1-Wire_Search_Algorithm

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1、Maxim>AppNotes>1-Wire®DEVICESBATTERYMANAGEMENTKeywords:1wire,1-Wiresearchalgorithm,iButtonsearchalgorithm,uniqueID,ROMnumber,networkMar28,2002addressAPPLICATIONNOTE1871-WireSearchAlgorithmAbstract:Maxim's1-Wire®deviceseachhavea64-bituniqueregistrationnumberinread-only-mem

2、ory(ROM)thatisusedtoaddressthemindividuallybya1-Wiremasterina1-Wirenetwork.IftheROMnumbersoftheslavedevicesonthe1-Wirenetworkarenotknown,thenusingasearchalgorithmcandiscoverthem.Thisdocumentexplainsthesearchalgorithmindetailandprovidesanexampleimplementationforrapidintegr

3、ation.Thisalgorithmisvalidforallcurrentandfuturedevicesthatfeaturea1-Wireinterface.IntroductionMaxim's1-Wiredeviceseachhavea64-bituniqueregistrationnumberinread-only-memory(ROM)thatisusedtoaddressthemindividuallybya1-Wiremasterina1-Wirenetwork.IftheROMnumbersoftheslavedev

4、icesonthe1-Wirenetworkarenotknown,thentheycanbediscoveredbyusingasearchalgorithm.Thisdocumentexplainsthesearchalgorithmindetailandprovidesanexampleimplementationforrapidintegration.Thisalgorithmisvalidforallcurrentandfuturedevicesthatfeaturea1-Wireinterface.Figure1.64-Bit

5、UniqueROM'Registration'Number.SearchAlgorithmThesearchalgorithmisabinarytreesearchwherebranchesarefolloweduntiladeviceROMnumber,orleaf,isfound.Subsequentsearchesthentaketheotherbranchpathsuntilalloftheleavespresentarediscovered.Thesearchalgorithmbeginswiththedevicesonthe1

6、-Wirebeingresetusingtheresetandpresencepulsesequence.Ifthisissuccessfulthenthe1-bytesearchcommandissent.Thesearchcommandreadiesthe1-Wiredevicestobeginthesearch.Therearetwotypesofsearchcommands.Thenormalsearchcommand(F0hex)willperformasearchwithalldevicesparticipating.Thea

7、larmorconditionalsearchcommand(EChex)willperformasearchwithonlythedevicesthatareinsomesortofalarmstate.Thisreducesthesearchpooltoquicklyrespondtodevicesthatneedattention.Followingthesearchcommand,theactualsearchbeginswithalloftheparticipatingdevicessimultaneouslysendingth

8、efirstbit(leastsignificant)intheirROMnumber(alsocalledregistrationnumber).(SeeFigure1.)Aswithall