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1、THEI2C-BUSSPECIFICATIONVERSION2.1JANUARY200011EXTENSIONSTOTHESTANDARD-MODEI2C-BUSSPECIFICATIONTheStandard-modeI2C-busspecification,withitsdatatransferrateofupto100kbit/sand7-bitaddressing,hasbeeninexistencesincethebeginningofthe1980’s.Thisconceptrapidlygrewinpopula
2、rityandistodayacceptedworldwideasadefactostandardwithseveralhundreddifferentcompatibleICsonofferfromPhilipsSemiconductorsandothersuppliers.Tomeetthedemandsforhigherspeeds,aswellasmakeavailablemoreslaveaddressforthegrowingnumberofnewdevices,theStandard-modeI2C-bussp
3、ecificationwasupgradedovertheyearsandtodayisavailablewiththefollowingextensions:·Fast-mode,withabitrateupto400kbit/s.·High-speedmode(Hs-mode),withabitrateupto3.4Mbit/s.·10-bitaddressing,whichallowstheuseofupto1024additionalslaveaddresses.Therearetwomainreasonsforex
4、tendingtheregularI2C-busspecification:·Manyoftoday’sapplicationsneedtotransferlargeamountsofserialdataandrequirebitratesfarinexcessof100kbit/s(Standard-mode),oreven400kbit/s(Fast-mode).Asaresultofcontinuingimprovementsinsemiconductortechnologies,I2C-busdevicesareno
5、wavailablewithbitratesofupto3.4Mbit/s(Hs-mode)withoutanynoticeableincreasesinthemanufacturingcostoftheinterfacecircuitry.·Asmostofthe112addressesavailablewiththe7-bitaddressingschemeweresoonallocated,itbecameapparentthatmoreaddresscombinationswererequiredtopreventp
6、roblemswiththeallocationofslaveaddressesfornewdevices.Thisproblemwasresolvedwiththenew10-bitaddressingscheme,whichallowedaboutatenfoldincreaseinavailableaddresses.NewslavedeviceswithaFast-orHs-modeI2C-businterfacecanhavea7-ora10-bitslaveaddress.Ifpossible,a7-bitadd
7、ressispreferredasitisthecheapesthardwaresolutionandresultsintheshortestmessagelength.Deviceswith7-and10-bitaddressescanbemixedinthesameI2C-bussystemregardlessofwhetheritisanF/S-orHs-modesystem.Bothexistingandfuturemasterscangenerateeither7-or10-bitaddresses.12FAST-
8、MODEWiththeFast-modeI2C-busspecification,theprotocol,format,logiclevelsandmaximumcapacitiveloadfortheSDAandSCLlinesquotedintheStandard-modeI2C-bu
