HT82B42RE datasheet(23/84 Pages) HOLTEK

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HT82B42R/HT82B42RE

I/O MCU with USB Interface

Look-up Table Registers – TBLP, TBLH, TBHP

Thesetwospecialfunctionregistersareusedtocontroloperationofthelook-uptablewhichisstored

intheProgramMemory.TBLPandTBHParethetablepointersandindicatethelocationwherethe

tabledataislocated.Theirvaluemustbesetupbeforeanytablereadcommandsareexecuted.Their

valuescanbechanged,forexampleusingthe"INC"or"DEC"instructions,allowingforeasytable

datapointingandreading.TBLHisthelocationwherethehighorderbyteofthetabledataisstored

afteratablereaddatainstructionhasbeenexecuted.

Status Register – STATUS

This8-bitregistercontainsthezeroflag(Z),carryflag(C),auxiliarycarryflag(AC),overflowflag

(OV),powerdownflag(PDF),andwatchdogtime-outflag(TO).Thesearithmetic/logicaloperation

andsystemmanagementflagsareusedtorecordthestatusandoperationofthemicrocontroller.

WiththeexceptionoftheTOandPDFflags,bitsinthestatusregistercanbealteredbyinstructions

likemostotherregisters.AnydatawrittenintothestatusregisterwillnotchangetheTOorPDFflag.

Inaddition,operationsrelatedtothestatusregistermaygivedifferentresultsduetothedifferent

instructionoperations.TheTOflagcanbeaffectedonlybyasystempower-up,aWDTtime-outor

byexecutingthe"CLRWDT"or"HALT"instruction.ThePDFflagisaffectedonlybyexecuting

the"HALT"or"CLRWDT"instructionorduringasystempower-up.

TheZ,OV,ACandCflagsgenerallyreflectthestatusofthelatestoperations.

• Cissetifanoperationresultsinacarryduringanadditionoperationorifaborrowdoesnottake

placeduringasubtractionoperation;otherwiseCiscleared.Cisalsoaffectedbyarotatethrough

carryinstruction.

• ACissetifanoperationresultsinacarryoutofthelownibblesinaddition,ornoborrowfrom

thehighnibbleintothelownibbleinsubtraction;otherwiseACiscleared.

• Zissetiftheresultofanarithmeticorlogicaloperationiszero;otherwiseZiscleared.

• OVissetifanoperationresultsinacarryintothehighest-orderbitbutnotacarryoutofthe

highest-orderbit,orviceversa;otherwiseOViscleared.

• PDFisclearedbyasystempower-uporexecutingthe"CLRWDT"instruction.PDFissetby

executingthe"HALT"instruction.

• TOisclearedbyasystempower-uporexecutingthe"CLRWDT"or"HALT"instruction.TOis

setbyaWDTtime-out.

Inaddition,onenteringaninterruptsequenceorexecutingasubroutinecall,thestatusregisterwill

notbepushedontothestackautomatically.Ifthecontentsofthestatusregistersareimportantandif

theinterruptroutinecanchangethestatusregister,precautionsmustbetakentocorrectlysaveit.

HT82B42RE Datasheet(PDF) 23 Page - Holtek Semiconductor Inc