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DS2480Serial1–WireTMLineDriverDS24800424981/26FEATURESUniversal,common–groundserialportto1–WireTMlinedriverforMicroLANTMapplicationsWorkswithalliButtonsandMicroLAN–compatible1–WireslavedevicesCommunicatesatregularandOverdrive1–Wirespeedandserialportdataratesof9600(default),19200,57600and115200bpsSupports12VEPROMprogrammingandstiff5Vpull–upforCryptoiButton,sensorsandEEPROMSelf–calibratingtimebasewith±5%toleranceforserialand1–WirecommunicationSlewratecontrolled1–Wirepull–downandactivepull–uptoaccommodatelonglinesandreduceradi-ationUser–selectableRXD/TXDpolarityminimizescom-ponentcountwheninterfacingto5VbasedRS232systemsordirectlytoUARTsProgrammable1–Wiretiminganddrivercharacteris-ticsaccommodateawiderangeofMicroLANconfigu-rationsatregularspeedSmartprotocolcombinesdataandcontrolinformationwithoutrequiringextrapinsCompatibletooptical,IRandRFtoRS232convertersLowcost8–pinSOICsurfacemountpackageOperatesover4.
5Vto5.
5Vfrom–40°Cto+85°CPINASSIGNMENTRXD1–WGNDPOLTXDVPP87658–PINSOIC(150MIL)NCVDD1234PINDESCRIPTIONGNDGround1–W1–WireInput/OutputNCNoConnectionVDD4.
5to5.
5VoltsVPPOptionalEPROMProgrammingVoltagePOLRXD/TXDPolaritySelectTXDSerialDatafromUARTRXDSerialDatatoUARTORDERINGINFORMATIONDS2480S8–pinSOICDESCRIPTIONTheDS2480isaserialportto1–WireinterfacechipthatsupportsstandardandOverdrivespeeds.
ItconnectsdirectlytoUARTsand5VRS232systems.
InterfacingtoRS232C(±12Vlevels)requiresapassiveclampingcir-cuitandone5Vto±12Vleveltranslator.
Internaltimersrelievethehostoftheburdenofgeneratingthetime–critical1–Wirecommunicationwaveforms.
IncontrasttotheDS9097(E)whereafullcharactermustbesentbythehostforeach1–Wiretimeslot,theDS2480cantranslateeachcharacterintoeight1–Wiretimeslotstherebyincreasingthedatathroughputsignificantly.
Inaddition,theDS2480canbesettocommunicateatfourdifferentdataratesincluding115.
2kbps,57.
6kbpsand19.
2kbpswith9.
6kbpsbeingthepower–ondefault.
Commandcodesreceivedfromthehost'scrystalcon-trolledUARTserveasareferencetocontinuouslycali-bratetheon–chiptiminggenerator.
TheDS2480usesauniqueprotocolthatmergesdataandcontrolinforma-tionwithoutrequiringcontrolpins.
Thisapproachmain-tainscompatibilitytooff–the–shelfserialtowirelessconvertersallowingeasyrealizationof1–Wiremediajumpers.
ThevariouscontrolfunctionsoftheDS2480areoptimizedforMicroLAN1–Wirenetworksandsup-portthespecialneedsofallcurrent1–WiredevicesincludingtheCryptoiButton,EPROM–basedAdd–OnlyMemories,EEPROMdevicesand1–WireThermome-ters.
DS24800424982/26DETAILEDPINDESCRIPTIONPINSYMBOLDESCRIPTION1GNDGroundPin:commongroundreferenceandgroundreturnfor1–Wirebus21–W1–WireInput/OutputPin:1–Wirebuswithslew–rate–controlledpull–down,activepull–up,abilitytoswitchinVPPtoprogramEPROM,andabilitytoswitchinVDDthroughalow–impedancepathtoprogramEEPROM,performatemper-atureconversionoroperatetheCryptoiButton.
3NCNoConnectionPin.
4VDDPowerInputPin:powersupplyforthechipand1–Wirepull–upvoltage.
5V±10%;maybederivedfrom12VVPPwithanexternalvoltageregulator.
5VPPEPROMProgrammingVoltage:12VsupplyinputforEPROMprogramming;ifEPROMprogrammingisnotrequired,thispinmustbetiedtoVDD.
VPPmustcomeupbeforeVDD.
6POLRXD/TXDPolaritySelect:RXD/TXDpolarityselect;tiedtoGNDforRS232(12Vor5V)connection,tiedtoVDDfordirectconnectiontoUARTchip.
7TXDSerialDatafromUART:datainputfromhost(invertedortrue);maximumvolt-ageswing–0.
3VtoVDD+0.
3V;forlogicthresholdsseeDCspecifications.
8RXDSerialDatatoUART:signaloutputtohost;push–pulldriverwithCMOScom-patiblelevels;fortrue±12VRS232systemsanexternallevel–translatormustbeprovided.
OVERVIEWTheDS2480directlyinterfacesa5Vserialcommunica-tionportwithitslinesTXD(transmit)andRXD(receive)toa1–Wirebus.
Inadditionthedeviceperformsaspeedconversionallowingthedatarateatthecommunicationporttobedifferentfromthe1–Wiredaterate.
Severalparametersrelatingtothe1–Wireportanditstimingaswellasthecommunicationspeedatboththeportandthe1–Wirebusareconfigurable.
ThecircuittoachievethesefunctionsisoutlinedinFigure1,BlockDiagram.
Thedevicegetsitsinputdatafromtheserialcommu-nicationportofthehostcomputerthroughpinTXD.
Forcompatibilitywithactive–highaswellasactive–lowsys-tems,theincomingsignalcanbeinvertedbymeansofthepolarityinputPOL.
Thepolaritychosenbyhard–wir-ingthelogiclevelofthispinisalsovalidfortheoutputpinRXD.
Ifforminimizingtheinterfacehardwareanasym-metrybetweenRXDandTXDisdesired,thiscanbeachievedbysettingthemostsignificantbitoftheSpeedControlparametertoa1(seeConfigurationParameterValueCodes).
WiththeMSbitofthespeedcontrolsetto1,thepolarityatTXDisstillselectedbythelogiclevelatPOL,butthepolarityatRXDwillbetheoppositeofwhatthelogiclevelatPOLspecifies.
AsdataentersthecoreoftheDS2480'slogiccircuitry,itisanalyzedtoseparatedataandcommandbytesandtocalibratethedevice'stiminggenerator.
Thetiminggen-eratorcontrolsallspeedrelationsofthecommunicationinterfaceandthe1–Wirebusaswellasthewaveformsonthe1–Wirebus.
Commandbyteseitheraffecttheconfigurationsettingorgeneratecertainwaveformsonthe1–Wirebus.
Databytesaresimplytranslatedbytheprotocolconverterintotheappropriate1–Wireactivities.
Eachdatabytegeneratesareturnbytefromthe1–Wirebus,thatiscommunicatedbacktothehostthroughtheRXDpinassoonastheactivityonthe1–Wirebusiscompleted.
The1–Wiredrivershapestheslopesofthe1–Wirewaveforms,appliesprogrammingpulsesorstrongpull–upto5voltsandreadsthe1–Wirebususinganon–TTLthresholdtomaximizethenoisemarginforbestperformanceonlarge1–WireMicroLANnetworks.
DS24800424983/26DS2480BLOCKDIAGRAMFigure1MUXCONFIGURATIONREGISTERPROTOCOLANALYZERPROTOCOLANALYZERTIMINGGENERATORPROTOCOLCONVERTER1–WIREDRIVERMSBITOFSPEEDCONTROL(1=RXDISINVERTED)VPP1–WRXDPOLTXDDEVICEOPERATIONTheDS2480canbedescribedasacomplexstatemachinewithtwostaticandseveraldynamicstates.
Twodevice–internalflagsaswellasfunctionsassignedtocertainbitpositionsinthecommandcodesdeterminethebehaviorofthechip,asshowninthestatetransitiondiagram(Figure2).
TheDS2480requiresandgener-atesacommunicationprotocolof8databitspercharac-ter,1stopbitandnoparity.
ItispermissibletousetwostopbitsontheTXDline.
However,theDS2480willonlyassertasinglestopbitonRXD.
Whenpoweringup,theDS2480performsamasterresetcycleandenterstheCommandMode,whichisoneofthetwostaticstates.
Thedevicenowexpectstoreceiveone1–WireresetcommandontheTXDlinesentbythehostatadatarateof9600bitspersecond(seesectionCommunicationCommandsfordetails).
ThiscommandbyteisrequiredsolelyforcalibrationofthetiminggeneratortheDS2480andisnottranslatedintoanyactivityonthe1–Wirebus.
Afterthisfirstcom-mandbytethedeviceisreadytoreceiveandexecuteanycommandasdescribedlaterinthisdocument.
Amasterresetcyclecanalsobegeneratedbymeansofsoftware.
Thismaybenecessaryifthehostforanyrea-sonhaslostsynchronizationwiththedevice.
TheDS2480willperformamasterresetcycleequivalenttothepower–onresetifitdetectsstartpolarityinplaceofthestopbit.
Thehosthasseveraloptionstogeneratethiscondition.
TheseincludemakingtheUARTgener-ateabreaksignal,sendingaNULLcharacteratadatarateof4800bpsandsendinganycharacterwithparityenabledandselectingspacepolarityfortheparitybit.
Aswiththepower–onreset,theDS2480requiresa1–Wireresetcommandsentbythehostatadatarateof9600bpsforcalibration.
DS24800424984/26STATETRANSITIONDIAGRAMFigure2INACTIVECOMMANDMODECONFIGURATIONCHECKMODETXARRIVALCODESINGLEBITFUNCTIONSEARCHACCEL.
PULSERESETSOFTWAREMASTERRESETTXE3hTXBYTE110XSS01111T11Q1N.
C.
N.
C.
N.
C.
N.
C.
N.
C.
N.
C.
N.
C.
N.
C.
0ZZZVVV1N.
C.
101HSS01100VSSP1POWERONARRIVALPOWEROFFCODE=E3hE3h100VSSP1101HSS010ZZZVVV1111T11Q1110XSS01E1hALLOTHERCODESACC.
ONSTR.
PULL–UPARMEDACC.
OFFSTR.
PULL–UPNOTARMEDN.
C.
=UNCONDITIONALPOWEROFFGENERATESTRONGPULL–UPTO5VLEGEND:VBINARYVALUE(TYPEOFWRITETIMESLOT)SS1–WIRESPEEDSELECTIONCODEPIFLOGIC1,GENERATESSTRONGPULL–UPTO5VIMMEDIATELYFOLLOWINGTHETIMESLOTTTYPEOFPULSE;0=STRONGPULL–UP(5V),1=PROGRAMMINGPULSE(12V)Q1=ARMSTRONGPULL–UPAFTEREVERYBYTE;0=DISARMHSEARCHACCELERATORCONTROL;1=ACCELERATORON,0=ACCELERATOROFFZZZCONFIGURATIONPARAMETERCODE(WRITE),000=READCONFIGURATIONPARAMETERVVVCONFIGURATIONPARAMETERVALUECODE(WRITE),CONFIGURATIONPARAMETERCODE(READ)XDON'TCARECHECKSEARCHACCELERATORFLAGDATAMODEPERFORMSEARCHSEQUENCEDS24800424985/26AftertheDS2480hasreachedthecommandmode,thehostcansendcommandssuchas1–WireReset,Pulse,Configuration,SearchAcceleratorandSingleBitfunc-tionsorswitchovertothesecondstaticstatecalledDataMode.
IndatamodetheDS2480simplyconvertsbytesitreceivesattheTXDpinintotheirequivalent1–WirewaveformsandreportstheresultsbacktothehostthroughtheRXDpin.
IftheSearchAcceleratorison,eachbyteseenatTXDwillgeneratea12–bitsequenceonthe1–Wirebus(seesectionSearchAcceleratorfordetails).
IftheStrongPull–upto5Visenabled(seePulsecommand)eachbyteonthe1–Wirebuswillbefollowedbyapauseofpredefineddurationwherethebusispulledto5Vviaalowimpedancetran-sistorinthe1–Wiredrivercircuit.
WhilebeingintheDataModetheDS2480checkseachbytereceivedfromthehostforthereservedcodethatisusedtoswitchbacktoCommandMode.
Tobeabletowriteanypossiblecode(includingthereservedone)tothe1–Wirebus,thetransitiontotheCommandModeisasfollows:AfterhavingreceivedthecodeforswitchingtoCommandMode,thedevicetemporarilyenterstheCheckModewhereitwaitsforthenextbyte.
Ifbothbytesarethesame,thebyteissentoncetothe1–WirebusandthedevicereturnstotheDataMode.
Ifthesecondbyteisdifferentfromthereservedcode,itwillbeexecutedascommandandthedevicefinallyenterstheCommandMode.
Asaconsequence,ifthereservedcodethatnormallyswitchestoCommandModeistobewrittentothe1–Wirebus,thiscodebytemustbesenttwice(duplicated).
Thisdetailmustbeconsideredcare-fullywhendevelopingsoftwaredriversfortheDS2480.
Afterhavingcompletedamemoryfunctionwithadeviceonthe1–WirebusitisrecommendedtoissueaResetPulse.
ThismeansthattheDS2480hastobeswitchedtoCommandmode.
Thehostthensendstheappropri-atecommandcodeandcontinuesperformingothertasks.
Ifduringthistimeadevicearrivesatthe1–Wirebusitwillgenerateapresencepulse.
TheDS2480willrecognizethisunsolicitedpresencepulseandnotifythehostbysendingabytesuchasXXXXXX01b.
TheXsrepresentundefinedbitvalues.
Thefactthatthehostreceivesthebyteunsolicitedtogetherwiththepattern01bintheleastsignificanttwobitsmarksthebusarrival.
IftheDS2480isleftinDataModeaftercompletingamemoryfunctioncommanditwillnotreportanybusarrivaltothehost.
COMMANDCODEOVERVIEWTheDS2480iscontrolledbyavarietyofcommands.
Allcommandcodesare8bitslong.
Themostsignificantbitofeachcommandcodedistinguishesbetweencommu-nicationandconfigurationcommands.
Configurationcommandsaccesstheconfigurationregisters.
Theycanwriteorreadanyoftheconfigurableparameters.
Communicationcommandsusedataoftheconfigura-tionregisterinordertogenerateactivityonthe1–Wirebusand/or(dis)armthestrongpull–upaftereverybyteor(de)activatetheSearchAcceleratorwithoutgenerat-ingactivityonthe1–Wirebus.
DetailsonthecommandcodesareincludedintheStateTransitiondiagram(Figure2).
AfullexplanationisgiveninthesubsequentsectionsCommunicationCommandsandConfigura-tionCommands.
Inadditiontothecommandcodesexplainedinthesub-sequentsectionstheDS2480understandsthefollow-ingreservedcommandcodes:E1hswitchtoDataModeE3hswitchtoCommandModeF1hpulseterminationExceptforthesereservedcommands,theSearchAcceleratorcontrolandthefirstbyteafterpower–onresetormasterresetcycle,everylegalcommandbytegeneratesaresponsebyte.
Thepulseterminationcodetriggerstheresponsebyteoftheterminatedpulsecom-mand.
Illegalcommandbytesdonotgenerateacom-mandresponsebyte.
OncethedeviceisswitchedbackfromDataModetoCommandModeonemustnotrepeattheE3hcom-mandwhiletheCommandModeisstillactive.
COMMUNICATIONCOMMANDSTheDS2480supportsfourcommunicationfunctioncommands:Reset,SingleBit,Pulse,andSearchAccel-eratorcontrol.
DetailsontheassignmentofeachbitofthecommandcodesareshowninTable1.
Thecorre-spondingcommandresponsebytesaredetailedinTable2.
TheReset,SearchAcceleratorControlandSingleBitcommandsincludebitstoselectthe1–Wirecommunicationspeed(regular,flexibleregular,Over-drive).
Evenifacommanddoesnotgenerateactivityonthe1–Wirebus,thesebitsarelatchedinsidethedeviceandwilltakeeffectimmediately.
DS24800424986/26COMMUNICATIONCOMMANDCODESTable1FUNCTIONBIT7BIT6BIT5BIT4BIT3,BIT2BIT1BIT0SingleBit1000=write01=write100reg.
speed01flex.
speed10OD.
speed11reg.
speedSeeText1SearchAcceleratorControl1010=acceleratoroff1=acceleratoronSeeText00reg.
speed01flex.
speed10OD.
speed11reg.
speed01Reset110(don'tcare)00reg.
speed01flex.
speed10OD.
speed11reg.
speed01Pulse1110=5Vstrongpull–up1=12Vprog.
pulse11pulseSeeText1COMMUNICATIONCOMMANDRESPONSETable2FUNCTIONBIT7BIT6BIT5BIT4BIT3BIT2BIT1BIT0SingleBit100sameassent1–Wirereadback,bothbitssamevalueReset11SeeText01000=1–Wireshorted01=presencepulse10=alarmingpresencepulse11=nopresencepulsePulse111sameassentundefined(TheSearchAcceleratorControlcommanddoesnotgeneratearesponsebyte.
)ResetTheResetcommandmustbeusedtobeginall1–Wirecommunication.
Thespeedselectionincludedinthecommandcodeimmediatelytakeseffect.
Theresponsebyteincludesacodeforthereactiononthe1–Wirebus(bits0and1)andacodeforthechiprevision(bits2to4).
Ifbit5oftheresponsebytereads'1',aprogrammingvoltageispresentontheVPPpin,indicatingthatonemaytryprogrammingEPROMdevices.
SingleBitTheSingleBitcommandisusedtogenerateasingletimeslotonthe1–Wirebusatthespeedindicatedbybits2and3.
Thetypeofthetimeslot(writezeroorwriteone)isdeterminedbythelogicvalueofbit4.
Areaddatatimeslotisidenticaltothewriteonetimeslot.
Bits0and1oftheresponsebytetransmittedbytheDS2480attheendofthetimeslotrevealthevaluefoundonthe1–Wirebuswhenreading.
Foratimeslotwithoutasubsequentstrongpull–up,bit1ofthecommandmustbesetto0.
Foratimeslotimmedi-atelyfollowedbyastrongpull–upbit1mustbesetto1.
Assoonasthestrongpull–upisover,thedevicewillsendasecondresponsebyte,codeEFh(read1)orECh(read0),dependingonthevaluefoundonthe1–Wirebuswhenreading.
Thestrongpull–updirectlyfollowingthesinglebitisusedinconjunctionwiththeCryptoiButton.
SearchAcceleratorControlTheSearchAcceleratorControlcommandisusedtosetorresettheSearchAcceleratorcontrolflag.
Bit4ofthecommandcodecontainsthestatetowhichtheacceler-DS24800424987/26atorcontrolflagistobeset.
Iftheflagissettoa1(on)thedevicetranslateseverybytereceivedindatamodeintoa12–bitsequenceonthe1–Wirebus.
FordetailsonhowtheSearchAcceleratorworkspleaserefertothesectionSearchAcceleratorOperation.
Beforeactivat-ingtheSearchAccelerator,onemustmakesurethatthestrongpull–upaftereverybyteisdisarmed(seePulseCommand).
TheSearchAcceleratorcommanddoesnotgenerateacommandresponsebyte.
AlthoughtheSearchAcceleratorControlcommanditselfdoesnotgenerateany1–Wireactivity,itcanbeusedtoselectthecommunicationspeedonthe1–Wirebus.
Thespeedselection(ifdifferentfromtheprevioussetting,e.
g.
,fromaResetcommand)willtakeeffectimmediately.
PulseThePulsecommandservesseveralfunctionsthatareselectedbythecontentsofbit1andbit4ofthecom-mandcode.
Themainfunctionsaregeneratingastrongpull–upto5Vandgenerating12VprogrammingpulsesforEPROMdevices(ifthe12VareavailableattheVPPpin).
Thesecondaryfunctionofthepulsecommandisarminganddisarmingastrongpull–upaftereverysub-sequentbyteindatamode.
Thearm/disarmfunctioniscontrolledbybit1ofthecommandcode.
Bit4deter-mineswhetherthedevicewillgenerateastrongpull–upto5Vora12Vprogrammingpulse.
Thetablebelowsummarizestheseoptions.
BIT4BIT1FUNCTION00strongpull–upto5Vanddisarm1012VProgrammingPulseanddisarm01strongpull–upto5Vandarm1112VProgrammingPulseandarmThestrongpull–upto5VisrequiredtoprogramEEPROMdevicesortooperatespecialfunctiondevicesthatrequireahighercurrentforalimitedtimeafterhavingreceiveda"goandconvert"command.
Thereforeandbecauseitsignificantlyreducestheeffectivedatathroughputonthe1–Wirebus,thestrongpull–upisdisarmedmostofthetime.
Althougharmingordisarmingissimultaneouslypossiblewhilegeneratingaprogrammingpulse,thisisnotrecommendedsinceitislikelytodestroytheDS2480ifnon–EPROMdevicesareconnectedtothe1–Wirebus.
Thedurationofthestrongpull–uporprogrammingpulseisdeterminedbyconfigurationparametersandrangesfromafewmicrosecondsuptounlimited(seesectionConfigurationCommands).
However,unlimiteddurationisnotallowedinconjunctionwitharmingthestrong–pull–upaftereverybyte.
AslongastheDS2480isinCommandModethehostmayterminateastrongpull–uporprogrammingpulseprematurelyatanytimebysendingthecommandcodeF1h.
Theresponsebyteisgeneratedassoonasthestrongpull–uporprogrammingpulseisover(eitherbecausethepredefinedtimehaselapsedorduetotermination).
Theresponsebytemainlyreturnsthecommandcodeassentbythehost,butthetwoleastsignificantbitsareundefined.
Ifthestrongpull–upisarmedandthedeviceisinDataMode,theendofthestrongpull–upwillbesignaledascodeF6hifthemostsignificantbitoftheprecedingdatabyteonthe1–Wirebuswasa1and76hotherwise.
Thehostwillseethisresponsebyteinadditiontotheresponseonthedatabytesent(seealsosectionWaveFormslaterinthisdocument).
SEARCHACCELERATORINTRODUCTIONTheSearchAcceleratorisalogicblockinsidetheDS2480thatallowsusingtheSearchROMfunctionveryefficientlyundermodernoperatingsystemssuchasWindowsandWindows95/NT.
WithouttheDS2480all1–Wireportadaptershavetoinvolvethecomputer'sCPUforeverysingletimeslotorpulsetobegeneratedonthe1–Wirebus.
UnderDOS,accessingperipheralssuchastheUARTorparallelportisverystraightforwardandthereforefast.
UnderWindowsthesituationisdifferentanditmaytakeseveralmillisecondsormoretogetthefirsttimeslotgeneratedonthe1–Wirebus.
Everysubsequenttimeslotwillbegeneratedinmuchlesstime,sincethecomputersimplysendsout("streams")alongchainofbytes.
Thisworksreasonablywellwhenreadingorwrit-inglargeblocksofdata.
DS24800424988/26Searchingthe1–WirebustoidentifyallROMIDsofthedevicesconnected,however,requiresreadingtwobits,makingadecisionandthenwritingabit.
Thisprocedureistoberepeated64timestoidentifyandaddressasingledevice.
Withtheoverheadofmodernoperatingsystemsthisfairlysimpleprocesstakesalotoftime,reducingthediscoveryrateofdevicesonthe1–Wirebusfromatypicalvalueof40to50persecondunderDOStolessthan10underWindows.
Tosolvethisprob-lemtheSearchAcceleratorwasdeveloped.
TheSearchAcceleratorreceivesfromthehostinforma-tiononthepreferredpathtochoseduringtheexecutionoftheSearchROMfunctionasonecontiguouschainofbytesandthentranslatesitintotheappropriatetimeslotsonthe1–Wirebus.
Inaddition,theSearchAcceler-atorreportsbacktothehosttheROMIDofthedeviceactuallyaddressedandthebitpositionsinwhichcon-flictswerefound.
(IftheROMIDofonedevicehasa0inabitpositionwhereanotherdevicehasa1,thisiscalleda"conflict"ontheelectricalleveland"discrepancy"onthelogicallevel.
SeetheBookofDS19xxiButtonStan-dardsforamoredetaileddiscussionoftheSearchROM).
ThishelpsthehosttoselectthepreferredpathforthenextSearchROMactivity.
SincetheROMIDofallMicroLANcompatibledevicesis64bitslongandaconflictmayoccurinanyofthesebits,thetotallengthofdatareportedtothehostis128bitsor16bytes.
Toavoiddataoverrun(iftheCPUsendsdatafasterthanitcanbeprocessed)theprotocolfortheSearchAcceleratoroperationwasdefinedsothatonehastosendasmanybytesasonewillreceive.
ThiswaytheCPUsends16bytesforeachpathandtheUARTguaranteesthecorrectdatatimingandfreestheCPUforothertaskswhiletheDS2480performsaSearchROMfunction.
SEARCHACCELERATOROPERATIONAftertheSearchAcceleratorisactivatedandthedatamodeisselected,thehostmustsend16bytestocom-pleteasingleSearchROMpassonthe1–Wirebus.
Thesebytesareconstructedasfollows:firstbyte76543210r3x3r2x2r1x1r0x0etcetera16thbyte76543210r63x63r62x62r61x61r60x60Inthisscheme,theindex(valuesfrom0to63,"n")des-ignatesthepositionofthebitintheROMIDofaMicro-LANcompatibledevice.
Thecharacter"x"marksbitsthatactasfilleranddonotrequireaspecificvalue(don'tcarebits).
Thecharacter"r"marksthepathtogoatthatparticularbitincaseofaconflictduringtheexecutionoftheROMSearch.
Foreachbitpositionn(valuesfrom0to63)theDS2480willgeneratethreetimeslotsonthe1–Wirebus.
Thesearereferencedas:b0forthefirsttimeslot(readdata)b1forthesecondtimeslot(readdata)andb2forthethirdtimeslot(writedata).
Thetypeoftimeslotb2(write1orwrite0)isdeterminedbytheDS2480asfollows:b2=rnifconflict(aschosenbythehost)=b0ifnoconflict(thereisnoalternative)=1iferror(thereisnoresponse)TheresponsethehostwillreceiveduringacompletepassthroughaSearchROMfunctionusingtheSearchAcceleratorconsistsof16bytesasfollows:firstbyte76543210r'3d3r'2d2r'1d1r'0d0etcetera16thbyte76543210r'63d63r'62d62r'61d61r'60d60Asbefore,theindex(valuesfrom0to63,"n")desig-natesthepositionofthebitintheROMIDofaMicroLANcompatibledevice.
Thecharacter"d"marksthediscrep-ancyflaginthatparticularbitposition.
Thediscrepancyflagwillbe1ifthereisaconflictornoresponseinthatparticularbitpositionand0otherwise.
Thecharacter"r'"markstheactuallychosenpathatthatparticularbitposition.
Thechosenpathisidenticaltob2forthepartic-ularbitpositionoftheROMID.
DS24800424989/26ToperformaSearchROMsequenceonestartswithallbitsrnbeing0s.
Incaseofabuserror,allsubsequentresponsebitsr'nare1'suntiltheSearchAcceleratorisdeactivated.
Thus,ifr'63andd63areboth1,anerrorhasoccurredduringthesearchprocedureandthelastsequencehastoberepeated.
Otherwiser'n(n=0.
.
.
63)istheROMcodeofthedevicethathasbeenfoundandaddressed.
ForthenextSearchROMsequenceonere–usestheprevioussetrn(n=0.
.
.
63)butsetsrmto1with"m"beingtheindexnumberofthehighestdiscrepancyflagthatis1andsetsallrito0withi>m.
Thisprocessisrepeateduntilthehighestdiscrepancyoccursinthesamebitpositionfortwoconsecutivepasses.
Thetablebelowshowsanexampleforthecommunica-tionbetweenhostandDS2480toperformonepassthroughtheSearchROMfunctionusingtheSearchAccelerator.
Afteradevicehasbeenidentifiedandaddressed,a(notspecifiedhere)memoryfunctionisexecutedandfinallyaresetpulseisgenerated.
ThisexampleassumesthattheDS2480wasinCommandModeandthatregular1–Wirespeedisused.
SearchAcceleratorUsageExampleActionSequenceHostTXHostRXGenerateResetPulseC1C9SetDataModeE1(nothing)SearchROMcommandF0(assent)SetCommandModeE3(nothing)SearchAcceleratorOnB1(nothing)SetDataModeE1(nothing)Send16bytesdataresponseSetCommandModeE3(nothing)SearchAcceleratorOffA1(nothing)SetDataModeE1(nothing)DoMemoryFunctionSetCommandModeE3(nothing)GenerateResetPulseC1C9CONFIGURATIONCOMMANDSTheDS2480isdesignedtobeconfigurableforthevary-ingrequirementsofitsapplication.
Whenthedevicepowersupand/orperformsamasterresetcycle,thehard–wireddefaultconfigurationsettingstakeeffect.
Thesesettingswillworkonashort1–Wirebusandassumeregular1–Wirecommunicationspeed.
Tochangethesedefaultsettingsandtoverifythecurrentsettings,thelogicoftheDS2480supportsconfigurationcommands.
Asummaryoftheavailableconfigurationparameters,theirdefaultsettingsatregularandOver-drivespeedandtheirapplicabilityisshowninTable3.
Parametersnotrelatedtothecommunicationspeedonthe1–Wirebusspecifythedurationofthe12Vprogram-mingpulse,thedurationofthestrongpull–upto5VandthebaudrateontheinterfacethatconnectstheDS2480tothehost.
Theremainingthreeparametersareusedtomodifythe1–Wirecommunicationwaveformsifoneselects"FlexibleSpeed"(see"CommunicationCom-mands"forspeedselection).
Flexiblespeedisimplementedtoimprovetheperfor-manceoflargeMicroLANNetworks.
Thisisaccom-plishedby:limitingtheslewrateonfallingedges(e.
g.
,atthebeginningoftimeslots,toreduceringing),extendingtheWrite1lowtime(allowsthecurrentflowthroughthenetworktoendslowly,topreventvoltagespikesfrominductivekickback),delayingthetimepointwhenreadingabitfromthe1–Wirebus(givesthenetworkmoretimetostabilize,togetahighervoltagemargin)andaddingextrarecoverytimebetweenWrite0timeslots(allowsmoreenergytransferthroughthenetwork,toreplenishtheparasitepowersupplyofthedevicesonthebus).
Thelattertwofunctionsarecontrolledbyasingleparameter.
Takingadvantageofflexiblespeedrequireschangingoneormoreoftheseparametersfromtheirdefaultvalues.
Otherwisethewaveformswillbeidenti-caltothoseatregularspeed.
Eachconfigurationparameterisidentifiedbyits3–bitparametercodeandcanbeprogrammedforoneofamaximum8differentvaluesusinga3–bitvaluecode.
AmatrixofparametercodesandvaluecodeswiththeassociatedphysicalvaluesinshowninTable4.
DS248004249810/26CONFIGURATIONCOMMANDOVERVIEWTable3PDiiPCdConfigurableatDefaultParameterDescriptionPar.
CodeRegularFlexibleOverdriveReg.
/Flex.
OverdrivePull–DownSlewRateControl001√15V/s15V/sProgrammingPulseDuration010√√√512s512sStrongPull–upDuration011√√√524ms524msWrite1lowtime100√8s1sDataSampleOffsetandWrite0RecoveryTime101√3s3s1s3sRS232BaudRate111√√√9.
6kbits/s9.
6kbits/sThenumbersgivenforparameter001(Pull–DownSlewRateControl)arenominalvalues.
TheymayvaryasspecifiedintheElectricalCharacteristicssectionandarealmostindependentoftheloadonthe1–Wirebus.
Informationonhowtoselecttheoptimumvalueofthisparameterisgiveninsection"ControlledEdges".
Fortheparameters010(ProgrammingPulseDuration)and011(StrongPull–UpDuration)onemayselectindefiniteduration.
Thisvalue,however,shouldonlybeselectedifoneisnotgoingtoswitchthedevicetoDataMode.
AslongasthedevicestaysinCommandMode,anypulsefunction(programmingorstrongpull–up)thatusesoneoftheseparameterscanbeterminatedbysendingthecommandcodeF1h.
Terminationisnotpos-sibleifthedeviceisinDataMode.
Parameter111(RS232BaudRate)hastwofunctions.
ItselectsthebaudrateandallowsinversionofthesignalattheRXDpin.
Usingoneofthevaluecodes100to111willsetthepolarityatRXDtotheoppositeofwhatisdefinedbythelogiclevelatthePOLpin(asymmetrybit,seeFigure1).
Thismayreducethecomponentcountinsomeapplicationsofthedevice.
Notethatwhenchang-ingthebaudrate,theDS2480willsendthecommandresponsebyteatthenewdatarate.
Ashortexplanationontheuseofparameters100(Write1lowtime)and101(DataSampleOffset/Write0Recov-eryTime)isgiveninthesection"TimingDiagrams"laterinthisdocument.
Theparametercode110isreservedforfutureextensions;oneshouldnotchangethevaluecodefromitsdefaultsetting.
CONFIGURATIONPARAMETERVALUECODESTable4PCdValueCodesUiParameterCode000001010011100101110111Unit001(PDSRC)152.
21.
651.
371.
10.
830.
70.
55V/s010(PPD)326412825651210242048∞s011(SPUD)16.
465.
513126252410482096∞ms100(W1LT)89101112131415s101(DSO/W0RT)345678910s111(RBR)9.
619.
257.
6115.
29.
619.
257.
6115.
2kbits/sDS248004249811/26Thesyntaxofconfigurationcommandsisverysimple.
Each8–bitcodewordcontainsa3–bitparametercodetospecifytheparameterandthe3–bitvaluecodetobeselected.
Bit7ofthecommandcodeissetto0andbit0isalwaysa1.
Toreadthevaluecodeofaparameter,onewritesallzerosfortheparametercodeandputstheparametercodeinplaceoftheparametervaluecode.
Table5showsthedetails.
Theconfigurationcommandresponsebyteissimilartothecommandbyteitself.
Bit0oftheresponsebyteisalways0.
Whenwritingaparameter,theupper7bitsaretheechoofthecommandcode.
Whenreadingaparam-eter,thecurrentvaluecodeisreturnedinbitpositions1to3withtheupper4bitsbeingthesameassent(seeTable6).
CONFIGURATIONCOMMANDCODESTable5FUNCTIONBIT7BIT6BIT5BIT4BIT3BIT2BIT1BIT0WriteParameter0parametercodeparametervaluecode1ReadParameter0000parametercode1CONFIGURATIONCOMMANDRESPONSEBYTETable6FUNCTIONBIT7BIT6BIT5BIT4BIT3BIT2BIT1BIT0WriteParameter0sameassentsameassent0ReadParameter0sameassentparametervaluecode0DS248004249812/26CONTROLLEDEDGESOneofthetasksoftheDS2480istoactivelyshapetheedgesofthe1–Wirecommunicationwaveforms.
Thisspeedsuptherechargingofthe1–Wirebus(risingedges)andreducesringingoflonglines(fallingedges).
Thecircuitryforshapingrisingedgesisalwayson.
Theslewrateoffallingedgesisactivelycontrolledonlyatflexiblespeedandrequirestheparameterforslewratecontrolbeingdifferentfromitspower–ondefaultvalue.
AllRisingEdgesTheactivepull–upoftherisingedgesreducestherisetimeonthe1–Wirebussignificantlycomparedtoasim-pleresistivepull–up.
Figure4showshowtheDS2480isinvolvedinshapingarisingedge.
ACTIVEPULL–UPFigure45VVIAPTOVIAPO0V1–WIREBUSISDISCHARGEDt1t2t3tAPUOTThecircuitoperatesasfollows:Att1thepull–down(inducedbytheDS2480oradeviceonthebus)ends.
Fromthispointonthe1–Wirebusispulledhighbytheweakpull–upcurrentIWEAKPUprovidedbytheDS2480.
Theslopeisdeterminedbytheloadonthebusandthevalueofthepull–upcurrent.
Att2thevoltagecrossesthethresholdvoltageVIAPO.
NowtheDS2480switchesoverfromtheweakpull–upcurrentIWEAKPUtothehighercurrentIACTPU.
Asaconsequence,thevoltageonthebusnowrisesfaster.
AsthevoltageonthebuscrossesthethresholdVIAPTOatt3,atimerisstarted.
Aslongasthistimerison(tAPUOT),theIACTPUcurrentwillcontinuetoflow.
Afterthetimerisexpired,theDS2480willswitchbacktotheweakpull–upcurrent.
FallingEdges(DS2480–initiated)WhenevertheDS2480beginspullingthe1–Wirebuslowtoinitiateatimeslot,forexample,itfirstturnsofftheweakpull–upcurrentIWEAKPU.
Then,atregularandOverdrivespeeditwillgenerateafallingedgeataslewrateoftypically15V/s.
Thisvalueisacceptableforshort1–WirebussesandadequateforcommunicationatOverdrivespeed.
ForMicroLANnetworksofmorethanroughly30meterslengthoneshouldalwaysuseflexiblespeed.
OneoftheparametersthatisadjustableatflexiblespeedistheslewrateofDS2480–initiatedfal-lingedges.
TheeffectoftheslewratecontrolisshowninFigure5.
SLEWRATECONTROLFigure55VHIGHSLEWRATE0.
8V0V1–WIREBUSISPULLEDUPWEAKPULL–UPENDS,PULL–DOWNBEGINSt1LOWSLEWRATETARGETFORLONGLINES:4±0.
5stFAsextensivetestshaveshown,MicroLANnetworksatalengthofupto300meterswillperformbestifthefalltimetFisintherangeof4±0.
5s.
Thistranslatesintoaslewrateofapproximately1V/s.
Thisslewrateistypicallyachievedbysettingtheconfigurationparameter001(Pull–DownSlewRateControl)toavalueof100(seeTable4).
Iftheactualmeasuredfalltimeislongerthanthetargetvalue,oneshoulduseavaluecodeof011orlower.
Ifthefalltimeisshorter,oneshoulduseavaluecodeof101orhigher.
Oncedetermined,thevaluecodeforthePull–DownSlewRateControlparametershouldbestoredinthehostandalwaysbeloadedintotheDS2480afterapower–onormasterresetcycle.
DS248004249813/26TIMINGDIAGRAMSThissectionexplainsthewaveformsgeneratedbytheDS2480onthe1–Wirebusindetail.
Firstthecommu-nicationwaveformssuchastheReset/PresenceDetectSequenceandthetimeslotsarediscussed.
Afterthatfollowsadetaileddescriptionofthepulsefunctionundervariousconditions.
ThewaveformsasgeneratedbytheDS2480maydeviateslightlyfromspecificationsfoundinthe"BookofDS19xxiButtonStandards"orindatasheetsof1–Wireslavedevices.
However,atacloserlookonewillfindthatallofthetim-ingrequirementsaremet.
1–WIRECOMMUNICATIONWAVEFORMSOneofthemajorfeaturesoftheDS2480isthatitrelievesthehostfromgeneratingthetimingofthe1–Wiresignalsandsamplingthe1–Wirebusattheappropriatetimes.
Howthisisdoneforthereset/pres-encedetectsequenceisshowninFigure6a.
Thissequenceiscomposedoffourtimingsegments:theresetlowtimetRSTL,theshort/interruptsamplingoffsettSI,thepresencedetectsamplingoffsettPDTandadelaytimetFILL.
ThetimingsegmentstSI,tPDTandtFILLcom-prisetheresethightimetRSTHwhere1–Wireslavedevicesasserttheirpresenceorinterruptpulse.
DuringthistimetheDS2480pullsthe1–Wirebushighwithitsweakpull–upcurrent.
Thevaluesofalltimingsegmentsforall1–Wirespeedoptionsareshowninthetable.
Sincethereset/presencesequenceisslowcomparedtothetimeslots,thevaluesforregularandflexiblespeedarethesame.
Exceptforthefallingedgeofthepresencepulsealledgesarecon-trolledbytheDS2480.
Theshapeoftheuncontrolledfallingedgeisdeterminedbythecapacitanceofthe1–Wirebusandthenumber,speedandsinkcapabilityoftheslavedevicesconnected.
Reset/PresenceDetectFigure6aTESTINGFORSHORTAND/ORINTERRUPTPRESENCETESTINGUNCONTROLLEDFALLINGEDGEtSIRESET/PRESENCESEQUENCEtRSTHtRSTLPRESENCEPULSE5V0VtFILLTIMESLOTIDLETIMEtPDTSpeedtRSTLtSItPDTtFILLtRSTHRegular512s8s64s512s584sOverdrive64s2s8s64s74sFlexible512s8s64s512s584sAfterhavingreceivedthecommandcodeforgeneratingareset/presencesequence,theDS2480pullsthe1–WirebuslowfortRSTLandthenletsitgobackto5V.
TheDS2480willnowwaitfortheshort/interruptsam-plingoffsettSItoexpireandthentestthevoltageonthe1–Wirebustodetermineifthereisashortoraninterruptsignal.
Ifthereisnoshortorinterrupt(asshowninthepicture),theDS2480willwaitfortPDTandtestthevolt-ageonthe1–Wirebusforapresencepulse.
Regardlessoftheresultofthepresencetest,theDS2480willthenwaitfortFILLtoexpireandthensendthecommandresponsebytetothehost.
Ifthetestforinterruptorshortrevealsalogic0,theDS2480willwaitfor4096sandthentestthe1–Wirebusagain.
Ifalogic0isdetected,the1–WirebusisshortedandacommandresponsebytewiththecodeforSHORTwillbesentimmediately.
Ifalogic1isdetected,thedevicewillwaitfortFILLtoexpireafterwhichitwillsendthecommandresponsebytewiththecodeforanalarmingpresencepulse.
Noadditionaltestingforapresencepulsewillbedone.
TheDS2480willperformtheshort/interrupttestingasdescribedalsoatOver-drivespeed,althoughinterruptsignalingisonlydefinedforregularspeed.
DS248004249814/26TheidletimefollowingtheReset/PresenceDetectsequencedependsontheserialcommunicationspeedandthehost'sresponsetime.
AWrite1andReadDatatimeslotiscomprisedofthesegmentstLOW1,tDSOandtHIGH.
Duringwrite1timeslots,afterthewrite1lowtimetLOW1isover,theDS2480waitsforthedurationofthedatasampleoffsetandthensamplesthevoltageatthe1–Wirebustoreadtheresponse.
Afterthis,thewaitingtimetHIGH1mustexpirebeforethetimeslotiscomplete.
AWrite0timeslotonlyconsistsofthetwosegmentstLOW0andtREC0.
Ifthenetworkislargeorheavilyloaded,oneshouldselectflexiblespeedandextendtLOW1tomorethan8stoallowthe1–Wirebustocompletelydischarge.
Sincealargeorheavilyloadednetworkneedsmoretimetorecharge,itisalsorecommendedtodelaysam-plingthebusforreading.
AhighervaluefortDSOwillincreasethevoltagemarginandalsoprovideextraenergytotheslavedeviceswhengeneratingalongseriesofwrite0timeslots.
However,thetotaloftLOW1+tDSOshouldnotexceed22s*.
Otherwisetheslavedevicerespondingmayhavestoppedpullingthebuslowwhentransmittingalogic0.
Theidletimebetweentimeslotswithinabyteorduringa12–bitsequencewhiletheSearchAcceleratorisoniszero.
Betweenbytes,12–bitsearchsequencesandsinglebitstheidletimedependsontheRS232datarateandthehost'sresponsetime.
Theresponsebyteissenttothehostassoonasthelasttimeslotofabyte,12–bitsequenceorthecommandiscompleted.
WRITE1ANDREADDATATIMESLOTFigure6btHIGH1tLOW1tDSOTIMESLOTDURATIONtSLOTNEXTT.
S.
IDLETIMESAMPLING5V0VSpeedtLOW1tDSOtHIGH1tSLOT*Regular8s3s49s60sOverdrive1s1s8s10sFlexible8to15s3to10s49s60to74sWRITE0TIMESLOTFigure6cTIMESLOTDURATIONtSLOTIDLETIMEtRECOtLOW0NEXTT.
S.
5V0VSpeedtLOW0*tREC0tSLOT*Regular57s3s60sOverdrive7s3s10sFlexible57s3to10s60to67s*Ina5Venvironment(±1V,fulltemperaturerange)thetoleranceoftheinternaltimebaseof1–Wireslavedevicesismuchnarrowerthanwhatitiswhenoperatedattheminimumvoltageof2.
8V.
Therefore,thetiminggeneratedbytheDS2480isincompliancewiththerequirementsofallMicroLAN–compatible1–Wiredevices.
DS248004249815/26PULSEWAVEFORMS,DISARMEDThepulsecommandcanbeusedtogenerateastrongpull–upto5Vanda12Vprogrammingpulse,respec-tively.
Thedurationofthepulseispredefinediftheparametervaluecodeofparameter010(ProgrammingPulseDuration)andparameter011(StrongPull–UpDuration),hasavaluefrom000to110(seeTable4).
Figures7aand7bshowthetimingofapulsewithprede-finedduration,whichshouldbeconsideredthenormalcase.
Ifaninfinitedurationischosen(parametervaluecode111),thehostmustterminatethepulsecommand,asshowninFigures7cand7d.
AllversionsofFigure7assumethatbit1ofthepulsecommandis0,i.
e.
,dis-armedmode.
SeesectionCommunicationCommands,Pulse,formoredetailsonpossibilitiesofthepulsecommand.
STRONGPULL–UPTO5V,PREDEFINEDDURATIONFigure7aENDOFPREVIOUSTIMESLOT5V0VBEGINOFNEXTTIMESLOTtSPUt1t2t3t4IDLETIMEIDLETIMETheprocessingofapulsecommandisessentiallythesame,regardlessifastrongpull–uporaprogrammingpulseisrequested.
Att1thehoststartssendingthepulsecommandbyte.
Att2theDS2480hasreceivedthecommandandimmediatelygeneratesthepulse.
Thepulseendsatt3andtheDS2480sendsoutthecom-mandresponsebytetoinformthehostthatthecom-mandiscompleted.
Theidletimebetweent1andt2isdeterminedbythetimetotransmitthecommandbyteattheselectedbaudrate.
Theidletimebetweent3andt4iscomprisedofthetimetotransmittheresponsebyte,plustheresponsetimeofthehostplusthetimetotrans-mitthecommandand/ordatatogeneratethenexttimeslot.
12VPROGRAMMINGPULSE,PREDEFINEDDURATIONFigure7bt1t3t4t2tPP5VENDOFPREVIOUSTIMESLOTBEGINOFNEXTTIMESLOT12V0VSTEEPSLOPESIDLETIMEIDLETIMEAcorrectprogrammingpulsecanonlybegeneratedifthe12VprogrammingvoltageisavailableattheVpppinoftheDS2480.
Theslewrateoftherisingandfallingedgeoftheprogrammingpulse("steepslopes")isnotactivelycontrolledbyDS2480.
ForEPROMprogramming,onlyasingleslavedeviceshouldbeconnectedtothe1–Wirebusandthecablemusttobeshort,nottoexceedafewmeters.
Oneshouldnotattemptgeneratingaprogrammingpulsewithanon–EPROMdeviceonthebus;thismaydam-agethedeviceaswellastheDS2480.
DS248004249816/26Certainapplicationsmayrequireadurationforastrongpull–uporprogrammingpulsethatcannotberealizedusingoneofthepredefinedvalues.
Selectinginfinitedurationallowsthehosttogeneratepulsesofanylength.
Asaconsequence,however,thehostbecomesresponsibletoactivelycontrolthedurationofthepulse.
Failingtodosomayrequireapower–onresetormasterresetcycleoftheDS2480.
Forthisreason,infinitedura-tionshouldonlybeusedifabsolutelynecessary.
ThetimetoendapulseofinfinitedurationstronglydependsonthebaudrateofthecommunicationbetweenhostandDS2480.
Neglectingtheresponsetimeofthehost,theminimumpulsedurationsare:86.
8sat115.
2kbps,173.
6sat57.
6kbps,520sat19.
2kbpsand1.
04msat9.
6kbps.
STRONGPULL–UPTO5V,INFINITEDURATIONFigure7cENDOFPREVIOUSTIMESLOT5V0VBEGINOFNEXTTIMESLOTSTRONGPULL–UPONt1t2t3t4IDLETIMEIDLETIMEAsbefore,processingthecommandisessentiallythesame,regardlessifitisforastrongpull–uporapro-grammingpulse.
Att1thehoststartssendingthepulsecommandbyte.
Att2theDS2480hasreceivedthecom-mandandimmediatelyactivatesthestrongpull–uporswitchesinthe12Vprogrammingvoltage.
Toendthepulse,theDS2480mustreceiveaterminationcom-mand,codeF1h,whichoccursatt3.
Theterminationcommanddoesnotgeneratearesponsebyte.
TheDS2480willimmediatelyendthepulseandsendouttheresponsebyteofthepulsecommand.
Theidletimebetweent1andt2isdeterminedbythetimetotransmitthecommandbyteattheselectedbaudrate.
Theidletimebetweent3andt4iscomprisedofthetimetotrans-mitthepulseresponsebyte,plustheresponsetimeofthehostplusthetimetotransmitthecommandand/ordatatogeneratethenexttimeslot.
12VPROGRAMMINGPULSE,INFINITEDURATIONFigure7dt1t3t4t25VENDOFPREVIOUSTIMESLOTBEGINOFNEXTTIMESLOT12V0VSTEEPSLOPESPROGRAMMINGVOLTAGEISAPPLIEDIDLETIMEIDLETIMEDS248004249817/26PULSEWAVEFORM,ARMEDAsexplainedinsectionCommunicationCommands,bit1ofthepulsecommandallowsthearmingofastrongpull–upto5Vifthebitissetto1.
Ifthestrongpull–upisarmedandthedeviceisswitchedtodatamode,therewillbeastrongpull–upimmediatelyfollowingeverybyteonthe1–Wirebus.
ThismodeisimplementedtoprovideextraenergywhenwritingtoEEPROMdevicesortodoatemperatureconversionwiththeDS1920Tempera-tureiButton,forexample.
Thesedevicesneedastrongpull–upimmediatelyafterthepower–consumingactivityhasbeeninitiatedbyacommandcode.
Toarmthestrongpull–up,oneusuallygeneratesa"dummy"pulsewithbit1being1whilethedeviceisincommandmode.
Tosavetime,thedummypulsemayimmediatelybeterminatedbysendingtheterminationcommand,codeF1h.
Thenoneswitchestodatamodeandsendsacommandcodethatmakesoneormoreslavesonthe1–Wirebusrequireextraenergy.
Afterthecommandexecutionisfinished,oneswitchesbacktocommandmodeanddisarmsthestrongpull–upbygen-eratinganotherdummypulse.
AcompletetemperatureconversionsequencethatshowstheuseofthearmedpulseisincludedinSection"SoftwareDriverExamples".
STRONGPULL–UPTO5V,ARMED,PREDEFINEDDURATIONFigure8ENDOF8thTIMESLOT5V0VIDLETIMEBEGINOFNEXTTIMESLOTtSPUt1t2t3Figures8showsthetimingofthestrongpull–upindatamode.
Att1the8thtimeslotofthebytesenttothe1–Wirebusiscompleted.
WithoutanydelaytheDS2480nowactivatesthestrongpull–upandsimulta-neouslystartssendingthedataresponsebytetothehost.
Att2thestrongpull–upendsandtheDS2480sendsapulseresponsebytetothehost.
Theidletimebetweent2andt3iscomprisedofthetimetotransmitthepulseresponsebyte,plustheresponsetimeofthehostplusthetimetotransmitthecommandand/ordatatogeneratethenexttimeslot.
Sinceindatamodethepulseterminationcommandisnotapplicable,thedurationofthestrongpull–upmustbelimited.
SeeTable4,parameter011(StrongPull–UpDuration)fordetails.
Selectinginfinitedurationwillrequireapower–onormasterresetcycletogettheDS2480backtocommunicatingwiththehost.
DS248004249818/26SINGLEBITWITHSTRONGPULL–UPSimilartothepulsecommandtheSingleBitcommandalsoallowsgeneratingastrongpull–upimmediatelyfol-lowingatimeslot.
Thestrongpull–upoftheSingleBitcommand,however,iscontrolleddirectlybybit1ofthecommandcodeandthereforeneedsnotbearmed.
SincetheDS2480remainsincommandmodewhenusingtheSingleBitcommand,anydurationofthestrongpull–upincludinginfinitemaybeselected.
Figure9showsthetimingoftheSingleBitcommandwiththeimmediatelyfollowingstrongpull–up.
Strongpull–upimmediatelyfollowingasingletimeslotisimple-mentedtosupporttheDS1954CryptoiButton.
Afterhavingreceivedthecommandcodetorunaprogram,theCryptoiButtonsendsoutanacknowledgebitandthenstartsthemicrocomputertorunthefirmwarepro-gramforapredefinedtime.
SINGLEBITWITHSTRONGPULL–UP,PREDEFINEDDURATIONFigure9aENDOFPREVIOUSTIMESLOT5V0VIDLETIMEBEGINOFNEXTACTIVITYtSPUt1t2t3Forpredefinedduration(Figure9a)thetimingisasfol-lows:Att1thetimeslotiscompleted.
NowtheDS2480activatesthestrongpull–upandsimultaneouslystartssendingtheresponsebyteoftheSingleBitcommandtothehost.
Att2thestrongpull–upendsandtheDS2480sendsoutapulseresponsebyte.
Theidletimebetweent2andt3iscomprisedofthetimetotransmitthepulseresponsebyte,plustheresponsetimeofthehostplusthetimetotransmitthecommandand/ordatatogener-atethenexttimeslot.
Forinfiniteduration(Figure9b)thestrongpull–upalsobeginsimmediatelyafterthetimeslotiscompleted.
Toendthestrongpull–up,theDS2480mustreceiveater-minationcommand,codeF1h,whichoccursatt2.
Theterminationcommanddoesnotgeneratearesponsebyte.
TheDS2480willthenimmediatelyendthestrongpull–upandsendoutapulseresponsebyte.
Everythingelseisthesameaswithpredefinedduration.
SINGLEBITWITHSTRONGPULL–UP,INFINITEDURATIONFigure9bENDOFPREVIOUSTIMESLOT5V0VIDLETIMEBEGINOFNEXTACTIVITYSTRONGPULL–UPONt1t2t3Theminimumdurationofastrongpull–upofinfinitedurationstronglydependsonthebaudrateofthecom-municationbetweenhostandDS2480.
Thehostmustfirstreceivetheresponsebyteofthesingle–bitcom-mand,reacttoitandthentransmittheterminationcom-mand.
Neglectingthehostsresponsetime,theshortestdurationofaninfinitestrongpull–upthereforeis173.
6sat115.
2kbps,347.
2sat57.
6kbps,1.
04msat19.
2kbpsand2.
08msat9.
6kbps.
DS248004249819/26SOFTWAREDRIVEREXAMPLESTheDS2480requiresasoftwaredriverthattranslatestheactivitiestobegeneratedonthe1–Wirebusintotheappropriatecommands.
Theexamplesbelowcovertyp-icalsituations,suchasreadingtheROM,writingtothescratchpadofaMemoryiButton,readingthememoryofaMemoryiButton,programminganAdd–OnlyiButtonEPROMandperformingatemperatureconversionwiththeTemperatureiButtonDS1920.
AnexamplefortheuseoftheSearchAcceleratorisincludedinthedescrip-tionoftheSearchAccelerator,earlierinthisdocument.
TheDS2480commandcodesusedintheseexamplesarevalidforregularspeedandwillworkproperlyonshort1–Wirebusses(<10meters).
Theresponsebyteontheresetcommandassumesanormalpresencepulse,noalarmorshort.
TheDS2480includesa1–bytebufferthatstoresabytereceivedfromthehostwhilethepreviousbyteisbeingtranslatedintoactivityonthe1–Wirebus.
Forthisrea-sonthehostmaysendanotherbyteevenwithouthavingreceivedtheresponsebyte.
Sendingbytesfasterthantheycanbetranslatedinto1–Wireactivitiesmayresultinlossofdataand/orsynchronizationandthereforeshouldbeavoided.
READROMSEQUENCEActionSequenceHostTXHostRXGenerateResetPulseC1C9SetdatamodeE1(nothing)ReadROMCommand33(assent)ReadROMID(8bytes)FF(x8)ROMIDSetcommandmodeE3(nothing)GenerateResetPulseC1C9WRITESCRATCHPADSEQUENCEWrite2bytestoscratchpadatmemorylocations16hand17hActionSequenceHostTXHostRXGenerateResetPulseC1C9SetdatamodeE1(nothing)SkipROMCommandCCCCWriteScratchpadCmd.
0F(assent)StartingAddressTA116(assent)StartingAddressTA200(assent)WritetotheScratchpad(2bytes)(assent)SetcommandmodeE3(nothing)GenerateResetPulseC1C9READMEMORYSEQUENCERead8bytesfrommemoryaddress0040hActionSequenceHostTXHostRXGenerateResetPulseC1C9SetdatamodeE1(nothing)SkipROMCommandCC(assent)ReadMemoryCommandF0(assent)StartingAddressTA140(assent)StartingAddressTA200(assent)Read8bytesofdataFF(x8)dataSetcommandmodeE3(nothing)GenerateResetPulseC1C9DS248004249820/26WRITEEPROMSEQUENCE(DS2505)Writememorystartingataddress40hActionSequenceHostTXHostRXSetVppdur.
=512s2928GenerateResetPulseC1C9SetdatamodeE1(nothing)SkipROMCommandCC(assent)WriteMemoryCommand0F(assent)StartingAddressTA140(assent)StartingAddressTA200(assent)***Senddatabyte(data)(assent)ReceiveCRC16FF(x2)CRC16SetcommandmodeE3(nothing)GenerateProgramPulseFDresponseSetdatamodeE1(nothing)ReadwrittenbyteFF(data)Goto***towritethenextbyteorendthesequenceasshownbelow.
SetcommandmodeE3(nothing)GenerateResetPulseC1C9TEMPERATURECONVERSIONSEQUENCEActionSequenceHostTXHostRXSetpull–updur.
=524ms3938GenerateResetPulseC1C9SetdatamodeE1(nothing)SkipROMCommandCC(assent)SetcommandmodeE3(nothing)Armstrongpull–upEF(nothing)TerminatepulseF1responseSetdatamodeE1(nothing)ConvertTemperature44(assent)Waitforpulseresponse(nothing)responseSetcommandmodeE3(nothing)Disarmstrongpull–upED(nothing)TerminatepulseF1responseGenerateResetPulseC1C9DS248004249821/26HARDWAREAPPLICATIONEXAMPLESThissectiondiscussesfivetypicalapplicationscenariosoftheDS2480.
Whendirectlydesignedintoanewprod-uct,thedevicecanbeconnectedasshowninFigure10a.
Thecircuitbecomesmorecomplexifa1–Wirebusistobeinterfacedtoaportthatprovidesandexpectsinvertedsignals,butdoesnotnecessarilymeettheRS232C(±12V)standard(Figure10b).
UARTDIRECTFigure10aSTART1–WIREBUSRETURNVDDVPPRXDTXDPOL1–WGNDUARTORCSIN(RXD)SOUT(TXD)12V(5V)STOP01LM5VDS2480+/(–)5VRS232Figure10bSTART1–WIREBUSRETURNVDDVPPRXDTXDPOL1–WGNDUARTORC5V(5V)STOP01LMDTRVOLTAGEREGULATORDS248012VRTSRXDTXDGNDSEETEXTPOWERSTEALINGDRIVER/LEVELSHIFTERThesignalsDTRandRTSprovidethepowertooperatetheDS2480.
TheresistorintheTXDlineandtheSchottkydiodelimitthenegativevoltageattheTXDpinoftheDS2480to0.
3Vmaximum.
Theresistoristypi-cally4.
7k.
Iftheinvertingdriveriscurrent–limitedto1mAtheresistorisnotrequired.
FromtheDS2480'sperspective,thiscircuitwillworkwithinvertedsignalsof±5Vaswellas0to5V.
Depend-ingonthevoltagelevelsthehostexpects,itmaybenec-essarytogenerateanegativevoltageontheRXDline.
Figure10cshowshowthiscanbeaccomplishedforatrueRS232Csystem.
DS248004249822/26+12VRS232Figure10cSTART1–WIREBUSRETURNVDDVPPRXDTXDPOL1–WGNDUARTORC5V(5V)STOP01LMDTRVOLTAGEREGULATORDS248012VRTSRXDTXDGNDSEETEXTPOWERSTEALING2.
7k6.
8k4.
7V1BSS110SDIntheinterfacetoatrueRS232Csystem(±12V,Figure10c)thepowerfortheDS2480isstolenfromDTRandRTS.
Thesoftwaremustmakesurethatatleastoneofthesesignalsconstantlyprovidesthe12Voperatingvoltage.
The6.
8kresistorandthe4.
7VZenerdiodeintheTXDlinelimitthepositivevoltageattheTXDpinoftheDS2480.
TheSchottkydiodelimitsthenegativevolt-ageto0.
3Vmaximum.
TheSchottkydiodeinserieswiththecapacitorformsaparasiticsupplytogeneratethenegativebiasforthehost'sreceivechannel.
Theposi-tivesignalisswitchedinthroughtheP–channelMOS-FETthatconnectstotheRXDoutputoftheDS2480.
InthiscircuitdiagramtheMOSFETswitchestheRXDlineto+5V,whichnormallyissufficientforRS232Csystems.
Switchingto12Visalsopossible,butrequiresaP–channeltransistorwithadifferentthresholdvoltage.
Thesignalinversioncausedbythetransistoriscom-pensatedthroughtheDS2480byusingavaluecodeof100,101,110or111fortheRS232baudratesetting.
UARTDIRECTOPTOISOLATEDFigure10dSTART1–WIREBUSRETURNVDDVPPRXDTXDPOL1–WGNDUARTORC5V(5V)STOP01LMSINDS248012VHCPL–2300OPTOCOUPLER5VSOUT2.
7k6.
8k2.
7kDCTODCCONVERTERThecircuitinFigure10disessentiallythesameasinFigure10a.
Themaindifferenceistheopto–isolation.
Thecharacteristicsoftheopto–isolatorsarenotverycritical.
Usingadifferenttype,willaffectthevaluesoftheresistorsthatlimitthecurrentthroughtheLEDsandbiasthephototransistors.
DS248004249823/26+5TO12VRS232OPTOISOLATEDFigure10eSTART1–WIREBUSRETURNVDDVPPRXDTXDPOL1–WGNDUARTORC5VSTOP01LMDTR5VREGULATORDS2480RTSRXDTXDGNDPOWERSTEALING1HCPL–23005.
1kHCPL–22021.
5kPOWERSUPPLY12V2.
7kThecircuitinFigure10ecombinesthetrueRS232Cinterfacewithopto–isolation.
TheenergytopowertheLEDintheTXDchannelandtoprovidethepositivevolt-ageforthehost'sRXDinputisstolenfromDTRandRTS.
ThenegativevoltagefortheRXDinputistakenfromtheTXDlinethroughaparasiticsupplyconsistingofaSchottkydiodeinserieswithacapacitor.
TheHCPL–2202opto–isolatorhasatotempoleoutputthatallowsswitchinginpositiveaswellasnegativevoltage.
The+5VaresufficientformostRS232Csystems.
Switchingin12Vrequiresaopto–isolatorwithdifferentvoltagecharacteristics.
IntheschematictheHCPL–2202opto–isolatorissourcedbytheRXDpinoftheDS2480.
ItcanaswellbeconnectedthetraditionalwaywheretheDS2480sinksthecurrentthroughtheLED.
This,however,causesasignalinversionthathastobecompensatedthroughtheDS2480byusingavaluecodeof100,101,110or111fortheRS232baudratesetting.
Usingothertypesofopto–isolatorsthanshownintheschematicwillatleastrequirechangingthevaluesoftheresistors.
RS232DATATIMINGRXDLINEFigure11STARTtFRtIDLERBIT0BIT1BIT2BIT3BIT4BIT5BIT6BIT7STOPTR(DIAGRAMDRAWNFORPOL=5V)10TRtRRRECEIVEDELAYTIMINGFigure12tRESPINPUTSAMPLING8.
5TR9.
5TRRXDTXDSTARTBIT0BIT6BIT7STOP(DIAGRAMDRAWNFORPOL=5V)DS248004249824/26RS232DATATIMINGTXDLINEFigure13STARTBIT0BIT1BIT2BIT3BIT4BIT5BIT6BIT7STOPTTTT=1/BAUDRATEOFUART10TT1.
5TR2.
5TR3.
5TR4.
5TR5.
5TR6.
5TR7.
5TR8.
5TR9.
5TRTR=1/BAUDRATEOFDEVICEVILVIHtIDLETDIAGRAMDRAWNFORPOL=5V)FUNCTIONANDSPEEDMATRIXTable7BdR1–WireSpeedFiBaudRateRegularFlexibleOverdriveFunction9600bps√√√Search9600bps√√√Command/Data19200bpsXX√Search19200bps√X√Command/Data57600bpsXX√Search57600bpsXX√Command/Data115200bpsXXXSearch115200bpsXX√Command/Data√tIDLETisguaranteedbytheUART;noprecautionsnecessaryXnotrecommendedunlesstIDLETiscontrolledbythehostthroughawaitfunctionTXDLINEASYMMETRYFigure142TT(DIAGRAMDRAWNFORPOL=5V)tSTART=TT+(–)tASYMtBIT0=TT–(+)tASYM2tASYMSTOPSTARTBIT0BIT1DS248004249825/26ABSOLUTEMAXIMUMRATINGS*Voltageon1–WtoGround–0.
5Vto+14.
0VVoltageonRXD,TXD,POLtoGround–0.
5Vto+7.
0VOperatingTemperature–40°Cto+85°CStorageTemperature–55°Cto+125°CSolderingTemperature260°Cfor10seconds*Thisisastressratingonlyandfunctionaloperationofthedeviceattheseoranyotherconditionsabovethoseindicatedintheoperationsectionsofthisspecificationisnotimplied.
Exposuretoabsolutemaximumratingconditionsforextendedperiodsoftimemayaffectreliability.
DCELECTRICALCHARACTERISTICS(VDD=4.
5Vto5.
5V;–40°Cto85°C)PARAMETERSYMBOLMINTYPMAXUNITSNOTESSupplyVoltageVCC4.
55.
05.
5VProgrammingVoltageVPP11.
7512.
25V1OperatingCurrentIDD3.
05.
0mAIdleCurrentonVPPIPP20A2ActivePull–upTimerThresholdVIAPTOVDD–1.
4VDD–1.
1VActivePull–upOnThresholdVIAPO0.
951.
2V1–WireInputHighVIH13.
4V1–WireInputLowVIL11.
8VTXD/POLinputresistorRI30k3TXD/POLinputlevelsVIH2.
7VTXD/POLinputlevelsVIL0.
8V1–Wireweakpull–upcurrentIWEAKPU1.
53.
05.
0mA1–Wireactivepull–upcurrentIACTPU915mAStrongpull–upvoltagedrop@10mAloadon1–WVSTRPU0.
6V4Programmingvoltagedrop@10mAloadon1–WVPROG0.
24V5RXDsinkcurrent@0.
4VIOLR6mARXDsourcecurrent@VDD–0.
4VIOHR–4mAPowerOnResetTripPointVPOR3.
3VVPPSensorTripPointVPPTRIP9.
5VCAPACITANCES(tA=25°C)PARAMETERSYMBOLMINTYPMAXUNITSNOTESTXD/POLinputcapacitanceCIN5pF1–WireinputcapacitanceCIN110pFDS248004249826/26ACELECTRICALCHARACTERISTICS(VDD=4.
5Vto5.
5V;–40°Cto85°C)PARAMETERSYMBOLMINTYPMAXUNITSNOTESUARTBitTimeTT8.
68104s6DeviceBitTimeTR8.
68104s6,7FallTimeRXDtFR820ns8RiseTimeRXDtRR1327ns8TransmitIdleTimetIDLET0s9ReceiveIdleTimetIDLERtIDLETsAsymmetrytASYM1s10ArrivalResponseTimetARR4.
452s11MasterResetTimetMR104s12ActivePull–UponTimetAPUOT0.
52.
0s13ResponseTimetRESP8.
68+104+s11,14NOTES:1.
VPP–VPROGmustbewithin11.
5to12.
0V.
2.
Appliesonlyifa12.
0Vsupplyisconnected.
IfVPPandVDDaretiedtogether,currentislessthan1A.
3.
InputloadistoGND.
4.
VoltagedifferencebetweenVDDand1–W.
5.
VoltagedifferencebetweenVPPand1–W.
6.
8.
68s(115.
2kbps),52s(19.
2kbps),17.
36s(57.
6kbps),104s(9.
6kbps).
7.
Nominalvalues;tolerance=±5%.
8.
AtVCC=5.
0Vand100pFloadtoGND.
9.
SeeTable7,FunctionandSpeedMatrix.
10.
Independentofbaudrate.
11.
Minimumat115.
2kbps,maximumat9.
6kbps.
12.
ThemasterresetcycleiscompleteaftertMRisover.
13.
MinimumvalueatOverdrivespeed;maximumvalueatregularspeed.
14.
isthetimetocompletetheactivityonthe1–Wirebus;valuesrangefrom0(configurationcommand)upto5130s(alarmingpresencepulse)