实时操作系统基本概念.pdf

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1、ByMatsPettersson,IARSystemsBasicConceptsforRealTimeOperatingSystemsThisarticlewillexplainsomeRealTimeOperatingSystems(RTOS)basics.ThematerialpresentedhereisnotintendedasacompletecoverageofdifferentRTOSandtheirfeatures.Forthepurposesofsimplification,Iwillbrieflycoverthemostimpor

2、tantfeaturesofarepresentativeRTOS.AfterweexplorewhatconstitutesanRTOSandwhywemightwanttouseone,I’llexplaineachofthebasiccomponentsofatypicalRTOSandshowhowthesebuildingblocksareintegratedintothesystem.ForthefewcodeexamplesinthisarticlewewilluseThreadXfromExpressLogic.Thread-orie

3、nteddesignDesigningapplicationsforanembeddedapplicationisalmostalwayschallenging,tosaytheleast.Onewaytodecreasethecomplexityofyourapplicationistouseathread-orienteddesignanddivideaprojectintomoremanageablepieces(orthreads).Eachthreadisthenresponsibleforsomepartoftheapplication.

4、Withsuchasystemyouwouldliketobeabletospecifythatsomethreadismoreimportantthanothers.Thatis,somethreadshavereal-timerequirements.Theyhavetorespondquicklyandcorrectly.IfyoursystememploysaprofessionalRTOS,featuresthatprioritizethreadsarealreadypartofthepackage.Inadditiontothreadpr

5、ioritization,acleanandwell-testedAPIisincludedthateasescommunicatebetweendifferentthreads.SoifwetouseaprofessionalRTOSwewillhavethetoolsto:•Ensurethattime-criticalpartsofthecodeexecutewithintheirreal-timeconstraints.Perhapsequallyimportantly,thereal-timebehaviorofthehigh-priori

6、tythreadsisnotaffectedbythenumberorprocessingoflessimportant,lower-prioritythreads.•Makecomplexapplicationseasiertodevelopandmaintain.It’seasiertodevelopandmaintainsmallerthreads,thantohavetodealwiththeentireapplicationasawhole.Inaddition,changestotheprocessingoflowerpriorityth

7、readsdonotaffectthereal-timeprocessingofhigher-prioritythreads.•Distributedifferentpartsoftheapplicationamongseveraldevelopers.EachdevelopercanberesponsibleforoneormorethreadswithintheapplicationandacleanApplicationProgrammingInterface(API)willbeavailableforcommunicationbetween

8、thedifferentmodules/threadsastheyaredeveloped.Applicat