Embedded system terminology 嵌入式系统词汇.docx

Embedded system terminology 嵌入式系统词汇.docx

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Embeddedsystemterminology嵌入式系统词汇

~

（not）1.res.Theunarybitwise-NOToperatorinCandvariousrelatedlanguages.SometimesconfusedwiththelogicalNOToperator!

thoughtheirfunctionsareverydifferent.Makesureyouusetherightone;yourcompilerwon'tknowtowarnyouoftheerror.

EXAMPLE:

If16-bitxis0x0123,~xis0xFEDC;!

xis0（Booleanfalse）.

2.symb.Aprefixusedonschematicdiagramsandinlogicequationstoindicateactivelowsignals.

μC/O

（micro-kos）N.Areal-timeoperatingsystemforsmallmicrocontrollers.Derivedfromatwo-partexpositoryarticleinEmbeddedSystemsProgramminginMay–June1992,thislittleRTOStookonalifeofitsownwiththepublicationofabook-lengthtreatmentofthesubjectbycreatorJeanLabrosse.Nowintheoperatingsystem'ssecondrelease（μC/OS-II）,therevisedbookincludescompletesourcecodeandexplanationsofeverythingitdoes.

1-Wire 

N.Alow-costbidirectionalserialcommunicationsbusrequiringjustasinglewiretoimplement.Anasynchronous,half-duplex,single-mastercomponentbus,1-Wireminimizesdevicepincountbyusingextraon-chipcircuitrytoenableeach1-Wirecomponenttocommunicateserially（overasharedconnection）withother1-Wiredevices.CompatibleserialEEPROMs,A/Dconverters,temperaturesensors,andotherdevicesareavailable.Electricalfeaturesincludelowdatarates（about16kbps,max）,flexiblevoltageandtimingrequirements,longmaxiumdistances（upto1,000feet）,andoptionalparasiticpoweringofslaves.Each1-Wiredevicehasaunique48-bitserialnumber,somultipleslavescansharethesamebus.SeealsoI2C,SPI.

HISTORY:

The1-WireprotocolwasinventedbyDallasSemiconductor,whichholdsarelatedpatent.

Arepresentationofthecircuitryusedtoconnect1-Wiredevices.

1489

（fourteeneighty-nine）num.AnobsoletechipusedtoreceiveRS-232signals.A1970spartoriginallyfromMotorola,the1489wasalinereceiverthattranslatedthe+/-15VRS-232levelstoTTLsignals.Nowreplacedbycombinedreceiver/transmitterchipssuchastheMAX232fromMaxim.

4004

（fourthousandfour）num.Thefirstmicroprocessor.InventedbyIntel（amemorycompanyatthetime）in1971,the4004wastheworld'sfirstgeneral-purposemicroprocessor.Afarcryfrommodernprocessors,the4004hada12-bitinstructionpointer,fortysix8-bitopcodes,andsixteen4-bitregisters.The4004wasa16-pinDIPpart,containingabout2,000transistors.SeealsoBusicom.

Theworld'sfirstsingle-chipprocessor.

8051

（eightyfifty-one）num.An8-bitmicrocontrollerfamily.Theoriginal8051wasdesignedinthelate1970sbyIntel.Itsmanyvariantsarestillpopularwithembeddedsystemsdevelopersandarenowavailablefrommultiplesuppliers.RelatedchipsincludeSiemens'80C517,TI'sTMS370,andthe80251.

8N1

（aslettersandnumbers）abbr.Acommonflavorofserialcommunicationsthatfeatures8databits,noparity,and1stopbit.Otherspecificationshavethesameformat,withEandOindicatingevenandoddparity,respectively.Thisinformationisnormallycoupledwiththenumberofdatabitspersecond,suchas9600bpsor57.6kbps.

A/Dconverter

n.Ahardwaredevicethatreadsananalogsignal—typicallyavoltage—comparesittoareferencesignal,andconvertstheresultingpercentagetoadigitalvalue.Shortforanalog-to-digitalconverter.AbbreviatedADC.Thereferencesignalrepresents100%.Ann-bitA/Dconverterhasamaximumvalueof2**n-1andaresolutionofVref/2**n.SeealsoD/Aconverter.

activelow

adj.Denotesalogicdeviceorcircuitwherealogic1isalowervoltagethanalogic0.

addressbus

n.Asetofwiresconnectedtoaprocessorandalloftheperipheralswithwhichitcommunicates,forthepurposeofselectingaspecificmemorylocationorregisterwithinaparticularperipheral.Iftheaddressbuscontainsnelectricallines,theprocessorcanaddressupto2**nuniquelocations.Addressdecodinglogicbetweentheprocessorandthedevicesconnectedtothebusselecttheproperdevice,typicallybasedontheuppermostbits.

applicationsoftware

n.Softwarethatisspecifictoaparticularembeddedsystem.Suchapplication-specificcodeisgenerallybuiltonalayeredarchitectureofreusablecomponents,suchasareal-timeoperatingsystemandnetwork-protocolstackorothermiddleware.Ifthereisnosucharchitecture,thenthistermmaynotbeused.Theapplicationsoftwareisunlikelytobereusableacrossembeddedplatforms,simplybecauseeachembeddedsystemhasadifferentapplication.

application-specificintegratedcircuit

n.Apieceofcustom-designedhardwareinamass-producedchip.AbbreviatedASIC.

assembler

n.Asoftwaredevelopmenttoolthattranslateshuman-readableassemblylanguageprogramsintomachine-readablecodethatthetargetprocessorcanunderstandandexecute. 

USAGE:

Assembleralsocanmeanassemblylanguage,asin,"Iwrotethatpartofthecodeinassembler."

assemblylanguage

n.Ahuman-writableformofaprocessor'snativeinstructionset.Initstypicalform,eachlineofassemblycoderepresentsasingleCPUinstruction.Thehuman-readablerepresentationofeachopcodeiscalledamnemonic.

GetHexByte:

callSerialReceive;getnewbytefromserialport

addlw0xBF;add-'A'toASCIIhighbyte

btfssSTATUS,C;checkifpositive

addlw0x07;ifnot,add17（'0'to'9'）

addlw0x0A;elseadd10（'A'to'F'） 

movwfHexByte;savenibble

swapfHexByte,F;movenibbletohighposition

callSerialReceive;getnewbytefromserialport

addlw0xBF;add-'A'toASCIIlowbyte

btfssSTATUS,C;checkifpositive

addlw0x07;ifnot,add17（'0'to'9'）

addlw0x0A;elseadd10（'A'to'F'） 

iorwfHexByte,F;addlownibbletohighnibble

movfHexByte,W;putresultinWreg

return

AnexampleofanassemblylanguagesubroutineforthePIC16F877microcontroller.ThecodereadstwoASCIIbytesfromtheserialport,interpretsthemashexdigits（0...F）,andcombinesthemtoformabyteofbinarydata.

BASICStamp

N.Atinysingle-boardcomputermanufacturedbyParallaxbasedonan8051,PIC,orothermicrocontroller.TheBASICStampisaboutthesizeofapostagestamp（hencethename）andexecutesavariantofBASICcalledPBASIC.Inexpensive,self-contained,andeasytoprogram,they'reusedineducationandsimpleembeddedsystemsthatrequirelittlehorsepowerbutrapiddelivery.

ABASICStampcollection.

bidirectional

adj.Describesatypeofdeviceorbusthatsupportstwo-waydatatransfers.Toreducewiring,connectors,andpincounts,it'scommontosharedataononebus.DatacanmovefromdeviceAtoBorfromBtoA,thoughnotatthesametime.Contrastwithunidirectional.

EXAMPLE:

Abidirectionaldatabusispresentonprettymucheverymicroprocessor.AsinglebustransfersdatatoandfrommemoryandI/O.Controlsignalspolicethetransfers,ensuringthattherearenoattemptstotransferdatainbothdirectionsatthesametime.

big-endian

adj.Adatarepresentationforamultibytevaluethathasthemostsignificantbytestoredatthelowestmemoryaddress.Notethatonlythebytesarereordered,neverthenibblesorbitsthatcomprisethem.Everyprocessorstoresitsdataineitherbig-endianorlittle-endianformat.Sun'sSPARC,Motorola's68k,andthePowerPCfamiliesareallbig-endian.TheJavavirtualmachineisbig-endianaswell.Similarly,everycommunicationsprotocolmustdefinethebyteorderofitsmultibytevalues.TCP/IPusesbig-endianrepresentation.

EXAMPLE:

Ifthe32-bitvalue0x12345678islocatedataddress1000dinmemory,itsmostsignificantbyte,0x12,wouldbefoundatlocation1000d.Location1001dwouldcontainthenextmostsignificantbyte,0x34;location1002dwouldcontain0x56;andlocation1003dwouldcontaintheleastsignificantbyte,0x78.

binarysemaphore

n.Atypeofsemaphorewithjusttwostates.Oftenusedtoguaranteemutualexclusion.Comparetomutex.

boardsupportpackage

n.Partofasoftwarepackagethatisprocessororplatformdependent.AbbreviatedBSP.Typically,samplesourcecodefortheBSPisprovidedbythepackagedeveloper.Toportthelargerpackage,onlythecodeintheboardsupportpackagemustbemodified.Mostcommercialreal-timeoperatingsystemshaveaBSPtomakeportingeasy.

bond-outprocessor

n.Aspecialversionofaprocessorthathassomeoftheinternalsignalsbroughtouttoexternalpins.Bond-outprocessorsaredesignedtobeusedwithinanin-circuitemulatorandarenottypicallyusedinanyotherkindofsystem.

breakpoint

n.Alocationinaprogramatwhichexecutionistobestoppedandcontroloftheprocessorswitchedtothedebugger.Mechanismsforcreatingandremovingbreakpointsareprovidedbymostdebuggingtools.Seealsotracepoint,hardwarebreakpoint.

C99

N.A1999updatetotheinternationalstandardfortheCprogramminglanguage.TheupdatedstandardisformallyknownasISO/IEC9899:

ProgrammingLanguages—C.Fromanembeddedsystemsprogrammingperspective,oneofC99'smostexcitingenhancementsisbuilt-indefinitionofsignedandunsignedintegerdatatypesof8,16,and32bits.（Theyaretypedef'dasuint8_t,int8_t,uint16_t,etc.intheplatform-specificlibraryheaderfilestdint.h.）TheC99standardalsorecognizesC++-stylecomments（//）andmakesseveralotherlong-overduelanguageimprovements. 

USAGE:

InstandardC,thesizeofprimitivetypesshort,int,andlongareonlylooselydefined.Ononeplatform,anintcanbe16bits;onanother,32bits.Formanyyears,embeddedsystemsprogrammershavedefinedtheirowntypedefsforfixed-sizedsignedandunsignedintegers.Finally,standardnameswereassignedintheC99updatedlanguagestandard.Ifyou