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PIE
Event Trigger
Module Logic
CTR=Zero
CTR=PRD
CTR=CMPA
EPWMxINTn
CTR=CMPB
CTR_dir
Direction
qualifier
CTRU=CMPA
ETSEL reg
EPWMxSOCA
/n
/n
/n
EPWMxSOCB
ADC
clear
count
count
clear
count
clear
CTRD=CMPA
CTRU=CMPB
CTRD=CMPB
ETPS reg
ETFLG reg
ETCLR reg
ETFRC reg
Event-Trigger(ET)Submodule
Figure2-40.Event-TriggerSubmoduleShowingEventInputsandPrescaledOutputs
Thekeyregistersusedtoconfiguretheevent-triggersubmoduleareshowninTable2-19:
Table2-19.Event-TriggerSubmoduleRegisters
RegisterNameAddressoffsetShadowedDescription
ETSEL0x0019NoEvent-triggerSelectionRegister
ETPS0x001ANoEvent-triggerPrescaleRegister
ETFLG0x001BNoEvent-triggerFlagRegister
ETCLR0x001CNoEvent-triggerClearRegister
ETFRC0x001DNoEvent-triggerForceRegister
•ETSEL—ThisselectswhichofthepossibleeventswilltriggeraninterruptorstartanADCconversion
•ETPS—Thisprogramstheeventprescalingoptionsmentionedabove.
•ETFLG—Theseareflagbitsindicatingstatusoftheselectedandprescaledevents.
•ETCLR—ThesebitsallowyoutocleartheflagbitsintheETFLGregisterviasoftware.
•ETFRC—Thesebitsallowsoftwareforcingofanevent.Usefulfordebuggingors/wintervention.
AmoredetailedlookathowthevariousregisterbitsinteractwiththeInterruptandADCstartof
conversionlogicareshowninFigure2-41,Figure2-42,andFigure2-43.
Figure2-41showstheevent-trigger'sinterruptgenerationlogic.Theinterrupt-period(ETPS[INTPRD])bits
specifythenumberofeventsrequiredtocauseaninterruptpulsetobegenerated.Thechoicesavailable
are:
•Donotgenerateaninterrupt.
•Generateaninterruptoneveryevent
•Generateaninterruptoneverysecondevent
•Generateaninterruptoneveryverythirdevent
Whicheventcancauseaninterruptisconfiguredbytheinterruptselection(ETSEL[INTSEL])bits.The
eventcanbeoneofthefollowing:
•Time-basecounterequaltozero(TBCTR=0x0000).
•Time-basecounterequaltoperiod(TBCTR=TBPRD).
•Time-basecounterequaltothecompareAregister(CMPA)whenthetimerisincrementing.
•Time-basecounterequaltothecompareAregister(CMPA)whenthetimerisdecrementing.
•Time-basecounterequaltothecompareBregister(CMPB)whenthetimerisincrementing.
•Time-basecounterequaltothecompareBregister(CMPB)whenthetimerisdecrementing.
SPRU791D–November2004–RevisedOctober2007ePWMSubmodules65
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