英语,I2C总线规范2.1部分.doc

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1、THEI2C-BUSSPECIFICATIONVERSION2.1JANUARY200011EXTENSIONSTOTHESTANDARD-MODEI2C-BUSSPECIFICATIONTheStandard-modeI2C-busspecification,withitsdatatransferrateofupto100kbit/sand7-bitaddressing,hasbeeninexistencesincethebeginningofthe1980’s.Thisconceptrapidlygrewinpopularityandistodayacceptedworldwideas

2、adefactostandardwithseveralhundreddifferentcompatibleICsonofferfromPhilipsSemiconductorsandothersuppliers.Tomeetthedemandsforhigherspeeds,aswellasmakeavailablemoreslaveaddressforthegrowingnumberofnewdevices,theStandard-modeI2C-busspecificationwasupgradedovertheyearsandtodayisavailablewiththefollow

3、ingextensions:·Fast-mode,withabitrateupto400kbit/s.·High-speedmode(Hs-mode),withabitrateupto3.4Mbit/s.·10-bitaddressing,whichallowstheuseofupto1024additionalslaveaddresses.TherearetwomainreasonsforextendingtheregularI2C-busspecification:·Manyoftoday’sapplicationsneedtotransferlargeamountsofseriald

4、ataandrequirebitratesfarinexcessof100kbit/s(Standard-mode),oreven400kbit/s(Fast-mode).Asaresultofcontinuingimprovementsinsemiconductortechnologies,I2C-busdevicesarenowavailablewithbitratesofupto3.4Mbit/s(Hs-mode)withoutanynoticeableincreasesinthemanufacturingcostoftheinterfacecircuitry.·Asmostofth

5、e112addressesavailablewiththe7-bitaddressingschemeweresoonallocated,itbecameapparentthatmoreaddresscombinationswererequiredtopreventproblemswiththeallocationofslaveaddressesfornewdevices.Thisproblemwasresolvedwiththenew10-bitaddressingscheme,whichallowedaboutatenfoldincreaseinavailableaddresses.Ne

6、wslavedeviceswithaFast-orHs-modeI2C-businterfacecanhavea7-ora10-bitslaveaddress.Ifpossible,a7-bitaddressispreferredasitisthecheapesthardwaresolutionandresultsintheshortestmessagelength.Deviceswith7-and10-bitaddressescanbemixedinthesameI2C-bussystemregardlessofwhetheritisanF/S-orHs-modesystem.Bothe

7、xistingandfuturemasterscangenerateeither7-or10-bitaddresses.12FAST-MODEWiththeFast-modeI2C-busspecification,theprotocol,format,logiclevelsandmaximumcapacitiveloadfortheSDAandSCLlinesquotedintheStandard-modeI2C-bu