HT66F005 datasheet(29/109 Pages) HOLTEK

29 / 109 page

Rev. 1.30

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Rev. 1.30

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HT66F005/HT66F006

Cost-Effective A/D Flash MCU with EEPROM

HT66F005/HT66F006

Cost-Effective A/D Flash MCU with EEPROM

Reading Data from the EEPROM

ToreaddatafromtheEEPROM,thereadenablebit,RDEN,intheEECregistermustfirstbeset

hightoenablethereadfunction.TheEEPROMaddressofthedatatobereadmustthenbeplaced

intheEEAregister.IftheRDbitintheEECregisterisnowsethigh,areadcyclewillbeinitiated.

SettingtheRDbithighwillnotinitiateareadoperationiftheRDENbithasnotbeenset.When

thereadcycleterminates,theRDbitwillbeautomaticallyclearedtozero,afterwhichthedatacan

bereadfromtheEEDregister.ThedatawillremainintheEEDregisteruntilanotherreadorwrite

operationisexecuted.TheapplicationprogramcanpolltheRDbittodeterminewhenthedatais

validforreading.

Writing Data to the EEPROM

TowritedatatotheEEPROM,thewriteenablebit,WREN,intheEECregistermustfirstbeset

hightoenablethewritefunction.TheEEPROMaddressofthedatatobewrittenmustthenbe

placedintheEEAregisterandthedataplacedintheEEDregister.IftheWRbitintheEECregister

isnowsethigh,aninternalwritecyclewillthenbeinitiated.SettingtheWRbithighwillnotinitiate

awritecycleiftheWRENbithasnotbeenset.AstheEEPROMwritecycleiscontrolledusingan

internaltimerwhoseoperationisasynchronoustomicrocontrollersystemclock,acertaintimewill

elapsebeforethedatawillhavebeenwrittenintotheEEPROM.Detectingwhenthewritecycle

hasfinishedcanbeimplementedeitherbypollingtheWRbitintheEECregisterorbyusingthe

EEPROMinterrupt.Whenthewritecycleterminates,theWRbitwillbeautomaticallyclearedto

zerobythemicrocontroller,informingtheuserthatthedatahasbeenwrittentotheEEPROM.The

applicationprogramcanthereforepolltheWRbittodeterminewhenthewritecyclehasended.

Write Protection

Protectionagainstinadvertentwriteoperationisprovidedinseveralways.Afterthedevices

arepowered-ontheWriteEnablebitinthecontrolregisterwillbeclearedpreventinganywrite

operations.Alsoatpower-ontheBankPointer,BP,willberesettozero,whichmeanthatData

MemoryBank0willbeselected.AstheEEPROMcontrolregisterislocatedinBank1,thisaddsa

furthermeasureofprotectionagainstspuriouswriteoperations.Duringnormalprogramoperation,

ensuringthattheWriteEnablebitinthecontrolregisterisclearedwillsafeguardagainstincorrect

writeoperations.

EEPROM Interrupt

TheEEPROMwriteinterruptisgeneratedwhenanEEPROMwritecyclehasended.TheEEPROM

interruptmustfirstbeenabledbysettingtheDEEbitintherelevantinterruptregister.Whenan

EEPROMwritecycleends,theDEFrequestflagwillbeset.IftheglobalandEEPROMinterrupts

areenabledandthestackisnotfull,ajumptotheassociatedInterruptvectorwilltakeplace.When

theinterruptisservicedtheEEPROMinterruptflagwillbeautomaticallyreset.Moredetailscanbe

obtainedintheInterruptsection.

Programming Considerations

CaremustbetakenthatdataisnotinadvertentlywrittentotheEEPROM.Protectioncanbe

enhancedbyensuringthattheWriteEnablebitisnormallyclearedtozerowhennotwriting.Also

theBankPointercouldbenormallyclearedtozeroasthiswouldinhibitaccesstoBank1where

theEEPROMcontrolregisterexist.Althoughcertainlynotnecessary,considerationmightbegiven

intheapplicationprogramtothecheckingofthevalidityofnewwritedatabyasimplereadback

process.

HT66F005 Datasheet(PDF) 29 Page - Holtek Semiconductor Inc

HT66F005 Datasheet(HTML) 29 Page - Holtek Semiconductor Inc

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