SD卡操作时序说明

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1、HowtoUseMMC/SDCUpdate:November3,2010TheSecureDigitalMemoryCard(SDCbelow)isthedefactostandardmemorycardformobileequipments.TheSDCwasdeveloppedasupper-compatibletoMultiMediaCard(MMCbelow).SDCcompleantequipmentscanalsouseMMCsinmostcase.Therearealsoreducedsizeversions,suchasRS-MMC,miniSDandm

2、icroSD,withthesamefunction.TheMMC/SDChasamicrocontrollerinit.Theflashmemorycontrols(erasing,reading,writing,errorcontrolsandwearleveling)arecompletedinsideofthememorycard.Thedataistransferredbetweenthememorycardandthehostcontrollerasdatablocksinunitof512bytes,sothatitcanbeseenlikeageneri

3、charddiskdrivesfromviewpointofupperlevellayers.ThecurrentrydefinedfilesystemforthememorycardisFAT12/16withFDISKpatitioningrule.TheFAT32isdefinedforonlyhighcapacity(>=4G)cards.ThispagedescribesthebasicknowledgeandmiscellaneousthingsthatIbecomeaware,onusingMMC/SDCwithsmallembeddedsystem.Ib

4、elievethatthisinformationmustbeausefulgettingstartednotesforthepeoplewhoisgoingtouseMMC/SDContheelectronicshandiworkprojects.PinoutminiSD

5、microSDRightphotoshowsthecontactsurfaceoftheSDC/MMC.TheMMChassevencontactpadsandtheSDChasninecontactpadsthattwoadditionalcontactstoMMC.Thethreeoftheco

6、ntactsareassignedforpowersupplysothatthenumberofeffectivesignalsarefour(MMC)andsix(SDC).Therforethedatatransferbetweenthehostandthecardisdoneviaasynchronousserialinterface.Theworkingsupplyvoltagerangeisindicatedintheoperationconditionsregister(OCR)anditshouldbereadandcomfirmedtheoperatin

7、gvoltagerange.However,thesupplyvoltagecanbefixedto3.0/3.3voltsbecausetheallMMC/SDCworkatsupplyvoltageof2.7to3.6voltsatleast.Thecurrentconsumptiononwriteoperationcanreachuptosometenmiliamperes,sothatthehostsystemshouldconsidertosupply100miliamperestothacard.SPIModeThisdocumentdescribesthe

8、protocoltocontrolMMC/SDCsinSPImode.TheSPImodeisanalternativeoperatingmodethatdefinedtousetheMMC/SDCswithoutnativehostinterface.ThecommunicationprotocolfortheSPImodeissimplecomparedtoitsnativeoperatingmode.TheMMC/SDCcanbeattachedtothemostmicrocontrollersviaagenericSPIinter