HT45F39 datasheet(85/102 Pages) HOLTEK

85 / 102 page

Rev. 1.10

July 01, 2016

Rev. 1.10

July 01, 2016

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

Interrupt Wake-up Function

Eachoftheinterruptfunctionshasthecapabilityofwakingupthemicrocontrollerwheninthe

SLEEPMode.Awake-upisgeneratedwhenaninterruptrequestflagchangesfromlowtohighand

isindependentofwhethertheinterruptisenabledornot.Therefore,eventhoughthedevicesarein

theSLEEPModeanditssystemoscillatorstopped,situationssuchasexternaledgetransitionon

theexternalinterruptpin,FIFO10setsdataarereceivedortransmittedmaycausetheirrespective

interruptflagtobesethighandconsequentlygenerateaninterrupt.Caremustthereforebetaken

ifspuriouswake-upsituationsaretobeavoided.Ifaninterruptwake-upfunctionistobedisabled

thenthecorrespondinginterruptrequestflagshouldbesethighbeforethedevicesentertheSLEEP

Mode.Theinterruptenablebitshavenoeffectontheinterruptwake-upfunction.

Programming Considerations

Bydisablingtherelevantinterruptenablebits,arequestedinterruptcanbepreventedfrombeing

serviced,however,onceaninterruptrequestflagisset,itwillremaininthisconditioninthe

interruptregisteruntilthecorrespondinginterruptisservicedoruntiltherequestflagisclearedby

theapplicationprogram.

Itisrecommendedthatprogramsdonotusethe"CALL"instructionwithintheinterruptservice

subroutine.Interruptsoftenoccurinanunpredictablemannerorneedtobeservicedimmediately.

Ifonlyonestackisleftandtheinterruptisnotwellcontrolled,theoriginalcontrolsequencewillbe

damagedonceaCALLsubroutineisexecutedintheinterruptsubroutine.

EveryinterrupthasthecapabilityofwakingupthemicrocontrollerwhenitisinSLEEPMode,the

wakeupbeinggeneratedwhentheinterruptrequestflagchangesfromlowtohigh.Ifitisrequired

topreventacertaininterruptfromwakingupthemicrocontrollerthenitsrespectiverequestflag

shouldbefirstsethighbeforeenterSLEEPMode.

AsonlytheProgramCounterispushedontothestack,thenwhentheinterruptisserviced,ifthe

contentsoftheaccumulator,statusregisterorotherregistersarealteredbytheinterruptservice

program,theircontentsshouldbesavedtothememoryatthebeginningoftheinterruptservice

routine.

Toreturnfromaninterruptsubroutine,eitheraRETorRETIinstructionmaybeexecuted.TheRETI

instructioninadditiontoexecutingareturntothemainprogramalsoautomaticallysetstheEMI

bithightoallowfurtherinterrupts.TheRETinstructionhoweveronlyexecutesareturntothemain

programleavingtheEMIbitinitspresentzerostateandthereforedisablingtheexecutionoffurther

interrupts.

HT45F39 Datasheet(PDF) 85 Page - Holtek Semiconductor Inc