1. SYEN 3330 Digital SystemsJung H. Kim 1 SYEN 3330 Digital Systems Chapter 6 – Part 1

2. SYEN 3330 Digital Systems Chapter 6-1 Page 2 Sequential Circuits Combina- tional Logic Storage Elements Inputs Outputs State Next State

3. SYEN 3330 Digital Systems Chapter 6-1 Page 3 Sequential Circuits Combina- tional Logic Storage Elements Inputs Outputs State Next State

4. SYEN 3330 Digital Systems Chapter 6-1 Page 4 Overview of Chapter 6 Types of Sequential Circuits Storage Elements  Latches  Flip-Flops Sequential Circuit Analysis  State Tables  State Diagrams Sequential Circuit Design  Specification  Assignment of State Codes  Implementation  HDL Representation

5. SYEN 3330 Digital Systems Chapter 6-1 Page 5 Types of Sequential Circuits Depends on time at which inputs are observed by storage elements and state of storage elements change Synchronous  Behavior defined from knowledge of its signals at discrete instances of time  Storage elements affected by inputs and can change state only in relation to a timing signal (clock pulses from a clock) Asynchronous  Behavior defined from knowledge of inputs at any instant of time and the order in continuous time in which inputs change  If clock just regarded as another input, all circuits are asynchronous!  Nevertheless, the synchronous abstraction makes complex designs tractable!

6. SYEN 3330 Digital Systems Chapter 6-1 Page 6 Discrete Event Simulation

7. SYEN 3330 Digital Systems Chapter 6-1 Page 7 Simulated NAND Gate

8. SYEN 3330 Digital Systems Chapter 6-1 Page 8 Storing State

9. SYEN 3330 Digital Systems Chapter 6-1 Page 9 Storing State (Continued) The circuit becomes:

10. SYEN 3330 Digital Systems Chapter 6-1 Page 10 Storing State (Continued)

11. SYEN 3330 Digital Systems Chapter 6-1 Page 11 Storing State (Continued)

12. SYEN 3330 Digital Systems Chapter 6-1 Page 12 Basic NAND  S -  R Latch

13. SYEN 3330 Digital Systems Chapter 6-1 Page 13 Simulating  S -  R Latch

14. SYEN 3330 Digital Systems Chapter 6-1 Page 14 Basic S - R Latch

15. SYEN 3330 Digital Systems Chapter 6-1 Page 15 Clocked S - R Latch

16. SYEN 3330 Digital Systems Chapter 6-1 Page 16 Clocked S - R Latch (Continued)

17. SYEN 3330 Digital Systems Chapter 6-1 Page 17 Characteristic Equation for S - R Latch

18. SYEN 3330 Digital Systems Chapter 6-1 Page 18 D Latch

19. SYEN 3330 Digital Systems Chapter 6-1 Page 19 J-K Latch

20. SYEN 3330 Digital Systems Chapter 6-1 Page 20 T Latch