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1DesignoftheTemperatureControlSystemBasedonAT89C51ABSTRACTTheprincipleandfunctionsofthetemperaturecontrolsystembasedonmicrocontrollerAT89C51arestudied,andthetemperaturemeasurementunitconsistsofthe1-WirebusdigitaltemperaturesensorDS18B20.Thesystemcanbeexpectedtodetectthepresettemperature,displaytimeandsavemonitoringdata.Analarmwillbegivenbysystemifthetemperatureexceedstheupperandlowerlimitvalueofthetemperaturewhichcanbesetdiscretionarilyandthenautomaticcontrolisachieved,thusthetemperatureisachievedmonitoringintelligentlywithinacertainrange.Basingonprincipleofthesystem,itiseasytomakeavarietyofothernon-linearcontrolsystemssolongasthesoftwaredesignisreasonablychanged.Thesystemhasbeenprovedtobeaccurate,reliableandsatisfiedthroughfieldpractice.KEYWORDS:AT89C51;microcontroller;DS18B20;temperature1INTRODUCTIONTemperatureisaveryimportantparameterinhumanlife.Inthemodernsociety,temperaturecontrol(TC)isnotonlyusedinindustrialproduction,butalsowidelyusedinotherfields.Withtheimprovementofthelifequality,wecanfindtheTCapplianceinhotels,factoriesandhomeaswell.AndthetrendthatTCwillbetterservethewholesociety,soitisofgreatsignificancetomeasureandcontrolthetemperature.BasedontheAT89C51andtemperaturesensorDS18B20,thissystemcontrolstheconditiontemperatureintelligently.Thetemperaturecanbesetdiscretionarilywithinacertainrange.ThesystemcanshowthetimeonLCD,andsavemonitoringdata;andautomaticallycontrolthetemperaturewhentheconditiontemperatureexceedstheupperandlowerlimitvalue.Bydoingsoitistokeepthetemperatureunchanged.Thesystemisofhighanti-jamming,highcontrolprecisionandflexibledesign;italsofitstheruggedenvironment.Itismainlyusedinpeople'slifetoimprovethequalityoftheworkandlife.Itisalsoversatile,sothatitcanbeconvenienttoextendtheuseofthesystem.Sothedesignisofprofoundimportance.Thegeneraldesign,hardwaredesignandsoftwaredesignofthesystemarecovered.1.1IntroductionThe8-bitAT89C51CHMOSmicrocontrollersaredesignedtohandlehigh-speedcalculationsandfastinput/outputoperations.MCS51microcontrollersaretypically2usedforhigh-speedeventcontrolsystems.Commercialapplicationsincludemodems,motor-controlsystems,printers,photocopiers,airconditionercontrolsystems,diskdrives,andmedicalinstruments.TheautomotiveindustryuseMCS51microcontrollersinengine-controlsystems,airbags,suspensionsystems,andantilockbrakingsystems(ABS).TheAT89C51isespeciallywellsuitedtoapplicationsthatbenefitfromitsprocessingspeedandenhancedon-chipperipheralfunctionsset,suchasautomotivepower-traincontrol,vehicledynamicsuspension,antilockbraking,andstabilitycontrolapplications.Becauseofthesecriticalapplications,themarketrequiresareliablecost-effectivecontrollerwithalowinterruptlatencyresponse,abilitytoservicethehighnumberoftimeandeventdrivenintegratedperipheralsneededinrealtimeapplications,andaCPUwithaboveaverageprocessingpowerinasinglepackage.Thefinancialandlegalriskofhavingdevicesthatoperateunpredictablyisveryhigh.Onceinthemarket,particularlyinmissioncriticalapplicationssuchasanautopilotoranti-lockbrakingsystem,mistakesarefinanciallyprohibitive.Redesigncostscanrunashighasa$500K,muchmoreifthefixmeans2backannotatingitacrossaproductfamilythatsharethesamecoreand/orperipheraldesignflaw.Inaddition,fieldreplacementsofcomponentsisextremelyexpensive,asthedevicesaretypicallysealedinmoduleswithatotalvalueseveraltimesthatofthecomponent.Tomitigatetheseproblems,itisessentialthatcomprehensivetestingofthecontrollersbecarriedoutatboththecomponentlevelandsystemlevelunderworstcaseenvironmentalandvoltageconditions.Thiscompleteandthoroughvalidationnecessitatesnotonlyawell-definedprocessbutalsoaproperenvironmentandtoolstofacilitateandexecutethemissionsuccessfully.IntelChandlerPlatformEngineeringgroupprovidespostsiliconsystemvalidation(SV)ofvariousmicro-controllersandprocessors.Thesystemvalidationprocesscanbebrokenintothreemajorparts.Thetypeofthedeviceanditsapplicationrequirementsdeterminewhichtypesoftestingareperformedonthedevice.1.2TheAT89C51providesthefollowingstandardfeatures4KbytesofFlash,128bytesofRAM,32I/Olines,two16-bittimer/counters,afivevectortwo-levelinterruptarchitecture,afulldupleser-ialport,on-chiposcillatorandclockcircuitry.Inaddition,theAT89C51isdesignedwithstaticlogicforoperationdowntozerofrequencyandsupportstwosoftwareselectablepowersavingmodes.TheIdleModestopstheCPUwhileallowingtheRAM,timer/counters,serialportandinterruptsys-temtocontinuefunctioning.ThePower-downModesavesthe3RAMcontentsbutfreezestheoscil–latordisablingallotherchipfunctionsuntilthenexthardwarereset.1.3PinDescriptionVCCSupplyvoltage.GNDGround.Port0：Port0isan8-bitopen-drainbi-directionalI/Oport.Asanoutputport,eachpincansinkeightTTLinputs.When1sarewrittentoport0pins,thepinscanbeusedashighimpedanceinputs.Port0mayalsobeconfiguredtobethemultiplexedloworderaddress/databusduringaccessestoexternalprogramanddatamemory.InthismodeP0hasinternalpullups.Port0alsoreceivesthecodebytesduringFlashprogramming,andoutputsthecodebytesduringprogramverification.Externalpullupsarerequiredduringprogramverification.Port1：Port1isan8-bitbi-directionalI/Oport