M16_3_ch01

M16_3_ch01 - INTRODUCTION TO DIGITAL SYSTEMS DESCRIPTION...

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Unformatted text preview: INTRODUCTION TO DIGITAL SYSTEMS DESCRIPTION AND DESIGN OF DIGITAL SYSTEMS FORMAL BASIS: SWITCHING ALGEBRA IMPLEMENTATION: MODULES (ICs) AND NETWORKS IMPLEMENTATION OF ALGORITHMS IN \HARDWARE" COURSE EMPHASIS: CONCEPTS, ANALYSIS AND DESIGN Follow-on courses: { Digital Lab { Computer Architecture { Computer Architecture Lab { Digital Design - Advanced Topics Introduction to Digital Systems 1 1 { Introduction OVERVIEW WHAT IS A DIGITAL SYSTEM? HOW IT DIFFERS FROM AN ANALOG SYSTEM? WHY ARE DIGITAL SYSTEMS IMPORTANT? BASIC TYPES OF DIGITAL SYSTEMS: COMBINATIONAL AND SEQUENTIAL SPECIFICATION AND IMPLEMENTATION OF DIGITAL SYSTEMS ANALYSIS AND DESIGN OF DIGITAL SYSTEMS DESIGN PROCESS AND CAD TOOLS 2 Introduction to Digital Systems 1 { Introduction WHAT IS DIGITAL DIGITAL SYSTEMS { inputs and outputs: nite number of discrete values ANALOG SYSTEMS { inputs and output values from a continuous (in nite) set Example: digital vs. analog scale for measuring weights MAIN USE OF DIGITAL SYSTEMS: INFORMATION PROCESSING (text, audio, visual, video) TRANSMISSION (communication) STORAGE Introduction to Digital Systems 3 1 { Introduction SYSTEM AND SIGNALS x,z x 4 S z z(t) x(t) (a) (b) t x,z 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 t z(t) x(t) t x(t) z(t) 0 2 5 1 3 4 2 2 7 3 5 7 4 4 6 5 5 6 6 3 2 7 3 4 (c) (d) Figure 1.1: System S: a) Block diagram. b) Analog I/O signals. c) Digital I/O signals. d) I/O sequence pair. Introduction to Digital Systems 1 { Introduction WHY DIGITAL 5 1. FOR BOTH NUMERICAL AND NONNUMERICAL INFORMATION PROCESSING 2. INFORMATION PROCESSING CAN USE A GENERAL-PURPOSE SYSTEM (a computer) 3. DIGITAL REPRESENTATION: { vector of signals with just two values (binary signals) Example: { All signals binary { Simple devices to process binary signals: (SWITCHES with two STATES: open and closed). Introduction to Digital Systems digit 0 1 2 3 4 5 6 7 8 9 vector 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1 { Introduction WHY DIGITAL (cont.) 6 4. DIGITAL SIGNALS INSENSITIVE TO VARIATIONS OF COMPONENT PARAMETER VALUES Signal Value 2 1 0 Time Figure 1.2: Separation of digital signal values. Introduction to Digital Systems 1 { Introduction WHY DIGITAL (cont.) 7 5. Numerical digital systems can be made MORE ACCURATE by simply increasing the number of digits used in the representation. 6. PHENOMENAL ADVANCES OF MICROELECTRONICS TECHNOLOGY: Possible to fabricate extremely complex digital systems, which are small, fast, and cheap Digital systems built as integrated circuits composed of a large number of very simple devices Introduction to Digital Systems 1 { Introduction WHY DIGITAL (cont.) 8 7. DIFFERENT IMPLEMENTATIONS OF SYSTEMS WHICH TRADEOFF SPEED AND AMOUNT OF HARDWARE (COST) Example: { add two integers represented by six decimal digits X5 Y5 X4 Y4 X3 Y3 X2 Y2 X1 Y1 X0 Y0 X5 Y5 X4 Y4 X3 Y3 X2 Y2 X1 Y1 X0 Y0 6-Digit Adder One-Digit Adder (carry storage inside) Z5 Z4 Z3 (a) Z2 Z1 Z0 Z5 Z4 Z3 Z2 (b) Z1 Z0 Figure 1.3: Six-digit adder: a) Parallel implementation. b) Serial implementation. Introduction to Digital Systems 1 { Introduction SUMMARY 9 DIGITAL REPRESENTATION AND PROCESSING METHODS WIDELY USED EXTRAORDINARY PROGRESS IN DIGITAL TECHNOLOGY AND USE INDISPENSABLE IN MODERN SOCIETY NEW APPLICATIONS FUELED BY THE DEVELOPMENT OF COMPUTER TECHNOLOGY KNOWLEDGE ABOUT THE DESIGN AND USE OF DIGITAL SYSTEMS REQUIRED IN A LARGE VARIETY OF HUMAN ACTIVITIES Introduction to Digital Systems 1 { Introduction MIXED ANALOG/DIGITAL SYSTEMS Microphone Analog-to-Digital Converter ADC Signal Processing & Storage Digital-to-Analog Converter DAC Speaker 10 ... 110110 110111 010110 101101... ... 011000 110101 110101 101101... Digital signals Analog signal (not too good) (a) (Much better analog signal) Signal value Analog Digital 11 10 01 00 Time 00 01 01 10 01 11 11 11 11 10 01 Sequence of digital signals (b) Figure 1.4: a) A system with analog and digital signals. b) Analog-to-digital conversion. Introduction to Digital Systems 1 { Introduction COMBINATIONAL AND SEQUENTIAL SYSTEMS DIGITAL SYSTEMS - TWO CLASSES: 11 COMBINATIONAL SYSTEMS z (t) = F (x(t)) { no memory, the output does not depend on previous inputs SEQUENTIAL SYSTEMS z (t) = F (x(0 t)) x(0 t): input sequence from time 0 to time t { z (t) depends also on previous inputs - the system has MEMORY Introduction to Digital Systems 1 { Introduction COMBINATIONAL AND SEQUENTIAL SYSTEMS (cont.) 12 x z Time x z Time t (a) t (b) Figure 1.5: Input-output functions for: a) Combinational system b) Sequential system. Introduction to Digital Systems 1 { Introduction EXAMPLE 1.1: SEQUENTIAL SYSTEM INPUT x with VALUES 0,1, or 2 OUTPUT z with VALUES 0 or 1 FUNCTION: 8 > AN INPUT-OUTPUT PAIR: t 0 1 2 3 4 5 6 7 8 9 10 11 x1220120002 1 1 z1011000000 1 0 13 > 1 if (x(0) x(1) : : : x(t)) > < z (t) = > even 2 s and odd 1 s > > 0 otherwise : 0 0 has Introduction to Digital Systems 1 { Introduction EXAMPLE 1.2: COMBINATIONAL SYSTEM INPUT x(t) with values from the set of letters (upper and lower case) INPUT y(t) with values 0 and 1 FUNCTION: { change x(t) to opposite case when y(t) = 1 { leave it unchanged when y(t) = 0 AN INPUT-OUTPUT PAIR: t x y z 14 0 E 0 E 1 X 1 x 2 A 0 A 3 M 0 M 4 P 0 P 5 L 1 l 6 E 0 E Introduction to Digital Systems 1 { Introduction SPECIFICATION AND IMPLEMENTATION. ANALYSIS AND DESIGN. Specification (Function and other characteristics) 15 Analysis Design Implementation (Network of modules) Figure 1.6: Relationship among system speci cation and implementation. Introduction to Digital Systems 1 { Introduction SPECIFICATION AND IMPLEMENTATION (cont.) 16 SPECIFICATION of a system describes its function. Objective: to use the system as a component in more complex systems and to serve as the basis for the implementation of the system by a network of simpler components. Introduction to Digital Systems 1 { Introduction SPECIFICATION LEVELS HIGH-LEVEL BINARY-LEVEL ALGORITHMIC-LEVEL Spec. of combinational systems: Chapter 2 Spec. of sequential systems: Chapter 7 Spec. of algorithmic systems: Chapter 13 17 Introduction to Digital Systems 1 { Introduction IMPLEMENTATION 18 As a DIGITAL NETWORK { interconnection of modules SEVERAL LEVELS depending on the complexity of the primitive modules { from very simple gates to complex processors Need for HIERARCHICAL IMPLEMENTATION PHYSICAL LEVEL: interconnection of electronic elements such as transistors, resistors, and so on (Chapter 3). IMPLEMENTATION OF COMBINATIONAL SYSTEMS { at the gate level: Chapters 5 and 6 { at the module level: Chapters 9, 10, and 12 IMPLEMENTATION OF SEQUENTIAL SYSTEMS { elementary: Chapter 8 { more complex: Chapters 11 and 12 IMPLEMENTATION OF ALGORITHMIC SYSTEMS: Chapters 13-15 Introduction to Digital Systems 1 { Introduction 19 Level: System Top level Modules Gates and flip-flops Transistors A B C D Bottom level A B C D (a) (b) Figure 1.7: Hierarchical implementation: a) Top-down approach. b) Bottom-up approach. Introduction to Digital Systems 1 { Introduction STRUCTURED ANALYSIS AND DESIGN 20 ANALYSIS: * get speci cation from an implementation DESIGN: * obtain an implementation that satis es the speci cation Use of MULTILEVEL APPROACH necessary The TOP-DOWN and BOTTOM-UP approaches A combination of the two approaches Introduction to Digital Systems 1 { Introduction LEVELS OF AN IMPLEMENTATION: MODULE, LOGICAL, PHYSICAL Example: Z (t) = P =0 X (i) t i Logical (gate and flip-flop) level Module level Input X(i) Clock clk xin 21 Clock Flip-Flop Registers RX xreg RY yreg Gates Adder ADD addout z Output Z (a) +5V (b) Physical (transistor) level Transistor (c) Figure 1.8: Digital system: a) module level b) logical level and c) physical level. Introduction to Digital Systems 1 { Introduction COMPUTER-AIDED DESIGN TOOLS Design of digital systems an involved and laborious process Various computer-aided design (CAD) tools available Main types of CAD tools support the main phases of digital design: (i) description (speci cation), 22 (ii) design (synthesis) including various optimizations to reduce cost and improve performance, and (iii) checking of the design with respect to its speci cation. The design phases typically require several passes Introduction to Digital Systems 1 { Introduction CAD (cont.) 23 DESCRIPTION of digital systems for design purposes { At a high-level, use hardware-description language (HDL) { At the binary level, use HDLs to describe the system structure { Editors used to produce HDL programs { Graphical forms - logic diagrams also used for structure Introduction to Digital Systems 1 { Introduction vhdl description 24 USE WORK.ALL ENTITY sample_system IS PORT (xin: IN BIT_VECTOR z : OUT BIT_VECTOR clk: IN BIT ) END sample_system ARCHITECTURE structural OF sample_system IS SIGNAL xreg, yreg, addout: BIT_VECTOR(7 DOWNTO 0) BEGIN RX: ENTITY BitReg8 PORT MAP(xin,xreg,clk) RY: ENTITY BitReg8 PORT MAP(addout,yreg,clk) ADD: ENTITY Adder PORT MAP(xreg,yreg,addout) z <= addout END structural Figure 1.9: vhdl-based description of a system. Introduction to Digital Systems 1 { Introduction CAD (cont.) 25 SYNTHESIS AND OPTIMIZATION { Semi-automated SIMULATION tools generate behavior of a system for given input { Logic simulation { Timing simulation Introduction to Digital Systems 1 { Introduction ...
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This note was uploaded on 02/09/2011 for the course M 16 taught by Professor . during the Spring '10 term at UCLA.

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