Chat with us, powered by LiveChat Explain the basic differences between analog and digital technology. Explain the basic differences between the different numbering ?systems (binary, octal, hexadecimal, and decima - Writeedu

05 Apr Explain the basic differences between analog and digital technology. Explain the basic differences between the different numbering ?systems (binary, octal, hexadecimal, and decima

• Explain the basic differences between analog and digital technology.
• Explain the basic differences between the different numbering  systems (binary, octal, hexadecimal, and decimal) presented in this  unit.

EET 130– Digital Systems I

Digital Concepts

2

Outline of the lecture

Digital and Analog quantities

Binary Digits, logic levels and digital waveforms

Classification of Integrated Circuit( IC) Packages

Objective of the Lecture

 After successful completion of the lecture students

will be able to:  Name examples of analog and digital signals

 Identify and define the differences between analog and digital signals

and their characteristics

 Show how voltage levels are used to represent digital quantities

 Identify typical digital signals & a timing diagram

 Describe various parameters of pulse waveform

Introduction

 Digital electronics is essential to understanding the

design and working of a wide range of applications

 consumer and industrial electronics

 Communications, embedded systems

 Computers, security, military equipment

 Integrated Circuits that operate on Digital Data are in

95% of every electrical powered device in the U.S

 The job market for electronic designers and

technicians with Digital Design skills is at an all time

high and will continue growing

5

Analog and Digital Signals

 The term “ signal will appear many times in

this course

 It is anything which conveys information

 It could be a voltage or current waveform from

electronic circuits

 It could be one, two or three dimensional

 Quantifying signals helps us to decide how

to store and transmit messages

Analog and Digital signals…

 Signals are met in diverse fields of engineering

 Elec. Eng. – voltages/currents in a circuit, speech signals,

image signals, video signals

 Mech. Eng. – vibration studies

 Astronomy – (2-D) pulsars, distant stars

 Biomedicine – EEG, ECG, retinoscopy, MRI

 Seismology – tectonic plate movement, earthquake

prediction

 Economics – level of trading in stock market

 Metrology – weather forecast, GPS

Analog and Digital Signals …

 Examples of signals

Analog Signals and Digital Signals

 Analog signals are signals in which the independent variable

is continuous

 These signals are defined for a continuum of values of the

independent variable

 They are continuous in value, in time, or both.

 They are electrical signals whose values vary in analogy

with a physical quantity, e.g., temperature, force,

acceleration

 Digital Signals are signals in which the independent variable

takes a discrete set of values

 These signals are defined only at discrete times. Digital

signals are discrete in value, in time, or both.

Analog Signals

 In analog representation a quantity is

represented by a voltage, current, or meter

movement that is proportional to the value of

that quantity

 Analog quantities vary over a continuous

range of values

Digital Signals

 In digital representation the quantities are

represented by discrete quantities (symbols)

called digits

 Digital watch is the best example of digital

representation

Difference between analog and digital signal

 ANALOG SIGNAL – continuous in value, in time, or both

 It is an electrical signal whose value varies in an analogy with a physical quantity, e.g., temperature, force, acceleration

 DIGITAL SIGNAL – discrete

in value, in time, or both

Analog signal- one whose output varies continuously in step with the input.

Example:

Analog

Digital signal- one whose output varies at discrete voltage levels commonly called HIGH or LOW (1 or 0).

Example:

Digital HIGH or 1

LOW or 0

Time

Difference between analog and digital signal

Difference between analog and digital signal

Difference between analog and digital signal

Analog signals could take any value at any given time

Digital signals take one of two values at any given time

Examples of Analog Signals

Examples of Digital Signals

• Serial transfer of data between computers

• Parallel transfer of data between computer & printer

Application of Analog and Digital Circuits

 Is used to amplify sound so that it can be heard

by a large audience

 It is a simple example of analog systems

Application of Analog and Digital Circuits…

 Compact Disk Players

 is an example of a system in which both digital and

analog circuits are used

Application of Analog and Digital Circuits…

 Digital Watches: in our day to day activity we often see and

use these electronic devices

Application of Analog and Digital Circuits…

 Robotics and control applications

 digital circuits are widely applied in a wide range of applications

from the flight and propulsion systems of commercial airliners to

the cruise control present in many modern automobiles

 Robotic systems could be applied in industries for different

applications where humans could not reach due to environmental

hazards and life hazards

Application of Analog and Digital Circuits…

 Automation

 digital systems are widely applied in process automation in industries

 an automated tablet counting system for pharmaceutical industries is

shown in the next slide

22

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 The most common advantages of digital systems over analog

systems are:

 Easier to design – exact values of voltage or current are

not important, only the range (HIGH or LOW) in which

they fall.

 Flexibility – a digital system can be reconfigured for some

other operations by simply changing the software program

and hardware change is not required

 Accuracy- analog systems suffer from component

tolerance, breakdown etc, whereas accuracy in digital

systems is decided by the resolution of the A/D converter

and number of bits used to represent digital data.

24

 Easy storage- in digital systems storage is very easy and due to

which remote processing of digital signals is possible.

 Mathematical Processing- complex mathematical algorithms

can be performed and implemented easily in digital systems

 Cost- when there is large complexity in the application then

digital systems are cheaper compared to analog systems. In

digital systems the software algorithm may be complex but it

can be implemented accurately with less effort

 Repeatability- Digital systems does not depend on strict

component tolerances and they can be duplicated easily

25

can be reconfigured for other applications as they are software

controlled and no hardware change is required to adapt them

for other applications

 Simplicity- some complex operations in analog systems can

be easily implemented using digital systems

 Noise Immunity and security- digital systems have definite

and quantized levels and they are not corrupted by noise

 Security systems such as encryption and scrambling can be easily done

in digital systems

 Digital systems can be stored in magnetic tape and disks without

deterioration

Drawbacks of Digital Systems …

 The real world is mainly analog

 Most signals of practical interest are analog –

speech, image, video, sonar, radar etc…

 To take advantage of digital techniques when dealing

followed

 Process (operate on) the digital information.

 Convert the digital outputs back to real-world analog form.

(DAC)

Drawbacks of Digital Systems…

 In a collective sense some of the drawbacks

of digital systems are:  Digital techniques are limited to signals with relatively

low bandwidths. Currently digital systems are used for

signals up to video bandwidths (about 10 MHz)

 The cost of high-speed ADCs and DACs and the amount

of digital circuitry required to implement very high-speed

designs (> 100 MHz) makes them impractical for many

applications.

 The need for an ADC and DAC makes digital systems not

economical for simple applications (e.g., a simple filter)

Elements of digital systems

 The figure below shows the most basic elements of digital

systems which allow the processing of analog signals

Reasons to the Shift to Digital Tech

 Chief reasons for the shift to digital technology:  Digital systems are generally easier to design.

 Information storage is easy.

 Accuracy and precision are easier to maintain throughout the

system.

 Operations can be programmed.

 Digital circuits are less affected by noise.

 More digital circuitry can be fabricated on IC chips.

There have been remarkable recent advances in digital technology.

Advances will continue as digital technology expands and improves.

Binary Digits and Logic Levels

 The two digits in the binary system, 1 and 0, are called bits

– a contraction of the words binary digit

 In digital circuits two different voltage levels are used to

represent the two bits

 Generally 1 is represented by the higher voltage, which we

will refer to as HIGH and a zero is represented by the

lower voltage level, which we will refer to as LOW –

Positive Logic

 The reverse of the above notation where we represent 1

with LOW and 0 with HIGH is called Negative Logic

Logic Levels …

 The voltages used to represent a 1 and a 0

are called logic levels

 Ideally, one voltage level represents a

HIGH and another voltage level represents

a LOW

Type of logic Bit “1” Bit “0”

Positive Logic HIGH LOW

Negative Logic LOW HIGH

Logic Levels …

 In practical digital circuits  A HIGH can be any voltage between

a specified minimum value and a

specified maximum value

 A LOW can be any voltage between

a specified minimum value and a

specified maximum

 There is no overlap between the

accepted ranges of HIGH and LOW

levels

Logic Levels …

 In digital systems there are two types of circuit

implementations:

 TTL ( circuits made up of bipolar transistors)

 CMOS ( circuits made up of MOSFET transistors)

 In TTL circuits we adopt the following definitions for HIGH

and LOW levels.

 LOW ≤ 15 % of the supply voltage ( VCC)

 High ≥ 40 % of the supply voltage ( VCC)

 For example, if the supply voltage is +5 volt then the logic

levels become

 LOW ≤ 0.8 V and High ≥ 2 V

Logic Levels …

 In CMOS circuits we adopt the following

definitions for HIGH and LOW levels.

 LOW ≤ 30 % of the supply voltage (Vcc )

 High ≥ 70 % of the supply voltage (Vcc)

 For example, if the supply voltage is +5 volt

then the logic levels become

 LOW ≤ 1.5 V, High ≥ 3.5 V

Logic levels …

 The figure shows the defining levels of

HIGH and LOW for TTL and CMOS logic

Logic levels …

 Binary values are represented by voltage levels

 For ideal voltage levels as in the above figure has zero rise

time and fall time

 This is not practically feasible

Components of Practical Digital Pulse

 Major parts of a digital pulse

 Base line

 Amplitude

 Rise time (tr)

 Pulse width (tw)

 Fall time (tf)

Digital Waveforms

 tw = pulse width

 T = period of the waveform

 f = frequency of the waveform

 The duty cycle of a binary waveform is defined as:

T

1 f 

%100 T

t cycle Duty w 

  

 

Integrated Circuits

 An Integrated circuit (IC) is a number of logic

gates fabricated on a single silicon chip.

 ICs can be classified according to how many

gates they contain as follows:

 Small-Scale Integration (SSI): Contain 1 to 20 gates.

 Medium-Scale Integration (MSI): Contain 20 to 200

gates. Examples: Registers, decoders, counters.

 Large-Scale Integration (LSI): Contain 200 to 200,000

gates. Include small memories, some microprocessors,

programmable logic devices.

 Very Large-Scale Integration (VLSI): Usually stated in

terms of number of transistors contained usually over

1,000,000. Includes most microprocessors and memories.

IC Packaging

 IC packages are classified according to the

way they are mounted on the printed circuit

boards as

 Through – hole mounted – example DIP

 Surface mounted – example SOIC

SMT Package Examples

 IC package styles

 Dual in-line package (DIP) – through hole technology

 Small-outline IC (SOIC) – surface mount technology

Fixed Function Integrated Circuits

 Flat pack (FP) 

Fixed Function Integrated Circuits

Summary

Digital and Analog quantities

Binary Digits, logic levels and digital waveforms

Classification of Integrated Circuit( IC) Packages

Decimal Number System

Binary Number System

Decimal to Binary and Binary to Decimal Conversion

Binary Arithmetic

,

EET 130– Digital Systems I

Number Systems

2

Outline of the lecture

Decimal Number System

Binary Number System

Binary to decimal and Decimal to Binary conversions

Octal Number System

1’s and 2’s complement of binary numbers

Signed numbers

Binary Coded Decimal ( BCD)

Digital Codes

Objective of the Lecture

 After successful completion of the lecture students

will be able to:  State the place values for decimal and binary number systems.

 Convert decimal to binary and binary to decimal number system

 Perform Binary Arithmetic Operations

 State the place values for octal and hexadecimal number systems.

 Convert octal to binary, octal to decimal, binary to octal and decimal

to octal number system

 Determine 1’s and 2’s complement of a binary number

 Express binary numbers in BCD form

 Convert between binary system and Gray code

 Interpret ASCII codes

Number Systems

 Understanding digital systems requires an

understanding of the Number systems.

 Many number systems are in use in digital

technology

 The most common are the decimal, binary, octal,

 The decimal system is clearly the most familiar to us

because it is a tool that we use every day

 Most operations performed in decimal number

system are applied in other number systems too

Decimal Number System

 The decimal system is composed of 10 numerals or symbols.

 These 10 symbols are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9; using these

symbols as digits of a number, we can express any quantity

 The decimal system is also called the base-10 system

because it has 10 digits

 The position of each digit in a decimal number indicates the

magnitude of the quantity represented and can be assigned a

weight:

… 105 104 103 102 101 100 . 10-1 10-2 10-3 10-4 10-5 …

Decimal Number System …

 Example: Express the decimal number 47

as a sum of the values of each digit.

 Solution:

The digit 4 has a weight of 10 (101), as indicated

by its position. The digit 7 has a weight of

1(100), as indicated by its position.

47 = (4 X 101) + (7 X 100)

= (4 X 10) + (7 X 1) = 40 + 7  Exercise: Determine the value of each digit in 939

Decimal Number System…

 Example 2: Express the decimal number 568.25 as a sum

of the values of each digit.

 Solution:

 The whole number digit 5 has a weight of 100 (102), the

digit 6 has a weight of 10(101), the digit 8 has a weight

of 1(100)

 the fractional digit 2 has a weight of 0.1 (10-1), and the

fractional digit 5 has a weight of 0.01 (10-2).

568.25 = (5 X 102) + (6 X 101) + (8 X 100) + (2 X 10-1) + (5 X 10-2)

= (5 X 100) + (6 X 10) + (8 X 1) + (2 X 0.1) + (5 X 0.01)

= 500 + 60 + 8 + 0.2 + 0.05

 Exercise: Determine the value of each digit in 67.924

Binary Number System

 In the binary system, there are only two symbols or possible

digit values, 0 and 1

 This base-2 system can be used to represent any quantity that

can be represented in decimal or other number system

 In a binary number system the number values are

determined by

 The position of the digits multiplied by their positional weighting

Positive Powers of Two (whole numbers Negative Powers of Two (fractional numbers)

28 27 26 25 24 23 22 21 2 2-1 2-2 2-3 2-4 2-5 2-6

256 128 64 32 16 8 4 2 1 ½ 1/4 1/8 1/16 1/32 1/64

0.5 0.25 0.125 0.0625 0.03125 0.015625

Binary Counting

Binary to Decimal Conversion

 Any binary number can be converted to its decimal equivalent

simply by

 summing together the weights of the various positions in the binary

number which contain a 1

 Example 1: Determine the decimal value of the binary whole

number 1101101

Solution:

Determine the weight of each bit that is a 1 and then find the

sum of the weights

Weight: 26 25 24 23 22 21 20

Binary number: 1 1 0 1 1 0 1

1101101 = 26 25 23 22 2 = 64 +32+ 8+ 4+ 1 = 109

 Exercise: What is the decimal value of the binary number 10010001

Binary to Decimal Conversion …

 Example 2: Determine the decimal value of

the fractional binary number 0.1011.

Solution:

First, determine the weight of each bit that is a 1,

and then sum the weights.

Weight: 2-1 2-2 2-3 2-4

Binary number: 0 . 1 0 1 1

0.1011 = 2-1 + 2-3 + 2-4 = 0.5 + 0.125 + 0.0625

= 0.6875

 Exercise: Evaluate the binary number 10.111

Binary to Decimal Conversion …

 The maximum value a binary number can have is

determined by the number of Binary digits or BITS present.

 Therefore: Largest decimal number = 2n – 1

 with five bits (n=5) the biggest decimal number that can be

represented is:

25 – 1 = 32 – 1 = 3110

 To keep track of the digits in a binary numbering system

 the Rightmost digit having the LOWEST weighting is

referred to as the Least Significant Bit, LSB

 the Leftmost digit having the HIGHEST weighting is

referred to as the Most Significant Bit, MSB.

Decimal to Binary Conversion

 Sum of weights method

 Any decimal number can be converted to its

binary equivalent simply

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