Chapter 3 Charateristics and Quality Attributes of Embedded System

IT-51061
Introduction to
EMBEDDED SYSTEM
(2nd Edition)
SHIBU K V
Dr Moe Moe Myint
Department of Computer Engineering & Information Technology
Mandalay Technological University
www.slideshare.net/MoeMoeMyint
moemoemyint@moemyanmar.ml
moe2myint.mdy@gmail.com
drmoemoemyint.blogspot.com

Agenda
3.1 Characteristics of Embedded Systems
3.2 Quality Attributes of Embedded Systems
2
Department of Computer Engineering and Information Technology
Lecture Slides for Textbook Introduction to Embedded Systems, Moe Moe Myint, 2017-2018

Learning Objectives
 Learn the characteristics describing an embedded system
 Learn the non-functional requirements that needs to be addressed in the design
of an embedded system
 Learn the important quality attributes of the embedded system that needs to be
addressed for the operational mode (online mode) of the system. This includes
Response, Throughput, Reliability, Maintainability, Security, Safety, etc.
 Learn the important quality attributes of the embedded system that needs to be
addressed for the non-operational mode (offline mode) of the system. This
includes Testability, Debug-ability, Evolvability, Portability, Time to prototype
and market, Per unit cost and revenue, etc.
 Understand the Product Life Cycle (PLC)
3

Introduction
 The characteristics of embedded system are different from
those of a general purpose computer and so are its Quality
metrics.
 This chapter gives a brief introduction on the
characteristics of an embedded system and the attributes
that are associated with its quality.
4

3.1 Characteristics of an Embedded System
 Unlike general purpose computing systems, embedded systems possess
certain specific characteristics and these characteristics are unique to each
embedded system.
 Some of the important characteristics of an embedded system are:
1. Application and domain specific
2. Reactive and Real Time
3. Operates in harsh environments
4. Distributed
5. Small size and weight
6. Power concerns
5

1. Application and Domain Specific
 An embedded system is designed for a specific purpose only.
 It will not do any other task.
 Ex. Air conditioner’s embedded control unit, it cannot replace microwave
oven…
 Ex. A washing machine can only wash, it cannot cook..
 Because the embedded control units of microwave oven and air conditioner
are specifically designed to perform certain specific tasks.
 Certain embedded systems are specific to a domain: ex. A hearing aid is an
application that belongs to the domain of signal processing and telecom with
another control unit designed to serve another domain like consumer
electronics.
6

2. Reactive and Real Time
 Certain embedded systems are designed to react to the events that occur in
the nearby environment. These events also occur real-time.
 Ex. Flight control systems, Antilock Brake Systems (ABS), etc. are examples
of Real Time systems
 Ex. An air conditioner adjusts its mechanical parts as soon as it gets a signal
from its sensors to increase or decrease the temperature when the user
operates it using a remote control.
 An embedded system uses Sensors to take inputs and has actuators to bring
out the required functionality.
7

3. Operation in Harsh Environment
 Certain embedded systems are designed to operate in harsh
environments like a dusty one or a high temperature zone or an area
subject to vibrations and shock or very high temperature of the deserts
or very low temperature of the mountains or extreme rains.
 These embedded systems have to be capable of sustaining the
environmental conditions it is designed to operate in.
8

4. Distributed
 The term distributed means that embedded systems may be a part of a
larger system.
 These components are independent of each other but have to work
together for the larger system to function properly.
 Ex. An automatic vending machine is a typical example for this. The
vending machine contains a card reader (for pre-paid vending
systems), a vending unit, etc. Each of them are independent
embedded units but they work together to perform the overall
vending function.
 Ex. Automatic Teller Machine (ATM) contains a card reader
embedded unit, responsible for reading and validating the user’s ATM
card, transaction unit for performing transactions, a currency
counter for dispatching/vending currency to the authorized person and
a printer unit for printing the transaction details.
 This can visualize these as independent embedded systems. But they
work together to achieve a common goal.
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5. Small Size and Weight
 An embedded system that is compact in size and has light weight will
be desirable or more popular than one that is bulky and heavy.
 Ex. Currently available cell phones. The cell phones that have the
maximum features are popular but also their size and weight is an
important characteristic.
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6. Power Concerns
 It is desirable that the power utilization and heat dissipation of any
embedded system be low.
 If more heat is dissipated then additional units like heat sinks or
cooling fans need to be added to the circuit.
 Ex. The production of high amount of heat demands cooling
requirements like cooling fans which in turn occupies additional
space and make the system bulky. Nowadays ultra low power
components are available in the market.
 Select the design according to the low power components like low
dropout regulators, and controllers/processors with power saving
modes.
 Also power management is a critical constraint in battery operated
application.
 The more the power consumption the less is the battery life.
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3.2 Quality Attributes of Embedded Systems
 Quality attributes are the non-functional requirements that need to be
documented properly in any system design.
 If the quality attributes are more concrete and measurable, it will give a
positive impact on the system development process and the end
product.
 The various quality attributes that needs to be addressed in any
embedded system development are broadly classified into two, namely
i. Operational Quality Attributes
ii. Non-Operational Quality Attributes
12

1. Operational Quality Attributes
 The operational quality attributes represent the relevant quality
attributes related to the embedded system when it is in the operational
mode or ‘online’ mode. The important quality attributes coming under
this category are listed below:
i. Response
ii. Throughput
iii. Reliability
iv. Maintainability
v. Security
vi. Safety
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Reading Assignment
14

i. Response
 Response is a measure of quickness of the system.
 It gives you an idea about how fast your system is tracking the input
variables.
 Most of the embedded system demand fast response which should be
real-time.
 Ex. An embedded system deployed in flight control application
should respond in a Real Time manner.
 Any response delay in the system will create potential damages to
the safety of the flight as well as the passengers.
 It is not necessary that all embedded systems should be Real Time in
response.
 For example, the response time requirement for an electronic toy is
not at all time-critical.
15

ii. Throughput
 Throughput deals with the efficiency of system.
 It can be defined as rate of production or process of a defined
process over a stated period of time.
 The rates can be expressed in terms of units of products, batches
produced, or any other meaningful measurements.
 In case of card reader like the ones used in buses, throughput
means how much transactions the Reader can perform in a minute
or hour or day.
 Throughput is generally measured in terms of ‘Benchmark’. A
‘Benchmark’ is a reference point by which something can be
measured.
 Benchmark can be a set of performance criteria that a product is
expected to meet or a standard product that can be used for
comparing other products of the same product line.
16

iii. Reliability
 Reliability is a measure of how much percentage you rely upon the
proper functioning of the system or what is the % susceptibility of the
system to failure.
 Mean Time Between Failures (MTBF) and Mean Time To Repair
(MTTR) are the terms used in defining system reliability.
 MTBF gives the frequency of failures in hours/weeks/months.
 MTTR specifies how long the system is allowed to be out of order
following a failure.
 For an embedded system with critical application need, it should be of
the order of minutes.
17

iv. Maintainability
 Maintainability deals with support and maintenance to the end user or client in case of technical
issues and product failures or on the basis of a routine system checkup.
 Reliability and maintainability are considered as two complementary disciplines. A more reliable
system means a system with less corrective maintainability requirements and vice versa.
 Maintainability can be classified into two types:
1. Scheduled or Periodic Maintenance (Preventive Maintenance)
An inkjet printer uses ink cartridges, which are consumable components and as per the printer
manufacturer the end use should replace the cartridge after each ‘n’ number of printouts to get
quality prints.
2. Maintenance to Unexpected Failures (Corrective Maintenance)
If the paper feeding part of the printer fails the printer fails to print and it requires immediate
repairs to rectify this problem.
Hence it is obvious that maintainability is simply an indication of the availability of the product
for use. In any embedded system design, the ideal value for availability is expressed as
𝑨𝒊 = 𝑴𝑻𝑩𝑭/(𝑴𝑻𝑩𝑭 + 𝑴𝑻𝑻𝑹)
Where Ai=Availability in the ideal condition, MTBF=Mean Time Between Failures, and MTTR=
Mean Time To Repair
18

v. Security
 ‘Confidentially’, ‘Integrity’, and ‘Availability’ are three major measures of
information security.
 ‘Confidentially’ deals with the protection of data and application from
unauthorized disclosure.
 ‘Integrity’ deals with the protection of data and application from
unauthorized modification.
 ‘Availability’ deals with protection of data and application from unauthorized
users.
 Certain embedded systems have to make sure they conform to the security
measures.
 Ex. An electronic safety Deposit Locker can be used only with a pin number
like a password.
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vi. Safety
 Safety deals with the possible damages that can happen to the operators,
public and the environment due to the breakdown of an embedded system or
due to the emission of radioactive or hazardous materials from the
embedded products.
 The breakdown of an embedded system may occur due to a hardware failure
or a firmware failure.
 Safety analysis is a must in product engineering to evaluate the anticipated
damages and determine the best course of action to bring down the
consequences of the damages to an acceptable level.
20

2. Non Operational Attributes
 The quality attributes that needs to be addressed for the product ‘not’ on the
basic of operational aspects are grouped under this category. The important
quality attributes coming under this category are listed below:
i. Testability & Debug-ability
ii. Evolvability
iii. Portability
iv. Time to prototype and market
v. Per unit and total cost
21

i. Testability & Debug-ability
 Testability deals with how easily one can test his/her design, application and by
which means he/she can test it.
 For an embedded product, testability is applicable to both the embedded
hardware and firmware.
 Debug-ability is a means of debugging the product as such for figuring out the
probable sources that create unexpected behavior in the total system.
 Debug-ability has two aspects in the embedded system development context,
namely, hardware level debugging and firmware level debugging.
 Hardware debugging is used for figuring out the issues created by hardware
problems whereas firmware debugging is employed to figure out the probable
errors that appear as a result of flaws in the firmware.
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ii. Evolvability
 Evolvability is a term which is closely related to Biology.
 Evolvability is referred as the non-heritable variation.
 For an embedded system, the quality attribute ‘Evolvability’ refers to
the ease with which the embedded product (including firmware and
hardware) can be modified to take advantage of new firmware or
hardware technologies.
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iii. Portability
 Portability is a measure of ‘system independence’.
 An embedded product can be called portable if it is capable of
functioning in various environments, target processors/controllers and
embedded operating systems.
 A standard embedded product should always be flexible and portable.
24

iv. Time-to-Prototype and Market
 Time-to-market is the time elapsed between the conceptualization of a
product and the time at which the product is ready for selling (for
commercial product) or use (for non-commercial products).
 The commercial embedded product market is highly competitive
and time to market the product is a critical factor in the success of a
commercial embedded product.
 Product prototyping helps a lot in reducing time-to-market.
25

v. Per Unit Cost and Revenue
 Cost is a factor which is closely monitored by both end user (those
who buy the product) and product manufacturer (those who build the
product).
 Cost is a highly sensitive factor for commercial products.
 Proper market study and cost benefit analysis should be carried out
before taking decision on the per unit cost of the embedded product.
 When the product is introduced in the market, for the initial period
the sales and revenue will be low.
 There won’t be much competition when the product sales and
revenue increase.
 During the maturing phase, the growth will be steady and revenue
reaches highest point and at retirement time there will be a drop in
sales volume.
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Cont’d27
Product life cycle (PLC) curve

Objective Questions28
1. Embedded systems are application and domain specific. State True or
False
(a) True (b) False
2. Which of the following is true about Embedded Systems?
(a) Reactive and Real Time (b) Distributed
(c) Operates in harsh environment (d) All of these
(e) None of these
3. Which of the following is a distributed embedded system?
(a) Cell phone (b) Notebook Computer (c) SCADA system
(d) All of these (e) None of these
4. Quality attributes of an embedded system are
(a) Functional requirements (b) Non-functional requirements
(c) Both (d) None of these
5. Response is a measure of
(a) Quickness of the system
(b) How fast the system tracks changes in Input

Cont’d29
6. Throughput of an embedded system is a measure of
(a) The efficiency of the system
(b) The output over a stated period of time
7. Benchmark is
(a) A reference point (b) A set of performance criteria
(c) (a) or (b) (d) None of these
8. Mean Time Between Failures (MTBF) and Mean Time To Repair (MTTR) defines
the reliability of an embedded system. State True or False
(a) True (b) False
9. MTBF gives the frequency of failures of an embedded system. State True or False
(a) True (b) False
10. Which of the following is true about the quality attribute ‘maintainability’?
(a) The corrective maintainability requirement for a highly reliable embedded
system is very less
(b) Availability of an embedded system is directly related to the
maintainability of the system
(c) Both of these
(d) None of these

Cont’d30
11. The Mean Time Between Failure (MTBF) for an embedded product is very high.
This means:
(a) The product is highly reliable
(b) The availability of the product is very high
(c) The preventive maintenance requirement for the product is very less
(d) All of these
(e) None of these
12. The Mean Time Between Failure (MTBF) of an embedded product is 4 months and
the Mean Time To Repair (MTTR) of the product is 2 weeks. What is the
availability of the product?
(a) 100% (b) 50% (c) 89% (d) 10%
13. Which of the following are the three measures of information security in
embedded systems?
(a) Confidentiality, secrecy, integrity (b) Confidentiality, integrity, availability
(c) Confidentiality, transparency, availability
(d) Integrity, transparency, availability

Review Questions31
1. Explain the different characteristics of embedded systems in detail.

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 This PPT is only for fair academic use.
32

Chapter 3 Charateristics and Quality Attributes of Embedded System

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