HT67F488 datasheet(19/171 Pages) HOLTEK

19 / 171 page

Rev. 1.60

�ove��e� �� 016

HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

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

6 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.

Device

Program Counter

Program Counter High Byte

PCL Register

HT67F488

PC11~PC8

PCL7~PCL0

HT67F489

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.

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