HT68F005 datasheet(77/93 Pages) HOLTEK

77 / 93 page

Rev. 1.00

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Rev. 1.00

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HT68F005/HT68F006

Enhanced I/O Flash Type MCU

HT68F005/HT68F006

Enhanced I/O Flash Type MCU

Programming Considerations

Bydisablingtherelevantinterruptenablebits,arequestedinterruptcanbepreventedfrombeing

serviced,however,onceaninterruptrequestflagisset,itwillremaininthisconditioninthe

interruptregisteruntilthecorrespondinginterruptisservicedoruntiltherequestflagisclearedby

theapplicationprogram.

WhereacertaininterruptiscontainedwithinaMulti-functioninterrupt,thenwhentheinterrupt

serviceroutineisexecuted,asonlytheMulti-functioninterruptrequestflags,MFnF,willbe

automaticallycleared,theindividualrequestflagforthefunctionneedstobeclearedbythe

applicationprogram.

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.

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