Digital Fundamentals
CHAPTER 1
Digital Concepts
Digital and Analog Quantities
Analog quantities have
continuous values
Digital quantities have
discrete sets of values
2
Binary Digits, Logic Levels, and 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
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Figure 1–3
A basic audio public address system.
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Figure 1–5
Logic level ranges of voltage for a digital circuit.
2.0 V
0.8 V
0V
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Figure 1–6
Ideal pulses.
Binary values are also represented by voltage levels.
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Figure 1–7
Nonideal pulse characteristics.
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Binary Digits, Logic Levels, and Digital Waveforms
• tw = pulse width
• T = period of the waveform
• f = frequency of the waveform
1
f
T
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Binary Digits, Logic Levels, and Digital Waveforms
The duty cycle of a binary waveform is
defined as:
 tw 
Duty cycle  
100%
 T 
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Figure 1–9
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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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Figure 1–12
Illustration of serial and parallel transfer of binary data. Only the data lines are shown.
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Figure 1–13
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Figure 1–14
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Basic Logic Operations
There are only three basic logic operations:
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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.
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Basic Logic Operations
• The AND operation
– When any input is LOW,
the output is LOW
– When both inputs are
HIGH, the output is
HIGH
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Basic Logic Operations
• The OR operation
– When any input is
HIGH, the output is
HIGH
– When both inputs are
LOW, the output is LOW
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Overview of 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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Figure 1–19
The comparison function.
Comparison function
• Compares two binary values and determines
whether or not they are equal
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Overview of Basic Logic Functions
Arithmetic functions
• Perform the basic arithmetic
operations on two binary values:
– Addition
– Subtraction of two values
– Multiplication
– Division
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Figure 1–20
The addition function.
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Code conversion function
• Converts, or translates, information
from one code format to another
Encoding function
• Converts non-binary information
into a binary code
Decoding function
• Converts binary-coded information
into a non-binary form
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Figure 1–21
An encoder used to encode a calculator keystroke into a binary code for storage or for calculation.
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Figure 1–22
A decoder used to convert a special binary code into a 7-segment decimal readout.
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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
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Figure 1–23
Illustration of a basic multiplexing/demultiplexing application.
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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
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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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Figure 1–25
Example of the operation of a 4-bit parallel shift register.
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Figure 1–26
Illustration of basic counter operation.
Counting function
• Generates sequences of digital
pulse that represent numbers
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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)
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Figure 1–27
Cutaway view of one type of fixed-function IC package showing the chip mounted inside, with connections to
input and output pins.
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Fixed-Function Integrated Circuits
• Dual in-line package (DIP)
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Fixed-Function Integrated Circuits
• Small-outline IC (SOIC)
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Figure 1–29
Examples of SMT package configurations.
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Figure 1–30
Pin numbering for two standard types of IC packages. Top views are shown.
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Introduction to Programmable Logic
• SPLD—Simple programmable logic
devices
• CPLD—Complex programmable logic
devices
• FPGA—Field-programmable gate arrays
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Figure 1–31
Programmable logic.
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Introduction to Programmable Logic
• SPLD
– PAL (programmable array logic)
– GAL (generic array logic)
– PLA (programmable logic array)
– PROM (programmable read-only memory)
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Figure 1–32
Block diagrams of simple programmable logic devices (SPLDs).
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Figure 1–34
General block diagram of a CPLD.
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Figure 1–36
Basic structure of an FPGA.
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Figure 1–38
Basic configuration for programming a PLD or FPGA.
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Test and Measurement Instruments
•
•
•
•
Analog Oscilloscope
Digital Oscilloscope
Logic Analyzer
Logic Probe, Pulser, and Current
Probe
• DC Power Supply
• Function Generator
• Digital Multimeter
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Figure 1–40
A typical dual-channel oscilloscope. Used with permission from Tektronix, Inc.
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Figure 1–41
Comparison of analog and digital oscilloscopes.
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Figure 1–42
Block diagram of an analog oscilloscope.
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Figure 1–43
Block diagram of a digital oscilloscope.
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Figure 1–44
A typical dual-channel oscilloscope. Numbers below screen indicate the values for each division on the vertical
(voltage) and horizontal (time) scales and can be varied using the vertical and horizontal controls on the scope.
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Figure 1–45
Comparison of an untriggered and a triggered waveform on an oscilloscope.
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Figure 1–46
Displays of the same waveform having a dc component.
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Figure 1–47
An oscilloscope voltage probe. Used with permission from Tektronix, Inc.
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Figure 1–48
Probe compensation conditions.
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Figure 1–49
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Figure 1–50
Typical logic analyzer. Used with permission from Tektronix, Inc.
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Figure 1–51
Simplified block diagram of a logic analyzer.
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Figure 1–52
Two logic analyzer display modes.
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Figure 1–53
A typical multichannel logic analyzer probe. Used with permission from Tektronix, Inc.
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Figure 1–54
Typical signal generators. Used with permission from Tektronix, Inc.
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Figure 1–55
Illustration of how a logic pulser and a logic probe can be used to apply a pulse to a given point and check for
resulting pulse activity at another part of the circuit.
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Figure 1–56
Typical dc power supplies. Courtesy of B+K Precision.®
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Figure 1–57
Typical DMMs. Courtesy of B+K Precision.®
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Figure 1–60
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Figure 1–61
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Figure 1–62
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Figure 1–63
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Figure 1–64
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