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MandarChitre

EE5903Real-time Systems

Real-time System Design

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Course Outline

Introduction to real-time systems Real-time system design

Inter-process communication

Inter-process synchronization

Implementation of concurrency

Case studies

Real-time operating systems

Process scheduling

Verification and validation

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What to avoid!

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Desi n Lan ua es

AlarmClockUser

TimeAlarm Time

Time

Alarm

Time Server

Context Diagram

Stop Alarm

Data FlowDiagrams (DFD) Unified Modeling

Language (UML)

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Data Flow Dia rams

ExternalEntity Data StoreProcess Data Flow

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La ered DFDs

ExternalEntity

Process

Context Diagram

ExternalEntity

Process1

Level 1 DFD

Process

2

Data Store

Process 1

Process2a

Level 2 DFD - Process 2

Process2b

Data Store

ExternalEntity

Process1a

Level 2 DFD - Process 1

Process1b

Data Store

Process 2

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Real-time Extensions

PulseGenerator

SonarControlSystem

MatchedFilter

SonarTransmitter

Sonar Pulse

Sonar

Receiver

TargetTracker

TargetsSonar

Display

SonarPulse

SonarPulse

SonarReturn

SonarPulse

Detections

TransmitTrigger

ReceiveEnable

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DFD Desi n Guidelines

Most process must have at least one input dataflow(violators are called "magic" processes)

Most process must have at least one output dataflow(violators are called "black hole" processes)

Every dataflow must connect two elements one ofthem must be a process; the other can be a terminator, adata store or another process

Each dataflow diagram should contain no more than 6-7processes and no more than 6-7 data stores, and all the

processes should be conceptually at the same level ofdetail

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Mess DFD!

Sourcehttp://www.astro.princeton.edu/PBOOK/datasys/dataproc.gif

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DFD Desi n Guidelines

For every process, one of the following must eventuallybe true:

The description label is so simple and unambiguousthat every reader will understand it in exactly thesame way

It is expanded or decomposed into a separate lower-level dataflow diagram that preserves exactly the samenet inputs and outputs, but shows internal detail, suchas data stores and internal processes

It is rigorously described by a separate processspecification (business rule, decision rule, functiondefinition, algorithm, etc.)

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Internet Alarm Clock

AlarmClockUser

TimeAlarm Time

Time

Alarm

Time Server

Context Diagram

Stop Alarm

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Internet Alarm Clock

User

TimeAlarm Time

Time

Alarm

Time Server

Level 1 Diagram : Alarm Clock

Clock

Oscillator

Alarm

Current TimeAlarm Time

Tick

Stop Alarm

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Internet Alarm Clock

User

Level 2 Diagram : Clock

Time

Time Server

SyncTime

Current Time

Oscillator

Tick

KeepTime

DisplayTime

Time

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Internet Alarm Clock

User

TimeAlarm Time

Time

Alarm

Time Server

Level 1 Diagram : Alarm Clock

Clock

Oscillator

Alarm

Current TimeAlarm Time

Tick

Stop Alarm

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Internet Alarm Clock

User

Alarm Time

Level 2 Diagram : Alarm

CompareTime

Alarm Time

Set Alarm

Current TimeBeeper

AlarmTrigger

Alarm

StopAlarm

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Unified Modelin Lan ua e

UML2.0

StructuralDiagrams

BehavioralDiagrams

FunctionalDiagrams

InteractionDiagrams

ClassDiagram

StructureDiagram

ObjectDiagram

DeploymentDiagram

ComponentDiagram

SequenceDiagram

CommunicationDiagram

ActivityDiagram

StatechartDiagram

Info FlowDiagram

Use CaseDiagram

TimingDiagram

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Use Case Dia rams

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Activit Dia rams

Like flowcharts, but more flexible

Definitions:

An action has a "run to completion" semantics

An activity is like an action, but it may be terminatedby received events

Token execution semantics

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Activit Dia rams

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Statechart Dia rams

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Statechart Dia rams

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Class Dia rams

Classname

Attributedefinitions

Methoddefinitions

Visibility:

- Private

# Protected+ Public

Method signature

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Class Dia rams Association the related classes have a link that

allows them to invoke services from each other Aggregation ()one or more of the "part" class is

aggregated to form the "whole" class

Composition () stronger aggregation relationship,

with the "whole" class having the responsibility ofcreating and destroying the "part" objects

Generalization () one class defines a set of

features that are specialized or extended by anotherclass

Dependency(---) a relation between two classesthat does not fall into one of the other types

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Class Dia rams

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Class Dia rams

An operation is an abstraction of a method withoutspecifying the steps needed to provide the service

An interface is a named collection of services

The services provided by an interface are represented by

operations A class is said to realize an interface, if it provides

methods for each of the interface operations

Interfaces are denoted in UML using stereotypes or thelollipop notation

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Class Dia rams

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Se uence Dia rams

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Com onent Dia rams

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De lo ment Dia rams

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Theres lots more to UML Notes

Stereotypes

References

Loops

Options

Parallel Execution Other diagrams

Self study!

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Process

RequirementGathering

URS

HLD

Implementation

Code DocsCode

TestingTest Reports

SystemDesign

Reviews

DetailedDesign

Test Plan

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Waterfall Model

Source: Wikipedia

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S iral Model

Source: Wikipedia

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V-Model

Source: Wikipedia

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Summar

Data flow diagrams Layered data flow design

UML

Use case diagrams

Activity diagrams

Statechart diagrams

Class diagrams

Sequence diagrams

Component diagrams

Deployment diagrams

Development processes