2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 1

Lesson 9: Lesson 9: Challenges in Embedded Challenges in Embedded System Design: Optimizing the Design System Design: Optimizing the Design

Metrics and Formalism of System Metrics and Formalism of System DesignDesign

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 2

Amount and type of hardware needed� Optimizing the microprocessors, ASIPs and

single purpose processors in the system � Optimizing according to the performance,

power dissipation, cost and other design metrics the system

� Optimizing hardware (memory RAM, ROM or internal and external flash or secondary memory in the system, peripherals and devices internal and external to the system, ports and buses in the system and power source or battery in the system).

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 3

Taking into account the design metricsTaking into account the design metrics

� Design metrics examples –power dissipation, physical size, number of gates and engineering, prototype development and manufacturing costs.

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 4

Optimizing the Power Dissipation� Clock Rate Reduction� Operating Voltage Reduction� Wait, Stop and Cache Disable Instructions –

Clever real- time programming. It is by using of 'Wait' and 'Stop' instructions and disabling or controlling certain units when not needed is one method of saving power during program execution

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 5

Disable use of certain structural units of Disable use of certain structural units of the processor to reduce power dissipation the processor to reduce power dissipation � Caches—when not necessary and � Keep in disconnected state those structure

units that are not needed during a particular software-portion execution, for example, display screen, timers or IO units

� Control of power requirement, for example, by screen auto-brightness control

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 6

� Meeting the deadline of all processes in the system while keeping the memory, power dissipation, processor clock rate and cost at minimum is a challenge

Process DeadlinesProcess Deadlines

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 7

Flexibility and Upgradeability� Ability to offer the different versions

of a product for marketing and offering the product in advanced versions later on.

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 8

ReliabilityReliability� Designing reliable product by appropriate

design and thorough testing, verification and validation is a challenge.

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 9

Testing, Verification and ValidationTesting, Verification and Validation� Testing – to find errors and to validate that

the implemented software is as per the specifications and requirements to get reliable product.

� Verification – refers to an activity to ensure that specific functions are correctly implemented.

� Validation – refers to an activity to ensure that the system that has been created is as per requirements agreed upon at the analysis phase, and to ensure its quality

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 10

ModulesModules� Be clearly understood and maintain

continuity. � Appropriate protection strategies are

necessary for each module. A module is not permitted to change or modify another module functionality.

� For example, protection from a device driver modifying the configuration of another device

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 11

Formalism of System Design Formalism of System Design

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 12

Formalism of Steps � Requirements and Specifications of

hardware and software� Define architectures of hardware and

software� Coding and implementation as per

architecture� Testing, validation and verification of

system

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 13

Diagrammatic modelDiagrammatic model

� UML (Universal Modeling Language)

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 14

UML (Universal Modeling Language)UML (Universal Modeling Language)� Conceptual design modeling � Classes and Objects to describe identity,

attributes, components and behaviour– Inheritances in classes and objects– Interfaces with the objects and their

implementation in the objects, � Structural description of the design

components

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 15

UML (Contd.)– Behavioral description in terms of

states, state machine and signals– Events description

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 16

Disable use of certain structural units of Disable use of certain structural units of the processor to reduce power dissipation the processor to reduce power dissipation � Caches—when not necessary and � Keep in disconnected state those structure

units that are not needed during a particular software-portion execution, for example, display screen, timers or IO units

� Control of power requirement, for example, by screen auto-brightness control

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 17

� Meeting the deadline of all processes in the system while keeping the memory, power dissipation, processor clock rate and cost at minimum is a challenge

Process DeadlinesProcess Deadlines

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 18

Flexibility and Upgradeability� Ability to offer the different versions

of a product for marketing and offering the product in advanced versions later on.

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 19

ReliabilityReliability� Designing reliable product by appropriate

design and thorough testing, verification and validation is a challenge.

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 20

Testing, Verification and ValidationTesting, Verification and Validation� Testing – to find errors and to validate that

the implemented software is as per the specifications and requirements to get a reliable product.

� Verification – refers to an activity to ensure that specific functions are correctly implemented.

� Validation – refers to an activity to ensure that the system that has been created is as per the requirements agreed upon at the analysis phase, and to ensure its quality

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 21

ModulesModules� Be clearly understood and maintain

continuity. � Appropriate protection strategies are

necessary for each module. A module is not permitted to change or modify another module functionality.

� For example, protection from a device driver modifying the configuration of another device

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 22

We learnt� Challenges in system design� Meeting design metrics� Power dissipation reduction� Enabling and controlling of processes

and hardware units� Flexibility, upgradeability and

reliability

Summary Summary

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 23

We learnt� Formalism of System design Processes� Use of UML for diagrammatically

modeling the system design Processes

Summary Summary

2008 Chapter-1: "Embedded Systems - " , Raj Kamal, Publs.: McGraw-Hill Education 24

End of Lesson 9End of Lesson 9