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HT82B42R Scheda tecnica(PDF) 34 Page - Holtek Semiconductor Inc |
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HT82B42R Scheda tecnica(HTML) 34 Page - Holtek Semiconductor Inc |
34 / 84 page Rev. 1.10 3� �ove��e� 0�� �01� Rev. 1.10 3� �ove��e� 0�� �01� HT82B42R/HT82B42RE I/O MCU with USB Interface +1 +2 +3 +4 Ti me r Ex te rn al T im er Pi n I npu t T0 ON o r T1 ON (w it h T0 E or T 1E =0 ) Pr es c al er O ut put In c re me nt Ti me r C oun te r Pr es c al er O ut put i s sa mp le d at e ve ry fa lli ng edge o f T1 . Pulse Width Capture Mode Timing Chart I/O Interfacing TheTimer/EventCounter,whenconfiguredtorunintheeventcounterorpulsewidthmeasurement mode,requiretheuseoftheexternalTMR0andTMR1pinsforcorrectoperation.Asthesepins aresharedpinstheymustbeconfiguredcorrectlytoensuretheyaresetupforuseasTimer/Event CounterinputsandnotasanormalI/Opins.Thisisimplementedbyensuringthatthemodeselect bitsintheTimer/EventCountercontrolregister,selecteithertheeventcounterorpulsewidth measurementmode.AdditionallythePortControlRegisterbitsforthesepinsmustbesethighto ensurethatthepinissetupasaninput.Anypull-highresistorconfigurationoptiononthesepinswill remainvalidevenifthepinisusedasaTimer/EventCounterinput. Programming Considerations Whenconfiguredtoruninthetimermode,theinternalsystemclockisusedasthetimerclock sourceandisthereforesynchronisedwiththeoveralloperationofthemicrocontroller.Inthismode whentheappropriatetimerregisterisfull,themicrocontrollerwillgenerateaninternalinterrupt signaldirectingtheprogramflowtotherespectiveinternalinterruptvector.Forthepulsewidth measurementmode,theinternalsystemclockisalsousedasthetimerclocksourcebutthetimer willonlyrunwhenthecorrectlogicconditionappearsontheexternaltimerinputpin.Asthisis anexternaleventandnotsynchronisedwiththeinternaltimerclock,themicrocontrollerwillonly seethisexternaleventwhenthenexttimerclockpulsearrives.Asaresult,theremaybesmall differencesinmeasuredvaluesrequiringprogrammerstotakethisintoaccountduringprogramming. Thesameappliesifthetimerisconfiguredtobeintheeventcountingmode,whichagainisan externaleventandnotsynchronisedwiththeinternalsystemortimerclock. WhentheTimer/EventCounterisread,orifdataiswrittentothepreloadregister,theclockis inhibitedtoavoiderrors,howeverasthismayresultinacountingerror,thisshouldbetakeninto accountbytheprogrammer.Caremustbetakentoensurethatthetimersareproperlyinitialised beforeusingthemforthefirsttime.Theassociatedtimerenablebitsintheinterruptcontrol registermustbeproperlysetotherwisetheinternalinterruptassociatedwiththetimerwillremain inactive.Theedgeselecttimermodeandclocksourcecontrolbitsintimercontrolregistermust alsobecorrectlysettoensurethetimerisproperlyconfiguredfortherequiredapplication.Itis alsoimportanttoensurethataninitialvalueisfirstloadedintothetimerregistersbeforethetimer isswitchedon;thisisbecauseafterpower-ontheinitialvaluesofthetimerregistersareunknown. Afterthetimerhasbeeninitialisedthetimercanbeturnedonandoffbycontrollingtheenablebitin thetimercontrolregister.Notethatsettingthetimerenablebithightoturnthetimeron,shouldonly beexecutedafterthetimermodebitshavebeenproperlysetup.Settingthetimerenablebithigh togetherwithamodebitmodification,mayleadtoimpropertimeroperationifexecutedasasingle timercontrolregisterbytewriteinstruction. |
Codice articolo simile - HT82B42R_14 |
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Descrizione simile - HT82B42R_14 |
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