SYEN 3330 Digital Systems Chapter 6 Part 1

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

Sequential Circuits Inputs Storage Elements Combinational Logic State SYEN 3330 Digital Systems Outputs Next State 2

Sequential Circuits Inputs Storage Elements Combinational Logic State SYEN 3330 Digital Systems Outputs Next State 3

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 SYEN 3330 Digital Systems 4

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! SYEN 3330 Digital Systems 5

Discrete Event Simulation SYEN 3330 Digital Systems 6

Simulated NAND Gate SYEN 3330 Digital Systems 7

Storing State SYEN 3330 Digital Systems 8

Storing State (Continued) • The circuit becomes: SYEN 3330 Digital Systems 9

Storing State (Continued) SYEN 3330 Digital Systems 10

Storing State (Continued) SYEN 3330 Digital Systems 11

Basic NAND S - R Latch SYEN 3330 Digital Systems 12

Simulating S - R Latch SYEN 3330 Digital Systems 13

Basic S - R Latch SYEN 3330 Digital Systems 14

Clocked S - R Latch SYEN 3330 Digital Systems 15

Clocked S - R Latch (Continued) SYEN 3330 Digital Systems 16

Characteristic Equation for S R Latch SYEN 3330 Digital Systems 17

D Latch SYEN 3330 Digital Systems 18

J-K Latch SYEN 3330 Digital Systems 19

T Latch SYEN 3330 Digital Systems 20