HT82B42R datasheet(33/86 Pages) HOLTEK

33 / 86 page

Rev. 1.00

October 27, 2011

Rev. 1.00

October 27, 2011

HT82B42R/HT82B42RE

I/O MCU with USB Interface

Ti me r+ 2

Ex te rn al E ve nt

In cr em en t

Ti me r C oun te r

Ti me r+ 3

Ti me r+ 1

Event Counter Mode Timing Chart

Configuring the Pulse Width Measurement Mode

Inthismode,theTimer/EventCountercanbeutilisedtomeasurethewidthofexternalpulses

appliedtotheexternaltimerpin.Tooperateinthismode,theOperatingModeSelectbitpair,

T0M1/T0M0orT1M1/T1M0,intheTimerControlRegistermustbesettothecorrectvalueas

shown.

Control Register Operating Mode

Select Bits for the Pulse Width Capture Mode

Bit7

Bit6

Inthismodetheinternalclock,fSYS/4isusedastheinternalclockfortheTimer/EventCounters.

AftertheotherbitsintheTimerControlRegisterhavebeensetup,theenablebitT0ONorT1ON,

whichisbit4oftheTimerControlRegister,canbesethightoenabletheTimer/EventCounter,

howeveritwillnotactuallystartcountinguntilanactiveedgeisreceivedontheexternaltimerpin.

IftheActiveEdgeSelectbitT0EorT1E,whichisbit3oftheTimerControlRegister,islow,oncea

hightolowtransitionhasbeenreceivedontheexternaltimerpin,TMR0orTMR1,theTimer/Event

Counterwillstartcountinguntiltheexternaltimerpinreturnstoitsoriginalhighlevel.Atthispoint

theenablebitwillbeautomaticallyresettozeroandtheTimer/EventCounterwillstopcounting.If

theActiveEdgeSelectbitishigh,theTimer/EventCounterwillbegincountingoncealowtohigh

transitionhasbeenreceivedontheexternaltimerpinandstopcountingwhentheexternaltimerpin

returnstoitsoriginallowlevel.Asbefore,theenablebitwillbeautomaticallyresettozeroandthe

Timer/EventCounterwillstopcounting.ItisimportanttonotethatinthePulseWidthMeasurement

Mode,theenablebitisautomaticallyresettozerowhentheexternalcontrolsignalontheexternal

timerpinreturnstoitsoriginallevel,whereasintheothertwomodestheenablebitcanonlybereset

tozerounderprogramcontrol.

TheresidualvalueintheTimer/EventCounter,whichcannowbereadbytheprogram,therefore

representsthelengthofthepulsereceivedontheexternaltimerpin.Astheenablebithasnowbeen

reset,anyfurthertransitionsontheexternaltimerpinwillbeignored.Notuntiltheenablebitis

againsethighbytheprogramcanthetimerbeginfurtherpulsewidthmeasurements.Inthisway,

singleshotpulsemeasurementscanbeeasilymade.

ItshouldbenotedthatinthismodetheTimer/EventCounteriscontrolledbylogicaltransitions

ontheexternaltimerpinandnotbythelogiclevel.WhentheTimer/EventCounterisfulland

overflows,aninterruptsignalisgeneratedandtheTimer/EventCounterwillreloadthevaluealready

loadedintothepreloadregisterandcontinuecounting.Theinterruptcanbedisabledbyensuring

thattheTimer/EventCounterInterruptEnablebitintheInterruptControlRegister,INTC0,isreset

tozero.

AstheexternaltimerpinissharedwithanI/Opin,toensurethatthepinisconfiguredtooperateas

apulsewidthmeasurementpin,twothingshavetohappen.ThefirstistoensurethattheOperating

ModeSelectbitsintheTimerControlRegisterplacetheTimer/EventCounterinthePulseWidth

MeasurementMode,thesecondistoensurethattheportcontrolregisterconfiguresthepinasan

input.

HT82B42R Datasheet(PDF) 33 Page - Holtek Semiconductor Inc

HT82B42R Datasheet(HTML) 33 Page - Holtek Semiconductor Inc

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