HT45F56 datasheet(73/90 Pages) HOLTEK

73 / 90 page

Rev. 1.11

April 11, 2017

Rev. 1.11

April 11, 2017

HT45F56

Shock Detector Flash MCU

HT45F56

Shock Detector Flash MCU

Interrupt Wake-up Function

Eachoftheinterruptfunctionshasthecapabilityofwakingupthemicrocontrollerwheninthe

SLEEPorIDLEMode.Awake-upisgeneratedwhenaninterruptrequestflagchangesfromlow

tohighandisindependentofwhethertheinterruptisenabledornot.Therefore,eventhoughthese

devicesareintheSLEEPorIDLEModeanditssystemoscillatorstopped,situationssuchas

externaledgetransitionsontheexternalinterruptpins,alowpowersupplyvoltageorcomparator

inputchangemaycausetheirrespectiveinterruptflagtobesethighandconsequentlygenerate

aninterrupt.Caremustthereforebetakenifspuriouswake-upsituationsaretobeavoided.Ifan

interruptwake-upfunctionistobedisabledthenthecorrespondinginterruptrequestflagshouldbe

sethighbeforethedeviceenterstheSLEEPorIDLEMode.Theinterruptenablebitshavenoeffect

ontheinterruptwake-upfunction.

Programming Considerations

Bydisablingtherelevantinterruptenablebits,arequestedinterruptcanbepreventedfrombeing

serviced,however,onceaninterruptrequestflagisset,itwillremaininthisconditioninthe

interruptregisteruntilthecorrespondinginterruptisservicedoruntiltherequestflagisclearedby

theapplicationprogram.

Itisrecommendedthatprogramsdonotusethe“CALL”instructionwithintheinterruptservice

subroutine.Interruptsoftenoccurinanunpredictablemannerorneedtobeservicedimmediately.

Ifonlyonestackisleftandtheinterruptisnotwellcontrolled,theoriginalcontrolsequencewillbe

damagedonceaCALLsubroutineisexecutedintheinterruptsubroutine.

EveryinterrupthasthecapabilityofwakingupthemicrocontrollerwhenitisintheSLEEPorIDLE

Mode,thewakeupbeinggeneratedwhentheinterruptrequestflagchangesfromlowtohigh.Ifitis

requiredtopreventacertaininterruptfromwakingupthemicrocontrollerthenitsrespectiverequest

flagshouldbefirstsethighbeforeenterSLEEPorIDLEMode.

AsonlytheProgramCounterispushedontothestack,thenwhentheinterruptisserviced,ifthe

contentsoftheaccumulator,statusregisterorotherregistersarealteredbytheinterruptservice

program,theircontentsshouldbesavedtothememoryatthebeginningoftheinterruptservice

routine.

Toreturnfromaninterruptsubroutine,eitheraRETorRETIinstructionmaybeexecuted.TheRETI

instructioninadditiontoexecutingareturntothemainprogramalsoautomaticallysetstheEMI

bithightoallowfurtherinterrupts.TheRETinstructionhoweveronlyexecutesareturntothemain

programleavingtheEMIbitinitspresentzerostateandthereforedisablingtheexecutionoffurther

interrupts.

HT45F56 Datasheet(PDF) 73 Page - Holtek Semiconductor Inc