Download Chapter 1:Digital concepts

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DKT 122/3 - DIGITAL SYSTEM I
Chapter 1: Digital Concepts
Mohd ridzuan mohd nor
[email protected]
019-3806067
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Introduction
Digital
 derived from the way computers perform
 operation by counting digits
Applications
 computers
 communications systems
 entertainment
 medical instruments
 consumer electronics
 so much more
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Analogue and Digital
Analogue
 Is a quantity with continuous values
 Most of the things around us are analogue in nature
 Eg: temperature, sound, heat, time etc
Digital
 Is a quantity with a discrete set of values
 consists of logic high “1” and logic low “0”
 analogue quantity is sampled at certain
 interval and represented by a digital code.
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Example: Analog
Figure 1–1 Graph of an analog quantity (temperature versus time).
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Example: Digital
Figure 1–2 Sampled-value representation (quantization) of the analog quantity in Figure
1–1. Each value represented by a dot can be digitized by representing it as a digital code
that consists of a series of 1s and 0s.
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Advantages of Digital
 Can be processed (computer) and transmitted
(communications) more efficiently and reliably than analogue
 can produce greater accuracy and clarity (eg: process that
requires storage – CD,DVD)
 Effective data can retreive
 Noise (unwanted attribute) does not affect digital data nearly
as much as with analog signals
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Example: Basic audio public system
Figure 1–3 A basic audio public address system
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Example: Block diagram of CD player
Figure 1–4 Basic block diagram of a CD player. Only one channel is shown.
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Binary Digits – Logic Levels – Digital
Waveform
Binary Digits
 In binary systems – “1” & “0” is called a bit
 therefore “1” & “0” is a binary digit
 In digital circuits; two different voltage values
- High voltage = “1”
- Low voltage = “0”
 # This is +ve logic;
 # -ve logic is the other way round
 Group of bits; combination of 1s & 0s we called as codes
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Binary Digits – Logic Levels – Digital
Waveform
Logic Levels
• The voltages
to represent
a 1 and a 0
• must be a certain
values of
voltages
Figure 1–5 Logic level ranges of voltage for a digital
circuit.
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Binary Digits – Logic Levels – Digital
Waveform
Digital waveform
Figure 1–6 Ideal pulses.
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Example: Non-ideal Pulse
Characteristics
Figure 1–7 Nonideal pulse characteristics
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Waveform Characteristic
 Most waveform in digital sys composed of series of pulses,
called pulse train
 These pulse train can be:
- periodic – repeated at fixed interval
- non periodic – not repeated at fixed interval
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Question:
Measure:
(a)Period T (b) frequency f (c) duty cycle = (tw/T)100%
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The Clock
 -Is a periodic waveform in which each interval between
pulses(period) equals the time for one bit
Figure 1–10 Example of a clock waveform synchronized with a waveform representation of a
sequence of bits.
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Timing Diagram
 A graph of digital waveform showing the actual time
relationship of two or more waveforms and how each
changes in relation to others
Figure 1–11 Example of a timing diagram.
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Example: Serial and Parallel
Figure 1–12 Illustration of serial and parallel transfer of binary data. Only the data lines are shown.
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Question:
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Basic Logic Gate
Figure 1–15 The basic logic operations and symbols.
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Not gate (Inverter)
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AND gate
 AND Operation = Produces HIGH (1) output when all input
are HIGH
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OR gate
 OR Operation  Produces HIGH ouput when one or more
inputs are HIGH
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Comparator
Figure 1–19 The comparison function.
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Adder
Figure 1–20 The addition function.
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Encoder
Figure 1–21 An encoder used to encode a calculator keystroke into a binary code for storage
or for calculation.
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Decoder
Figure 1–22 A decoder used to convert a special binary code into a 7-segment
decimal readout.
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MUX/DEMUX
Figure 1–23 Illustration of a basic multiplexing/demultiplexing application.
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4-bit Serial Shift Register
Figure 1–24 Example of the operation of a 4-bit serial shift register. Each block represents
one storage “cell” or flip-flop.
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4-bit Parallel Shift Register
Figure 1–25 Example of the operation of a 4-bit parallel shift register.
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Basic Counter
Figure 1–26 Illustration of basic counter operation.
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IC Pin Numbering
Figure 1–30 Pin numbering for two standard types of IC packages. Top views are shown.
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Q&A
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