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.