HT45FH4M
Lithium Battery Backup Power ASSP MCU
Bank Pointer – BP
Forꢀthisꢀdevice,ꢀtheꢀDataꢀMemoryꢀisꢀdividedꢀintoꢀtwoꢀbanks,ꢀBank0ꢀandꢀBank1.ꢀSelectingꢀtheꢀ
requiredꢀDataꢀMemoryꢀareaꢀisꢀachievedꢀusingꢀtheꢀBankꢀPointer.ꢀBitꢀ0ꢀofꢀtheꢀBankꢀPointerꢀisꢀusedꢀtoꢀ
selectꢀDataꢀMemoryꢀBanksꢀ0~1.ꢀ
TheꢀDataꢀMemoryꢀisꢀinitialisedꢀtoꢀBankꢀ0ꢀafterꢀaꢀreset,ꢀexceptꢀforꢀaꢀWDTꢀtime-outꢀresetꢀinꢀtheꢀPowerꢀ
DownꢀMode,ꢀinꢀwhichꢀcase,ꢀtheꢀDataꢀMemoryꢀbankꢀremainsꢀunaffected.ꢀItꢀshouldꢀbeꢀnotedꢀthatꢀtheꢀ
SpecialꢀFunctionꢀDataꢀMemoryꢀisꢀnotꢀaffectedꢀbyꢀtheꢀbankꢀselection,ꢀwhichꢀmeansꢀthatꢀtheꢀSpecialꢀ
FunctionꢀRegistersꢀcanꢀbeꢀaccessedꢀfromꢀwithinꢀanyꢀbank.ꢀDirectlyꢀaddressingꢀtheꢀDataꢀMemoryꢀ
willꢀalwaysꢀresultꢀinꢀBankꢀ0ꢀbeingꢀaccessedꢀirrespectiveꢀofꢀtheꢀvalueꢀofꢀtheꢀBankꢀPointer.ꢀAccessingꢀ
dataꢀfromꢀBank1ꢀmustꢀbeꢀimplementedꢀusingꢀIndirectꢀAddressing.ꢀ
BP Register
Bit
7
6
5
4
3
2
1
0
DMBP0
R/W
0
Name
R/W
—
—
—
—
—
—
—
—
—
—
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—
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—
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—
—
—
POR
Bitꢀ7ꢀ~ꢀ1ꢀ
Bitꢀ0ꢀ
Unimplemented,ꢀreadꢀasꢀ"0"
DMBP0:ꢀSelectꢀDataꢀMemoryꢀBanksꢀ
ꢀ 0:ꢀBankꢀ0ꢀ
ꢀ 1:ꢀBankꢀ1
Accumulator – ACC
TheꢀAccumulatorꢀisꢀcentralꢀtoꢀtheꢀoperationꢀofꢀanyꢀmicrocontrollerꢀandꢀisꢀcloselyꢀrelatedꢀwithꢀ
operationsꢀcarriedꢀoutꢀbyꢀtheꢀALU.ꢀTheꢀAccumulatorꢀisꢀtheꢀplaceꢀwhereꢀallꢀintermediateꢀresultsꢀ
fromꢀtheꢀALUꢀareꢀstored.ꢀWithoutꢀtheꢀAccumulatorꢀitꢀwouldꢀbeꢀnecessaryꢀtoꢀwriteꢀtheꢀresultꢀofꢀ
eachꢀcalculationꢀorꢀlogicalꢀoperationꢀsuchꢀasꢀaddition,ꢀsubtraction,ꢀshift,ꢀetc.,ꢀtoꢀtheꢀDataꢀMemoryꢀ
resultingꢀinꢀhigherꢀprogrammingꢀandꢀtimingꢀoverheads.ꢀDataꢀtransferꢀoperationsꢀusuallyꢀinvolveꢀ
theꢀtemporaryꢀstorageꢀfunctionꢀofꢀtheꢀAccumulator;ꢀforꢀexample,ꢀwhenꢀtransferringꢀdataꢀbetweenꢀ
oneꢀuser-definedꢀregisterꢀandꢀanother,ꢀitꢀisꢀnecessaryꢀtoꢀdoꢀthisꢀbyꢀpassingꢀtheꢀdataꢀthroughꢀtheꢀ
Accumulatorꢀasꢀnoꢀdirectꢀtransferꢀbetweenꢀtwoꢀregistersꢀisꢀpermitted.
Program Counter Low Register – PCL
Toꢀprovideꢀadditionalꢀprogramꢀcontrolꢀfunctions,ꢀtheꢀlowꢀbyteꢀofꢀtheꢀProgramꢀCounterꢀisꢀmadeꢀ
accessibleꢀtoꢀprogrammersꢀbyꢀlocatingꢀitꢀwithinꢀtheꢀSpecialꢀPurposeꢀareaꢀofꢀtheꢀDataꢀMemory.ꢀByꢀ
manipulatingꢀthisꢀregister,ꢀdirectꢀjumpsꢀtoꢀotherꢀprogramꢀlocationsꢀareꢀeasilyꢀimplemented.ꢀLoadingꢀ
aꢀvalueꢀdirectlyꢀintoꢀthisꢀPCLꢀregisterꢀwillꢀcauseꢀaꢀjumpꢀtoꢀtheꢀspecifiedꢀProgramꢀMemoryꢀlocation,ꢀ
however,ꢀasꢀtheꢀregisterꢀisꢀonlyꢀ8-bitꢀwide,ꢀonlyꢀjumpsꢀwithinꢀtheꢀcurrentꢀProgramꢀMemoryꢀpageꢀareꢀ
permitted.ꢀWhenꢀsuchꢀoperationsꢀareꢀused,ꢀnoteꢀthatꢀaꢀdummyꢀcycleꢀwillꢀbeꢀinserted.
Look-up Table Registers – TBLP, TBHP, TBLH
Theseꢀthreeꢀspecialꢀfunctionꢀregistersꢀareꢀusedꢀtoꢀcontrolꢀoperationꢀofꢀtheꢀlook-upꢀtableꢀwhichꢀisꢀ
storedꢀinꢀtheꢀProgramꢀMemory.ꢀTBLPꢀandꢀTBHPꢀareꢀtheꢀtableꢀpointersꢀandꢀindicateꢀtheꢀlocationꢀ
whereꢀtheꢀtableꢀdataꢀisꢀlocated.ꢀTheirꢀvalueꢀmustꢀbeꢀsetupꢀbeforeꢀanyꢀtableꢀreadꢀcommandsꢀareꢀ
executed.ꢀTheirꢀvalueꢀcanꢀbeꢀchanged,ꢀforꢀexampleꢀusingꢀtheꢀ“INC”ꢀorꢀ“DEC”ꢀinstructions,ꢀallowingꢀ
forꢀeasyꢀtableꢀdataꢀpointingꢀandꢀreading.ꢀTBLHꢀisꢀtheꢀlocationꢀwhereꢀtheꢀhighꢀorderꢀbyteꢀofꢀtheꢀtableꢀ
dataꢀisꢀstoredꢀafterꢀaꢀtableꢀreadꢀdataꢀinstructionꢀhasꢀbeenꢀexecuted.ꢀNoteꢀthatꢀtheꢀlowerꢀorderꢀtableꢀ
dataꢀbyteꢀisꢀtransferredꢀtoꢀaꢀuserꢀdefinedꢀlocation.
Rev. 1.10
ꢅ4
�anꢀaꢁꢂ 1ꢃꢄ ꢅ01ꢆ
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