The document provides an overview of digital logic design, emphasizing the differences between digital and analog systems, basic digital logic functions, and characteristics of digital waveforms. It covers essential concepts such as binary representation, timing parameters, the use of integrated circuits, and the functionality of logic gates. Additionally, it discusses the applications of digital electronics in various fields and the measurement and troubleshooting of digital circuits.

1. EE-227 Digital Logic Design
EE-227
Digital Logic
Design
Spring-2019
Course Instructor: Engr. Khalid Iqbal Soomro
Chapter 1
Introductory Concepts

2. EE-227 Digital Logic Design
■ Explain the basic differences between digital & analog quantities
■ Show how voltage levels are used to represent digital quantities
■ Describe various parameters of a pulse waveform such as rise
time, fall time, pulse width, frequency, period, and duty cycle
■ Explain the basic logic functions of NOT, AND, and OR
■ Describe several types of logic operations and explain their
application in an example system
■ Identify fixed-function digital integrated circuits according to their
complexity and the type of circuit packaging
■ Identify pin numbers on integrated circuit packages
■ Recognize various instruments and understand how they are used
in measurement and troubleshooting digital circuits and systems
CHAPTER OBJECTIVES
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3. EE-227 Digital Logic Design
The term digital is derived from the way operations are performed,
by counting digits. For many years, applications of digital
electronics were confined to computer systems. Today, digital
technology is applied in a wide range of areas in addition to
computers.
Such applications as television, communications systems, radar,
navigation and guidance systems, military systems, medical
instrumentation, industrial process control, and consumer
electronics use digital techniques.
Over the years digital technology has progressed from vacuum-tube
circuits to discrete transistors to complex integrated circuits, many
of which contain millions of transistors, and many of which are
programmable.
Introduction
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4. EE-227 Digital Logic Design
Most natural quantities that we see are analog and vary
continuously. Analog systems can generally handle higher
power than digital systems. Example: Temperature, Time…
Digital systems can process, store, and transmit data more
efficiently but can only assign discrete values to each point.
Analog Quantities
1
100
A .M.
95
90
85
80
75
2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12
P.M.
Temperature
(°F)
70
Time of day
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5. EE-227 Digital Logic Design
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.
Analog and Digital Systems
Digital data
CD drive
10110011101
Analog
reproduction
of music audio
signal
Speaker
Sound
waves
Digital-to-analog
converter
Linear amplifier
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6. EE-227 Digital Logic Design
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.
Binary Digits and Logic Levels
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
LOW
VH(max)
VH(min)
VL(max)
VL(min)
Invalid
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7. EE-227 Digital Logic Design
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.
Digital Waveforms
Falling or
leading edge
(b) Negative–going pulse
HIGH
Rising or
trailing edge
LOW
(a) Positive–going pulse
HIGH
Rising or
leading edge
Falling or
trailing edge
LOW
t0
t1
t0
t1
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8. EE-227 Digital Logic Design
Actual pulses are not ideal but are described by the rise time,
fall time, amplitude, and other characteristics.
Pulse Definitions
90%
50%
10%
Base line
Pulse width
Rise time Fall time
Amplitude tW
tr tf
Undershoot
Ringing
Overshoot
Ringing
Droop
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9. EE-227 Digital Logic Design
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.
Periodic Pulse Waveforms
T
f
1

f
T
1

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?



GHz
2
.
3
1
1
f
T 313 ps
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10. EE-227 Digital Logic Design
Pulse Definitions
In addition to frequency and period, repetitive pulse waveforms
are described by the amplitude (A), pulse width (tW) and duty
cycle. Duty cycle is the ratio of tW to T.
Volts
Time
Amplitude (A)
Pulse
width
(tW)
Period, T
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11. EE-227 Digital Logic Design
A timing diagram is used to show the relationship between
two or more digital waveforms,
Timing Diagrams
Clock
A
B
C
A diagram like this can be observed
directly on a logic analyzer.
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12. EE-227 Digital Logic Design
Data can be transmitted by either serial transfer or parallel
transfer.
Serial and Parallel Data
Computer Modem
1 0 1 1 0 0 1 0
t0 t1 t2 t3 t4 t5 t6 t7
Computer Printer
0
t0 t1
1
0
0
1
1
0
1
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13. EE-227 Digital Logic Design
Basic Logic Functions
True only if all input conditions
are true.
True only if one or more input
conditions are true.
Indicates the opposite condition.
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14. EE-227 Digital Logic Design
Basic System Functions
And, or, and not elements can be combined to form
various logic functions. A few examples are:
The comparison function
Basic arithmetic functions Adder
Two
binary
numbers
Carry out
A
B
Cout
Cin
Carry in
Sum
Σ
Two
binary
numbers
Outputs
A
B
A< B
A= B
A> B
Comparator
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15. EE-227 Digital Logic Design
Basic System Functions
The encoding function
The decoding function
Decoder
Binary input
7-segment display
Encoder
9
8 9
4 5 6
1 2 3
0 . +/–
7
Calculator keypad
8
7
6
5
4
3
2
1
0
HIGH
Binary code
for 9 used for
storage and/or
computation
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16. EE-227 Digital Logic Design
Basic System Functions
The data selection function
Multiplexer
A
Switching
sequence
control input
B
C
∆t2
∆t3
∆t1
∆t2
∆t3
∆t1
Demultiplexer
D
E
F
Data from
Ato D
Data from
Bto E
Data from
Cto F
Data from
Ato D
∆t1 ∆t2 ∆t3 ∆t1
Switching
sequence
control input
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17. EE-227 Digital Logic Design
Basic System Functions
The counting function
…and other functions such as code conversion
and storage.
Input pulses
1
Counter 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.
2 3 4 5
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18. EE-227 Digital Logic Design
Basic System Functions
One type of storage function is the shift register,
that moves and stores data each time it is clocked.
0 0 0 0
0101
Initially
, the register contains onlyinvalid
data or all zeros as shown here.
1 0 0 0
010
First bit (1) is shifted serially into the
register.
0 1 0 0
01
Second bit (0) is shifted serially into
register and first bit is shifted right.
1 0 1 0
0
Third bit (1) is shifted into register and
the first and second bits are shifted right.
0 1 0 1
Fourth bit (0) is shifted into register and
the first, second,and third bits are shifted
right.The register now stores all four bits
and is full.
Serial bits
on input line
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19. EE-227 Digital Logic Design
Integrated Circuits
Plastic
case
Pins
Chip
Cutaway view of DIP (Dual-In-line Pins) chip:
The TTL series, available as DIPs are popular
for laboratory experiments with logic.
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20. EE-227 Digital Logic Design
An example of laboratory prototyping is shown. The circuit
is wired using DIP chips and tested.
Integrated Circuits
In this case, testing can
be done by a computer
connected to the system.
DIP chips
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21. EE-227 Digital Logic Design
Integrated Circuits
DIP chips and surface mount chips
Pin 1
Dual in-line package Small outline IC (SOIC)
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22. EE-227 Digital Logic Design
Test and Measurement Instruments
The logic analyzer can display multiple channels of digital
information or show data in tabular form.
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23. EE-227 Digital Logic Design
Test and Measurement Instruments
V
1 s
1 s
40 m A
10 A
C O M
Ra nge
Autora nge
Touc h/Hold
Fused
O FF V
V
Hz
m V
A
0.01 V
The DMM can make three basic
electrical measurements.
Voltage
Resistance
Current
In digital work, DMMs are useful for checking power
supply voltages, verifying resistors, testing continuity,
and occasionally making other measurements.
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24. Selected Key Terms
Analog
Digital
Binary
Bit
Pulse
Being continuous or having continuous values.
Related to digits or discrete quantities; having a set
of discrete values.
Having two values or states; describes a number
system that has a base of two and utilizes 1 and 0
as its digits.
A binary digit, which can be a 1 or a 0.
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.

25. Selected Key Terms
Clock
Gate
NOT
AND
OR
A basic timing signal in a digital system; a periodic
waveform used to synchronize actions.
A logic circuit that performs a basic logic
operations such as AND or OR.
A basic logic function that performs inversion.
A basic logic operation in which a true (HIGH)
output occurs only when all input conditions are
true (HIGH).
A basic logic operation in which a true (HIGH)
output occurs when when one or more of the input
conditions are true (HIGH).

26. Selected Key Terms
Fixed-function
logic
Programmable
logic
A category of digital integrated circuits having
functions that cannot be altered.
A category of digital integrated circuits capable of
being programmed to perform specified functions.

27. 1. Compared to analog systems, digital systems
a. are less prone to noise.
b. can represent an infinite number of values
c. can handle much higher power
d. all of the above

28. 2. The number of values that can be assigned to a bit are
a. one
b. two
c. three
d. ten

29. 3. The time measurement between the 50% point on the
leading edge of a pulse to the 50% point on the trailing edge
of the pulse is called the
a. rise time
b. fall time
c. period
d. pulse width.

30. 4. The time measurement between the 90% point on the
trailing edge of a pulse to the 10% point on the trailing edge
of the pulse is called the
a. rise time
b. fall time
c. period
d. pulse width

31. 5. The reciprocal of the frequency of a clock signal is the
a. rise time
b. fall time
c. period
d. pulse width

32. 6. If the period of a clock signal is 500 ps, the frequency is
a. 20 MHz
b. 200 MHz
c. 2 GHz.
d. 20 GHz

33. 7. AND, OR, and NOT gates can be used to form
a. storage devices
b. comparators
c. data selectors
d. all of the above

34. 8. A shift register is an example of a
a. storage device
b. comparator
c. data selector
d. counter

35. 9. A device that is used to switch one of several input lines to
a single output line is called a
a. comparator
b. decoder
c. counter
d. multiplexer

36. Answers:
1. a
2. b
3. d
4. b
5. c
6. c
7. d
8. a
9. d
10. b