Download Basic System Functions

Digital
Fundamentals
Tenth Edition
Floyd
Chapter 1
Floyd, Digital Fundamentals, 10th ed
© 2008 Pearson Education
Outline
•
•
•
•
•
•
1-1 Digital and Analog Quantities
1-2 Digits, Logic Levels, and Digital Waveforms
1-3 Basic Logic Operations
1-4 Basic System Functions
1-5 Fixed-Function Integrated Circuits
1-6 Test and Measurement Instruments
Floyd, Digital Fundamentals, 10th ed
Analog Quantities
• Most natural quantities that we see are analog and vary continuously.
• Digital systems: (1) changes occur discretely
Temperature
(°F)
100
95
90
85
80
75
70
Time of day
1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
A .M .
Floyd, Digital Fundamentals, 10th ed
P.M .
Digital Signal
(2) can take values from fix levels (of the Y-axis) only!
Floyd, Digital Fundamentals, 10th ed
Example
Floyd, Digital Fundamentals, 10th ed
Digital vs. Analog Signal
• Pros:
– reduce transmission noise
– can process, store, and transmit data more efficiently
• Cons:
– can only assign discrete values to each point.
Signal to send: 2V
Transmission
Error: 0.3V
How about when transmission error is 0.7V?
Floyd, Digital Fundamentals, 10th ed
Analog signal
Domain: 0-5 V
Signal received: 2.3V
Final error: 0.3V
Digital signal
Domain: {0,1,2,3,4,5} V
Signal received: 2V
Final Error: 0V
A Complete Digital Systems
Analog
Input
Analog-toDigital
Converter
(ADC)
Digital
Processing
System
Digital-toAnalog
Converter
(DAC)
Computer,
Calculator,
Watch,
Measuring instrument
etc.
Floyd, Digital Fundamentals, 10th ed
Analog
Output
Analog and Digital Systems Example
• Many systems use a mix of analog and digital electronics to take
advantage of each technology.
• A typical CD player accepts digital data from the CD drive and converts it
to an analog signal for amplification.
CD drive
10110011101
Digital data
Digital-to-analog
converter
Linear amplifier
Analog
reproduction
of music audio
signal
Speaker
Sound
waves
Floyd, Digital Fundamentals, 10th ed
Digital System Hierarchy
Digital Systems
Sub Systems
Modules
Basic Units
Circuits
Floyd, Digital Fundamentals, 10th ed
Latches, Flip-flops
Logic Gates
Transistors, Resistors, Capacitors
Outline
•
•
•
•
•
•
1-1 Digital and Analog Quantities
1-2 Digits, Logic Levels, and Digital Waveforms
1-3 Basic Logic Operations
1-4 Basic System Functions
1-5 Fixed-Function Integrated Circuits
1-6 Test and Measurement Instruments
Floyd, Digital Fundamentals, 10th ed
Binary Digits and Logic Levels
Digital electronics uses circuits that have two states, which are represented
by two different voltage levels called HIGH and LOW. The voltages represent
numbers in the binary system.
VH(max)
In binary, a single number is called a bit (for
binary digit). A bit can have the value of
either a 0 or a 1, depending on if the voltage
is HIGH or LOW.
HIGH
VH(min)
Invalid
VL(max)
LOW
VL(min)
Floyd, Digital Fundamentals, 10th ed
Digital Waveforms
• Digital waveforms change between the LOW and HIGH levels.
• A positive going pulse is one that goes from a normally LOW logic level to
a HIGH level and then back again.
• Digital waveforms are made up of a series of pulses.
HIGH
HIGH
Rising or
leading edge
LOW
Falling or
trailing edge
t0
(a) Positive–going pulse
Floyd, Digital Fundamentals, 10th ed
t1
Falling or
leading edge
LOW
Rising or
trailing edge
t0
(b) Negative–going pulse
t1
Pulse
Actual pulses are not ideal but are described by the rise time, fall time,
amplitude, and other characteristics.
Overshoot
Ringing
Droop
90%
Amplitude
tW
50%
Pulse width
10%
Ringing
Base line
Floyd, Digital Fundamentals, 10th ed
Undershoot
tr
tf
Rise time
Fall time
Periodic Pulse Waveforms
Periodic pulse waveforms are composed of pulses that repeats in a fixed
interval called the period. The frequency is the rate it repeats and is
measured in hertz.
f 
1
T
T
1
f
The clock is a basic timing signal that is an example of a periodic wave.
What is the period of a repetitive wave if f = 3.2 GHz?
T
Floyd, Digital Fundamentals, 10th ed
1
1

 313 ps
f 3.2 GHz
Pulse Definitions
• Repetitive pulse waveforms are described by
–
–
–
–
frequency and period
amplitude (A)
pulse width (tW)
duty cycle: the ratio of tW to T
Volts
Amplitude (A)
Pulse
width
(tW)
Time
Period, T
Floyd, Digital Fundamentals, 10th ed
Timing Diagrams
• A timing diagram is used to show the relationship between two or more
digital waveforms,
• A diagram like this can be observed directly on a logic analyzer.
Clock
A
B
C
Floyd, Digital Fundamentals, 10th ed
Serial and Parallel Data
Data can be transmitted by either serial transfer or parallel transfer.
1
serial
t0
0
t1
1
t2
1
t3
0
0
t 4 t 5 t6
1
0
t7
Computer
Modem
1
Computer
Printer
0
1
1
0
parallel
0
1
0
t0
Floyd, Digital Fundamentals, 10th ed
t1
Outline
•
•
•
•
•
•
1-1 Digital and Analog Quantities
1-2 Digits, Logic Levels, and Digital Waveforms
1-3 Basic Logic Operations
1-4 Basic System Functions
1-5 Fixed-Function Integrated Circuits
1-6 Test and Measurement Instruments
Floyd, Digital Fundamentals, 10th ed
Basic Logic Operations
True only if all input conditions are
true.
True only if one or more input
conditions are true.
Indicates the opposite condition.
Floyd, Digital Fundamentals, 10th ed
Basic System Functions
• AND, OR, and NOT elements can be combined to form various logic
functions. A few examples are:
The comparison function
A
Comparator
A> B
Two
binary
numbers
A= B
B
A< B
Adder
Basic arithmetic functions
A
Two
binary
numbers
B
Carry in
Floyd, Digital Fundamentals, 10th ed
Outputs
Cin
Σ
Cout
Sum
Carry out
Basic System Functions
HIGH
The encoding function
7
4
8
5
9
6
1
2
3
0
.
+/–
9
8
7
6
5
4
3
2
1
0
Encoder
Binary code
for 9 used for
storage and/or
computation
Calculator keypad
The decoding function
Decoder
Binary input
7-segment display
Floyd, Digital Fundamentals, 10th ed
Basic System Functions
The data selection function
Multiplexer
A
∆t1
B
Demultiplexer
Data from
A to D
Data from
B to E
Data from
C to F
Data from
A to D
∆ t1
∆ t2
∆ t3
∆t 1
D
∆t1
E
∆t2
∆t2
∆t3
∆t3
Switching
sequence
control input
Switching
sequence
control input
C
Floyd, Digital Fundamentals, 10th ed
F
Basic System Functions
The counting function
Counter
1
2
3
4
Input pulses
5
Floyd, Digital Fundamentals, 10th ed
Parallel
output lines
Binary
code
for 1
Binary
code
for 2
Binary
code
for 3
Binary
code
for 4
Binary
code
for 5
Sequence of binary codes that represent
the number of input pulses counted.
Outline
•
•
•
•
•
•
1-1 Digital and Analog Quantities
1-2 Digits, Logic Levels, and Digital Waveforms
1-3 Basic Logic Operations
1-4 Basic System Functions
1-5 Fixed-Function Integrated Circuits
1-6 Test and Measurement Instruments
Floyd, Digital Fundamentals, 10th ed
Integrated Circuits
Cutaway view of DIP (Dual-In-line Pins) chip:
Chip
Plastic
case
Pins
DIPs are popular for laboratory experiments with logic.
Floyd, Digital Fundamentals, 10th ed
Integrated Circuits
Laboratory prototyping. The circuit is wired using DIP chips and tested.
Testing can be done by a
computer connected to the
system.
DIP chips
Floyd, Digital Fundamentals, 10th ed
Integrated Circuits
Pin 1
Dual in-line package
Floyd, Digital Fundamentals, 10th ed
Small outline IC (SOIC)
Outline
•
•
•
•
•
•
1-1 Digital and Analog Quantities
1-2 Digits, Logic Levels, and Digital Waveforms
1-3 Basic Logic Operations
1-4 Basic System Functions
1-5 Fixed-Function Integrated Circuits
1-6 Test and Measurement Instruments
Floyd, Digital Fundamentals, 10th ed
Test and Measurement Instruments
The front panel controls for a general-purpose oscilloscope can be divided
into four major groups.
VERTICAL
CH 1
CH 2
HORIZONTAL
TRIGGER
BOTH
SLOPE
Ð
POSITION
POSITION
VOLTS/DIV
VOLTS/DIV
+
LEVEL
POSITION
SEC/DIV
SOURCE
CH 1
CH 2
5V
2 mV
5V
2 mV
5s
5 ns
EXT
LINE
COUPLING
COUPLING
AC-DC-GND
AC-DC-GND
TRIG COUP
DC
DISPLAY
PROBE COMP
5V
INTENSITY
Floyd, Digital Fundamentals, 10th ed
CH 1
CH 2
EXT TRIG
AC
Test and Measurement Instruments
The logic analyzer can display multiple channels of digital information or
show data in tabular form.
Floyd, Digital Fundamentals, 10th ed
Test and Measurement Instruments
The Digital Multimeter (DMM) can make three
basic electrical measurements.
0.01 V
OFF
V
Hz
V
Voltage
Resistance
Current
mV
A
Range
Autorange
Touc h/Hold
Floyd, Digital Fundamentals, 10th ed
1s
V
40 m A
COM
Fused
DMMs are useful for
• checking power supply voltages
• verifying resistors
• testing continuity
1s
10 A
Programmable Logic Devices (PLDs)
• an alternative to fixed function devices.
• can be programmed for a specific purpose.
• cost less and use less board space
• e.g.: programmable logic array with AND and OR gates
Programmable
AND array
Floyd, Digital Fundamentals, 10th ed
Fixed OR
array and
output logic
Selected Key Terms
Analog Being continuous or having continuous values.
Digital Related to digits or discrete quantities; having a set of
discrete values.
Binary Having two values or states; describes a number system that
has a base of two and utilizes 1 and 0 as its digits.
Bit A binary digit, which can be a 1 or a 0.
Pulse A sudden change from one level to another, followed after a
time, called the pulse width, by a sudden change back to the
original level.
Floyd, Digital Fundamentals, 10th ed
Selected Key Terms
Clock A basic timing signal in a digital system; a periodic waveform
used to synchronize actions.
Gate A logic circuit that performs a basic logic operations such as
AND or OR.
NOT A basic logic function that performs inversion.
AND A basic logic operation in which a true (HIGH) output occurs
only when all input conditions are true (HIGH).
OR A basic logic operation in which a true (HIGH) output occurs
when when one or more of the input conditions are true
(HIGH).
Floyd, Digital Fundamentals, 10th ed
Selected Key Terms
Fixed-function A category of digital integrated circuits having functions that
logic cannot be altered.
Programmable A category of digital integrated circuits capable of being
logic programmed to perform specified functions.
Floyd, Digital Fundamentals, 10th ed