HT66F20 datasheet(49/298 Pages) HOLTEK

49 / 298 page

Rev. 1.90

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Rev. 1.90

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HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit MCU with EEPROM

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit 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.Afterthedeviceis

powered-ontheWriteEnablebitinthecontrolregisterwillbeclearedpreventinganywrite

operations.Alsoatpower-ontheBankPointer,BP,willberesettozero,whichmeansthatData

MemoryBank0willbeselected.AstheEEPROMcontrolregisterislocatedinBank1,thisaddsa

furthermeasureofprotectionagainstspuriouswriteoperations.Duringnormalprogramoperation,

ensuringthattheWriteEnablebitinthecontrolregisterisclearedwillsafeguardagainstincorrect

writeoperations.

EEPROM Interrupt

TheEEPROMwriteorreadinterruptisgeneratedwhenanEEPROMwriteorreadcyclehas

ended.TheEEPROMinterruptmustfirstbeenabledbysettingtheDEEbitintherelevantinterrupt

multi-functioninterruptenablebitmustalsobeset.WhenanEEPROMwritecycleends,the

DEFrequestflaganditsassociatedmulti-functioninterruptrequestflagwillbothbeset.Ifthe

global,EEPROMandMulti-functioninterruptsareenabledandthestackisnotfull,ajumpto

theassociatedMulti-functionInterruptvectorwilltakeplace.Whentheinterruptisservicedonly

theMulti-functioninterruptflagwillbeautomaticallyreset,theEEPROMinterruptflagmustbe

manuallyresetbytheapplicationprogram.MoredetailscanbeobtainedintheInterruptsection.

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