Page 45 - DCAP608_REAL TIME SYSTEMS

Real Time Systems Gurwinder Kaur, Lovely Professional University

Notes Unit 4: A Reference Model of Real-time Systems

CONTENTS
Objectives
Introduction

4.1 Processors and Resources
4.2 Temporal Parameters of Real-time Workload
4.2.1 Fixed Jittered and Sporadic Release Times

4.2.2 Execution Time
4.3 Periodical Task Model
4.3.1 Periods, Execution Times and Phases of Periodic Tasks
4.3.2 Aperiodic and Sporadic Jobs
4.4 Precedence Constraint and Data Dependency

4.4.1 Precedence Graph and Task Graph
4.4.2 Data Dependency
4.5 Summary

4.6 Keywords
4.7 Review Questions
4.8 Further Readings

Objectives

After studying this unit, you will be able to:

 Describe Processors and Resources
 Enumerate Temporal Parameters of Real-time Workload
 Define Periodical Task Model

 Explain Precedence Constraint and Data Dependency
Introduction

A reference model of real-time systems is needed to focus on aspects of the system relevant to its
real-time timing and resource properties. A system may be characterized by 3 models: A
workload model describing the applications (i.e. control laws and their time complexity)
supported by the system; a resource model describing the system resources (e.g., compute cycles
or time on the processor hardware to be used) available to the applications. The scheduling and
resource management algorithms define how the application uses the resources (i.e. how the
workload is scheduled on the system).

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