HT82B42RE datasheet(29/84 Pages) HOLTEK

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Rev. 1.10

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HT82B42R/HT82B42RE

I/O MCU with USB Interface

Configuring the Timer/Event Counter Input Clock Source

TheTimer/EventCounter'sclockcanoriginatefromvarioussources.Thesystemclocksourceis

usedwhentheTimer/EventCounter0isinthetimermodeorinthepulsewidthmeasurementmode.

Theinstructionclocksource(systemclocksourcedividedby4)isusedwhentheTimer/Event

Counter1isinthetimermodeorinthepulsewidthmeasurementmode.Theexternalclocksourceis

usedwhentheTimer/EventCounterisintheeventcountingmode,theclocksourcebeingprovided

ontheexternaltimerpin,TMR0orTMR1.DependingupontheconditionoftheT0EorT1Ebit,

eachhightolow,orlowtohightransitionontheexternaltimerpinwillincrementthecounterby

one.

T MR 0

T0 E

Ti me r/ Ev ent C oun te r

M ode C on tr ol

T0 ON

Pr el oad R eg is te r

Ti me r/ Ev ent

Co un te r

Da ta B us

Re l oad

Ov er fl ow

to In te rr up t

8 -B it T im er /E ve nt C o unt er

T0 M1 T0 M0

f SY S /4

8-bit Timer/Event Counter 0 Structure

TM R1

T1 E

Ti me r/ Ev ent C oun te r

M ode C on tr ol

16 -B it

Pr el oad R eg is te r

Da ta B us

Re l oad

Ov er fl ow

to I nt er ru p t

Lo w By te

Bu ff er

T1 M1

T1 M0

T1 ON

Hi gh B yt e Lo w By te

16 -B it T im er /E ve n t C o unt er

f SYS /4

16-bit Timer/Event Counter 1 Structure

Timer Register – TMR0, TMR1L/TMR1H

ThetimerregistersarespecialfunctionregisterslocatedintheSpecialPurposeRAMDataMemory

andaretheplaceswheretheactualtimervaluesarestored.For8-bitTimer/EventCounter0,this

registerisknownasTMR0.For16-bitTimer/EventCounter1,thetimerregistersareknownas

TMR1LandTMR1H.Thevalueinthetimerregistersincreasesbyoneeachtimeaninternalclock

pulseisreceivedoranexternaltransitionoccursontheexternaltimerpin.Thetimerwillcountfrom

theinitialvalueloadedbythepreloadregistertothefullcountofFFHforthe8-bittimerorFFFFH

forthe16-bittimeratwhichpointthetimeroverflowsandaninternalinterruptsignalisgenerated.

Thetimervaluewillthenberesetwiththeinitialpreloadregistervalueandcontinuecounting.

ToachieveamaximumfullrangecountofFFHforthe8-bittimerorFFFFHforthe16-bittimer,

thepreloadregistersmustfirstbeclearedtoallzeros.Itshouldbenotedthatafterpower-on,the

preloadregisterwillbeinanunknowncondition.NotethatiftheTimer/EventCounterisswitched

offanddataiswrittentoitspreloadregisters,thisdatawillbeimmediatelywrittenintotheactual

timerregisters.However,iftheTimer/EventCounterisenabledandcounting,anynewdatawritten

intothepreloaddataregistersduringthisperiodwillremaininthepreloadregistersandwillonlybe

writtenintothetimerregistersthenexttimeanoverflowoccurs.

HT82B42RE Datasheet(PDF) 29 Page - Holtek Semiconductor Inc

HT82B42RE Datasheet(HTML) 29 Page - Holtek Semiconductor Inc

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