HT45F39 datasheet(16/102 Pages) HOLTEK

16 / 102 page

Rev. 1.10

July 01, 2016

Rev. 1.10

July 01, 2016

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

HT45F39/HT45F391

Ultrasonic Distance Measurement 8-bit Flash MCU

Stack

ThisisaspecialpartofthememorywhichisusedtosavethecontentsoftheProgramCounter

only.Thestackisorganizedinto4levelsandisneitherpartoftheDataorProgramMemoryspace,

andisneitherreadablenorwriteable.TheactivatedlevelisindexedbytheStackPointer,SP,andis

neitherreadablenorwriteable.Atasubroutinecallorinterruptacknowledgesignal,thecontentsof

theProgramCounterarepushedontothestack.Attheendofasubroutineoraninterruptroutine,

signaledbyareturninstruction,RETorRETI,theProgramCounterisrestoredtoitspreviousvalue

fromthestack.Afteradevicereset,theStackPointerwillpointtothetopofthestack.

Pr og ra m Co un te r

St ac k Le ve l 1

St ac k Le ve l 2

St ac k Le ve l 3

St ac k Le ve l 4

Pr og ra m

Me mo ry

T op o f S ta ck

St ac k

Po in te r

Bo tt om o f St ac k

Ifthestackisfullandanenabledinterrupttakesplace,theinterruptrequestflagwillberecordedbut

theacknowledgesignalwillbeinhibited.WhentheStackPointerisdecremented,byRETorRETI,

theinterruptwillbeserviced.Thisfeaturepreventsstackoverflowallowingtheprogrammertouse

thestructuremoreeasily.However,whenthestackisfull,aCALLsubroutineinstructioncanstill

beexecutedwhichwillresultinastackoverflow.Precautionsshouldbetakentoavoidsuchcases

whichmightcauseunpredictableprogrambranching.

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

HT45F39 Datasheet(PDF) 16 Page - Holtek Semiconductor Inc

HT45F39 Datasheet(HTML) 16 Page - Holtek Semiconductor Inc

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