Chapter 1 – Introductory Concepts
ANALOG AND DIGITAL SIGNAL
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OBJECTIVES
Selected areas covered in this chapter:
Analog & digital representations.
How information is represented using two states.
Advantages/drawbacks of digital/analog techniques.
Analog-to-digital and digital-to-analog converters.
Basic characteristics of the binary number system.
Convert binary numbers to decimal equivalents.
Identify typical digital signals & a timing diagram.
Differences between parallel & serial transmission.
Major parts of a digital computer, their functions.
Properties of memory.
Distinguish among microcomputers, micro-processors, and micro-controllers.
1-1 INTRODUCTION TO ANALOG SIGNAL
An analog signal is a continuous wave denoted by a sine wave and may vary in signal strength (amplitude) or frequency (waves per unit time).
The sine wave’s amplitude value can be seen as the higher and lower points of the wave, while the frequency value is measured in the sine wave’s physical length from left to right.
Analog Signal
1-1 INTRODUCTION TO DIGITAL 1S AND 0S
Digital signals carry the data although it is a bit different. These signals are discrete or not continuous. A digital signal carries the data in the form of binary because it signifies in the bits.
The electric signal is either on or off at all times.
This relates to modern digital systems that use electrical signals to represent 1s and 0s.
Digital Signal
1-1 INTRODUCTION TO DIGITAL 1S AND 0S
By displaying one or more digital signals using test instruments such as an oscilloscope, we can compare actual signals to expected operation.
Example of digital signal around us:
HDMI for video (and audio)
1-2 NUMERICAL REPRESENTATIONS
Physical systems use quantities which must be manipulated arithmetically.
Quantities may be represented numerically in either analog or digital form.
1-2 NUMERICAL REPRESENTATIONS
Analog Representation—a continuously variable, proportional indicator.
Sound through a microphone causes voltage changes.
Automobile speedometer changes with speed.
Mercury thermometer varies over a range of values with temperature.
1-2 NUMERICAL REPRESENTATIONS
Digital Representation—varies in discrete (separate) steps.
Passing time is shown as a change in the display
on a digital clock at one minute intervals.
A change in temperature is shown on a digital
display only when the temperature changes
at least one degree.
1-3 DIGITAL AND ANALOG SYSTEMS
Digital system:
A combination of devices that manipulate values represented in digital form.
Analog system:
A combination of devices that manipulate values represented in analog form.
1-3 DIGITAL AND ANALOG SYSTEMS
Advantages of digital:
Ease of design
Well suited for storing information.
Accuracy and precision are easier to maintain.
Programmable operation.
Less affected by noise.
Ease of fabrication on IC chips.
1-3 DIGITAL AND ANALOG SYSTEMS
There are limits to digital techniques:
The analog nature of the world requires a time consuming conversion process:
Convert the physical variable to an electrical signal (analog).
Convert the analog signal to digital form.
Process (operate on) the digital information.
Convert the digital output back to real-world analog form.
1-3 DIGITAL AND ANALOG SYSTEMS
A digital system is a combination of devices designed to manipulate logical information or physical quantities represented in digital form.
Quantities can take on only discrete values.
An analog system manipulates physical quantities represented in analog form.
Quantities can vary over a continuous range
of values.
1-3 DIGITAL AND ANALOG SYSTEMS
Temperature-regulation system
using an analog-to-digital converter.
1-3 DIGITAL AND ANALOG SYSTEMS
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.
1-4 DIGITAL NUMBER SYSTEMS
Understanding digital systems requires an understanding of the decimal, binary, octal,
and hexadecimal numbering systems.
Decimal – 10 symbols (base 10)
Hexadecimal – 16 symbols (base 16)
Octal – 8 symbols (base 8)
Binary – 2 symbols (base 2)
1-4 DIGITAL NUMBER SYSTEMS
The Decimal (base 10) System
10 symbols: 0, 1, 2, 3, 4, 5, 6 , 7, 8, 9.
Each number is a digit (from Latin for finger).
Most significant digit (MSD) & least significant digit (LSD).
Positional value may be stated as a digit multiplied by a power of 10.
1-4 DIGITAL NUMBER SYSTEMS
1-4 DIGITAL NUMBER SYSTEMS
The Binary (base 2) System
2 symbols: 0,1
Lends itself to electronic circuit design since only
two different voltage levels are required.
Positional value may
be stated as a digit multiplied by a
power of 2.
1-4 DIGITAL NUMBER SYSTEMS
1-5 REPRESENTING BINARY QUANTITIES
Analog signals can be converted to digital by taking measurements or “samples” of the continuously varying signal at regular intervals.
Appropriate time between samples depends on
the maximum rate of change of the analog signal.
1-5 REPRESENTING BINARY QUANTITIES
Typical representation of the
two states of a digital signal.
A higher range of voltages represent a valid 1 and
a lower range of voltages represent a valid 0.
HIGH and LOW are often used to describe the states
of a digital system—instead
of “1” and “0”
1-5 REPRESENTING BINARY QUANTITIES
Two state devices:
Light bulb (off or on)
Diode (conducting or not conducting)
Relay (energized or not energized)
Transistor (cutoff or saturation)
Photocell (illuminated or dark)
1-5 REPRESENTING BINARY QUANTITIES
The oscilloscope and logic analyzer are used to produce timing diagrams.
Timing diagrams show voltage versus time.
Used to show how digital signals change with time,
or to compare two or more digital signals.
Horizontal scale represents regular intervals, starting
at time zero.
1-9 DIGITAL COMPUTERS
A computer is a system of hardware that performs arithmetic operations, manipulates data, and makes decisions.
Performs operations based on instructions in the
form of a program at high speed, and with a high degree of accuracy.
1-9 DIGITAL COMPUTERS
Major parts of a computer:
Input unit—Processes instructions and data
into the memory.
Memory unit—Stores data and instructions.
Control unit—Interprets instructions and sends appropriate signals to other units as instructed.
Arithmetic/logic unit—arithmetic calculations
and logical decisions are performed.
Output unit—presents information from the
memory to the operator or process.
1-9 DIGITAL COMPUTERS
The control and arithmetic/logic units are often treated
as one and called the central processing unit (CPU).
END of Chapter 1
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