Embedded system terminology 嵌入式系统词汇.docx
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Embedded system terminology 嵌入式系统词汇.docx
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Embeddedsystemterminology嵌入式系统词汇
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(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
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