ds18b20数字式温度传感器毕业论文中英文资料外文翻译文献

中英文资料外文翻译文献THEINTRODUCTIONTOTHEDS18B201DESCRIPTIONTHEDS18B20DIGITALTHERMOMETERPROVIDES9BITTO12BITCELSIUSTEMPERATUREMEASUREMENTSANDHASANALARMFUNCTIONWITHNONVOLATILEUSERPROGRAMMABLEUPPERANDLOWERTRIGGERPOINTSTHEDS18B20COMMUNICATESOVERA1WIREBUSTHATBYDEFINITIONREQUIRESONLYONEDATALINEFORCOMMUNICATIONWITHACENTRALMICROPROCESSORITHASANOPERATINGTEMPERATURERANGEOF55CTO125CANDISACCURATETO05COVERTHERANGEOF10CTO85CINADDITION,THEDS18B20CANDERIVEPOWERDIRECTLYFROMTHEDATALINE“PARASITEPOWER”,ELIMINATINGTHENEEDFORANEXTERNALPOWERSUPPLYEACHDS18B20HASAUNIQUE64BITSERIALCODE,WHICHALLOWSMULTIPLEDS18B20STOFUNCTIONONTHESAME1WIREBUSTHUS,ITISSIMPLETOUSEONEMICROPROCESSORTOCONTROLMANYDS18B20SDISTRIBUTEDOVERALARGEAREAAPPLICATIONSTHATCANBENEFITFROMTHISFEATUREINCLUDEHVACENVIRONMENTALCONTROLS,TEMPERATUREMONITORINGSYSTEMSINSIDEBUILDINGS,EQUIPMENT,ORMACHINERY,ANDPROCESSMONITORINGANDCONTROLSYSTEMS2FEATURESUNIQUE1WIREINTERFACEREQUIRESONLYONEPORTPINFORCOMMUNICATIONEACHDEVICEHASAUNIQUE64BITSERIALCODESTOREDINANONBOARDROMMULTIDROPCAPABILITYSIMPLIFIESDISTRIBUTEDTEMPERATURESENSINGAPPLICATIONSREQUIRESNOEXTERNALCOMPONENTSCANBEPOWEREDFROMDATALINEPOWERSUPPLYRANGEIS30VTO55VMEASURESTEMPERATURESFROM55CTO125C67FTO257F05CACCURACYFROM10CTO85CTHERMOMETERRESOLUTIONISUSERSELECTABLEFROM9TO12BITSCONVERTSTEMPERATURETO12BITDIGITALWORDIN750MSMAXUSERDEFINABLENONVOLATILENVALARMSETTINGSALARMSEARCHCOMMANDIDENTIFIESANDADDRESSESDEVICESWHOSETEMPERATUREISOUTSIDEPROGRAMMEDLIMITSSOFTWARECOMPATIBLEWITHTHEDS1822APPLICATIONSINCLUDETHERMOSTATICCONTROLS,INDUSTRIALSYSTEMS,CONSUMERPRODUCTS,THERMOMETERS,ORANYTHERMALLYSENSITIVESYSTEM3OVERVIEWFIGURE1SHOWSABLOCKDIAGRAMOFTHEDS18B20,ANDPINDESCRIPTIONSAREGIVENINTHEPINDESCRIPTIONTABLETHE64BITROMSTORESTHEDEVICESUNIQUESERIALCODETHESCRATCHPADMEMORYCONTAINSTHE2BYTETEMPERATUREREGISTERTHATSTORESTHEDIGITALOUTPUTFROMTHETEMPERATURESENSORINADDITION,THESCRATCHPADPROVIDESACCESSTOTHE1BYTEUPPERANDLOWERALARMTRIGGERREGISTERSTHANDTLANDTHE1BYTECONFIGURATIONREGISTERTHECONFIGURATIONREGISTERALLOWSTHEUSERTOSETTHERESOLUTIONOFTHETEMPERATURETODIGITALCONVERSIONTO9,10,11,OR12BITSTHETH,TL,ANDCONFIGURATIONREGISTERSARENONVOLATILEEEPROM,SOTHEYWILLRETAINDATAWHENTHEDEVICEISPOWEREDDOWNTHEDS18B20USESMAXIMSEXCLUSIVE1WIREBUSPROTOCOLTHATIMPLEMENTSBUSCOMMUNICATIONUSINGONECONTROLSIGNALTHECONTROLLINEREQUIRESAWEAKPULLUPRESISTORSINCEALLDEVICESARELINKEDTOTHEBUSVIAA3STATEOROPENDRAINPORTTHEDQPININTHECASEOFTHEDS18B20INTHISBUSSYSTEM,THEMICROPROCESSORTHEMASTERDEVICEIDENTIFIESANDADDRESSESDEVICESONTHEBUSUSINGEACHDEVICESUNIQUE64BITCODEBECAUSEEACHDEVICEHASAUNIQUECODE,THENUMBEROFDEVICESTHATCANBEADDRESSEDONONEDS18B20BUSISVIRTUALLYUNLIMITEDTHE1WIREBUSPROTOCOL,INCLUDINGDETAILEDEXPLANATIONSOFTHECOMMANDSAND“TIMESLOTS,”ISCOVEREDINTHE1WIREBUSSYSTEMSECTIONANOTHERFEATUREOFTHEDS18B20ISTHEABILITYTOOPERATEWITHOUTANEXTERNALPOWERSUPPLYPOWERISINSTEADSUPPLIEDTHROUGHTHE1WIREPULLUPRESISTORVIATHEDQPINWHENTHEBUSISHIGHTHEHIGHBUSSIGNALALSOCHARGESANINTERNALCAPACITORCPP,WHICHTHENSUPPLIESPOWERTOTHEDEVICEWHENTHEBUSISLOWTHISMETHODOFDERIVINGPOWERFROMTHE1WIREBUSISREFERREDTOAS“PARASITEPOWER”ASANALTERNATIVE,THEDS18B20MAYALSOBEPOWEREDBYANEXTERNALSUPPLYONVDD64BITROMAND1WIREPORTMEMORYCONTROLLOGICSCRATCHPADTEMPERATURESENSORALARMHIGHTRIGGERTHALARMLOWTRIGGERTLCONFIGURATIONREGISTER8BITCRCGENERATORPOWERSUPPLYSENSEINTERNALVDDPARASITEPOWERCIRCUITCPPVPU47KDQGNDVDDFIGURE1DS18B20BLOCKDIAGRAM4OPERATIONMEASURINGTEMPERATURTHECOREFUNCTIONALITYOFTHEDS18B20ISITSDIRECTTODIGITALTEMPERATURESENSORTHERESOLUTIONOFTHETEMPERATURESENSORISUSERCONFIGURABLETO9,10,11,OR12BITS,CORRESPONDINGTOINCREMENTSOF05C,025C,0125C,AND00625C,RESPECTIVELYTHEDEFAULTRESOLUTIONATPOWERUPIS12BITTHEDS18B20POWERSUPINALOWPOWERIDLESTATETOINITIATEATEMPERATUREMEASUREMENTANDATODCONVERSION,THEMASTERMUSTISSUEACONVERTT44HCOMMANDFOLLOWINGTHECONVERSION,THERESULTINGTHERMALDATAISSTOREDINTHE2BYTETEMPERATUREREGISTERINTHESCRATCHPADMEMORYANDTHEDS18B20RETURNSTOITSIDLESTATEIFTHEDS18B20ISPOWEREDBYANEXTERNALSUPPLY,THEMASTERCANISSUE“READTIMESLOTS”SEETHE1WIREBUSSYSTEMSECTIONAFTERTHECONVERTTCOMMANDANDTHEDS18B20WILLRESPONDBYTRANSMITTING0WHILETHETEMPERATURECONVERSIONISINPROGRESSAND1WHENTHECONVERSIONISDONEIFTHEDS18B20ISPOWEREDWITHPARASITEPOWER,THISNOTIFICATIONTECHNIQUECANNOTBEUSEDSINCETHEBUSMUSTBEPULLEDHIGHBYASTRONGPULLUPDURINGTHEENTIRETEMPERATURECONVERSIONTHEDS18B20OUTPUTTEMPERATUREDATAISCALIBRATEDINDEGREESCELSIUSFORFAHRENHEITAPPLICATIONS,ALOOKUPTABLEORCONVERSIONROUTINEMUSTBEUSEDTHETEMPERATUREDATAISSTOREDASA16BITSIGNEXTENDEDTWOSCOMPLEMENTNUMBERINTHETEMPERATUREREGISTERSEEFIGURE2THESIGNBITSSINDICATEIFTHETEMPERATUREISPOSITIVEORNEGATIVEFORPOSITIVENUMBERSS0ANDFORNEGATIVENUMBERSS1IFTHEDS18B20ISCONFIGUREDFOR12BITRESOLUTION,ALLBITSINTHETEMPERATUREREGISTERWILLCONTAINVALIDDATAFOR11BITRESOLUTION,BIT0ISUNDEFINEDFOR10BITRESOLUTION,BITS1AND0AREUNDEFINED,ANDFOR9BITRESOLUTIONBITS2,1,AND0AREUNDEFINEDTABLE1GIVESEXAMPLESOFDIGITALOUTPUTDATAANDTHECORRESPONDINGTEMPERATUREREADINGFOR12BITRESOLUTIONCONVERSIONSBIT7BIT6BIT5BIT4BIT3BIT2BIT1BIT0LSBYTE2322212021222324BIT15BIT14BIT13BIT12BIT11BIT10BIT9BIT8MSBYTESSSSS262524FIGURE2TEMPERATUREREGISTERFORMATTEMPERATUREDIGITALOUTPUTBINARYDIGITALOUTPUTHEX125000001111101000007D0H25062500000001100100010191H000000000000000000000H2506251111111001101111FE6FH551111110010010000FC90HTABLE1TEMPERATURE/DATARELATIONSHIP564BITLASEREDROMCODEEACHDS18B20CONTAINSAUNIQUE64BITCODESEEFIGURE3STOREDINROMTHELEASTSIGNIFICANT8BITSOFTHEROMCODECONTAINTHEDS18B20S1WIREFAMILYCODE28HTHENEXT48BITSCONTAINAUNIQUESERIALNUMBERTHEMOSTSIGNIFICANT8BITSCONTAINACYCLICREDUNDANCYCHECKCRCBYTETHATISCALCULATEDFROMTHEFIRST56BITSOFTHEROMCODETHE64BITROMCODEANDASSOCIATEDROMFUNCTIONCONTROLLOGICALLOWTHEDS18B20TOOPERATEASA1WIREDEVICEUSINGTHEPROTOCOLDETAILEDINTHE1WIREBUSSYSTEMSECTION8BITCRC48BITSERIALNUMBER8BITFAMILYCODEMSBLSBMSBLSBMSBFIGURE364BITLASEREDROMCODE6MEMORYTHEDS18B20SMEMORYISORGANIZEDASSHOWNINFIGURE4THEMEMORYCONSISTSOFANSRAMSCRATCHPADWITHNONVOLATILEEEPROMSTORAGEFORTHEHIGHANDLOWALARMTRIGGERREGISTERSTHANDTLANDCONFIGURATIONREGISTERNOTETHATIFTHEDS18B20ALARMFUNCTIONISNOTUSED,THETHANDTLREGISTERSCANSERVEASGENERALPURPOSEMEMORYBYTE0ANDBYTE1OFTHESCRATCHPADCONTAINTHELSBANDTHEMSBOFTHETEMPERATUREREGISTER,RESPECTIVELYTHESEBYTESAREREADONLYBYTES2AND3PROVIDEACCESSTOTHANDTLREGISTERSBYTE4CONTAINSTHECONFIGURATIONREGISTERDATABYTES5,6,AND7ARERESERVEDFORINTERNALUSEBYTHEDEVICEANDCANNOTBEOVERWRITTENBYTE8OFTHESCRATCHPADISREADONLYANDCONTAINSTHECRCCODEFORBYTES0THROUGH7OFTHESCRATCHPADTHEDS18B20GENERATESTHISCRCUSINGTHEMETHODDESCRIBEDINTHECRCGENERATIONSECTIONDATAISWRITTENTOBYTES2,3,AND4OFTHESCRATCHPADUSINGTHEWRITESCRATCHPAD4EHCOMMANDTHEDATAMUSTBETRANSMITTEDTOTHEDS18B20STARTINGWITHTHELEASTSIGNIFICANTBITOFBYTE2TOVERIFYDATAINTEGRITY,THESCRATCHPADCANBEREADUSINGTHEREADSCRATCHPADBEHCOMMANDAFTERTHEDATAISWRITTENWHENREADINGTHESCRATCHPAD,DATAISTRANSFERREDOVERTHE1WIREBUSSTARTINGWITHTHELEASTSIGNIFICANTBITOFBYTE0TOTRANSFERTHETH,TLANDCONFIGURATIONDATAFROMTHESCRATCHPADTOEEPROM,THEMASTERMUSTISSUETHECOPYSCRATCHPAD48HCOMMANDBYTE0TEMPERATURELSBBYTE1TEMPERATUREMSBBYTE2THREGISTERFORHIGHTEMPERATUREBYTE3TLREGISTERFORLOWTEMPERATUREBYTE4CONFIGURATIONREGISTERBYTE5RESERVED（FFH）BYTE6RESERVED（OCH）BYTE7RESERVED（IOH）BYTE8CYCLICREDUNDANCYCHECKS（CRC）FIGURE4DS18B20MEMORYMAP7CONFIGURATIONREGISTERBYTE4OFTHESCRATCHPADMEMORYCONTAINSTHECONFIGURATIONREGISTER,WHICHISORGANIZEDASILLUSTRATEDINFIGURE5THEUSERCANSETTHECONVERSIONRESOLUTIONOFTHEDS18B20USINGTHER0ANDR1BITSINTHISREGISTERASSHOWNINTABLE2THEPOWERUPDEFAULTOFTHESEBITSISR01ANDR1112BITRESOLUTIONNOTETHATTHEREISADIRECTTRADEOFFBETWEENRESOLUTIONANDCONVERSIONTIMEBIT7ANDBITS0TO4INTHECONFIGURATIONREGISTERARERESERVEDFORINTERNALUSEBYTHEDEVICEANDCANNOTBEOVERWRITTENBIT7BIT6BIT5BIT4BIT3BIT2BIT1BIT0TMR1R011111FIGURE5CONFIGURATIONREGISTERR0R1RESOLUTIONBITSMAXCONVERSIONTIMETABLE2THERMOMETERRESOLUTIONCONFIGURATION81WIREBUSSYSTEMTHE1WIREBUSSYSTEMUSESASINGLEBUSMASTERTOCONTROLONEORMORESLAVEDEVICESTHEDS18B20ISALWAYSASLAVEWHENTHEREISONLYONESLAVEONTHEBUS,THESYSTEMISREFERREDTOASA“SINGLEDROP”SYSTEMTHESYSTEMIS“MULTIDROP”IFTHEREAREMULTIPLESLAVESONTHEBUSALLDATAANDCOMMANDSARETRANSMITTEDLEASTSIGNIFICANTBITFIRSTOVERTHE1WIREBUSTHEFOLLOWINGDISCUSSIONOFTHE1WIREBUSSYSTEMISBROKENDOWNINTOTHREETOPICSHARDWARECONFIGURATION,TRANSACTIONSEQUENCE,AND1WIRESIGNALINGSIGNALTYPESANDTIMING9TRANSACTIONSEQUENCETHETRANSACTIONSEQUENCEFORACCESSINGTHEDS18B20ISASFOLLOWSSTEP1INITIALIZATIONSTEP2ROMCOMMANDFOLLOWEDBYANYREQUIREDDATAEXCHANGESTEP3DS18B20FUNCTIONCOMMANDFOLLOWEDBYANYREQUIREDDATAEXCHANGEITISVERYIMPORTANTTOFOLLOWTHISSEQUENCEEVERYTIMETHEDS18B20ISACCESSED,ASTHEDS18B20WILLNOTRESPONDIFANYSTEPSINTHESEQUENCEAREMISSINGOROUTOFORDEREXCEPTIONSTOTHISRULEARETHESEARCHROMF0HANDALARMSEARCHECHCOMMANDSAFTERISSUINGEITHEROFTHESEROMCOMMANDS,THEMASTERMUSTRETURNTOSTEP1INTHESEQUENCE（1）INITIALIZATIONALLTRANSACTIONSONTHE1WIREBUSBEGINWITHANINITIALIZATIONSEQUENCETHEINITIALIZATIONSEQUENCECONSISTSOFARESETPULSETRANSMITTEDBYTHEBUSMASTERFOLLOWEDBYPRESENCEPULSESTRANSMITTEDBYTHESLAVESTHEPRESENCEPULSELETSTHEBUS0011010191011129375MS1875MS375MS750MSMASTERKNOWTHATSLAVEDEVICESSUCHASTHEDS18B20AREONTHEBUSANDAREREADYTOOPERATE（2）ROMCOMMANDSAFTERTHEBUSMASTERHASDETECTEDAPRESENCEPULSE,ITCANISSUEAROMCOMMANDTHESECOMMANDSOPERATEONTHEUNIQUE64BITROMCODESOFEACHSLAVEDEVICEANDALLOWTHEMASTERTOSINGLEOUTASPECIFICDEVICEIFMANYAREPRESENTONTHE1WIREBUSTHESECOMMANDSALSOALLOWTHEMASTERTODETERMINEHOWMANYANDWHATTYPESOFDEVICESAREPRESENTONTHEBUSORIFANYDEVICEHASEXPERIENCEDANALARMCONDITIONTHEREAREFIVEROMCOMMANDS,ANDEACHCOMMANDIS8BITSLONGTHEMASTERDEVICEMUSTISSUEANAPPROPRIATEROMCOMMANDBEFOREISSUINGADS18B20FUNCTIONCOMMAND1SEARCHROMF0HWHENASYSTEMISINITIALLYPOWEREDUP,THEMASTERMUSTIDENTIFYTHEROMCODESOFALLSLAVEDEVICESONTHEBUS,WHICHALLOWSTHEMASTERTODETERMINETHENUMBEROFSLAVESANDTHEIRDEVICETYPESTHEMASTERLEARNSTHEROMCODESTHROUGHAPROCESSOFELIMINATIONTHATREQUIRESTHEMASTERTOPERFORMASEARCHROMCYCLEIE,SEARCHROMCOMMANDFOLLOWEDBYDATAEXCHANGEASMANYTIMESASNECESSARYTOIDENTIFYALLOFTHESLAVEDEVICESIFTHEREISONLYONESLAVEONTHEBUS,THESIMPLERREADROMCOMMANDCANBEUSEDINPLACEOFTHESEARCHROMPROCESS2READROM33HTHISCOMMANDCANONLYBEUSEDWHENTHEREISONESLAVEONTHEBUSITALLOWSTHEBUSMASTERTOREADTHESLAVES64BITROMCODEWITHOUTUSINGTHESEARCHROMPROCEDUREIFTHISCOMMANDISUSEDWHENTHEREISMORETHANONESLAVEPRESENTONTHEBUS,ADATACOLLISIONWILLOCCURWHENALLTHESLAVESATTEMPTTORESPONDATTHESAMETIME3MATCHROM55HTHEMATCHROMCOMMANDFOLLOWEDBYA64BITROMCODESEQUENCEALLOWSTHEBUSMASTERTOADDRESSASPECIFICSLAVEDEVICEONAMULTIDROPORSINGLEDROPBUSONLYTHESLAVETHATEXACTLYMATCHESTHE64BITROMCODESEQUENCEWILLRESPONDTOTHEFUNCTIONCOMMANDISSUEDBYTHEMASTERALLOTHERSLAVESONTHEBUSWILLWAITFORARESETPULSE4SKIPROMCCHTHEMASTERCANUSETHISCOMMANDTOADDRESSALLDEVICESONTHEBUSSIMULTANEOUSLYWITHOUTSENDINGOUTANYROMCODEINFORMATIONFOREXAMPLE,THEMASTERCANMAKEALLDS18B20SONTHEBUSPERFORMSIMULTANEOUSTEMPERATURECONVERSIONSBYISSUINGASKIPROMCOMMANDFOLLOWEDBYACONVERTT44HCOMMANDNOTETHATTHEREADSCRATCHPADBEHCOMMANDCANFOLLOWTHESKIPROMCOMMANDONLYIFTHEREISASINGLESLAVEDEVICEONTHEBUSINTHISCASE,TIMEISSAVEDBYALLOWINGTHEMASTERTOREADFROMTHESLAVEWITHOUTSENDINGTHEDEVICES64BITROMCODEASKIPROMCOMMANDFOLLOWEDBYAREADSCRATCHPADCOMMANDWILLCAUSEADATACOLLISIONONTHEBUSIFTHEREISMORETHANONESLAVESINCEMULTIPLEDEVICESWILLATTEMPTTOTRANSMITDATASIMULTANEOUSLY5ALARMSEARCHECHTHEOPERATIONOFTHISCOMMANDISIDENTICALTOTHEOPERATIONOFTHESEARCHROMCOMMANDEXCEPTTHATONLYSLAVESWITHASETALARMFLAGWILLRESPONDTHISCOMMANDALLOWSTHEMASTERDEVICETODETERMINEIFANYDS18B20SEXPERIENCEDANALARMCONDITIONDURINGTHEMOSTRECENTTEMPERATURECONVERSIONAFTEREVERYALARMSEARCHCYCLEIE,ALARMSEARCHCOMMANDFOLLOWEDBYDATAEXCHANGE,THEBUSMASTERMUSTRETURNTOSTEP1INITIALIZATIONINTHETRANSACTIONSEQUENCE（3）DS18B20FUNCTIONCOMMANDSAFTERTHEBUSMASTERHASUSEDAROMCOMMANDTOADDRESSTHEDS18B20WITHWHICHITWISHESTOCOMMUNICATE,THEMASTERCANISSUEONEOFTHEDS18B20FUNCTIONCOMMANDSTHESECOMMANDSALLOWTHEMASTERTOWRITETOANDREADFROMTHEDS18B20SSCRATCHPADMEMORY,INITIATETEMPERATURECONVERSIONSANDDETERMINETHEPOWERSUPPLYMODE1CONVERTT44HTHISCOMMANDINITIATESASINGLETEMPERATURECONVERSIONFOLLOWINGTHECONVERSION,THERESULTINGTHERMALDATAISSTOREDINTHE2BYTETEMPERATUREREGISTERINTHESCRATCHPADMEMORYANDTHEDS18B20RETURNSTOITSLOWPOWERIDLESTATEIFTHEDEVICEISBEINGUSEDINPARASITEPOWERMODE,WITHIN10SMAXAFTERTHISCOMMANDISISSUEDTHEMASTERMUSTENABLEASTRONGPULLUPONTHE1WIREBUSIFTHEDS18B20ISPOWEREDBYANEXTERNALSUPPLY,THEMASTERCANISSUEREADTIMESLOTSAFTERTHECONVERTTCOMMANDANDTHEDS18B20WILLRESPONDBYTRANSMITTINGA0WHILETHETEMPERATURECONVERSIONISINPROGRESSANDA1WHENTHECONVERSIONISDONEINPARASITEPOWERMODETHISNOTIFICATIONTECHNIQUECANNOTBEUSEDSINCETHEBUSISPULLEDHIGHBYTHESTRONGPULLUPDURINGTHECONVERSION2READSCRATCHPADBEHTHISCOMMANDALLOWSTHEMASTERTOREADTHECONTENTSOFTHESCRATCHPADTHEDATATRANSFERSTARTSWITHTHELEASTSIGNIFICANTBITOFBYTE0ANDCONTINUESTHROUGHTHESCRATCHPADUNTILTHE9THBYTEBYTE8CRCISREADTHEMASTERMAYISSUEARESETTOTERMINATEREADINGATANYTIMEIFONLYPARTOFTHESCRATCHPADDATAISNEEDED3WRITESCRATCHPAD4EHTHISCOMMANDALLOWSTHEMASTERTOWRITE3BYTESOFDATATOTHEDS18B20SSCRATCHPADTHEFIRSTDATABYTEISWRITTENINTOTHETHREGISTERBYTE2OFTHESCRATCHPAD,THESECONDBYTEISWRITTENINTOTHETLREGISTERBYTE3,ANDTHETHIRDBYTEISWRITTENINTOTHECONFIGURATIONREGISTERBYTE4DATAMUSTBETRANSMITTEDLEASTSIGNIFICANTBITFIRSTALLTHREEBYTESMUSTBEWRITTENBEFORETHEMASTERISSUESARESET,ORTHEDATAMAYBECORRUPTED4COPYSCRATCHPAD48HTHISCOMMANDCOPIESTHECONTENTSOFTHESCRATCHPADTH,TLANDCONFIGURATIONREGISTERSBYTES2,3AND4TOEEPROMIFTHEDEVICEISBEINGUSEDINPARASITEPOWERMODE,WITHIN10SMAXAFTERTHISCOMMANDISISSUEDTHEMASTERMUSTENABLEASTRONGPULLUPONTHE1WIREBUS5RECALLE2B8HTHISCOMMANDRECALLSTHEALARMTRIGGERVALUESTHANDTLANDCONFIGURATIONDATAFROMEEPROMANDPLACESTHEDATAINBYTES2,3,AND4,RESPECTIVELY,INTHESCRATCHPADMEMORYTHEMASTERDEVICECANISSUEREADTIMESLOTSFOLLOWINGTHERECALLE2COMMANDANDTHEDS18B20WILLINDICATETHESTATUSOFTHERECALLBYTRANSMITTING0WHILETHERECALLISINPROGRESSAND1WHENTHERECALLISDONETHERECALLOPERATIONHAPPENSAUTOMATICALLYATPOWERUP,SOVALIDDATAISAVAILABLEINTHESCRATCHPADASSOONASPOWERISAPPLIEDTOTHEDEVICE6READPOWERSUPPLYB4HTHEMASTERDEVICEISSUESTHISCOMMANDFOLLOWEDBYAREADTIMESLOTTODETERMINEIFANYDS18B20SONTHEBUSAREUSINGPARASITEPOWERDURINGTHEREADTIMESLOT,PARASITEPOWEREDDS18B20SWILLPULLTHEBUSLOW,ANDEXTERNALLYPOWEREDDS18B20SWILLLETTHEBUSREMAINHIGH10WIRESIGNALINGTHEDS18B20USESASTRICT1WIRECOMMUNICATIONPROTOCOLTOENSUREDATAINTEGRITYSEVERALSIGNALTYPESAREDEFINEDBYTHISPROTOCOLRESETPULSE,PRESENCEPULSE,WRITE0,WRITE1,READ0,ANDREAD1THEBUSMASTERINITIATESALLTHESESIGNALS,WITHTHEEXCEPTIONOFTHEPRESENCEPULSE（1）INITIALIZATIONPROCEDURERESETANDPRESENCEPULSESALLCOMMUNICATIONWITHTHEDS18B20BEGINSWITHANINITIALIZATIONSEQUENCETHATCONSISTSOFARESETPULSEFROMTHEMASTERFOLLOWEDBYAPRESENCEPULSEFROMTHEDS18B20THISISILLUSTRATEDINFIGURE6WHENTHEDS18B20SENDSTHEPRESENCEPULSEINRESPONSETOTHERESET,ITISINDICATINGTOTHEMASTERTHATITISONTHEBUSANDREADYTOOPERATEDURINGTHEINITIALIZATIONSEQUENCETHEBUSMASTERTRANSMITSTXTHERESETPULSEBYPULLINGTHE1WIREBUSLOWFORAMINIMUMOF480STHEBUSMASTERTHENRELEASESTHEBUSANDGOESINTORECEIVEMODERXWHENTHEBUSISRELEASED,THE5KPULLUPRESISTORPULLSTHE1WIREBUSHIGHWHENTHEDS18B20DETECTSTHISRISINGEDGE,ITWAITS15STO60SANDTHENTRANSMITSAPRESENCEPULSEBYPULLINGTHE1WIREBUSLOWFOR60STO240SMASTERTXRESETPULSE480SMINIMUMDS18B20WAITS1560SDS18B20PRESENCEPULSE60240SMASTERRX480SMINIMUMDS18B20INITIALIZATIONTIMINGVPUGND1WIREBUSBUSMASTERPULLINGLOWDS18B20PULLINGLOWRESISTORPULLUPFIGURE6INITIALIZATIONTIMING（2）READ/WRITETIMESLOTSTHEBUSMASTERWRITESDATATOTHEDS18B20DURINGWRITETIMESLOTSANDREADSDATAFROMTHEDS18B20DURINGREADTIMESLOTSONEBITOFDATAISTRANSMITTEDOVERTHE1WIREBUSPERTIMESLOT1WRITETIMESLOTSTHEREARETWOTYPESOFWRITETIMESLOTS“WRITE1”TIMESLOTSAND“WRITE0”TIMESLOTSTHEBUSMASTERUSESAWRITE1TIMESLOTTOWRITEALOGIC1TOTHEDS18B20ANDAWRITE0TIMESLOTTOWRITEALOGIC0TOTHEDS18B20ALLWRITETIMESLOTSMUSTBEAMINIMUMOF60SINDURATIONWITHAMINIMUMOFA1SRECOVERYTIMEBETWEENINDIVIDUALWRITESLOTSBOTHTYPESOFWRITETIMESLOTSAREINITIATEDBYTHEMASTERPULLINGTHE1WIREBUSLOWSEEFIGURE7TOGENERATEAWRITE1TIMESLOT,AFTERPULLINGTHE1WIREBUSLOW,THEBUSMASTERMUSTRELEASETHE1WIREBUSWITHIN15SWHENTHEBUSISRELEASED,THE5KPULLUPRESISTORWILLPULLTHEBUSHIGHTOGENERATEAWRITE0TIMESLOT,AFTERPULLINGTHE1WIREBUSLOW,THEBUSMASTERMUSTCONTINUETOHOLDTHEBUSLOWFORTHEDURATIONOFTHETIMESLOTATLEAST60STHEDS18B20SAMPLESTHE1WIREBUSDURINGAWINDOWTHATLASTSFROM15STO60SAFTERTHEMASTERINITIATESTHEWRITETIMESLOTIFTHEBUSISHIGHDURINGTHESAMPLINGWINDOW,A1ISWRITTENTOTHEDS18B20IFTHELINEISLOW,A0ISWRITTENTOTHEDS18B20MASTERWRITE“0”SLOT60US1US1US15USDS18B20SAMPLES15US30USDS18B20SAMPLES15US15US30USDS18B20WRITETIMESLOTSTARTOFSLOTVCCGND1WIREBUSMASTERWRITE“1”SLOTMINTYPMAXMINTYPMAXBUSMASTERPULLINGLOWRESISTORPULLUPSTARTOFSLOTFIGURE7DS18B20WRITETIMESLOT2READTIMESLOTSTHEDS18B20CANONLYTRANSMITDATATOTHEMASTERWHENTHEMASTERISSUESREADTIMESLOTSTHEREFORE,THEMASTERMUSTGENERATEREADTIMESLOTSIMMEDIATELYAFTERISSUINGAREADSCRATCHPADBEHORREADPOWERSUPPLYB4HCOMMAND,SOTHATTHEDS18B20CANPROVIDETHEREQUESTEDDATAINADDITION,THEMASTERCANGENERATEREADTIMESLOTSAFTERISSUINGCONVERTT44HORRECALLE2B8HCOMMANDSTOFINDOUTTHESTATUSOFTHEOPERATIONALLREADTIMESLOTSMUSTBEAMINIMUMOF60SINDURATIONWITHAMINIMUMOFA1SRECOVERYTIMEBETWEENSLOTSAREADTIMESLOTISINITIATEDBYTHEMASTERDEVICEPULLINGTHE1WIREBUSLOWFORAMINIMUMOF1SANDTHENRELEASINGTHEBUSSEEFIGURE8AFTERTHEMASTERINITIATESTHEREADTIMESLOT,THEDS18B20WILLBEGINTRANSMITTINGA1OR0ONBUSTHEDS18B20TRANSMITSA1BYLEAVINGTHEBUSHIGHANDTRANSMITSA0BYPULLINGTHEBUSLOWWHENTRANSMITTINGA0,THEDS18B20WILLRELEASETHEBUSBYTHEENDOFTHETIMESLOT,ANDTHEBUSWILLBEPULLEDBACKTOITSHIGHIDLESTATEBYTHEPULLUPRESISTEROUTPUTDATAFROMTHEDS18B20ISVALIDFOR15SAFTERTHEFALLINGEDGETHATINITIATEDTHEREADTIMESLOTTHEREFORE,THEMASTERMUSTRELEASETHEBUSANDTHENSAMPLETHEBUSSTATEWITHIN15SFROMTHESTARTOFTHESLOTMASTERREAD“0”SLOT15US15US30US15USDS18B20READTIMESLOTVCCGND1WIREBUSMASTERREAD“1”SLOTBUSMASTERPULLINGLOWDS18B20PULLINGLOWRESISTORPULLUPMASTERSAMPLESMASTERSAMPLES1US1US1USFIGURE8DS18B20READTIMESLOTDS18B20介绍1说明DS18B20数字式温度传感器提供9位到12位的摄氏温度测量，并且有用户可编程的、非易失性温度上下限告警出发点。DS18B20通过单总线通信，单总线被定义为只需要一根数据线与主微处理器相连进行通信。它的工作温度范围为55C到12C，且在10到85范围内的精度为05C。另外，DS18B20能够从数据线中直接获得能量（寄生电源），消除了对外部供电的需求。每一个DS18B20都有一个独一无二的64位序列码，这个序列码允许多个DS18B20在同一根单总线上工作。因此很容易用一片微处理器控制分布在较大领域的多个DS18B20。包括高压交流电环境控制、内置温度检测系统建筑，或者机器、处理器和控制系统在内的应用程序都会从这个特点中受益。2特点独特的单线接口，只需要一个接口引脚即可通信每个设备均由一个存储在板上R