毕业设计外文文献翻译.docx

毕业设计外文文献翻译.docx

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毕业设计外文文献翻译

学校代码：

10128

学号：

201020205056

本科毕业设计外文文献翻译

（

题目：

PacketHandlingHardwareSupport

学生姓名：

学院：

系别：

专业：

班级：

指导教师：

二〇一四年六月

PacketHandlingHardwareSupport

参考文献：

TexasInstruments.CC1101Low-PowerSub-1GHzRFTransceiver.www..2013

TheCC1101hasbuilt-inhardwaresupportforpacketorientedradioprotocols.

Intransmitmode,thepackethandlercanbeconfiguredtoaddthefollowingelementstothepacketstoredintheTXFIFO:

●Aprogrammablenumberofpreamblebytes

●Atwobytesynchronization（sync）word.Canbeduplicatedtogivea4-bytesyncword（recommended）.Itisnotpossibletoonlyinsertpreambleoronlyinsertasyncword

●ACRCchecksumcomputedoverthedatafield.

Therecommendedsettingis4-bytepreambleand4-bytesyncword,exceptfor500kBauddataratewheretherecommendedpreamblelengthis8bytes.Inaddition,thefollowingcanbeimplementedonthedatafieldandtheoptional2-byteCRCchecksum:

●WhiteningofthedatawithaPN9sequence

●ForwardErrorCorrection（FEC）bytheuseofinterleavingandcodingofthedata（convolutionalcoding）

Inreceivemode,thepackethandlingsupportwillde-constructthedatapacketbyimplementingthefollowing（ifenabled）:

●Preambledetection

●Syncworddetection

●CRCcomputationandCRCcheck

●Onebyteaddresscheck

●Packetlengthcheck（lengthbytecheckedagainstaprogrammablemaximumlength）

●De-whitening

●De-interleavinganddecoding

Optionally,twostatusbytes（seeTable27andTable28）withRSSIvalue,LinkQualityIndication,andCRCstatuscanbeappendedintheRXFIFO.

Table27:

ReceivedPacketStatusByte1（firstbyteappendedafterthedata）

Bit

FieldName

Description

7:

0

RSSI

RSSIvalue

Table28:

ReceivedPacketStatusByte2（secondbyteappendedafterthedata）

Bit

FieldName

Description

7

CRC_OK

1:

CRCforreceiveddataOK

（orCRCdisabled）

0:

CRCerrorinreceiveddata

6:

0

LQI

Indicatingthelinkquality

Note:

RegisterfieldsthatcontrolthepackethandlingfeaturesshouldonlybealteredwhenCC1101isintheIDLEstate.

1.Datawhitening

Fromaradioperspective,theidealovertheairdataarerandomandDCfree.Thisresultsinthesmoothestpowerdistributionovertheoccupiedbandwidth.Thisalsogivestheregulationloopsinthereceiveruniformoperationconditions（ondatadependencies）.

Realdataoftencontainlongsequencesofzerosandones.Inthesecases,performancecanbeimprovedbywhiteningthedatabeforetransmitting,andde-whiteningthedatainthereceiver.

WithCC1101,thiscanbedoneautomatically.BysettingPKTCTRLO.WHITE_DATA=1,alldata,exceptthepreambleandthesyncwordwillbeXOR-edwitha9-bitpseudo-random（PN9）sequencebeforebeingtransmitted.ThisisshowninFigure16.Atthereceiverend,thedataareXOR-edwiththesamepseudorandomsequence.Inthisway,thewhiteningisreversed,andtheoriginaldataappearinthereceiver.ThePN9sequenceisinitializedtoall1’s.

2.PacketFormat

Theformatofthedatapacketcanbeconfiguredandconsistsofthefollowingitems（seeFigure17）:

●Preamble

●Synchronizationword

●Optionallengthbyte

●Optionaladdressbyte

●Payload

●Optional2byteCRC

Thepreamblepatternisanalternatingsequenceofonesandzeros（10101010…）.TheminimumlengthofthepreambleisprogrammablethroughthevalueofMDMCFG1.NUM_PREAMBLE.WhenenablingTX,themodulatorwillstarttransmittingthepreamble.Whentheprogrammednumberofpreamblebyteshasbeentransmitted,themodulatorwillsendthesyncwordandthendatafromtheTXFIFOifdataisavailable.IftheTXFIFOisempty,themodulatorwillcontinuerosendpreamblebytesuntilthefirstbyteiswrittentotheTXFIFO.Themodulatorwillthensendthesyncwordandthenthedatabytes.

Thesynchronizationwordisatwo-bytevaluesetintheSYNC1andSYNC0registers.Thesyncwordprovidesbytesynchronizationoftheincomingpacket.Aone-bytesyncwordcanbeemulatedbysettingtheAYNC1valuetothepreamblepattern.Itisalsopossibletoemulatea32bitsyncwordbysettingMDMCFG2.SYNC_MODEto3or7.Thesyncwordwillthenberepeatedtwice.

CC1101supportsbothconstantpacketlengthprotocolsandvariablelengthprotocols.Variableorfixedpacketlengthmodecanbeusedforpacketsupto255bytes.Forlongerpackets,infinitepacketlengthmodemustbeused.

FixedpacketlengthmodeisselectedbysettingPKTCTRL0.LENGTH_CONFIG=0.ThedesiredpacketlengthissetbythePKTLENregister.Thisvaluemustbedifferentfrom0.

Invariablepacketlengthmode,PKTCTRL0.LENGTH_CONFIG=1,thepacketlengthisconfiguredbythefirstbyteafterthesyncword.Thepacketlengthisdefinedasthepayloaddata,excludingthelengthbyteandoptionalCRC.ThePKTLENregisterisusedtosetthemaximumpacketlengthallowedinRX.AnypacketreceivedwithalengthbytewithavaluegreaterthanPKTLENwillbediscarded.ThePKTLENvaluemustbedifferentfrom0.ThebytewrittentotheTXFIFOmustbedifferentfrom0.

WithPKTCTRL0.LENGTH_CONFIG=2,thepacketlengthissettoinfiniteandtransmissionandreceptionwillcontinueuntilturnedoffmanually.Asdescribedinthenextsection,thiscanbeusedtosupportpacketformatswithdifferentlengthconfigurationthannativelysupportedbyCC1101.oneshouldmakesurethatTXisnotturnoffduringthetransmissionofthefirsthalfofanybyte.RefertotheCC1101ErrataNotes[4]formoredetails.

Note:

Theminimumpacketlengthsupported（excludingtheoptionallengthbyteandCRC）isonebyteofpayloaddata.

2.1ArbitraryLengthFieldConfiguration

Thepacketlengthregister,PKTLEN,canbereprogrammedduringreceiveandtransmit.Incombinationwithfixedpacketlengthmode（PKTCTRL0.LENGTH_CONFIG=0）,thisopensthepossibilitytohaveadifferentlengthfieldconfigurationcansupportedforvariablelengthpackets（invariablepacketlengthmodethelengthbyteisthefirstbyteafterthesyncword）.Atthestartofreception,thepacketlengthissetalargevalue.TheMCUreadsoutenoughbytestointerpretthelengthfieldinthepacket.ThenthePKTLENvalueissetaccordingtothisvalue.TheendofpacketwilloccurwhenthebytecounterinthepackethandlerisequaltothePKTLENregister.Thus,theMCUmustbeabletoprogramthecorrectlength,beforetheinternalcounterreachesthepacketlength.

2.2PacketLength>255

Thepacketautomationcontrolregister,PKTCTRL0,canbereprogrammedduringTXandRX.Thisopensthepossibilitytotransmitandreceivepacketsthatarelongerthan256bytesandstillbeabletousethepackethandlinghardwaresupport.Atthestartofthepacket,theinfinitepacketlengthmode（PKTCTRL0.LENGTH_CONFIG=2）mustbeactive.OntheTXside,thePKTLENregisterissettomod（length,256）.OntheRXsidetheMCUreadsoutenoughbytestointerpretthelengthfieldinthepacketandsetsthePKTLENregistertomod（length,256）.Whenlessthan256bytesremainsofthepacket,theMCUdisablesinfinitepacketlengthmodeandactivatesfixedpacketlengthmode.WhentheinternalbytecounterreachesthePKTLENvalue,thetransmissionorreceptionends（theradioentersthestatedeterminedbyTXOFF_MODEorRXOFF_MODE）.AutomaticCRCappending/checkingcanalsobeused（bysettingPKTCTRL0.CRC_EN=1）.

Whenforexamplea600-bytepacketistobetransmitted,theMCUshoulddothefollowing（seealsoFigure18）

●SetPKTCTRL0.LENGTH_CONFIG=2.

●Pre-programthePKTLENregistertomod（600,256）=88.

●Transmitatleast345bytes（600-255）,forexamplebyfillingthe64-byteTXFIFOsixtimes（384bytestransmitted）.

●SetPKTCTRL0.LENGTH_CONFIG=0.

●Thetransmissionendswhenthepacketcounterreaches88.atotalof600bytesaretransmitted.

3PacketfilteringinReceiveMode

CC1101supportsthreedifferenttypesofpacket-filtering;addressfiltering,maximumlengthfiltering,andCRCfiltering.

3.1AddressingFiltering

SettingPKTCTRL1.ADR_CHKtoanyothervaluethanzeroenablesthepacketaddressfilter.ThepackethandlerenginewillcomparethedestinationaddressbyteinthepacketwiththeprogrammednodeaddressintheADDRregisterandthe0*00broadcastaddresswhenPKTCTRL1.ADR_CHK=10orboththe0*00and0*FFbroadcastaddresseswhenPKTCTRL1.ADR_CHK=11.Ifthereceivedaddressmatchesavalidaddress,thepacketisreceivedandwrittenintotheRXFIFO.Iftheaddressmatchfails,thepacketisdiscardedandreceivemoderestarted（regardlessoftheMCSM1.RXOFF_MODEsetting）.

Ifthereceivedaddressmatchesavalidaddresswhenusinginfinitepacketlengthmodeandaddressfilteringisenabled,0*FFwillbewrittenintotheRXFIFOfollowedbytheaddressbyteandthenthepayloaddata.

3.2MaximumLengthFiltering

Invariablepacketlengthmode,PKTCTRL0.LENGTH_CONFIG=1,thePKTLEN.PACKET_LENGTHregistervalueisusedtosetthemaximumallowedpacketlength.Ifthereceivedlengthbytehasalargervaluethanthis,thepacketisdiscardedandreceivemoderestarted（regardlessoftheMCSM1.RXOFF_MODEsetting）.

3.3CRCFiltering

ThefilteringofapacketwhenCRCcheckfailsisenabledbysettingPKTCTRL1.CRC_AUTOFLUSH=1.TheCRCautoflushfunctionwillflushtheentireRXFIFOiftheCRCcheckfails.AfterautoflushingtheRXFIFO,thenextstatedependsontheMCSM1.RXOFF_MODEsetting.

Whenusingtheautoflushfunction,themaximumpacketlengthis63bytesinvariablepacketlengthmode.NotethatwhenPKTCTRL1APPEND_STATUSisenabled,themaximumallowedpacketlengthisreducedbytwobytesinordertomakeroomintheRXFIFOforthetwostatusbytesappendedattheendofthepacket.SincetheentireRXFIFOisflushedwhentheCRCcheckfails,thepreviouslyreceivedpacketmustbereadoutoftheFIF