An embedded system is a microprocessor-based computer hardware system with software that is designed to perform a dedicated function, either as an independent system or as a part of a large system. At the core is an integrated circuit designed to carry out computation for real-time operations.

1. Introduction to Real-
time and Embedded
Systems
1

2. What is System?
System is an arrangement in
which all its unit assemble work
together according to a set of
rules.
System is a way of working,
organizing or doing one or many
tasks according to a fixed plan.
1

3. System—Time Display System
For example, a watch is a time
displaying system. Its
components follow a set of rules
to show time. If one of its parts
fails, the watch will stop
working. So we can say, in a
system, all its subcomponents
depend on each other.
Watch Parts: hardware, Needles,
Battery, Dial, Chassis and Strap.
2

4. System—Time Display System
Rules
1.All needles move clockwise only
2.A thin needle rotates every
second
3.A long needle rotates every
minute
4.A short needle rotates every hour
5.All needles return to the original
position after 12 hours
3

5. System—Automatic Clothes Washing System
WASHING MACHINE: It is
an automatic clothes washing
SYSTEM
Parts:
• Status display panel,
• Switches & Dials,
• Motor,
• Power supply & control unit,
• Inner water level sensor and
• solenoid valve.
4

6. System—Automatic Clothes Washing System
Rules
1.Wash by spinning
2.Rinse
3.Drying
4.Wash over by blinking
5.Each step display the
process stage
6.In case interruption, execute
only the remaining
5

7. What is Embedded System?
Definition 1: Embedded systems (ES)
= information processing systems
embedded into a larger product such
as telecommunication equipment's,
transportation services, etc.
Definition 2: It is a dedicated
computer based system for an
application(s) or product. It may be an
independent system or a part of large
system. Its software usually embeds
into a ROM (Read Only Memory) or
flash.”
6

8. What is Embedded System?
Definition 3: An embedded system is
one that has a dedicated purpose
software embedded in a computer
hardware.
Definition 4: It is a dedicated
computer based system for an
application(s) or product. It may be an
independent system or a part of large
system. Its software usually embeds
into a ROM (Read Only Memory) or
flash.”
7

9. What is Embedded System?
Definition 5: It is any device that
includes a programmable computer
but is not itself intended to be a
general purpose computer.”
Definition 6: Embedded Systems are
the electronic systems that contain a
microprocessor or a microcontroller,
but we do not think of them as
computers– the computer is hidden or
embedded in the system.” – Todd D.
Morton
8

10. Components of Embedded Systems
It has Hardware: Processor, Timers,
Interrupt controller, I/O Devices,
Memories, Ports, etc.
It has main Application Software:
Which may perform concurrently the
series of tasks or multiple tasks.
It has Real Time Operating System
(RTOS): RTOS defines the way the
system work. Which supervise the
application software. It sets the rules
during the execution of the
application program. A small scale
embedded system may not need an
RTOS.
9

11. Components of Embedded Systems
Most embedded systems do not use
keyboards, mice and large computer
monitors for their user-interface.
Instead, there is a dedicated user-
interface consisting of push-buttons,
steering wheels, pedals etc. Because of
this, the user hardly recognizes that
information processing is involved.
10

12. Characteristics of an Embedded
System
o Single-functioned
o Reactive and Real time
o Distributed systems
o Heterogeneous architecture
o Harsh environment
o System safety and reliability
o Control of psychical system
o Small and low weight
o Cost sensitivity
o Power management
o Connected
11

13. Single-functioned
o Embedded systems are dedicated
towards a certain application. For
example, processors running control
software in a car or a train will always
run that software, and there will be no
attempt to run a computer game or
spreadsheet program on the same
processor. There are mainly two
reasons for this:
12

14. Single-functioned
• Running additional programs would
make those systems less dependable
or reliable.
• Running additional programs is only
feasible if resources such as memory
are unused. No unused resources
should be present in an efficient
system.
13

15. Real-time Constraints
 Many embedded systems must meet real-
time constraints. Not completing
computations within a given time-frame can
result in a serious loss of the quality
provided by the system (for example, if the
audio or video quality is affected) or may
cause harm to the user (for example, if cars,
trains or planes do not operate in the
predicted way).
 A time-constraint is called hard if not meeting
that constraint could result in a catastrophe. All
other time constraints are called soft.
14

16. Distributed Systems
• A common characteristic of an
embedded system is one that consists
of communicating processes executing
on several CPUs or ASICs which are
connected by communication links.
• The reason for this is economy.
Economical 48-bit microcontrollers
may be cheaper than a 32-bit
processors.
• Even after adding the cost of the
communication links, this approach
may be preferable.
15

17. Distributed Systems
• In this approach, multiple
processors are usually required
to handle multiple time-critical
tasks. Devices under control of
embedded systems may also be
physically distributed.
16

18. Heterogeneous Architectures
o Embedded systems often are composed
of heterogeneous architectures.
o They may contain different processors in
the same system solution.
o They may also be mixed signal systems.
The combination of I/O interfaces, local
and remote memories, and sensors and
actuators makes embedded system
design truly unique.
o Embedded systems also have tight design
constraints, and heterogeneity provides
better design flexibility.
17

19. Harsh Environment
• Many embedded systems do not
operate in a controlled environment.
• Excessive heat is often a problem,
especially in applications involving
combustion (e.g., many transportation
applications).
• Additional problems can be caused for
embedded computing by a need for
protection from vibration, shock,
lightning, power supply fluctuations,
water, corrosion, fire, and general
physical abuse.
18

20. Harsh Environment
• For example, in the Mission Critical
example application the computer
must function for a guaranteed, but
brief, period of time even under
non-survivable fire conditions.
• These constraints present a unique
set of challenges to the embedded
system designer, including
accurately modeling the thermal
conditions of these systems.
19

21. System Safety and Reliability
• As embedded system complexity and
computing power continue to grow, they
are starting to control more and more of
the safety aspects of the overall system.
These safety measures may be in the form
of software as well as hardware control.
• Mechanical safety backups are normally
activated when the computer system
loses control in order to safely shut down
system operation. Software safety and
reliability is a bigger issue. Software
doesn't normally "break" in the sense of
hardware.
20

22. System Safety and Reliability
• However software may be so
complex that a set of unexpected
circumstances can cause software
failures leading to unsafe situations.
• The main challenge for embedded
system designers is to obtain low-
cost reliability with minimal
redundancy.
21

23. Control of Physical Systems
• One of the main reasons for
embedding a computer is to interact
with the environment. This is often
done by monitoring and controlling
external machinery.
• Embedded computers transform the
analog signals from sensors into
digital form for processing. Outputs
must be transformed back to analog
signal levels.
22

24. Control of Physical Systems
• When controlling physical equipment,
large current loads may need to be
switched in order to operate motors and
other actuators. To meet these needs,
embedded systems may need large
computer circuit boards with many
non-digital components.
• Embedded system designers must
carefully balance system tradeoffs
among analog components, power,
mechanical, network, and digital
hardware with corresponding software.
23

25. Small and Low Weight
• Many embedded computers are
physically located within some
larger system. The form factor
for the embedded system may
be dictated by aesthetics.
• For example, the form factor for
a missile may have to fit inside
the nose of the missile.
24

26. Small and Low Weight
• One of the challenges for embedded
systems designers is to develop non-
rectangular geometries for certain
solutions.
• Weight can also be a critical
constraint. Embedded automobile
control systems, for example, must
be light weight for fuel economy.
Portable CD players must be light
weight for portability purposes.
25

27. Cost sensitivity
• Cost is an issue in most systems, but
the sensitivity to cost changes can
vary dramatically in embedded
systems.
• This is mainly due to the effect of
computer costs have on profitability
and is more a function of the
proportion of cost changes
compared to the total system cost.
26

28. Power management
• Embedded systems have strict
constraints on power.
• Given the portability requirements
of many embedded systems, the
need to conserve power is important
to maintain battery life as long as
possible.
• Minimization of heat production is
another obvious concern for
embedded systems.
27

29. Connected
Frequently, embedded systems are
connected to the physical
environment through sensors
collecting information about that
environment and actuators
controlling that environment.
28

30. Functions of Embedded System
Embedded systems provide several
functions
• Monitor the environment; embedded
systems read data from input sensors.
• Control the environment; embedded
systems generate and transmit
commands for actuators.
• Transform the information;
embedded systems transform the data
collected in some meaningful way,
such as data
compression/decompression
29

31. Basic Structure of an Embedded
System
 The following illustration shows the basic
structure of an embedded system:
30

32. Basic Structure of an Embedded
System
 Sensor – It measures the physical quantity and
converts it to an electrical signal which can be
read by an observer or by any electronic
instrument like an A2D converter
 A-D Converter – An analog-to-digital
converter converts the analog signal sent by
the sensor into a digital signal.
 Processor & ASICs – Processors process the
data to measure the output and store it to the
memory.
 D-A Converter – A digital-to-analog converter
converts the digital data fed by the processor
to analog data.
31

33. Basic Structure of an Embedded
System
Actuator – An actuator compares the
output given by the D-A Converter to
the actual (expected) output stored in
it and stores the approved output.
32

34. Why Embedded Systems Are Different?
Differences between your desktop PC
and the typical embedded system.
o Embedded systems are dedicated to
specific tasks, whereas PCs are
generic computing platforms.
o Embedded systems have real-time
constraints.
o If an embedded system is using an
operating system at all, it is most
likely using a real-time operating
system (RTOS), rather than Windows
9X, Windows NT, Windows 2000,
Unix, Solaris, or HP- UX.
33

35. Why Embedded Systems Are Different?
Embedded systems have far
fewer system resources than
desktop systems.
Embedded systems store all their
object code in ROM
34

36. Application Areas
The following list comprises key
areas in which embedded
systems are used:
oAutomotive electronics
oAircraft electronics
oTrains
oTelecommunication
oConsumer electronics
oRobotics
35

37. Automotive electronics
Modern cars can be sold only if
they contain a significant amount
of electronics. These include air
bag control systems, engine control
systems, anti-braking systems
(ABS), air-conditioning, GPS-
systems, safety features, and many
more.
36

38. Aircraft electronics
A significant amount of the total
value of airplanes is due to the
information processing equipment,
including flight control systems,
anti-collision systems, pilot
information systems, and others.
Dependability is of utmost
importance.
37

39. Telecommunication
Mobile phones have been one of
the fastest growing markets in the
recent years. For mobile phones,
radio frequency (RF) design, digital
signal processing and low power
design are key aspects.
38

40. Consumer electronics
 Video and audio equipment is a very
important sector of the electronics
industry. The information processing
integrated into such equipment is steadily
growing.
 New services and better quality are
implemented using advanced digital
signal processing techniques. Many TV
sets, multimedia phones, and game
consoles comprise high performance
processors and memory systems. They
represent special cases of embedded
systems.
39

41. Robotics
Robotics is also a traditional area
in which embedded systems
have been used
40

42. Requirements for Embedded
Systems
Embedded systems are unique in
several ways. When designing
embedded systems, there are
several categories of
requirements that should be
considered;
• Functional Requirements
• Temporal Requirements
(Timeliness)
• Dependability Requirements
41

43. Functional Requirements
Functional requirements
describe the type of processing
the system will perform. This
processing varies, based on the
application.
Functional requirements
include the followings:
• Data Collection requirements
• Sensoring requirements
• Signal conditioning requirements
42

44. Functional Requirements
• Alarm monitoring requirements
• Direct Digital Control
requirements
• Actuator control requirements
• Man-Machine Interaction
requirements
43

45. Temporal Requirements
Embedded systems have many
tasks to perform, each having its
own deadline.
Temporal requirements define
the stringency in which these
time-based tasks must complete.
Examples include;
• Minimal latency jitter
• Minimal Error-detection
latency
44

46. Temporal Requirements
Temporal requirements can be
very tight (for example control-
loops ) or less stringent (for
example response time in a user
interface).
45

47. Dependability Requirements
Most embedded systems also have
a set of dependability
requirements.
Examples of dependability
requirements include;
• Reliability
• Safety
• Maintainability
• Availability
• Security
46

48. Reliability
Reliability; this is a complex
concept that should always be
considered at the system
rather than the individual
component level.
There are three dimensions to
consider when specifying
system reliability;
47

49. Reliability
• Hardware reliability;
probability of a hardware
component failing
• Software reliability;
probability that a software
component will produce an
incorrect result
• Operator reliability; how
likely that the operator of a
system will make an error.
48

50. Safety
• Safety; describe the
critical failure modes and
what types of certification
are required for the
system
49

51. Availability
• Availability; the
probability that the
system is available for use
at a given time.
50

52. Security
• Security; these
requirements are often
specified as “shall not”
requirements that define
unacceptable system
behavior rather than
required system
functionality.
51

53. Overview of Real-Time System
A real-time system is a system
that is required to react to stimuli
from the environment (including
the passage of physical time)
within time intervals dictated by
the environment.
The Oxford dictionary defines a
real-time system as “Any system
in which the time at which
output is produced is
significant”.
52

54. Overview of Real-Time System
This is usually because the input
corresponds to some movement
in the physical world, and the
output has to relate to that same
movement.
The lag from input time to
output time must be sufficiently
small for acceptable timeliness.
53

55. Overview of Real-Time System
Another way of thinking of real-
time systems is any information
processing activity or system
which has to respond to
externally generated input
stimuli within a finite and
specified period.
Generally, real-time systems are
systems that maintains a
continuous timely interaction with
its environment
54

56. Real-Time System—Definitions
Definition 1 (Real time system)
 A real time system is a system that
must satisfy explicit (bounded)
response-time constraints or risk
severe consequences, including
failure.
Definition 2 (Real time system)
 A real time system is one whose
logical correctness is based both
the correctness of the outputs and
their timeliness.
55

57. Types of Real-Time System
There are two types of real-time
systems:
 Reactive and
 Embedded
 Reactive real-time system involves a
system that has constant interaction
with its environment. (e.g. a pilot
controlling an aircraft).
An embedded real-time system is
used to control specialized hardware
that is installed within a larger
system. (e.g. a microprocessor that
controls the fuel-to-air mixture for
automobiles).
56

58. Examples of Real-Time System
Examples of real-time systems include
 Software for cruise missile
 Airline reservation system
 Industrial Process Control
 Banking ATM
Real-time systems can also be found in
many industries;
 Telecommunication systems
 Automotive control
 Air traffic control
 Satellite systems, etc.
57

59. Real-Time Event Characteristics
Real-time events fall into one of
the three categories:
 asynchronous,
 synchronous, or
 isochronous.
Asynchronous events are entirely
unpredictable. For example, the event
that a user makes a telephone call.
As far as the telephone company
is concerned, the action of making
a phone call cannot be predicted.
58

60. Real-Time Event Characteristics
 Synchronous events are predictable
and occur with precise regularity if
they are to occur. For example, the
audio and video in a movie take
place in synchronous fashion.
 Isochronous events occur with
regularity within a given window of
time. For example, audio bytes in a
distributed multimedia application
must appear within a window of
time when the corresponding video
stream arrives. Isochronous is a
sub-class of asynchronous.
59

61. Real-Time Vs Time Shared
System
 predictably fast response to
urgent events
 high degree of schedulability
 stability under transient overload
60

62. Characteristics of Real time
system
Real-time systems have many
special characteristics which are
inherent or imposed.
 The followings are the
important characteristics of real
time system.
 Large and Complex
 Manipulation of real numbers
 Reliable and safe
61

63. Characteristics of Real time
system
 Concurrent control of separate
system components
 Real-time Facilities
 Interaction with hardware
devices
 Efficient execution and the
execution environment
62

64. Large and Complex
Most of the problems
associated with developing
software are those related to
size and complexity.
Writing small programs
presents no significant
problem because they can be
designed, coded, maintained
and understood by a single
person.
63

65. Large and Complex
This largeness is related
mostly to variety. The variety
is that of needs and activities
in the real world and their
reflection in a program.
The real world is
continuously changing. It is
evolving. So too are,
therefore, the needs and
activities of society.
64

66. Large and Complex
Thus large programs, like all
complex systems, must
continuously evolve. Software
programs tend to exhibit the
undesirable property of largeness.
This is mainly due to continuous
change.
Real-time systems undergo
constant maintenance and
enhancements during their
lifetimes. They must therefore be
extensible.
65

67. Manipulation of real numbers
Many real-time systems involve
the control of some engineering
activity.
66

68. Reliable and safe
The more society relinquishes
control of its vital functions to
computers, the more it becomes
imperative that those computers do
not fail.
Failure in ATM machine can result
in millions of dollars lost
irretrievably. A faulty component in
electricity generation could fail a life
support system in an intensive care
unit.
67

69. Concurrent control of separate
system components
A typical real-time embedded system
consists of computers and sensors and
actuators.
There are usually several co-existing
external elements which the computer must
interact with simultaneously. The very
nature of these external elements is that
they exist in parallel.
Actions performed by the computer must
be carried out in sequence but give the
allusion of being simultaneous. In some
cases this is not possible.
68

70. Interaction with hardware
devices
Nature of embedded real-time systems
requires them to interact with the external
world. Sensors and actuators are used for a
wide variety of real-world devices. Many
of the operational requirements for real-
time systems are device and computer
dependent. These devices may generate
interrupts in response to certain events and
errors. Interrupts usually handled by
assembly language (although more and
more is now being done in higher level
languages).
69

71. Efficient execution and the
execution environment
Real-time systems are time critical. Therefore,
the efficiency of their implementation is more
important than in other systems.
One of the main benefits of using a higher
level language is to allow the programmer to
abstract away the details and concentrate on
solving the problem. This is not always true
in the embedded system world. Some higher
level languages have instruction 10 times
slower than assembly language. However,
higher level languages can be used in real-
time systems effectively.
70

72. Real-time Facilities
It is very difficult to design and implement
systems which will guarantee the appropriate
output will be generated at the appropriate
times under all possible conditions. Doing this a
making use of all computing resources at all
times is often impossible.
Real-time systems usually constructed using
processors with considerable space capacity.
This ensures worst case behavior does not
produce any unwelcome delays during critical
periods of the systems operation.
71

73. Embedded System Processors
 Processor is the heart of an
embedded system.
 It is the basic unit that takes inputs
and produces an output after
processing the data.
 For an embedded system designer,
it is necessary to have the
knowledge of both microprocessors
and microcontrollers.
72

74. Processors in a System
 A processor has two essential units:
Program Flow Control Unit (CU) and
Execution Unit (EU)
 Control Unit (CU): The CU includes a
fetch unit for fetching instructions from
the memory.
 Execution Unit (EU): The EU includes
the Arithmetic and Logical Unit (ALU)
and also the circuits that execute
instructions for a program control task
such as interrupt, or jump to another set
of instructions.
73

75. Types of Processors
 Processors can be of the following
categories:
(1). General Purpose Processor
(GPP): Microprocessor,
Microcontroller, Embedded
Processor, Digital Signal
Processor, and Media Processor
(2). Application Specific System
Processor (ASSP)
74

76. Types of Processors
(3). Application Specific
Instruction Processors
(ASIPs)
(4). GPP core(s) or ASIP core(s)
on either an Application
Specific Integrated Circuit
(ASIC) or a Very Large Scale
Integration (VLSI) circuit
75

77. General-purpose Processor
 General-purpose processors:
Programmable device used in a
variety of applications – Also known
as “microprocessor”
 Features: Program memory, General
datapath with large register file and
general ALU
 User benefits: Low time-to-market
and NRE costs, High flexibility
 Example: “Pentium” the most well-
known, but there are hundreds of
others
76

78. Application Specific System
Processor(ASSP)
 ASSP is an application specific
dependent system processor used for
processing signal of embedded
system.
 Therefore, for different application
performing task a unique set of
system processors is required.
77

79. Application Specific System
Processor(ASSP)
 ASSP is dedicated to specific tasks
and provides a faster solution.
 An ASSP is used as an additional
processing unit for running the
application in place of using
embedded software.
 Examples : IIM7100, W3100A
78

80. Application Specific Instruction
Processors (ASIPs)
 ASIP is a component used in system
on a chip design. The instruction set
architecture of an ASIP is tailored to
benefit a specific application.
79

81. Microprocessor
 A microprocessor is a single VLSI
chip having a CPU. In addition, it
may also have other units such as
coaches, floating point processing
arithmetic unit, and pipelining units
that help in faster processing of
instructions.
 Earlier generation microprocessors’
fetch-and-execute cycle was guided
by a clock frequency of order of ~1
MHz.
 Processors now operate at a clock
frequency of 2GHz.
80

82. Microprocessor
 The following illustration shows the
block diagram of a Microprocessor
81

83. Microcontroller
 A microcontroller is a single-
chip VLSI unit (also called
microcomputer) which,
although having limited
computational capabilities,
possesses enhanced
input/output capability and
a number of on-chip
functional units.
82

84. Microcontroller
 Microcontrollers are particularly
used in embedded systems for
real-time control applications
with on-chip program memory
and devices.
83

85. Microprocessor VS
Microcontroller
 Microprocessors are multitasking in
nature. Can perform multiple tasks at
a time, whereas microcontrollers are
single task oriented.
 In microprocessors RAM, ROM, I/O
Ports, and Timers can be added
externally and can vary in numbers,
whereas in case of microcontrollers
RAM, ROM, I/O Ports, and Timers
cannot be added externally. These
components are to be embedded
together on a chip and are fixed in
numbers.
84

86. Microprocessor VS
Microcontroller
 External support of external
memory and I/O ports makes a
microprocessor-based system
heavier and costlier, whereas
Microcontrollers are lightweight
and cheaper than a microprocessor.
 In case of microprocessors External
devices require more space and
their power consumption is higher,
whereas External devices require
more space and their power
consumption is higher.
85