ATmega16外文翻译.docx
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ATmega16外文翻译.docx
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ATmega16外文翻译
外文原文
TheAVRcorecombinesarichinstructionsetwith32generalpurposeworkingregisters.Allthe32registersaredirectlyconnectedtotheArithmeticLogicUnit(ALU),allowingtwoindependentregisterstobeaccessedinonesingleinstructionexecutedinoneclockcycle.TheresultingarchitectureismorecodeefficientwhileachievingthroughputsuptotentimesfasterthanconventionalCISCmicrocontrollers.
TheATmega16providesthefollowingfeatures:
16KbytesofIn-SystemProgrammableFlashProgrammemorywithRead-While-Writecapabilities,512bytesEEPROM,1KbyteSRAM,32generalpurposeI/Olines,32generalpurposeworkingregisters,aJTAGinterfaceforBoundary-scan,On-chipDebuggingsupportandprogramming,threeflexibleTimer/Counterswithcom-paremodes,InternalandExternalInterrupts,aserialprogrammableUSART,abyteorientedTwo-wireSerialInterface,an8-channel,10-bitADCwithoptionaldifferentialinputstagewithprogrammablegain(TQFPpackageonly),aprogrammableWatchdogTimerwithInternalOscil-lator,anSPIserialport,andsixsoftwareselectablepowersavingmodes.TheIdlemodestopstheCPUwhileallowingtheUSART,Two-wireinterface,A/DConverter,SRAM,Timer/Counters,SPIport,andinterruptsystemtocontinuefunctioning.ThePower-downmodesavestheregistercontentsbutfreezestheOscillator,disablingallotherchipfunctionsuntilthenextExternalInter-ruptorHardwareReset.InPower-savemode,theAsynchronousTimercontinuestorun,allowingtheusertomaintainatimerbasewhiletherestofthedeviceissleeping.TheADCNoiseReductionmodestopstheCPUandallI/OmodulesexceptAsynchronousTimerandADC,tominimizeswitchingnoiseduringADCconversions.InStandbymode,thecrystal/reso-natorOscillatorisrunningwhiletherestofthedeviceissleeping.Thisallowsveryfaststart-up
combinedwithlow-powerconsumption.InExtendedStandbymode,boththemainOscillatorandtheAsynchronousTimercontinuetorun.
ThedeviceismanufacturedusingAtme'lshighdensitynonvolatilememorytechnology.TheOn-chipISPFlashallowstheprogrammemorytobereprogrammedin-systemthroughanSPIserialinterface,byaconventionalnonvolatilememoryprogrammer,orbyanOn-chipBootprogramrunningontheAVRcore.ThebootprogramcanuseanyinterfacetodownloadtheapplicationprogramintheApplicationFlashmemory.SoftwareintheBootFlashsectionwillcontinuetorunwhiletheApplicationFlashsectionisupdated,providingtrueRead-While-Writeoperation.Bycombiningan8-bitRISCCPUwithIn-SystemSelf-ProgrammableFlashonamonolithicchip,theAtmelATmega16isapowerfulmicrocontrollerthatprovidesahighly-flexibleandcost-effec-tivesolutiontomanyembeddedcontrolapplications.
TheATmega16AVRissupportedwithafullsuiteofprogramandsystemdevelopmenttoolsincluding:
Ccompilers,macroassemblers,programdebugger/simulators,in-circuitemulators,andevaluationkits.
TheinterconnectionbetweenMasterandSlaveCPUswithSPIisshowninFigure66.ThesystemconsistsoftwoShiftRegisters,andaMasterclockgenerator.TheSPIMasterinitiatesthecommunicationcyclewhenpullinglowtheSlaveSelectSSpinofthedesiredSlave.MasterandSlavepreparethedatatobesentintheirrespectiveShiftRegisters,andtheMastergeneratestherequiredclockpulsesontheSCKlinetointerchangedata.DataisalwaysshiftedfromMastertoSlaveontheMasterOut-SlaveIn,MOSI,line,andfromSlavetoMasterontheMasterIn-SlaveOut,MISO,line.Aftereachdatapacket,theMasterwillsynchronizetheSlavebypullinghightheSlaveSelect,SS,line.
WhenconfiguredasaMaster,theSPIinterfacehasnoautomaticcontroloftheSSline.Thismustbehandledbyusersoftwarebeforecommunicationcanstart.Whenthisisdone,writingabytetotheSPIDataRegisterstartstheSPIclockgenerator,andthehardwareshiftstheeightbitsintotheSlave.Aftershiftingonebyte,theSPIclockgeneratorstops,settingtheendofTransmissionFlag(SPIF).IftheSPIInterruptEnablebit(SPIE)intheSPCRRegisterisset,aninterruptisrequested.TheMastermaycontinuetoshiftthenextbytebywritingitintoSPDR,orsignaltheendofpacketbypullinghightheSlaveSelect,SSline.ThelastincomingbytewillbekeptintheBufferRegisterforlateruse.
WhenconfiguredasaSlave,theSPIinterfacewillremainsleepingwithMISOtri-statedaslongastheSSpinisdrivenhigh.Inthisstate,softwaremayupdatethecontentsoftheSPIDataRegister,SPDR,butthedatawillnotbeshiftedoutbyincomingclockpulsesontheSCKpinuntiltheSSpinisdrivenlow.Asonebytehasbeencompletelyshifted,theendofTransmissionFlag,SPIFisset.IftheSPIInterruptEnablebit,SPIE,intheSPCRRegisterisset,aninterruptisrequested.TheSlavemaycontinuetoplacenewdatatobesentintoSPDRbeforereadingtheincomingdata.ThelastincomingbytewillbekeptintheBufferRegisterforlateruse.
VS1003isasingle-chipMP3/WMA/MIDIaudiodecoderandADPCMencoder.Itcontainsahighperformance,proprietarylow-powerDSPprocessorcoreVSDSP4,workingdatamemory,5KiBinstructionRAMand0.5KiBdataRAMforuserapplications,serialcontrolandinputdatainterfaces,4generalpurposeI/Opins,anUART,aswellasahigh-qualityvariable-sample-ratemonoADCandstereoDAC,followedbyanearphoneamplifierandagroundbuffer.
VS1003receivesitsinputbitstreamthroughaserialinputbus,whichitlistenstoasasystemslave.Theinputstreamisdecodedandpassedthroughadigitalvolumecontroltoan18-bitoversampling,multi-bit,sigma-deltaDAC.Thedecodingiscontrolledviaaserialcontrolbus.Inadditiontothebasicdecoding,itispossibletoaddapplicationspecificfeatures,likeDSPeffects,totheuserRAMmemory.
(1)SPIBuses
TheSPIBus-thatwasoriginallyusedinsomeMotoroladevices-hasbeenusedforbothVS1003'sSerialDataInterfaceSDI(Chapters7.4and8.4)andSerialControlInterfaceSCI.
(2)DataRequestPinDREQ
TheDREQpin/signalisusedtosignalifVS1003'sFIFOiscapableofreceivingdata.IfDREQishigh,VS1003cantakeatleast32bytesofSDIdataoroneSCIcommand.Whenthesecriteriaarenotmet,DREQisturnedlow,andthesendershouldstoptransferringnewdata.
Becauseofthe32-bytesafetyarea,thesendermaysendupto32bytesofSDIdataatatimewithoutcheckingthestatusofDREQ,makingcontrollingVS1003easierforlow-speedmicrocontrollers.
Note:
DREQmayturnloworhighatanytime,evenduringabytetransmission.Thus,DREQshouldonlybeusedtodecidewhethertosendmorebytes.Itshouldnotabortatransmissionthathasalreadystarted.
Note:
InVS10XXproductsuptoVS1002,DREQwasonlyusedforSDI.InVS1003DREQisalsousedtotellthestatusofSCI.
(3)SerialProtocolforSerialDataInterface(SDI)
TheserialdatainterfaceoperatesinslavemodesoDCLKsignalmustbegeneratedbyanexternalcircuit.
Data(SDATAsignal)canbeclockedinateithertherisingorfallingedgeofDCLK.
VS1003assumesitsdatainputtobebyte-sychronized.SDIbytesmaybetransmittedeitherMSborLSbfirst,dependingofcontentsofSCIMODE.
ThefirmwareisabletoacceptthemaximumbitratetheSDIsupports.
InVS1002nativemodes(SMNEWMODEis1),bytesynchronizationisachievedbyXDCS.ThestateofXDCSmaynotchangewhileadatabytetransferisinprogress.ToalwaysmaintaindatasynchronizationeveniftheremaybeglitchesintheboardsusingVS1003,itisrecommendedtoturnXDCSeverynowandthen,forinstanceonceaftereveryflashdatablockorafewkilobytes,justtokeepsurethehostandVS1003areinsync.
IfSMSDISHAREis1,theXDCSsignalisinternallygeneratedbyinvertingtheXCSinput.
Fornewdesigns,usingVS1002nativemodesarerecommended.
(4)SerialProtocolforSerialCommandInterface(SCI)
TheserialbusprotocolfortheSerialCommandInterfaceSCI(Chapter8.5)consistsofaninstructionbyte,addressbyteandone16-bitdataword.Eachreadorwriteoperationcanreadorwriteasingleregister.Databitsarereadattherisingedge,sotheusershouldupdatedataatthefallingedge.BytesarealwayssendMSbfirst.
Theoperationisspecifiedbyan8-bitinstructionopcode.Thesupportedinstructionsarereadandwrite.
Note:
VS1003setsDREQlowaftereachSCIoperation.Thedurationdependsontheoperation.ItisnotallowedtostartanewSCI/SDIoperationbeforeDREQishighagain.
MP3audioquality
ForMP3isalossycompressionformat,itoffersavarietyofdifferent"bitrate"(bitrate)option-thatisusedtorepresentasecondaudioencodingdataneededforthefigures.Typicalspeedbetween128KBPSand320KBPS(kbit/s).Incontrast,theCDonuncompressedaudiobitrateis1411.2KBPS(16/samplepointx44100x2channelsamplingHP/SEC).
UsinglowbitratecodingMP3fileplaybackqualityisusuallylow.Usinglowbitrate,thecompressnoise(compressionwillanartifact)"(no)intheoriginalrecordingwillbepresentedduringplayback.Agoodexampleofcompressnoiseis:
theshoutofcompression;Becauseofitsrandomnessandrapidchange,sotheencodererrorswillbemoreobvious,anditsoundslikeecho.
Inadditiontothecodefilebitrate;ThequalityoftheMP3file,alsorelatedtothequalityoftheencoderandthedifficultyofthecodedsignal.Usinghighqualitygeneralsignalencoderencoding,somepeoplethinkthat128kbit/s(MP3and44.1kHzCDsamplingsoundsimilartoCDquality,atthesametimegetaboutnowthecompressionratio.UndertheratioofcorrectcodingofMP3canonlygetbettersoundqualitythanFMradio,thisbasicallyisthesimulationofthemediumbandwidthconstraints,signal-to-noiseratioandotherrestrictions.Hearin
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