HT67F4892 datasheet(21/188 Pages) HOLTEK

21 / 188 page

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HT67F4892

Enhanced A/D Flash MCU with LCD & EEPROM

HT67F4892

Enhanced A/D Flash MCU with LCD & EEPROM

Fetch Inst. 1

MOV A�[1�H]

�

CALL DELAY

CPL [1�H]

�

� DELAY: �OP

Execute Inst. 1

Fetch Inst. �

Execute Inst. �

Fetch Inst. 3

Flush Pipeline

Fetch Inst. �

Execute Inst. �

Fetch Inst. 7

Instruction Fetching

Program Counter

Duringprogramexecution,theProgramCounterisusedtokeeptrackoftheaddressofthe

nextinstructiontobeexecuted.Itisautomaticallyincrementedbyoneeachtimeaninstruction

isexecutedexceptforinstructions,suchas"JMP"or"CALL"thatdemandsajumptoanon-

consecutiveProgramMemoryaddress.Onlythelower8bits,knownastheProgramCounterLow

Whenexecutinginstructionsrequiringjumpstonon-consecutiveaddressessuchasajump

instruction,asubroutinecall,interruptorreset,etc.,themicrocontrollermanagesprogramcontrol

byloadingtherequiredaddressintotheProgramCounter.Forconditionalskipinstructions,once

theconditionhasbeenmet,thenextinstruction,whichhasalreadybeenfetchedduringthepresent

instructionexecution,isdiscardedandadummycycletakesitsplacewhilethecorrectinstructionis

obtained.

Program Counter

Program Counter High Byte

PCL Register

PC1�~PC8

PCL7~PCL0

Program Counter

ThelowerbyteoftheProgramCounter,knownastheProgramCounterLowregisterorPCL,is

availableforprogramcontrolandisareadableandwriteableregister.Bytransferringdatadirectly

intothisregister,ashortprogramjumpcanbeexecuteddirectly.However,asonlythislowbyte

isavailableformanipulation,thejumpsarelimitedtothepresentpageofmemory,thatis256

locations.Whensuchprogramjumpsareexecuteditshouldalsobenotedthatadummycycle

willbeinserted.ManipulatingthePCLregistermaycauseprogrambranching,soanextracycleis

neededtopre-fetch.

Stack

ThisisaspecialpartofthememorywhichisusedtosavethecontentsoftheProgramCounteronly.

Thestackisorganizedinto8levelsandisneitherpartofthedatanorpartoftheprogramspace,

andisneitherreadablenorwriteable.TheactivatedlevelisindexedbytheStackPointer,andis

neitherreadablenorwriteable.Atasubroutinecallorinterruptacknowledgesignal,thecontentsof

theProgramCounterarepushedontothestack.Attheendofasubroutineoraninterruptroutine,

signaledbyareturninstruction,RETorRETI,theProgramCounterisrestoredtoitspreviousvalue

fromthestack.Afteradevicereset,theStackPointerwillpointtothetopofthestack.

HT67F4892 Datasheet(PDF) 21 Page - Holtek Semiconductor Inc

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