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PC card



BasicInterpretation

ThePCcardfordigitalcamerasisexactlythesameasthePCcardfornotebookcomputers.Itis68-pin.TherearealsoTypeIIandTypeIIIPCMCIAcards.TypeIIIPCMCIAcard,alsoknownasPCharddiskcard,hasthelargeststoragecapacityamongremovablestoragedevicesfordigitalcameras,withamaximumcapacityofmorethan500M.ThePCcardusedincurrentnotebookcomputersisadetachableoption.Justlikeamodem,anetworkinterfacecard,aharddisk,andamemory,itisaboutthesizeofacreditcard.ThePCcardisinstalledinaslotinthenotebookcomputer.ThePCcardsignificantlyenhancesthefunctionsofthenotebookcomputer.ThiscardisusuallycalledaPCMCIAcard.

ThePCMCIAslotisthemostimportantdeviceexpansioninterfaceonalaptop.Itcanbeusedtoinsertafaxcard/networkcard/memorycard/soundblastercard,etc.SomeprofessionalmagazinesevenpredictthatPCMCIAwillbecomeadesktopcomputerinthefuture,Standardinterfacesonautomobilesandhouseholdappliances.ThemainadvantageofPCMCIAisthatitcanbepluggedandunpluggedunderpower,andplug-and-playcanberealizedwithappropriatesoftware.

Basicknowledge

PCMCIA(theabbreviationofPersonalComputerMemoryCardInternationalAssociation)isaninternationalorganizationestablishedin1989,withmorethan300Theinternationalstandardsorganizationandtradefederationofmembercompanies,itsmembersareIntel,AMD,IBM,Compaq,TIandotherinternationallyrenownedcompanies.Thisinternationalorganizationismainlytoestablishapower-saving,small-volumeintegratedelectroniccardstandardtoimprovetheinterchangeabilityofmobilecomputers.

ThefirstproductthatPCMCIAlaunchedtomeetthisstandard-memorycard.Atthesametime,the68-pinspecificationswerealsodetermined.Atthesametime,theslotusageinstructionshavebeenadded.Manufacturersrealizethatthesoftwareneedstoimprovecompatibility,sothisstandardhasbeenappliedaccordingly.Butnowtherearemoreandmoreapplicationsthatrequiremassiveandfastdataaccess-suchasmultimediaandhigh-speednetworks.Inordertomeetthisdemand,PCMCIAhasformulatedanothertwonewspecifications-CardBusandZoomedVideo,enabling100MbitEthernetandMpegcompressionformattobeimplementedonPCMCIA.Becausethespeedcontinuestoincrease,PCMCIAhasbeensupplementingthisspecification,therebyimprovingcompatibilityandtakingintoaccountothermobilemachineissues.Inadditiontotheincreaseinspeed,PCMCIAhasalsodevelopeda3.3VstandardtomakePCMCIAcardsmorepower-saving.

Intheearlydays,thePCMCIAcardsweusedwereall16BIT,andthe16BITPCcardhadaslowerspeed.Asfarasthenetworkcardisconcerned,evenifitshowsthatitisa100Mnetworkcard,theactualusespeedisonlyabout25M.ThecommonlyusedPCMCIAcardsare32-bitCardBuscards,andtheoperatingfrequencyreaches33MHz,andthespeedcanmeettherequirementsofgenerallocalareanetworkandbroadbandapplications.Ifyouaremorecareful,youwillfindthatthePCMCIAslotonthenotebooknowhasTYPEI,TYPEIIandTYPEIII.ThesethreePCMCIAinterfaceshaveevolvedfromItoIIIandaredownwardcompatible.TYPEI/IIiswhatweusuallydo.ThecommonsinglePCMCIAslotdesign,andthedoubleslotisTYPEIII.(Duetotherapiddevelopmentofnotebookcomputers,thedemandforlight,thin,shortandsmallexpansiondeviceshasgreatlyincreased.Inordertomeettheneedsofvariousproductdesigns,PCMCIAhasformulatedthreethicknessspecificationsforelectroniccards-TypeI,TypeIIandTypeIII.Theorderincreasesfromsmalltolarge.TypeI-3.3MM,TypeII-5.0MM,TypeIII-10.5MM.Exceptforthethickness,thelengthandwidthofthethreespecificationsareexactlythesame.)

PCMCIAcard

Weight:about1ounce,about0.5ounces

Volume:85.6x54.0mm42.8x36.4mm

Specifications:TypeI(3.3mm),TypeII(5.0mm),TypeIII(10.5mm),CardBus,ZoomVideoTypeI(3.3mm),TypeII(5.0mm)

Applicationscope

Widelyusedinnotebookcomputers.Generallyspeaking,itconsumesmoreelectricity,butthecostislower.

ThePCMCIAslotisthemostimportantdeviceexpansioninterfaceonalaptop.Itcanbeusedtoinsertafaxcard/networkcard/memorycard/soundblastercard,etc.SomeprofessionalmagazinesevenpredictthatPCMCIAwillbecomeadesktopcomputerinthefuture,Standardinterfacesonautomobilesandhouseholdappliances.ThemainadvantageofPCMCIAisthatitcanbepluggedandunpluggedunderpower,andplug-and-playcanberealizedwithappropriatesoftware.

AlthougheveryoneisoptimisticaboutthedevelopmentprospectsofPCMCIA,usershavetofacemanyproblems.ThePCMCIAcards,PCMCIAslotsandslotdriversoftwareonthemarketdonotfollowstrictandconsistentstandards.Thereareproblemsinthemutualcompatibilityofproducts,anditisbestforgeneraluserstofindprofessionalnotebookcomputersellerstoprovideinstallationanddebuggingserviceswhenpurchasing.EachnotebookcomputerwillbeprovidedwiththeoriginalPCMCIAslotdriversoftwarewhenitissold.Usersshouldpayattentiontobackupandstorage.ThissoftwareisnecessarywhenaddingaPCMCIAexpansioncard.

Thelatestlaptop,ifithasthe"ZV"logoonthePCMCIAslot,itmeansthatitcansupportthelatestmoviedecompressioncardandvideodisplaysystem-relatedexpansionequipment;Ifthereisa"CB"markonthePCMCIAslot,itmeansthatitcansupportthelatest32-bitCARDBUS,andthedatatransferrateofthePCMCIAinterfaceishigher.

InadditiontonotebookcomputersthatcanusePCMCIAcards,therearealsoPDAs,digitalcameras,digitalTVs,set-topboxes...etc.TherearealsocorrespondingproductsthatcanusePCMCIAspecificationscard.

Inordertomeetthehigh-speedrequirementsofmultimediaandnetworkapplications,PCMCIApromulgatedthe68-pinPCcardstandardformemorycardsin1991,andnewlydevelopedCardBusandZVin1995.TwointerfacestandardsallownotebookstoconnecttoPCIdevices,suchashigh-speednetworkcards,videocapture/videoconferencingcards,SCSIcards,etc.ThefollowingtwoarticleswillexplainthecontentsoftheCardBusandZVstandardsrespectively.

IntroductiontotheCardBusinterface

CardBusisanext-generationhigh-performance32-bitbusmasterinterfacelaunchedbyPCMCIA.ItenablesadvancedfunctionsthatarecurrentlyonlyavailableondesktopsandlargersystemstobemovedintoCardBuscards,whichcanbeusedinmobileenvironments.ThenewfunctionsdevelopedforCardBuscanalsobeusedin32-bitdesktopsystemsiftheyareequippedwithaCardBusslot.

CharacteristicsoftheCardBusinterface

CardBusaddsavarietyofimportantfunctionstothePCcardandiscompatiblewiththenewfunctionsofthenewPCcardstandard.ThefeaturesandfunctionsoftheCardBusinterfaceinclude32-bitaddressanddata,33MHzoperatingfrequencyandbusmasteroperation.

·TheCardBusinterfacesupportsoperatingspeedsupto33MHz,creatingconditionsforexpandingtheexistingapplicationsofPCcardusers.

·CardBusinterfacesupportsmultiplebusfunctionsinanycombination.Thebusmasteringfunctioncansharetasksfortheprocessor,whichisconducivetoimprovingthethroughputofthesysteminamultitaskingenvironment.

·CardBussupportstheexistingaudiodigitalwaveform(ADW)modeandthenewpulsewidthmodulation(PWM)modeofthePCcard.EitherofthesetwomodescanbeusedinCardBus,butthesystemsoftwaremustbeapprovedbeforeuse.TheworkingrangeofPWMaudioismuchbetterthanthatofADWaudio.AlthoughtheindependenceofthesystemplatformistakenintoaccountwhendefiningCardBus,theinterfaceisdesignedfor32-bitsystems.Systemswith16-bitbusesbenefitlittlefromthisinterface.TheCardBusspecificationgreatlyenhancestheinterchangeabilitybetweensystems.

CardBusworkingprinciple

ThesignaltransmissionprotocoloftheCardBusinterfaceoriginatedfromthePCIlocalbussignaltransmissionprotocol.Therearesomedifferencesbetweenthetwo,butmostfunctionshavethesameoperation.

TheCardBussoftwaremodelcanbesharedwith16-bitPCcards.Sinceits32-bitCardServicesinterfaceisalsodefinedfor16-bitPCcards,thisinterfacecanbeusedtomanagebothCardBuscardsandnon-CardBuscards.

SincetheCardBuscardandslotusethelowvoltagekeydefinedfor3.3voltcards,theCardBuscardmustbedesignedtouse3.3voltsorlower,whichreducessystemenergyconsumption.Extendedbatterylife.

Intheinitialpower-onorresetoperation,thepowerconsumptionoftheCardBuscardmustbelimitedtoensurethattheinformationcanbereadfromtheCardBuscard,andtodeterminewhetherthesystemcanprovidesufficientpowerandotherhardwareresources,ToensurethattheCardBuscardworksnormally.Thelimitationofthepowersupplycanpreventexcessiveinstantaneouscurrentconsumptionofthebattery,andsmoothlyrejecttheCardBuscardwhenthepowerrequiredforoperationcannotbeprovided.

TheCardBusslotshallacceptandsupportall16-bitPCcardsinaccordancewiththeconditionssetbythehostsystem.TheCardBusinterfacesupportshotswappingofcards.Whenthecardisnotinserted,theslotmustbepoweredoff,andwhenthecardisinserted,theslotispoweredon.Forusers,thisislikehotplugging.

Adapter

Asmentionedearlier,CardBusmustalsosupportnon-CardBusPCcards.Whenacardisinsertedintotheslot,thePCaskstodeterminewhetheritneedsCardBussupport,andthenaddsappropriatepowerandotherresourcesaccordingtothesituation.Thispreventsdamagetotheinsertedboard.

DesignedtheCardDetect/VoltageSensealgorithm.AllCardBusandlow-voltagenon-CardBuscardssupportthisalgorithm.ItenablestheCardBusadaptertorecognizeanyPCcardinanyslot.Theinformationprovidedbytheadapterenablesthecorrespondingsoftwaretodeterminewhethertheinsertedcardcanbesupported,andtorejectitsmoothlyifnot.

Systemsoftware

NomatterwhetheranadaptersupportsCardBusornot,itwillprovideSocketServicessoftware.ButdifferentadapterdesignsrequiredifferentimplementationsofSocketServices.AsinglehostsystemcanincludeadaptersthatsupportCardBusandthosethatdonotsupportCardBus.Therefore,thecorrespondingSocketServiceshandlerscanalsoresideinthesamesingle-hostsystem.AlladaptersrequireonlyafewSocketServicesfunctions.

CardServicessoftwareisusedtoprovidebriefinformationaboutthespecificfunctionsandstatusofallPCcards.WhenonlysupportingCardBusisrequired,CardBusonlyneedstobemodifiedinasmallamount.ButwhenitisrequiredtoprovidefullcompatibilityforCardBusandnon-CardBus,significantchangesarerequiredwithinCardServices.

Configuration

WhendetectingthataPCcardisinserted,thePCwillestablishthevoltageandsignaltransmissionprotocolrequiredbythePCcard.Ifthesystemsupportsthecard'svoltageandotherrequirements,thePCwillprovidetheappropriatesignaltransmissionprotocolandvoltage;otherwise,theuserwillbeinformedthatthecardcannotworkinthissystem.Onceacardisrecognized,thecardcanonlyobtainalimitedcurrenttopreventexcessivebatterycurrent.Theconfigurationoperationcanalsoberealizedbyageneral-purposecircuit.TheCardBusinterfacealsoprovidessupportformultifunctionalCardBuscards.

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