HT67F488 datasheet(143/171 Pages) HOLTEK

143 / 171 page

Rev. 1.60

143

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

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.

EveryinterrupthasthecapabilityofwakingupthemicrocontrollerwhenitisinSLEEPorIDLE

Mode,thewakeupbeinggeneratedwhentheinterruptrequestflagchangesfromlowtohigh.Ifitis

requiredtopreventacertaininterruptfromwakingupthemicrocontrollerthenitsrespectiverequest

flagshouldbefirstsethighbeforeenterSLEEPorIDLEMode.

AsonlytheProgramCounterispushedontothestack,thenwhentheinterruptisserviced,ifthe

contentsoftheaccumulator,statusregisterorotherregistersarealteredbytheinterruptservice

program,theircontentsshouldbesavedtothememoryatthebeginningoftheinterruptservice

routine.

Toreturnfromaninterruptsubroutine,eitheraRETorRETIinstructionmaybeexecuted.TheRETI

instructioninadditiontoexecutingareturntothemainprogramalsoautomaticallysetstheEMI

bithightoallowfurtherinterrupts.TheRETinstructionhoweveronlyexecutesareturntothemain

programleavingtheEMIbitinitspresentzerostateandthereforedisablingtheexecutionoffurther

interrupts.

HT67F488 Datasheet(PDF) 143 Page - Holtek Semiconductor Inc