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HT45F12 Datasheet(PDF) 31 Page - Holtek Semiconductor Inc |
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HT45F12 Datasheet(HTML) 31 Page - Holtek Semiconductor Inc |
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31 / 104 page  Rev. 0.00 30 �e�te��e� ��� �01� Rev. 0.00 31 �e�te��e� ��� �01� HT45F12 8-Bit Flash MCU with Op Amps & Comparators HT45F12 8-Bit Flash MCU with Op Amps & Comparators Reading Data from the EEPROM ToreaddatafromtheEEPROM,thereadenablebit,RDEN,intheEECTRLregistermustfirst besethightoenablethereadfunction.TheEEPROMaddressofthedatatobereadmustthenbe placedintheEEADDRregister.IftheRDbitintheEECTRLregisterisnowsethigh,areadcycle willbeinitiated.SettingtheRDbithighwillnotinitiateareadoperationiftheRDENbithasnot beenset.Whenthereadcycleterminates,theRDbitwillbeautomaticallyclearedtozero,after whichthedatacanbereadfromtheEEDATAregister.ThedatawillremainintheEEDATAregister untilanotherreadorwriteoperationisexecuted.TheapplicationprogramcanpolltheRDbitto determinewhenthedataisvalidforreading. Writing Data to the EEPROM TowritedatatotheEEPROM,thewriteenablebit,WTEN,intheEECTRLregistermustfirstbe sethightoenablethewritefunction.TheEEPROMaddressofthedatatobewrittenmustthenbe placedintheEEADDRregisterandthedataplacedintheEEDATAregister.IftheWTbitinthe EECTRLregisterisnowsethigh,aninternalwritecyclewillthenbeinitiated.SettingtheWTbit highwillnotinitiateawritecycleiftheWTENbithasnotbeenset.AstheEEPROMwritecycle iscontrolledusinganinternaltimerwhoseoperationisasynchronoustomicrocontrollersystem clock,acertaintimewillelapsebeforethedatawillhavebeenwrittenintotheEEPROM.Detecting whenthewritecyclehasfinishedcanbeimplementedeitherbypollingtheWTbitintheEECTRL registerorbyusingtheEEPROMinterrupt.Whenthewritecycleterminates,theWTbitwillbe automaticallyclearedtozerobythemicrocontroller,informingtheuserthatthedatahasbeen writtentotheEEPROM.TheapplicationprogramcanthereforepolltheWTbittodeterminewhen thewritecyclehasended. Write Protection Protectionagainstinadvertentwriteoperationisprovidedinseveralways.Afterthedeviceis powered-ontheWriteEnablebitinthecontrolregisterwillbeclearedpreventinganywrite operations.Alsoatpower-ontheBankPointer,BP,willberesettozero,whichmeansthatData MemoryBank0willbeselected.AstheEEPROMcontrolregisterislocatedinBank1,thisaddsa furthermeasureofprotectionagainstspuriouswriteoperations.Duringnormalprogramoperation, ensuringthattheWriteEnablebitinthecontrolregisterisclearedwillsafeguardagainstincorrect writeoperations. EEPROM Interrupt TheEEPROMwriteorreadinterruptisgeneratedwhenanEEPROMwriteorreadcyclehasended. TheEEPROMinterruptmustfirstbeenabledbysettingtheE2Ibitintherelevantinterruptregister. HoweverastheEEPROMiscontainedwithinaMulti-functionInterrupt,theassociatedmulti- functioninterruptenablebitmustalsobeset.WhenanEEPROMwritecycleends,theE2Frequest flaganditsassociatedmulti-functioninterruptrequestflagwillbothbeset.Iftheglobal,EEPROM andMulti-functioninterruptsareenabledandthestackisnotfull,ajumptotheassociatedMulti- functionInterruptvectorwilltakeplace.WhentheinterruptisservicedonlytheMulti-function interruptflagwillbeautomaticallyreset,theEEPROMinterruptflagmustbemanuallyresetbythe applicationprogram.MoredetailscanbeobtainedintheInterruptsection. |
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