外文資料DS18B20DESCRIPTIONTHEDS18B20DIGITALTHERMOMETERPROVIDES9TO12BITCONFIGURABLETEMPERATUREREADINGSWHICHINDICATETHETEMPERATUREOFTHEDEVICEINFORMATIONISSENTTO/FROMTHEDS18B20OVERA1WIREINTERFACE,SOTHATONLYONEWIREANDGROUNDNEEDSTOBECONNECTEDFROMACENTRALMICROPROCESSORTOADS18B20POWERFORREADING,WRITING,ANDPERFORMINGTEMPERATURECONVERSIONSCANBEDERIVEDFROMTHEDATALINEITSELFWITHNONEEDFORANEXTERNALPOWERSOURCEBECAUSEEACHDS18B20CONTAINSAUNIQUESILICONSERIALNUMBER,MULTIPLEDS18B20SCANEXISTONTHESAME1WIREBUSTHISALLOWSFORPLACINGTEMPERATURESENSORSINMANYDIFFERENTPLACESAPPLICATIONSWHERETHISFEATUREISUSEFULINCLUDEHVACENVIRONMENTALCONTROLS,SENSINGTEMPERATURESINSIDEBUILDINGS,EQUIPMENTORMACHINERY,ANDPROCESSMONITORINGANDCONTROLFEATURES1UNIQUE1WIREINTERFACEREQUIRESONLYONEPORTPINFORCOMMUNICATION2MULTIDROPCAPABILITYSIMPLIFIESDISTRIBUTEDTEMPERATURESENSINGAPPLICATIONS3REQUIRESNOEXTERNALCOMPONENTS4CANBEPOWEREDFROMDATALINEPOWERSUPPLYRANGEIS30VTO55V5ZEROSTANDBYPOWERREQUIRED6MEASURESTEMPERATURESFROM55CTO125CFAHRENHEITEQUIVALENTIS67FTO257F7THERMOMETERRESOLUTIONISPROGRAMMABLEFROM9TO12BITS8CONVERTS12BITTEMPERATURETODIGITALWORDIN750MSMAX9USERDEFINABLE,NONVOLATILETEMPERATUREALARMSETTINGS10ALARMSEARCHCOMMANDIDENTIFIESANDADDRESSESDEVICESWHOSETEMPERATUREISOUTSIDEOFPROGRAMMEDLIMITSTEMPERATUREALARMCONDITION11APPLICATIONSINCLUDETHERMOSTATICCONTROLS,INDUSTRIALSYSTEMS,CONSUMERPRODUCTS,THERMOMETERS,ORANYTHERMALLYSENSITIVESYSTEMPINASSIGNMENTPINDESCRIPTIONGNDGROUNDDQDATAIN/OUTVDDPOWERSUPPLYVOLTAGENCNOCONNECTDETAILEDPINDESCRIPTIONOVERVIEWTHEBLOCKDIAGRAMOFFIGURE1SHOWSTHEMAJORCOMPONENTSOFTHEDS18B20THEDS18B20HASFOURMAINDATACOMPONENTS164BITLASEREDROM,2TEMPERATURESENSOR,3NONVOLATILETEMPERATUREALARMTRIGGERSTHANDTLTHEDEVICEDERIVESITSPOWERFROMTHE1WIRECOMMUNICATIONLINEBYSTORINGENERGYONANINTERNALCAPACITORDURINGPERIODSOFTIMEWHENTHESIGNALLINEISHIGHANDCONTINUESTOOPERATEOFFTHISPOWERSOURCEDURINGTHELOWTIMESOFTHE1WIRELINEUNTILITRETURNSHIGHTOREPLENISHTHEPARASITECAPACITORSUPPLYASANALTERNATIVE,THEDS18B20MAYALSOBEPOWEREDFROMANEXTERNAL3VOLT55VOLTSUPPLYDS18B20BLOCKDIAGRAMFIGURE1COMMUNICATIONTOTHEDS18B20ISVIAA1WIREPORTWITHTHE1WIREPORT,THEMEMORYANDCONTROLFUNCTIONSWILLNOTBEAVAILABLEBEFORETHEROMFUNCTIONPROTOCOLHASBEENESTABLISHEDTHEMASTERMUSTFIRSTPROVIDEONEOFFIVEROMFUNCTIONCOMMANDS1READROM,2MATCHROM,3SEARCHROM,4SKIPROM,OR5ALARMSEARCHTHESECOMMANDSOPERATEONTHE64BITLASEREDROMPORTIONOFEACHDEVICEANDCANSINGLEOUTASPECIFICDEVICEIFMANYAREPRESENTONTHE1WIRELINEASWELLASINDICATETOTHEBUSMASTERHOWMANYANDWHATTYPESOFDEVICESAREPRESENTAFTERAROMFUNCTIONSEQUENCEHASBEENSUCCESSFULLYEXECUTED,THEMEMORYANDCONTROLFUNCTIONSAREACCESSIBLEANDTHEMASTERMAYTHENPROVIDEANYONEOFTHESIXMEMORYANDCONTROLFUNCTIONCOMMANDSONECONTROLFUNCTIONCOMMANDINSTRUCTSTHEDS18B20TOPERFORMATEMPERATUREMEASUREMENTTHERESULTOFTHISMEASUREMENTWILLBEPLACEDINTHEDS18B20SSCRATCHPADMEMORY,ANDMAYBEREADBYISSUINGAMEMORYFUNCTIONCOMMANDWHICHREADSTHECONTENTSOFTHESCRATCHPADMEMORYTHETEMPERATUREALARMTRIGGERSTHANDTLCONSISTOF1BYTEEEPROMEACHIFTHEALARMSEARCHCOMMANDISNOTAPPLIEDTOTHEDS18B20,THESEREGISTERSMAYBEUSEDASGENERALPURPOSEUSERMEMORYTHESCRATCHPADALSOCONTAINSACONFIGURATIONBYTETOSETTHEDESIREDRESOLUTIONOFTHETEMPERATURETODIGITALCONVERSIONWRITINGTH,TL,ANDTHECONFIGURATIONBYTEISDONEUSINGAMEMORYFUNCTIONCOMMANDREADACCESSTOTHESEREGISTERSISTHROUGHTHESCRATCHPADALLDATAISREADANDWRITTENLEASTSIGNIFICANTBITFIRST1WIREBUSSYSTEMTHE1WIREBUSISASYSTEMWHICHHASASINGLEBUSMASTERANDONEORMORESLAVESTHEDS18B20BEHAVESASASLAVETHEDISCUSSIONOFTHISBUSSYSTEMISBROKENDOWNINTOTHREETOPICSHARDWARECONFIGURATION,TRANSACTIONSEQUENCE,AND1WIRESIGNALINGSIGNALTYPESANDTIMINGHARDWARECONFIGURATIONTHE1WIREBUSHASONLYASINGLELINEBYDEFINITIONITISIMPORTANTTHATEACHDEVICEONTHEBUSBEABLETODRIVEITATTHEAPPROPRIATETIMETOFACILITATETHIS,EACHDEVICEATTACHEDTOTHE1WIREBUSMUSTHAVEOPENDRAINOR3STATEOUTPUTSTHE1WIREPORTOFTHEDS18B20DQPINISOPENDRAINWITHANINTERNALCIRCUITEQUIVALENTTOTHATSHOWNINFIGURE9AMULTIDROPBUSCONSISTSOFA1WIREBUSWITHMULTIPLESLAVESATTACHEDTHE1WIREBUSREQUIRESAPULLUPRESISTOROFAPPROXIMATELY5KTHEIDLESTATEFORTHE1WIREBUSISHIGHIFFORANYREASONATRANSACTIONNEEDSTOBESUSPENDED,THEBUSMUSTBELEFTINTHEIDLESTATEIFTHETRANSACTIONISTORESUMEINFINITERECOVERYTIMECANOCCURBETWEENBITSSOLONGASTHE1WIREBUSISINTHEINACTIVEHIGHSTATEDURINGTHERECOVERYPERIODIFTHISDOESNOTOCCURANDTHEBUSISLEFTLOWFORMORETHAN480S,ALLCOMPONENTSONTHEBUSWILLBERESETHARDWARECONFIGURATIONTRANSACTIONSEQUENCETHEPROTOCOLFORACCESSINGTHEDS18B20VIATHE1WIREPORTISASFOLLOWS_INITIALIZATION_ROMFUNCTIONCOMMAND_MEMORYFUNCTIONCOMMAND_TRANSACTION/DATAINITIALIZATIONALLTRANSACTIONSONTHE1WIREBUSBEGINWITHANINITIALIZATIONSEQUENCETHEINITIALIZATIONSEQUENCECONSISTSOFARESETPULSETRANSMITTEDBYTHEBUSMASTERFOLLOWEDBYPRESENCEPULSESTRANSMITTEDBYTHESLAVESTHEPRESENCEPULSELETSTHEBUSMASTERKNOWTHATTHEDS18B20ISONTHEBUSANDISREADYTOOPERATEFORMOREDETAILS,SEETHE“1WIRESIGNALING”SECTIONROMFUNCTIONCOMMANDSONCETHEBUSMASTERHASDETECTEDAPRESENCE,ITCANISSUEONEOFTHEFIVEROMFUNCTIONCOMMANDSALLROMFUNCTIONCOMMANDSARE8BITSLONGALISTOFTHESECOMMANDSFOLLOWSREFERTOFLOWCHARTINFIGURE5READROM33HTHISCOMMANDALLOWSTHEBUSMASTERTOREADTHEDS18B20S8BITFAMILYCODE,UNIQUE48BITSERIALNUMBER,AND8BITCRCTHISCOMMANDCANONLYBEUSEDIFTHEREISASINGLEDS18B20ONTHEBUSIFMORETHANONESLAVEISPRESENTONTHEBUS,ADATACOLLISIONWILLOCCURWHENALLSLAVESTRYTOTRANSMITATTHESAMETIMEOPENDRAINWILLPRODUCEAWIREDANDRESULTMATCHROM55HTHEMATCHROMCOMMAND,FOLLOWEDBYA64BITROMSEQUENCE,ALLOWSTHEBUSMASTERTOADDRESSASPECIFICDS18B20ONAMULTIDROPBUSONLYTHEDS18B20THATEXACTLYMATCHESTHE64BITROMSEQUENCEWILLRESPONDTOTHEFOLLOWINGMEMORYFUNCTIONCOMMANDALLSLAVESTHATDONOTMATCHTHE64BITROMSEQUENCEWILLWAITFORARESETPULSETHISCOMMANDCANBEUSEDWITHASINGLEORMULTIPLEDEVICESONTHEBUSSKIPROMCCHTHISCOMMANDCANSAVETIMEINASINGLEDROPBUSSYSTEMBYALLOWINGTHEBUSMASTERTOACCESSTHEMEMORYFUNCTIONSWITHOUTPROVIDINGTHE64BITROMCODEIFMORETHANONESLAVEISPRESENTONTHEBUSANDAREADCOMMANDISISSUEDFOLLOWINGTHESKIPROMCOMMAND,DATACOLLISIONWILLOCCURONTHEBUSASMULTIPLESLAVESTRANSMITSIMULTANEOUSLYOPENDRAINPULLDOWNSWILLPRODUCEAWIREDANDRESULTSEARCHROMF0HWHENASYSTEMISINITIALLYBROUGHTUP,THEBUSMASTERMIGHTNOTKNOWTHENUMBEROFDEVICESONTHE1WIREBUSORTHEIR64BITROMCODESTHESEARCHROMCOMMANDALLOWSTHEBUSMASTERTOUSEAPROCESSOFELIMINATIONTOIDENTIFYTHE64BITROMCODESOFALLSLAVEDEVICESONTHEBUSALARMSEARCHECHTHEFLOWCHARTOFTHISCOMMANDISIDENTICALTOTHESEARCHROMCOMMANDHOWEVER,THEDS18B20WILLRESPONDTOTHISCOMMANDONLYIFANALARMCONDITIONHASBEENENCOUNTEREDATTHELASTTEMPERATUREMEASUREMENTANALARMCONDITIONISDEFINEDASATEMPERATUREHIGHERTHANTHORLOWERTHANTLTHEALARMCONDITIONREMAINSSETASLONGASTHEDS18B20ISPOWEREDUP,ORUNTILANOTHERTEMPERATUREMEASUREMENTREVEALSANONALARMINGVALUEFORALARMING,THETRIGGERVALUESSTOREDINEEPROMARETAKENINTOACCOUNTIFANALARMCONDITIONEXISTSANDTHETHORTLSETTINGSARECHANGED,ANOTHERTEMPERATURECONVERSIONSHOULDBEDONETOVALIDATEANYALARMCONDITIONSEXAMPLEOFAROMSEARCHTHEROMSEARCHPROCESSISTHEREPETITIONOFASIMPLETHREESTEPROUTINEREADABIT,READTHECOMPLEMENTOFTHEBIT,THENWRITETHEDESIREDVALUEOFTHATBITTHEBUSMASTERPERFORMSTHISSIMPLE,THREESTEPROUTINEONEACHBITOFTHEROMAFTERONECOMPLETEPASS,THEBUSMASTERKNOWSTHECONTENTSOFTHEROMINONEDEVICETHEREMAININGNUMBEROFDEVICESANDTHEIRROMCODESMAYBEIDENTIFIEDBYADDITIONALPASSESTHEFOLLOWINGEXAMPLEOFTHEROMSEARCHPROCESSASSUMESFOURDIFFERENTDEVICESARECONNECTEDTOTHESAME1WIREBUSTHEROMDATAOFTHEFOURDEVICESISASSHOWNROM100110101ROM210101010ROM311110101ROM400010001THESEARCHPROCESSISASFOLLOWS1THEBUSMASTERBEGINSTHEINITIALIZATIONSEQUENCEBYISSUINGARESETPULSETHESLAVEDEVICESRESPONDBYISSUINGSIMULTANEOUSPRESENCEPULSES2THEBUSMASTERWILLTHENISSUETHESEARCHROMCOMMANDONTHE1WIREBUS3THEBUSMASTERREADSABITFROMTHE1WIREBUSEACHDEVICEWILLRESPONDBYPLACINGTHEVALUEOFTHEFIRSTBITOFTHEIRRESPECTIVEROMDATAONTOTHE1WIREBUSROM1ANDROM4WILLPLACEA0ONTOTHE1WIREBUS,IE,PULLITLOWROM2ANDROM3WILLPLACEA1ONTOTHE1WIREBUSBYALLOWINGTHELINETOSTAYHIGHTHERESULTISTHELOGICALANDOFALLDEVICESONTHELINE,THEREFORETHEBUSMASTERSEESA0THEBUSMASTERREADSANOTHERBITSINCETHESEARCHROMDATACOMMANDISBEINGEXECUTED,ALLOFTHEDEVICESONTHE1WIREBUSRESPONDTOTHISSECONDREADBYPLACINGTHECOMPLEMENTOFTHEFIRSTBITOFTHEIRRESPECTIVEROMDATAONTOTHE1WIREBUSROM1ANDROM4WILLPLACEA1ONTOTHE1WIRE,ALLOWINGTHELINETOSTAYHIGHROM2ANDROM3WILLPLACEA0ONTOTHE1WIRE,THUSITWILLBEPULLEDLOWTHEBUSMASTERAGAINOBSERVESA0FORTHECOMPLEMENTOFTHEFIRSTROMDATABITTHEBUSMASTERHASDETERMINEDTHATTHEREARESOMEDEVICESONTHE1WIREBUSTHATHAVEA0INTHEFIRSTPOSITIONANDOTHERSTHATHAVEA1THEDATAOBTAINEDFROMTHETWOREADSOFTHETHREESTEPROUTINEHAVETHEFOLLOWINGINTERPRETATIONS4THEBUSMASTERWRITESA0THISDESELECTSROM2ANDROM3FORTHEREMAINDEROFTHISSEARCHPASS,LEAVINGONLYROM1ANDROM4CONNECTEDTOTHE1WIREBUS5THEBUSMASTERPERFORMSTWOMOREREADSANDRECEIVESA0BITFOLLOWEDBYA1BITTHISINDICATESTHATALLDEVICESSTILLCOUPLEDTOTHEBUSHAVE0SASTHEIRSECONDROMDATABIT6THEBUSMASTERTHENWRITESA0TOKEEPBOTHROM1ANDROM4COUPLED7THEBUSMASTEREXECUTESTWOREADSANDRECEIVESTWO0BITSTHISINDICATESTHATBOTH1BITSAND0BITSEXISTASTHE3RDBITOFTHEROMDATAOFTHEATTACHEDDEVICES8THEBUSMASTERWRITESA0BITTHISDESELECTSROM1,LEAVINGROM4ASTHEONLYDEVICESTILLCONNECTED9THEBUSMASTERREADSTHEREMAINDEROFTHEROMBITSFORROM4ANDCONTINUESTOACCESSTHEPARTIFDESIREDTHISCOMPLETESTHEFIRSTPASSANDUNIQUELYIDENTIFIESONEPARTONTHE1WIREBUS10THEBUSMASTERSTARTSANEWROMSEARCHSEQUENCEBYREPEATINGSTEPS1THROUGH711THEBUSMASTERWRITESA1BITTHISDECOUPLESROM4,LEAVINGONLYROM1STILLCOUPLED12THEBUSMASTERREADSTHEREMAINDEROFTHEROMBITSFORROM1ANDCOMMUNICATESTOTHEUNDERLYINGLOGICIFDESIREDTHISCOMPLETESTHESECONDROMSEARCHPASS,INWHICHANOTHEROFTHEROMSWASFOUND13THEBUSMASTERSTARTSANEWROMSEARCHBYREPEATINGSTEPS1THROUGH3NOTETHEBUSMASTERLEARNSTHEUNIQUEIDNUMBERROMDATAPATTERNOFONE1WIREDEVICEONEACHROMSEARCHOPERATIONTHETIMEREQUIREDTODERIVETHEPARTSUNIQUEROMCODEIS960S83X6461S1316MSTHEBUSMASTERISTHEREFORECAPABLEOFIDENTIFYING75DIFFERENT1WIREDEVICESPERSECOND外文資料翻譯譯文DS18B20描述DS18B20數(shù)字溫度計(jì)提供9至12位溫度讀數(shù)，指示器件的溫度。信息經(jīng)過單線接口送入DS18B20或送出，因此從中央處理器到DS18B20僅需連接一條（和地）。讀、寫和完成溫度變換所需的電源可以有數(shù)據(jù)線本身提供，而不需要外部電源。因?yàn)槊恳粋€(gè)DS18B20有唯一的系列號(hào)，因此多個(gè)DS18B20可以存在于同一條單線總線上。這允許在許多不同的地方放置溫度靈敏器件。此特性的應(yīng)用范圍包括HVAC環(huán)境控制，建筑物、設(shè)備或機(jī)械內(nèi)的溫度檢測(cè)，以及過程監(jiān)視和控制中的溫度檢測(cè)。特性1獨(dú)特的單線接口，只需一個(gè)接口引腳即可通信。2多點(diǎn)能力使分布式溫度檢測(cè)應(yīng)用得以簡化。3不需要外部元件。4可用數(shù)據(jù)線供電，提供30V到55V的電源。5不需備份電源。6測(cè)量范圍從55C到125C，等效的華氏溫標(biāo)范圍是67F到257F7以9到12位數(shù)字值方式讀出溫度。8在750毫秒內(nèi)把12位溫度變換為數(shù)字。9用戶可定義的，非易失性的溫度警告設(shè)置。10告警搜索命令識(shí)別和尋址溫度在編定的極限之外的器件（溫度告警情況）。11應(yīng)用范圍包括恒溫控制，工業(yè)系統(tǒng)，消費(fèi)類產(chǎn)品，溫度計(jì)或任何熱敏系統(tǒng)。引腳排列引腳說明GND地DQ數(shù)字輸入輸出VDD可選的VDDNC不連接詳細(xì)引腳說明綜述圖1的方框圖表示DS18B20的主要部件。DS18B20有三個(gè)主要的數(shù)據(jù)部件1）64為激光ROM，2）溫度靈敏元件，3）非易失性溫度告警觸發(fā)器TH和TL。器件從單線的通信線取得其電源，在信號(hào)線為高電平的時(shí)間周期內(nèi)，把能量貯存在內(nèi)部的電容器中，在單信號(hào)線為低電平的時(shí)間期內(nèi)斷開此電源，直到信號(hào)線變?yōu)楦唠娖街匦陆由霞纳娙荩╇娫礊橹?，作為另一種可供選擇的方法，DS18B20也用外部5V電源供電。與DS18B20的通信經(jīng)過一個(gè)單線接口。在單線接口情況下，在ROM操作未定建立之前不能使用存貯器和控制操作。主機(jī)必須首先提供五種ROM操作命令之一1）讀ROM，2）符合ROM，3）搜索ROM,4跳過ROM，5告警搜索。這些命令對(duì)每一個(gè)器件的64位激光ROM部分進(jìn)行操作。如果在單線上有許多器件，那么可以挑選出一個(gè)特定的器件，并給總線上的主機(jī)指示存在多少器件及其類型。在成功地執(zhí)行了ROM操作序列之后，可使用貯存2器和控制操作。然后主機(jī)可以提供六種存貯器和操作命令之一。一個(gè)操作命令指示DS18B20完成溫度測(cè)量。改測(cè)量的結(jié)果放入DS18B20的高速暫存存貯器，通過發(fā)出讀暫存存儲(chǔ)器內(nèi)容的存儲(chǔ)器操作命令可以讀出此結(jié)果。每一溫度告警觸發(fā)器TH和TL構(gòu)成一個(gè)字節(jié)的EPROM。如果不對(duì)DS18B20施加告警搜索命令，這些寄存器用作通用用戶存儲(chǔ)器。使用存儲(chǔ)器操作命令可以寫TH和TL。對(duì)這些寄存器的讀訪問通過便簮存儲(chǔ)器。所以數(shù)據(jù)均以最低有效位在前的方式被讀寫。單線總線系統(tǒng)單線總線是一種具有一個(gè)總線主機(jī)和一個(gè)或若干個(gè)從機(jī)的系統(tǒng)。DS18B20起從機(jī)的作用。這種總線系統(tǒng)的討論分為三個(gè)題目硬件接法，處理順序，以及單線信號(hào)（信號(hào)類型與定時(shí)）。硬件接法根據(jù)定義，單線總線只有一根線這一點(diǎn)很重要的，即線上的第一個(gè)器件能在適當(dāng)?shù)臅r(shí)間驅(qū)動(dòng)該總線。為了做到這一點(diǎn)第一個(gè)連接到總線上的器件必須具有漏極開路或三態(tài)輸出。DS18B20的單線接口。多站總線由單線總線和多個(gè)與之相連的從屬器件組成。單線總線要求近似等于5K單線總線的空閑狀態(tài)是高電平。不管任何原因，如果執(zhí)行需要被掛起，那么，若要重新恢復(fù)執(zhí)行，總線必須保持在空閑狀態(tài)。如果不滿足這一點(diǎn)且總線保持在低電平時(shí)間大于480微秒，那么總線上所有的器件均被復(fù)位。硬件連接圖處理順序經(jīng)過單線總線接口訪問DS18B20的協(xié)議如下初始化ROM操作命令存貯器操作命令處理/數(shù)據(jù)初始化單線總線上的所有處理均從初始化序列開始。初始化序列包括總線主機(jī)發(fā)出一復(fù)位脈沖，接著由從屬器件送出存在脈沖。ROM操作命令一旦總線主機(jī)檢測(cè)到從屬器件的存在，他便可以發(fā)出器件ROM操作命令之一。所有ROM操作命令均由8位長，這些命令列表如下1讀ROM33H此命令允許總線主機(jī)讀DS18B20的8位產(chǎn)品系列編碼，唯一的48位序列號(hào)，以及8位的CRC。此命令只能在總線上僅有一個(gè)DS18B20得情況下可以使用。如果總線上存在多于一個(gè)得從屬器件，那么所有從片企圖同時(shí)發(fā)送時(shí)將發(fā)生數(shù)據(jù)沖突的現(xiàn)象。2符合ROM55H符合ROM命令。后繼以64位的ROM數(shù)據(jù)序列，允許總線主機(jī)對(duì)多點(diǎn)總線上的DS18B20尋址。只有與64位ROM序列嚴(yán)格相符的DS18B20才能對(duì)后繼的存貯器操作命令作出響應(yīng)。所有與64位ROM序列不符的從片將等待復(fù)位脈沖。此命令在總線數(shù)據(jù)上有單個(gè)或多個(gè)器件的情況下均可使用。3跳過ROMCCH在單點(diǎn)總線系統(tǒng)中，此命令通過允許總線主機(jī)不提供64位ROM編碼而訪問存儲(chǔ)器操作來節(jié)省時(shí)間。如果在總線上存在多于一個(gè)得從屬器件而且在跳過ROM命令之后發(fā)出讀命令，那么由于多個(gè)從片同時(shí)發(fā)送數(shù)據(jù)，會(huì)在總線上發(fā)生數(shù)據(jù)沖突4搜索ROMF0H當(dāng)系統(tǒng)開始工作時(shí)，總線主機(jī)可能不知道單線總線上的器件個(gè)數(shù)或者不知道其64位ROM編碼。搜索ROM命令允許總線主機(jī)使用一種消去處理來識(shí)別總線上的所有從片的64位ROM編碼。5告警搜索E