HRT-HOOD [email protected] Real-Time Systems Lecture 4 Copyright, 2002 © Adam Czajka

HRT-HOOD HRT-HOOD

[email protected]

Real-Time SystemsReal-Time Systems

Lecture 4Lecture 4

Copyright, 2002 © Adam Czajka


Contents

Object types

Data flow

Object attributes

Decomposition

Classes

Distributed systems


Object types

Active (A)

Passive (Pa)

Cyclic (C)

Sporadic (S)

Protected (Pr)

Pr B u f f e r

Put

* Get

Pr B u f f e r

Put

* Get


Object typesPassive Objects

Pa Math Sum * Mul

Passive object == Set of operationsPassive object == Set of operations


Object typesActive Objects – operation types

A Hotel ASER PutKey HSER * GetKey LSER Reservation HSER Confirm

Asynchronous

(ASER)

Loosely

Synchronous (LSER)

Highly Synchronous

(HSER)

Functional Functional

activation activation

constraintsconstraints


Object typesActive Objects –

timeout constraints

Timeout constraints are related only to :

• HSER TOER_HSERTOER_HSER

• LSER TOER_LSERTOER_LSER

(Timed Operation Execution Request)


Object typesActive Objects –

timeout constraints

A Post_Office LSER Send_Letter TOER_HSER * Telephone_Call


Object typesCyclic Objects

C Sensor

Object is invoked periodicallyObject is invoked periodically


Object typesSporadic Objects

S Button

ASER Start

Start operation can be raised by interruptStart operation can be raised by interrupt


Object typesProtected Objects –

operation types

Asynchronous

(PAER) - in

Synchronous

(PSER) – in/outs

Pr Storage

LSER Put HSER * Get

Only PSER Only PSER operations can have functional operations can have functional activation constraintsactivation constraints


Data flow

InElem

PSER

PSER

A Producer A Consumer

Pr Storage

* PutElement * GetElement

OutElem


Data flowFunction calling rules

Active (A) Any other object

Cyclic (C), Sporadic (S) Any other object

except active (the asynchronous active

operations are allowed to be called)

Protected (Pr) Only Protected or Passive (the

asynchronous operations of all other objects are

allowed)

Passive (Pa) Only Passive


Data flowFunction calling rules

If A and B are passive (or protected) objects

and object A calls the operation from object

B, then it is NOT allowedit is NOT allowed to call any operation

from object A by object B.

General rule :


Exceptions

Pr Dispatcher

Schedule

In_El

Out_El

NoSpace

Pa Queue

PutElem GetElem


Object attributes

DEADLINE

THREAD BUDGET

THREAD WCET

OFFSET

PRIORITY

IMPORTANCE

INTEGRITY

PERIOD (Cyclic objects only)

Minimum Arrival Time (Sporadic objects only)


Object attributes

OPERATION BUDGET

OPERATION WCET

(WCET = BUDGET + ERROR_HANDLING)

CEILING PRIORITY

INTEGRITY

Operation attributes :

Protected object attributes : Goal : Goal :

To check the system To check the system

schedulability.schedulability.


Decomposition

Objects

Operations

Whole systemWhole system

(1 active object)(1 active object)

More detailed More detailed

componentscomponents

decompositiondecomposition

Decomposed system Decomposed system

(no active objects)(no active objects)


Decomposition

Active any other object

Passive only Passive objects

Protected Passive object + 1 Protected

Sporadic Passive, Protected, Cyclic + at least

1 Sporadic

Cyclic Passive, Protected, Sporadic + at least

1 Cyclic

Object decomposition rules :


DecompositionDecomposition rules (operation

decomposition examples) :

ASER ASER

ASER PAER

LSER PSER

PSER PSER

Decomposition is valid only if it doesn’t affect Decomposition is valid only if it doesn’t affect

the parent object properties.the parent object properties.


Decomposition

A Console

Display_Line

Read_Line

ASER

HSER

Decomposition example


Decomposition


Environmental objects


Classes


Distributed systems

Buffer :Buffer :

•Real objectReal object

•Client „stub”Client „stub”

•Server „stub”Server „stub”


SummarySummary

Object types

Data flow

Object attributes

Decomposition

Classes

Distributed systems

Documents

HRT-HOOD [email protected] Real-Time Systems Lecture 4 Copyright, 2002 © Adam Czajka