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5.18IEEE1149.1JTAG
TMS320DM355
DigitalMediaSystem-on-Chip(DMSoC)
SPRS463A–SEPTEMBER2007–REVISEDSEPTEMBER2007
TheJTAG
(1)
interfaceisusedforBSDLtestingandemulationofthedevice.
ThedevicerequiresthatbothTRSTandRESETbeasserteduponpoweruptobeproperlyinitialized.
WhileRESETinitializesthedevice,TRSTinitializesthedevice'semulationlogic.Bothresetsarerequired
forproperoperation.
WhilebothTRSTandRESETneedtobeasserteduponpowerup,onlyRESETneedstobereleasedfor
thedevicetobootproperly.TRSTmaybeassertedindefinitelyfornormaloperation,keepingtheJTAG
portinterfaceanddevice'semulationlogicintheresetstate.
TRSTonlyneedstobereleasedwhenitisnecessarytouseaJTAGcontrollertodebugthedeviceor
exercisethedevice'sboundaryscanfunctionality.Note:TRSTissynchronousandmustbeclockedby
TCK;otherwise,theboundaryscanlogicmaynotrespondasexpectedafterTRSTisasserted.
RESETmustbereleasedonlyinorderforboundary-scanJTAGtoreadthevariantfieldofIDCODE
correctly.Otherboundary-scaninstructionsworkcorrectlyindependentofcurrentstateofRESET.
Formaximumreliability,includesaninternalpulldown(PD)ontheTRSTpintoensurethatTRSTwill
alwaysbeasserteduponpowerupandthedevice'sinternalemulationlogicwillalwaysbeproperly
initialized.
JTAGcontrollersfromTexasInstrumentsactivelydriveTRSThigh.However,somethird-partyJTAG
controllersmaynotdriveTRSThighbutexpecttheuseofapullupresistoronTRST.
WhenusingthistypeofJTAGcontroller,assertTRSTtointializethedeviceafterpowerupandexternally
driveTRSThighbeforeattemptinganyemulationorboundaryscanoperations.Followingthereleaseof
RESET,thelow-to-hightransitionofTRSTmustbe"seen"tolatchthestateofEMU1andEMU0.The
EMU[1:0]pinsconfigurethedeviceforeitherBoundaryScanmodeorEmulationmode.Formoredetailed
information,seetheterminalfunctionssectionofthisdatasheet.
(1)IEEEStandard1149.1-1990Standard-Test-AccessPortandBoundaryScanArchitecture.
148PeripheralInformationandElectricalSpecificationsSubmitDocumentationFeedback