HT67F488 datasheet(35/171 Pages) HOLTEK

35 / 171 page

Rev. 1.60

�ove��e� �� 016

HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & 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

TheEEPROMaddressofthedatatobewrittenmustfirstbeplacedintheEEAregisterandthedata

placedintheEEDregister.TowritedatatotheEEPROM,thewriteenablebit,WREN,intheEEC

registermustfirstbesethightoenablethewritefunction.Afterthis,theWRbitintheEECregister

mustbeimmediatelysethightoinitiateawritecycle.Thesetwoinstructionsmustbeexecuted

consecutively.TheglobalinterruptbitEMIshouldalsofirstbeclearedbeforeimplementingany

writeoperations,andthensetagainafterthewritecyclehasstarted.SettingtheWRbithighwillnot

initiateawritecycleiftheWRENbithasnotbeenset.AstheEEPROMwritecycleiscontrolled

usinganinternaltimerwhoseoperationisasynchronoustomicrocontrollersystemclock,acertain

timewillelapsebeforethedatawillhavebeenwrittenintotheEEPROM.Detectingwhenthewrite

cyclehasfinishedcanbeimplementedeitherbypollingtheWRbitintheEECregisterorbyusing

theEEPROMinterrupt.Whenthewritecycleterminates,theWRbitwillbeautomaticallycleared

tozerobythemicrocontroller,informingtheuserthatthedatahasbeenwrittentotheEEPROM.

TheapplicationprogramcanthereforepolltheWRbittodeterminewhenthewritecyclehasended.

Write Protection

Protectionagainstinadvertentwriteoperationisprovidedinseveralways.Afterthedeviceis

powered-ontheWriteEnablebitinthecontrolregisterwillbeclearedpreventinganywrite

operations.Alsoatpower-onMP1L/MP1HandMP2L/MP2Hwillberesettozero,whichmeans

thatDataMemorySector0willbeselected.AstheEEPROMcontrolregisterislocatedinSector1,

thisaddsafurthermeasureofprotectionagainstspuriouswriteoperations.Duringnormalprogram

operation,ensuringthattheWriteEnablebitinthecontrolregisterisclearedwillsafeguardagainst

incorrectwriteoperations.

EEPROM Interrupt

TheEEPROMwriteinterruptisgeneratedwhenanEEPROMwritecyclehasended.TheEEPROM

interruptmustfirstbeenabledbysettingtheDEEbitintherelevantinterruptregister.Howeveras

theEEPROMiscontainedwithinaMulti-functionInterrupt,theassociatedmulti-functioninterrupt

enablebitmustalsobeset.WhenanEEPROMwritecycleends,theDEFrequestflagandits

associatedmulti-functioninterruptrequestflagwillbothbeset.Iftheglobal,EEPROMandMulti-

functioninterruptsareenabledandthestackisnotfull,ajumptotheassociatedMulti-function

Interruptvectorwilltakeplace.WhentheinterruptisservicedonlytheMulti-functioninterruptflag

willbeautomaticallyreset,theEEPROMinterruptflagmustbemanuallyresetbytheapplication

program.MoredetailscanbeobtainedintheInterruptsection.

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