BEE 2233 Digital Electronics. Chapter 1: Introduction

Transcription

1 BEE 2233 Digital Electronics Chapter 1: Introduction

2 Learning Outcomes Understand the basic concept of digital and analog quantities. Differentiate the digital and analog systems. Compare the advantages and disadvantages of digital and analog systems. 2

3 Digital and Analog Quantities Digital Analog BEE1213/Chapter1/rhs 3

4 Activities: List the differences between digital and analog quantities. Digital Quantities are represented not by proportional quantities but by symbols called digits. Examples: digital watch, tenposition switch. Discrete (step by step) Analog Quantity is represented by a voltage, current or meter movement that is proportional to the value of that quantity. Examples: automobile speedometer, mercury thermometer. Continuously varying BEE1213/Chapter1/rhs 4

5 Digital & Analog Quantities Digital Analog Digital quantities have discrete sets of values Analog quantities have continuous values BEE1213/Chapter1/rhs 5

6 Numerical Representation BEE1213/Chapter1/rhs 6

7 Numerical Representation BEE1213/Chapter1/rhs 7

8 Digital & Analog Quantities Types of electronic devices or instruments Digital Analog Combination of digital and analog Give your example : BEE1213/Chapter1/rhs 8

9 Digital Systems A combination of devices designed to manipulate physical quantities that are represented in digital form. Usually are electronic devices, but can be also mechanical, pneumatic or magnetic. Computer, calculator and digital telephone are some of the examples. BEE1213/Chapter1/rhs 9

10 Advantages of Digital Systems Generally easier to design - programmable Information storage is easy. Accuracy and precision are easier to maintain. More digital circuitry can be fabricated on IC chip. Less affected by noise. Robustness if the noise is less than the noise margin then the system performs as if there were no noise at all BEE1213/Chapter1/rhs 10

11 Advantages of Digital Systems BEE1213/Chapter1/rhs 11

12 Disadvantages of Digital Systems The real world is analog. Processing digitized signal takes time. To take advantage of digital technology: convert analog inputs to digital process the digital convert digital outputs to analog BEE1213/Chapter1/rhs 12

13 Brief Introduction to Digital Electronics BEE1213/Chapter1/rhs 13

14 Binary Digits, Logic Levels, and Digital Waveforms

15 Binary Digits, Logic Levels &Digital Waveforms The conventional numbering system uses ten digits: 0,1,2,3,4,5,6,7,8, and 9. The binary numbering system uses just two digits: 0 and 1.

16 Binary Digits, Logic Levels &Digital Waveforms The two binary digits are designated 0 and 1 They can also be called LOW and HIGH, where LOW = 0 and HIGH = 1 They can also be called ON and OFF, where ON = 1 and OFF = 0

17 Binary Digits, Logic Levels &Digital Waveforms Other two state devices: - Light bulb (off or on) - Diode (conducting or not conducting) - Relay (energized or not energized) - Transistor (cutoff & saturation/ linear & active) - Photocell (illuminated or dark)

18 Binary Digits, Logic Levels &Digital Waveforms Binary values are also represented by voltage levels

19 Binary Digits, Logic Levels &Digital Waveforms Timing diagrams show voltage versus time. Horizontal scale represents regular intervals of time beginning at time zero. Timing diagrams are used to show how digital signals change with time. Timing diagrams are used to compare two or more digital signals. The oscilloscope and logic analyzer are used to produce timing diagrams.

20 Binary Digits, Logic Levels &Digital Waveforms Major parts of a digital pulse Base line Amplitude Rise time (t r ) Pulse width (t w ) Fall time (t f )

21 Binary Digits, Logic Levels &Digital Waveforms t w = pulse width T = period of the waveform f = frequency of the waveform f 1 T

22 Binary Digits, Logic Levels &Digital Waveforms The duty cycle of a binary waveform is defined as: Duty cycle tw 100% T

23 Basic Logic Operation

24 Basic Logic Operations There are only three basic logic operations:

25 Basic Logic Operations The NOT operation When the input is LOW, the output is HIGH When the input is HIGH, the output is LOW The output logic level is always opposite the input logic level.

26 Basic Logic Operations The AND operation When any input is LOW, the output is LOW When both inputs are HIGH, the output is HIGH

27 Basic Logic Operations The OR operation When any input is HIGH, the output is HIGH When both inputs are LOW, the output is LOW

28 Overview of Basic Logic Function

29 Overview of Basic Logic Functions Comparison Arithmetic Code conversion Encoding Decoding Data selection Data storage Counting

30 Overview of Basic Logic Functions Comparison function Compares two binary values and determines whether or not they are equal

31 Overview of Basic Logic Functions Arithmetic functions Perform the basic arithmetic operations on two binary values: Addition Subtraction of two values Multiplication Division

32 Overview of Basic Logic Functions Code conversion function Converts, or translates, information from one code format to another

33 Overview of Basic Logic Functions Encoding function Converts non-binary information into a binary code

34 Overview of Basic Logic Functions Decoding function Converts binary-coded information into a non-binary form

35 Overview of Basic Logic Functions Data selection function Multiplexer (MUX) Switches digital data from any number of input sources to a single output line Demultiplexer (DEMUX) switches digital data from a single input to any number of output lines

36 Overview of Basic Logic Functions Data storage function Retains binary data for a period of time Flip-flops (bistable multvibrators) Registers Semiconductor memories Magnetic-media memories Optical-media memories

37 Overview of Basic Logic Functions Counting function Generates sequences of digital pulse that represent numbers

38 Application of digital system

39 Data transmission Serial each bit in a binary number is transmitted per some time interval. Serial is slower but requires a single path Parallel all bits in a binary number are transmitted simultaneously. A separate line is required for each bit. Parallel transmission is faster but requires more paths.

40 Memory / Memoryless System Memory: ability to retains a response to a momentary input Important to store binary numbers temporarily /permanently Memory elements: Magnetic, optical, electronic latching circuits Memory Memoryless

41 Fixed Function Integrated Circuit

42 Fixed-Function Integrated Circuits IC package styles Dual in-line package (DIP) Small-outline IC (SOIC) Flat pack (FP) Plastic-leaded chip carrier (PLCC) Leadless-ceramic chip carrier (LCCC)

43 Fixed-Function Integrated Circuits Dual in-line package (DIP)

44 Fixed-Function Integrated Circuits Small-outline IC (SOIC)

45 Fixed-Function Integrated Circuits Flat pack (FP)

46 Fixed-Function Integrated Circuits Plastic-leaded chip carrier (PLCC)

47 Fixed-Function Integrated Circuits Leadless-ceramic chip carrier (LCCC)

48 Introduction to Programmable Logic

49 Introduction to Programmable Logic SPLD Simple programmable logic devices CPLD Complex programmable logic devices FPGA Field-programmable gate arrays

50 Introduction to Programmable Logic SPLD PAL (programmable array logic) GAL (generic array logic) PLA (programmable logic array) PROM (programmable read-only memory)