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MandarChitre

EE5903Real-time Systems

Introduction to Real-time Systems

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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

Reliability, testing & fault tolerance

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What are RTS?

Timeliness is as important as thecorrectness of the outputs

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T es of RTS

Time

Acceptance

Level

Deadline

Hard RTS

Time

AcceptanceLevel

Deadline

Soft RTS

Time

AcceptanceLevel

Deadline

Firm RTS

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Formal Definition A system has a set of one or more inputs and a set of

one or more outputs

The time between the presentation of a set of inputs to asystem, and the appearance of the associated outputs iscalled the response time of the system

A real-time system is a system that must satisfy explicit

bounded response-time constraints

The logical correctness of a real-time system is based onboth the correctness of the outputs and their timeliness

SystemInputs:

i1 ... in

Outputs:o1 ... om

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Embedded S stems An embedded system is a special-purpose computer

system designed to perform one or a few dedicatedfunctions, often with real-time computing constraints

80-95% of computersworldwide are embedded!

Telecom

Industrial

Automation

Aerospace

& Defense

Office

Automation

Consumer

AutomotiveMedical

Other

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Characteristics of RTS

Interaction with the real world

Concurrency & inter-process communication

Long-term reliability & graceful degradation

Chernobyl1986

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Classes of RTS

Data acquisition/processing systems

Digital control systems

On-line transaction processing systems

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Control S stems

Environment

Real-time

System

Sensors Actuators

analog

digitaldigital

analog

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Exam le

A Volvo S80 has more than 50 embedded computers! 25-30% of the cost of the car

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RTS En ineerin

User requirement specifications (URS)

Software design

Implementation & testing

Choice of OS & implementation platform

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RTS En ineerin

User Requirement Specifications Capture real-time constraints

Software Design

High-level design decisions must keep real-timeconstraints in view

Concurrency, throughput, errorrecovery, response time to beaddressed at design time

Identify problems and weaknessesearly

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RTS En ineerin

Implementation & Testing Concurrency & timing issues to be addressed & tested

explicitly

Extensive validation & testing

Choice of OS & Platform

RTOS

Distributed processing

SoC, ASIC, FPGA implementations

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Summar

Definition and characteristics of real-time systems

Differences between hard, firm and soft real-timesystems

Embedded systems and real-time software are the mostprevalent computer systems around

Characteristics and classes of real-time systems

Engineering considerations for real-time systems