Holtek HT66F30 User Manual

Rev. 2.50 28 June 22, 2017 Rev. 2.50 29 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
Forinstructionsinvolvingbranches,suchasjumporcallinstructions,twomachinecyclesare
requiredtocompleteinstructionexecution.Anextracycleisrequiredastheprogramtakesone
cycletorstobtaintheactualjumporcalladdressandthenanothercycletoactuallyexecutethe
branch.Therequirementforthisextracycleshouldbetakenintoaccountbyprogrammersintiming
sensitiveapplications.
     
   
 






 
  
  
  



 
   
     
   
Instruction Fetching
Program Counter
Duringprogramexecution,theProgramCounterisusedtokeeptrackoftheaddressofthenext
instructiontobeexecuted.Itisautomaticallyincrementedbyoneeachtimeaninstructionis
executedexceptforinstructions,suchas"JMP"or"CALL"thatdemandajumptoanon-consecutive
ProgramMemoryaddress.Onlythelower8bits,knownastheProgramCounterLowRegister,are
directlyaddressablebytheapplicationprogram.
Whenexecutinginstructionsrequiringjumpstonon-consecutiveaddressessuchasajumpinstruction,
asubroutinecall,interruptorreset,etc.,themicrocontrollermanagesprogramcontrolbyloading
therequiredaddressintotheProgramCounter.Forconditionalskipinstructions,oncethecondition
hasbeenmet,thenextinstruction,whichhasalreadybeenfetchedduringthepresentinstruction
execution,isdiscardedandadummycycletakesitsplacewhilethecorrectinstructionisobtained.
Device
Program Counter
Porgram Counter High Byte PCL Register
HT66F20
PC9, PC8
PCL7~PCL0
HT66F30 PC10~PC8
HT66F40 PC11~PC8
HT66F50 PC12~PC8
HT66F60 PMBP0, PC12~PC8
Program Counter
ThelowerbyteoftheProgramCounter,knownastheProgramCounterLowregisterorPCL,is
availableforprogramcontrolandisareadableandwriteableregister.Bytransferringdatadirectly
intothisregister,ashortprogramjumpcanbeexecuteddirectly,however,asonlythislowbyte
isavailableformanipulation,thejumpsarelimitedtothepresentpageofmemory,thatis256
locations.Whensuchprogramjumpsareexecuteditshouldalsobenotedthatadummycycle
willbeinserted.ManipulatingthePCLregistermaycauseprogrambranching,soanextracycleis
neededtopre-fetch.

Holtek HT66F30 Specifications

General

Brand	Holtek
Model	HT66F30
Category	Computer Hardware
Language	English