HT45F77 datasheet(21/203 Pages) HOLTEK

21 / 203 page

Rev. 1.20

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Rev. 1.20

De�e��e� 1�� 201�

HT45F77

Body Fat Scale Flash MCU

HT45F77

Body Fat Scale Flash MCU

Forinstructionsinvolvingbranches,suchasjumporcallinstructions,twomachinecyclesare

requiredtocompleteinstructionexecution.Anextracycleisrequiredastheprogramtakesone

cycletofirstobtaintheactualjumporcalladdressandthenanothercycletoactuallyexecutethe

branch.Therequirementforthisextracycleshouldbetakenintoaccountbyprogrammersintiming

sensitiveapplications.

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.Itisautomaticallyincrementedbyoneeachtimeaninstructionisex-

ecutedexceptforinstructions,suchas"JMP"or"CALL"thatdemandsajumptoanon-consecutive

ProgramMemoryaddress.Onlythelower8bits,knownastheProgramCounterLowRegister,are

directlyaddressablebytheapplicationprogram.

Whenexecutinginstructionsrequiringjumpstonon-consecutiveaddressessuchasajump

instruction,asubroutinecall,interruptorreset,etc.,themicrocontrollermanagesprogramcontrol

byloadingtherequiredaddressintotheProgramCounter.Forconditionalskipinstructions,once

theconditionhasbeenmet,thenextinstruction,whichhasalreadybeenfetchedduringthepresent

instructionexecution,isdiscardedandadummycycletakesitsplacewhilethecorrectinstructionis

obtained.

Program Counter

Program Counter High Byte

PCL Register

PC12~PC8

PCL7~PCL0

Program Counter

ThelowerbyteoftheProgramCounter,knownastheProgramCounterLowregisterorPCL,is

availableforprogramcontrolandisareadableandwriteableregister.Bytransferringdatadirectly

intothisregister,ashortprogramjumpcanbeexecuteddirectly,however,asonlythislowbyte

isavailableformanipulation,thejumpsarelimitedtothepresentpageofmemory,thatis256

locations.Whensuchprogramjumpsareexecuteditshouldalsobenotedthatadummycycle

willbeinserted.ManipulatingthePCLregistermaycauseprogrambranching,soanextracycleis

neededtopre-fetch.

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