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HT45F2002

2-Wire Communication Flash MCU

HT45F2002

2-Wire Communication Flash MCU

Instruction Set

Introduction

Centraltothesuccessfuloperationofanymicrocontrollerisitsinstructionset,whichisasetof

programinstructioncodesthatdirectsthemicrocontrollertoperformcertainoperations.Inthecase

ofHoltekmicrocontroller,acomprehensiveandflexiblesetofover60instructionsisprovidedto

enableprogrammerstoimplementtheirapplicationwiththeminimumofprogrammingoverheads.

Foreasierunderstandingofthevariousinstructioncodes,theyhavebeensubdividedintoseveral

functionalgroupings.

Instruction Timing

Mostinstructionsareimplementedwithinoneinstructioncycle.Theexceptionstothisarebranch,

call,ortablereadinstructionswheretwoinstructioncyclesarerequired.Oneinstructioncycleis

equalto4systemclockcycles,thereforeinthecaseofan8MHzsystemoscillator,mostinstructions

wouldbeimplementedwithin0.5μsandbranchorcallinstructionswouldbeimplementedwithin

1μs.Althoughinstructionswhichrequireonemorecycletoimplementaregenerallylimitedto

theJMP,CALL,RET,RETIandtablereadinstructions,itisimportanttorealizethatanyother

instructionswhichinvolvemanipulationoftheProgramCounterLowregisterorPCLwillalsotake

onemorecycletoimplement.AsinstructionswhichchangethecontentsofthePCLwillimplya

directjumptothatnewaddress,onemorecyclewillberequired.Examplesofsuchinstructions

wouldbe“CLRPCL”or“MOVPCL,A”.Forthecaseofskipinstructions,itmustbenotedthatif

theresultofthecomparisoninvolvesaskipoperationthenthiswillalsotakeonemorecycle,ifno

skipisinvolvedthenonlyonecycleisrequired.

Moving and Transferring Data

Thetransferofdatawithinthemicrocontrollerprogramisoneofthemostfrequentlyused

operations.MakinguseofseveralkindsofMOVinstructions,datacanbetransferredfromregisters

totheAccumulatorandvice-versaaswellasbeingabletomovespecificimmediatedatadirectly

intotheAccumulator.Oneofthemostimportantdatatransferapplicationsistoreceivedatafrom

theinputportsandtransferdatatotheoutputports.

Arithmetic Operations

Theabilitytoperformcertainarithmeticoperationsanddatamanipulationisanecessaryfeatureof

mostmicrocontrollerapplications.WithintheHoltekmicrocontrollerinstructionsetarearangeof

addandsubtractinstructionmnemonicstoenablethenecessaryarithmetictobecarriedout.Care

mustbetakentoensurecorrecthandlingofcarryandborrowdatawhenresultsexceed255for

additionandlessthan0forsubtraction.TheincrementanddecrementinstructionssuchasINC,

INCA,DECandDECAprovideasimplemeansofincreasingordecreasingbyavalueofoneofthe

valuesinthedestinationspecified.