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Chapter 1
Introductory Digital
Concepts
1
Chapter Outline
• Digital and Analog Quantities
• Binary Digits, Logic Levels, and Digital
Waveforms
• Introduction to Basic Logic Operations
• Basic Overview of Logic Functions
• Fixed-Function Integrated Circuits
• Programmable Logic Devices (PLDs)
• Introduction to Test Instruments
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Figure 1--1
Graph of an analog quantity (temperature versus time).
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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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Digital Advantages
• Digital Data can be
processed/transmitted more efficiently
and reliably.
• Storage: can be stored more compactly
and reproduced w/ greater accuracy
and clarity.
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Analog Electronic System
Figure 1--3 A basic audio public address system.
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System Using Digital and Analog Methods
Figure 1--4
Basic principle of a CD player. Only one channel is shown.
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Binary Digits
• Two digits in BINARY system, 1 and 0,
called BIT (Binary digit)
• Positive Logic: HIGH=1, LOW=0
• Negative Logic: LOW=1, HIGH=0
• Code : Groups of bits to represent numbers,
letters, symbols, instructions, etc.
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Logic Levels
Voltages used to
represent 1 and 0.
Figure 1--5 Logic level ranges of voltage for a digital circuit.
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Digital Waveforms
Figure 1--6 Ideal pulses.
Figure 1--7
Nonideal pulse characteristics.
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Frequency and Period
• Frequency (f) # cycles per sec or Hertz (Hz)
• Period (T) in seconds.
• f=1/T, T = 1/f
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Periodic and Nonperiodic
Figure 1--8
Examples of digital waveforms.
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Pulse Width and Duty Cycle
Figure 1--9
Duty Cycle = (tw/T)100 %
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Digital Waveform Carries
Binary Information
Figure 1--10 Example of a clock waveform synchronized with a waveform representation
of a sequence of bits.
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Figure 1--11 Example of a timing diagram.
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Data Transfer
Figure 1--12
Illustration of serial and parallel transfer of binary data. Only the data lines are shown.
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Basic Logic Operations and
Symbols
Figure 1--15
The basic logic operations and symbols.
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NOT Operation
Figure 1--16 The NOT operation.
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AND Operation
Figure 1--17 The AND operation.
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OR Operation
Figure 1--18 The OR operation.
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Basic Logic Functions
•
•
•
•
•
•
•
•
Comparison Function
Arithmetic Functions
Code conversion function
Encoding function
Decoding function
Data selection function
Data storage function
Counting function
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Comparison Function
Figure 1--19 The comparison function.
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Arithmetic Function
Figure 1--20 The addition function.
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Code Conversion Function:
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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Code Conversion Function:
Decoder
Figure 1--22 A decoder used to convert a special binary code into a 7-segment decimal readout.
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Data Selection Function
Figure 1--23
Illustration of a basic multiplexing/demultiplexing application.
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Data Storage Function
Figure 1--24 Example of the operation of a 4-bit serial shift register. Each block represents one storage “cell” or flipflop.
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Data Storage Function
Figure 1--25
Example of the operation of a 4-bit parallel shift register.
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Counting Function
Figure 1--26 Illustration of basic counter operation.
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Fixed-Function Integrated
Circuits
Figure 1--27 Cutaway view of one type of fixed-function IC package showing the chip mounted
inside, with connection to input an output pins.
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IC Packages
Figure 1--28 Examples of through-hole and surface-mounted devices. The DIP is larger than the SOIC
with the same number of leads. This particular DIP is approximately 0.785 in. long, and the SOIC is
approximately 0.385 in. long.
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Figure 1--29 Examples of SMT package configurations.
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Pin Numbering
Figure 1--30
Pin numbering for two standard types of IC packages. Top views are shown.
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Integrated Circuit
Technologies
•
•
•
•
•
•
TTL
ECL
CMOS
NMOS
SSI and MSI use TTL or CMOS
VLSI and ULSI use CMOS or NMOS
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Programmable Logic Devices
(PLD)
• Programmable logic devices can replace fixedfunction logic - the major advantage is that the
logic function of the PLD can be changed
without rewiring.
• SPLD (Simple Programmable Logic Devices)
• CPLD (Complex Programmable Logic Devices)
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Types of SPLD
•
•
•
•
PAL (Programmable Array Logic)
GAL (Generic Array Logic)
PLA (Programmable Logic Array)
PROM (Programmable Read-only Memory)
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Types of CPLD
CPLDs
are made using 2 to 64 SPLDs
Figure 1--32 Typical CPLD packages.
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PLD programming
• Schematic Entry
• Text-Based Entry
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Test Equipment
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•
•
•
•
•
•
Analog Oscilloscope
Digital Oscilloscope
Logic Analyzer
Logic Probe, Pulser, and Current Probe
DC Power Supply
Function Generator
Digital Multimeter
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Oscilloscope
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Figure 1--34 A typical dual-channel digital oscilloscope. Numbers below screen are arbitrary and are
shown for illustration only.
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Figure 1--36 A typical dual-channel analog oscilloscope.
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Logic Analyzer
Figure 1--37 Typical logic analyzers
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Logic Probe
Figure 1--38 Illustration of how a logic probe is used to detect various voltage conditions at a
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given point in a circuit.
Figure 1--40 Typical test instruments
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Digital System Application
Figure 1--41
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Simplified basic block diagram for a tablet-counting and bottling control system.