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HT45FM2C Datasheet(PDF) 33 Page - Holtek Semiconductor Inc |
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HT45FM2C Datasheet(HTML) 33 Page - Holtek Semiconductor Inc |
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33 / 171 page  Rev. 1.10 �� �a� �0� �01� Rev. 1.10 �� �a� �0� �01� HT45FM2C Brushless DC Motor Flash Type 8-Bit MCU HT45FM2C Brushless DC Motor Flash Type 8-Bit MCU Preliminar� 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 TheEEPROMwriteorreadinterruptisgeneratedwhenanEEPROMwriteorreadcyclehasended. TheEEPROMinterruptmustfirstbeenabledbysettingtheEPWEbitintherelevantinterrupt register.HoweverastheEEPROMiscontainedwithinaMulti-functionInterrupt,theassociated multi-functioninterruptenablebitmustalsobeset.WhenanEEPROMwritecycleends,the EPWFrequestflaganditsassociatedmulti-functioninterruptrequestflagwillbothbeset.Ifthe global,EEPROMandMulti-functioninterruptsareenabledandthestackisnotfull,ajumpto theassociatedMulti-functionInterruptvectorwilltakeplace.Whentheinterruptisservicedonly theMulti-functioninterruptflagwillbeautomaticallyreset,theEEPROMinterruptflagmustbe manuallyresetbytheapplicationprogram.MoredetailscanbeobtainedintheInterruptsection. Programming Consideration CaremustbetakenthatdataisnotinadvertentlywrittentotheEEPROM.Protectioncanbe enhancedbyensuringthattheWriteEnablebitisnormallyclearedtozerowhennotwriting.Also theBankPointercouldbenormallyclearedtozeroasthiswouldinhibitaccesstoBank1where theEEPROMcontrolregisterexist.Althoughcertainlynotnecessary,considerationmightbegiven intheapplicationprogramtothecheckingofthevalidityofnewwritedatabyasimplereadback process. |
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