!Q0, !Q1, !Q pin 4, 5, 6;
NSRED, NSYEL, NSGRN pin 19, 18, 17;
EWRED, EWYEL, EWGRN pin 14, 13, 12;

6. Switching of traffic lamps at different states
NSGRN
NSYEL
NSRED
EWGRN
EWYEL
EWRED
NSG on
off
NSY
NSY2
NSR
EWG
EWY
EWY2
EWR

7. Equation definition for the turning on/off traffic lamps
Equations
NSRED = !MANUAL & (TRSTATE !=NSG) & (TRSTATE != NSY)
& (TRSTATE != NSY2);
NSYEL = !MANUAL & ((TRSTATE = = NSY) # (TRSTATE = = NSY2))
# MANUAL & FLASHCLK;
NSGRN = !MANUAL & (TRSTATE = = NSG);
EWRED = !MANUAL & (TRSTATE !=EWG) & (TRSTATE != EWY)
& (TRSTATE != EWY2);
EWYEL = !MANUAL & ((TRSTATE = = EWY) # (TRSTATE = = EWY2))
EWGRN = !MANUAL & (TRSTATE = = EWG);

8. S-R flip-flop Transition table
Flip-flop Inputs
Output Transitions S R Qt
Qt+1 x 1

9. Characteristic Equation for S-R Latch
SR/Qt 1 00 01 11 x 10

10. Characteristic equations of Latches and Flip-flops
Device Type
Characteristic Equation
S-R Latch
D Latch
Edge-triggered D flip-flop
J-K flip-flop

11. Clocked Synchronous State Machine based on D flip-flops

12. Excitation Equations for D flip-flop inputs D0 and D1
Excitation Inputs D0 D1

13. Transition Equations for D flip-flops

14. Transition Table for D flip-flop based State Machine
Present State
Next State
ENABLE=0
ENABLE=1 Q1 Q0 1

15. State table of a Mealy Machine
Present State
Next State
ENABLE=0
ENABLE=1
Output MAX A B C D 1

16. State Diagram of a Mealy Machine

17. State table of a Moore Machine
Present State
Next State
ENABLE=0
ENABLE=1
Output MAX A B C D 1

18. State Diagram of a Moore Machine

19. Clocked Synchronous State Machine based on J-K flip-flops

20. Traffic Light Controller

21. Excitation Equations for J-K flip-flop inputs J0 K0 and J1 K1
Excitation Inputs J0 K0 J1 K1

23. Transition Equations for J-K flip-flops

24. Transition Table for D flip-flop based State Machine
Present State
Next State
XY=00
XY=01
XY=10
XY=11 Q1 Q0 1

25. State Table of a Mealy Machine
Present State
Next State
Output Z XY 00 01 10 11 A C B 1 D

26. Traffic Light Controller
PLD Programming

27. Analysis of Synchronous State Machines

28. Digital Logic Design
Lecture 38