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

毕业设计_外文文献翻译

本科毕业设计外文文献翻译（题目：

packethandlinghardwaresupport

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二〇一四年六月

packethandlinghardwaresupport

参考文献：

texasinstruments1101low-powersub-1ghzrftransceiver.ti.2013

the1101hasbuilt-inhardwaresupportforpacketorientedradioprotocols.intransmitmode,thepackethandlercanbeconfiguredtoaddthefollowingelementstothepacketstoredinthetxfifo:

aprogrammablenumberofpreamblebytes

atwobytesynchronization（sync）word.canbeduplicatedtogivea4-byte

syncword（remended）.itisnotpossibletoonlyinsertpreambleoronlyinsertasyncword

acrcchecksumputedoverthedatafield.

theremendedsettingis4-bytepreambleand4-bytesyncword,exceptfor500kbauddataratewheretheremendedpreamblelengthis8bytes.inaddition,thefollowingcanbeimplementedonthedatafieldandtheoptional2-bytecrcchecksum:

whiteningofthedatawithapn9sequence

forwarderrorcorrection（fec）bytheuseofinterleavingandcodingofthe

data（convolutionalcoding）

inreceivemode,thepackethandlingsupportwillde-constructthedatapacketbyimplementingthefollowing（ifenabled）:

preambledetection

syncworddetection

crcputationandcrccheck

onebyteaddresscheck

packetlengthcheck（lengthbytecheckedagainstaprogrammablemaximum

length）

de-whitening

de-interleavinganddecoding

optionally,twostatusbytes（seetable27andtable28）withrssivalue,linkqualityindication,andcrcstatuscanbeappendedintherxfifo.1.datawhitening

fromaradioperspective,theidealovertheairdataarerandomanddcfree.thisresultsinthesmoothestpowerdistributionovertheoupiedbandwidth.thisalsogivestheregulationloopsinthereceiveruniformoperationconditions（ondatadependencies）.

realdataoftencontainlongsequencesofzerosandones.inthesecases,performancecanbeimprovedbywhiteningthedatabeforetransmitting,andde-whiteningthedatainthereceiver.

with1101,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

optional2bytecrcthepreamblepatternisanalternatingsequenceofonesandzeros（10101010…）.theminimumlengthofthepreambleisprogrammablethroughthevalueofmdmcfg1.num_preamble.whenenablingtx,themodulatorwillstarttransmittingthepreamble.whentheprogrammednumberofpreamblebyteshasbeen

transmitted,themodulatorwillsendthesyncwordandthendatafromthetxfifoifdataisavailable.ifthetxfifoisempty,themodulatorwillcontinuerosendpreamblebytesuntilthefirstbyteiswrittentothetxfifo.themodulatorwillthensendthesyncwordandthenthedatabytes.

thesynchronizationwordisatwo-bytevaluesetinthesync1andsync0registers.thesyncwordprovidesbytesynchronizationoftheiningpacket.aone-bytesyncwordcanbeemulatedbysettingtheaync1valuetothepreamblepattern.itisalsopossibletoemulatea32bitsyncwordbysettingmdmcfg2.sync_modeto3or7.thesyncwordwillthenberepeatedtwice.

1101supportsbothconstantpacketlengthprotocolsandvariablelengthprotocols.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,thiscanbeusedtosupportpacketformatswithdifferentlengthconfigurationthannativelysupportedby1101.oneshouldmakesurethattxisnotturnoffduringthetransmissionofthefirsthalfofanybyte.refertothe1101

2.1arbitrarylengthfieldconfiguration

thepacketlengthregister,pktlen,canbereprogrammedduringreceiveandtransmit.inbinationwithfixedpacketlengthmode（pktctrl0.length_config=0）,thisopensthepossibilitytohaveadifferentlengthfieldconfigurationcansupportedforvariablelengthpackets（invariablepacketlengthmodethelengthbyteisthefirstbyteafterthesyncword）.atthestartofreception,thepacketlengthissetalargevalue.themcureadsoutenoughbytestointerpretthelengthfieldinthepacket.thenthepktlenvalueissetaordingtothisvalue.theendofpacketwillourwhenthebytecounterinthepackethandlerisequaltothepktlenregister.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-bytetxfifo

sixtimes（384bytestransmitted）.

setpktctrl0.length_config=0.

thetransmissionendswhenthepacketcounterreaches88.atotalof600bytes

aretransmitted.3packetfilteringinreceivemode

1101supportsthreedifferenttypesofpacket-filtering;addressfiltering,maximumlengthfiltering,andcrcfiltering.

3.1addressingfiltering

settingpktctrl1.adr_chktoanyothervaluethanzeroenablesthepacketaddressfilter.thepackethandlerenginewillparethedestinationaddressbyteinthepacketwiththeprogrammednodeaddressintheaddrregisterandthe0*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,thepreviouslyreceivedpacketmustbereadoutofthefifobeforereceivingthecurrentpacket.themcumustnotreadfromthecurrentpacketuntilthecrchasbeencheckedasok.4packethandlingintransmitmode

thepayloadthatistobetransmittedmustbewrittenintothetxfifo.thefirstbytewrittenmustbethelengthbytewhenvariablepacketlengthisenabled.thelengthbytehasavalueequaltothepayloadofthepacket（includingtheoptionaladdressbyte）.ifaddressrecognitionisenabledonthereceiver,thesecondbytewrittentothetxfifomustbetheaddressbyte.

iffixedpacketlengthisenabled,thefirstbytewrittentothetxfifoshouldbetheaddress（assumingthereceiverusesaddressrecognition）.

themodulatorwillfirstsendtheprogrammednumberofpreamblebytes.ifdataisavaibleinthetxfifo,themodulatorwillsendthetwo-bytes（optionally4-byte）

syncwordfollowedbythepayloadinthetxfifo.ifcrcisenabled,thechecksumiscalculatedoverallthedatapulledfromthetxfifo,andtheresultissentastwoextrabytesfollowingthepayloaddata.ifthetxfiforunsemptybeforethepletepackethasbeentransmitted,theradiowillentertxfifo_underflowstate.theonlywaytoexitthisstateisbyissuingansftxstrobe.writingtothetxfifoafterithasbeenunderflowedwillnotrestarttxmode.

ifwhiteningisenabled,everythingfollowingthesyncwordswillbewhitened.thisisdonebeforetheoptionalfec/interleaverstage.whiteningisenabledbysettingpktctrl0.white_data=1.

iffec/interleavingisenabled,everythingfollowingthesyncwordswillbescrambledbytheinterleaverandfecencodedbeforebeingmodulated.fecisenabledbysettingmdmcfg1.fec_en=1.

5packethandlinginreceivemode

inreceivemode,thedemodulatorandpackethandlerwillsearchforavalidpreambleandthesyncword.whenfound,thesynchronismandwillreceivethefirstpayloadbyte.

iffec/interleavingisenabled,thefecdecoderwillstarttodecodethefirstpayloadbyte.theintrerleaverwillde-scramblethebitsbeforeanyotherprocessingisdonetothedata.

ifwhiteningisenabled,thedatawillbede-whitenedatthisstage.

whenvariablepacketlengthmodeisenabled,thefirstbyteisthelengthbyte.thepackethandlerstoresthisvalueasthepacketlengthandreceivesthenumberofbytesindicatedbythelengthbyte.iffixedpacketlengthmodeisused,thepackethandlerwillaepttheprogrammednumb