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HT45R4U датащи(PDF) 45 Page - Holtek Semiconductor Inc |
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HT45R4U датащи(HTML) 45 Page - Holtek Semiconductor Inc |
45 / 105 page Rev. 1.10 44 �a��� 1�� �01� Rev. 1.10 4� �a��� 1�� �01� HT45R4U TinyPowerTM A/D Type e-Banking ASSP OTP MCU with LCD Programmable Frequency Divider – PFD TheProgrammableFrequencyDividerprovidesameansofproducingavariablefrequencyoutput suitableforapplicationsrequiringaprecisefrequencygenerator. ThePFDoutputispin-sharedwiththeI/OpinPA3.ThePFDfunctionisselectedselectedviaa softwarecontrolbit,PFDC,however,ifnotselected,thepincanoperateasanormalI/Opin. TheclocksourceforthePFDcircuitoriginatesfromTimer/EventCounter0overflowsignal.The outputfrequencyiscontrolledbyloadingtherequiredvaluesintothetimerregistersandprescaler registerstogivetherequireddivisionratio.Thetimerwillbegintocount-upfromthispreload registervalueuntilfull,atwhichpointanoverflowsignalisgenerated,causingthePFDoutput tochangestate.Thetimerwillthenbeautomaticallyreloadedwiththepreloadregistervalueand continuecounting-up. ForthePFDoutputtofunction,itisessentialthatthecorrespondingbitofthePortAcontrolregisterPAC bit3issetupasanoutput.IfsetupasaninputthePFDoutputwillnotfunction,however,thepincanstill beusedasanormalinputpin.ThePFDoutputwillonlybeactivatedifbitPA3issetto″1″.Thisoutput databitisusedastheon/offcontrolbitforthePFDoutput.NotethatthePFDoutputwillbelowifthe PA3outputdatabitisclearedto″0″. Usingthismethodoffrequencygeneration,andifacrystaloscillatorisusedforthesystemclock, veryprecisevaluesoffrequencycanbegenerated. Ti me r Ov er fl ow PF D Cl oc k PA3 D at a PF D Ou tp ut a t PA3 PFD Output Control BitsT0PSC0~T0PSC2ofthecontrolregistercanbeusedtodefinethepre-scalingstagesofthe internalclocksourceoftheTimer/EventCounter.TheTimer/EventCounteroverflowsignalcanbe usedtogeneratesignalsforthePFDandTimerInterrupt. I/O Interfacing TheTimer/EventCounter,whenconfiguredtorunintheeventcounterorpulsewidthmeasurement mode,requiretheuseofexternalpinsforcorrectoperation.Asthesepinsaresharedpinsthey mustbeconfiguredcorrectlytoensuretheyaresetupforuseasTimer/EventCounterinputsand notasanormalI/Opins.ThisisimplementedbyensuringthatthemodeselectbitsintheTimer/ EventCountercontrolregister,selecteithertheeventcounterorpulsewidthmeasurementmode. AdditionallythePortControlRegistermustbesethightoensurethatthepinissetupasaninput. Anypull-highresistoronthesepinswillremainvalidevenifthepinisusedasaTimer/Event Counterinput. |
Аналогичный номер детали - HT45R4U |
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Аналогичное описание - HT45R4U |
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