HT45F23A datasheet(21/148 Pages) HOLTEK

21 / 148 page

Rev. 1.00

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Rev. 1.00

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HT45F23A

8-Bit Flash MCU with Op Amps & Comparators

HT45F23A

8-Bit Flash MCU with Op Amps & Comparators

Fe tc h In st . 1E xe cu te I ns t. 1

Fe tc h In st . 2

Fl us h Pi pel in e

DE LA Y:

MO V A, [1 2H ]

CA LL D EL AY

CP L [ 12H ]

NO P

Ex ec ut e In st . 2

Fe tc h In st . 3

Fe tc h In st . 6

Ex ec ut e In s t. 6

Fe tc h In st . 7

Instruction Fetching

Program Counter

Duringprogramexecution,theProgramCounterisusedtokeeptrackoftheaddressofthenext

instructiontobeexecuted.Itisautomaticallyincrementedbyoneeachtimeaninstructionis

executedexceptforinstructions,suchas"JMP"or"CALL"thatdemandajumptoanon-consecutive

ProgramMemoryaddress.NotethattheProgramCounterwidthvarieswiththeProgramMemory

capacitydependinguponwhichdeviceisselected.However,itmustbenotedthatonlythelower

8bits,knownastheProgramCounterLowRegister,aredirectlyaddressablebytheapplication

program.

Whenexecutinginstructionsrequiringjumpstonon-consecutiveaddressessuchasajump

instruction,asubroutinecall,interruptorreset,etc.,themicrocontrollermanagesprogramcontrol

byloadingtherequiredaddressintotheProgramCounter.Forconditionalskipinstructions,once

theconditionhasbeenmet,thenextinstruction,whichhasalreadybeenfetchedduringthepresent

instructionexecution,isdiscardedandadummycycletakesitsplacewhilethecorrectinstructionis

obtained.

Program Counter

Program Counter High Byte

PCL Register

PC10~PC8

PCL7~PCL0

ThelowerbyteoftheProgramCounter,knownastheProgramCounterLowregisterorPCL,is

availableforprogramcontrolandisareadableandwriteableregister.Bytransferringdatadirectly

intothisregister,ashortprogramjumpcanbeexecuteddirectly.However,asonlythislowbyte

isavailableformanipulation,thejumpsarelimitedtothepresentpageofmemorythatis256

locations.Whensuchprogramjumpsareexecuted,itshouldalsobenotedthatadummycyclewill

beinserted.

ThelowerbyteoftheProgramCounterisfullyaccessibleunderprogramcontrol.Manipulatingthe

PCLmightcauseprogrambranching,soanextracycleisneededtopre-fetch.Furtherinformation

onthePCLregistercanbefoundintheSpecialFunctionRegistersection.

HT45F23A Datasheet(PDF) 21 Page - Holtek Semiconductor Inc

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