Holtek HT66F0175 - Bank Pointer - BP; CC�M�Lator - �CC; Pro�Ram Co�Nter Low Re�Ister - PCL; Look-�P Table Re�Isters - TBLP� TBHP� TBLH

Rev. 1.50 34 August 28, 2017 Rev. 1.50 35 August 28, 2017
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
Bank Pointer – BP
FortheHT66F0185device,theDataMemoryisdividedintotwobanks,Bank0andBank1.
SelectingtherequiredDataMemoryareaisachievedusingtheBankPointer.Bit0oftheBank
PointerisusedtoselectDataMemoryBanks0~1.TheDataMemoryisinitialisedtoBank0aftera
reset,exceptforaWDTtime-outresetinthePowerDownMode,inwhichcase,theDataMemory
bankremainsunaffected.ItshouldbenotedthattheSpecialFunctionDataMemoryisnotaffected
bythebankselection,whichmeansthattheSpecialFunctionRegisterscanbeaccessedfrom
withinanybank.DirectlyaddressingtheDataMemorywillalwaysresultinBank0beingaccessed
irrespectiveofthevalueoftheBankPointer.AccessingdatafromBank1mustbeimplemented
usingIndirectAddressing.
BP Register – HT66F0185
Bit 7 6 5 4 3 2 1 0
Name — — — — — — — DMBP0
R/W — — — — — — — R/W
POR — — — — — — — 0
Bit7~1 Unimplemented,readas“0”
Bit0 DMBP0:SelectDataMemoryBanks
0:Bank0
1:Bank1
Accumulator – ACC
TheAccumulatoriscentraltotheoperationofanymicrocontrollerandiscloselyrelatedwith
operationscarriedoutbytheALU.TheAccumulatoristheplacewhereallintermediateresults
fromtheALUarestored.WithouttheAccumulatoritwouldbenecessarytowritetheresultof
eachcalculationorlogicaloperationsuchasaddition,subtraction,shift,etc.,totheDataMemory
resultinginhigherprogrammingandtimingoverheads.Datatransferoperationsusuallyinvolve
thetemporarystoragefunctionoftheAccumulator;forexample,whentransferringdatabetween
oneuserdefinedregisterandanother,itisnecessarytodothisbypassingthedatathroughthe
Accumulatorasnodirecttransferbetweentworegistersispermitted.
Program Counter Low Register – PCL
Toprovideadditionalprogramcontrolfunctions,thelowbyteoftheProgramCounterismade
accessibletoprogrammersbylocatingitwithintheSpecialPurposeareaoftheDataMemory.By
manipulatingthisregister,directjumpstootherprogramlocationsareeasilyimplemented.Loading
avaluedirectlyintothisPCLregisterwillcauseajumptothespeciedProgramMemorylocation,
however,astheregisterisonly8-bitwide,onlyjumpswithinthecurrentProgramMemorypageare
permitted.Whensuchoperationsareused,notethatadummycyclewillbeinserted.
Look-up Table Registers – TBLP, TBHP, TBLH
Thesethreespecialfunctionregistersareusedtocontroloperationofthelook-uptablewhichis
storedintheProgramMemory.TBLPandTBHParethetablepointerandindicatesthelocation
wherethetabledataislocated.Theirvaluemustbesetupbeforeanytablereadcommandsare
executed.Theirvaluecanbechanged,forexampleusingthe“INC”or“DEC”instructions,allowing
foreasytabledatapointingandreading.TBLHisthelocationwherethehighorderbyteofthetable
dataisstoredafteratablereaddatainstructionhasbeenexecuted.Notethatthelowerordertable
databyteistransferredtoauserdenedlocation.