HT68F005 datasheet(15/93 Pages) HOLTEK

15 / 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

Stack

ThisisaspecialpartofthememorywhichisusedtosavethecontentsoftheProgramCounteronly.

Thestackhastwolevelsdependinguponthedevicesandisneitherpartofthedatanorpartofthe

programspace,andisneitherreadablenorwriteable.TheactivatedlevelisindexedbytheStack

Pointer,andisneitherreadablenorwriteable.Atasubroutinecallorinterruptacknowledgesignal,the

contentsoftheProgramCounterarepushedontothestack.Attheendofasubroutineoraninterrupt

routine,signaledbyareturninstruction,RETorRETI,theProgramCounterisrestoredtoitsprevious

valuefromthestack.Afteradevicereset,theStackPointerwillpointtothetopofthestack.

Ifthestackisfullandanenabledinterrupttakesplace,theinterruptrequestflagwillberecordedbut

theacknowledgesignalwillbeinhibited.WhentheStackPointerisdecremented,byRETorRETI,

theinterruptwillbeserviced.Thisfeaturepreventsstackoverflowallowingtheprogrammertouse

thestructuremoreeasily.However,whenthestackisfull,aCALLsubroutineinstructioncanstill

beexecutedwhichwillresultinastackoverflow.Precautionsshouldbetakentoavoidsuchcases

whichmightcauseunpredictableprogrambranching.

Ifthestackisoverflow,thefirstProgramCountersaveinthestackwillbelost.

Pr og ra m Co un te r

St ac k Le ve l 1

St ac k Le ve l 2

Pr og ra m

Me mo ry

T op of S ta ck

St ac k

Po in te r

Bo tt om o f St ac k

Device

Stack Levels

HT68F005

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HT68F006

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Arithmetic and Logic Unit – ALU

Thearithmetic-logicunitorALUisacriticalareaofthemicrocontrollerthatcarriesoutarithmetic

andlogicoperationsoftheinstructionset.Connectedtothemainmicrocontrollerdatabus,theALU

receivesrelatedinstructioncodesandperformstherequiredarithmeticorlogicaloperationsafter

whichtheresultwillbeplacedinthespecifiedregister.AstheseALUcalculationoroperationsmay

resultincarry,borroworotherstatuschanges,thestatusregisterwillbecorrespondinglyupdatedto

reflectthesechanges.TheALUsupportsthefollowingfunctions:

• Arithmeticoperations:ADD,ADDM,ADC,ADCM,SUB,SUBM,SBC,SBCM,DAA

• Logicoperations:AND,OR,XOR,ANDM,ORM,XORM,CPL,CPLA

• RotationRRA,RR,RRCA,RRC,RLA,RL,RLCA,RLC

• IncrementandDecrementINCA,INC,DECA,DEC

• Branchdecision,JMP,SZ,SZA,SNZ,SIZ,SDZ,SIZA,SDZA,CALL,RET,RETI

HT68F005 Datasheet(PDF) 15 Page - Holtek Semiconductor Inc

HT68F005 Datasheet(HTML) 15 Page - Holtek Semiconductor Inc

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