HT46R003B datasheet(41/76 Pages) HOLTEK

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HT46R003B

Cost-Effective A/D 8-bit OTP MCU

HT46R003B

Cost-Effective A/D 8-bit OTP MCU

WhentheTimer/EventCounterisread,orifdataiswrittentothepreloadregister,theclockis

inhibitedtoavoiderrors,howeverasthismayresultinacountingerror,thisshouldbetakeninto

accountbytheprogrammer.Caremustbetakentoensurethatthetimersareproperlyinitialised

beforeusingthemforthefirsttime.Theassociatedtimerenablebitsintheinterruptcontrol

registermustbeproperlysetotherwisetheinternalinterruptassociatedwiththetimerwillremain

inactive.Theedgeselect,timermodeandclocksourcecontrolbitsintimercontrolregistermust

alsobecorrectlysettoensurethetimerisproperlyconfiguredfortherequiredapplication.Itis

alsoimportanttoensurethataninitialvalueisfirstloadedintothetimerregistersbeforethetimer

isswitchedon;thisisbecauseafterpower-ontheinitialvaluesofthetimerregistersareunknown.

Afterthetimerhasbeeninitialisedthetimercanbeturnedonandoffbycontrollingtheenablebitin

thetimercontrolregister.

WhentheTimer/EventCounteroverflows,itscorrespondinginterruptrequestflagintheinterrupt

controlregisterwillbeset.IftheTimer/EventCounterinterruptisenabledthiswillinturngenerate

aninterruptsignal.Howeverirrespectiveofwhethertheinterruptsareenabledornot,aTimer/Event

Counteroverflowwillalsogenerateawake-upsignalifthedeviceisinaPower-downcondition.This

situationmayoccuriftheTimer/EventCounterisintheEventCountingModeandiftheexternal

signalcontinuestochangestate.Insuchacase,theTimer/EventCounterwillcontinuetocount

theseexternaleventsandifanoverflowoccursthedevicewillbewokenupfromitsPower-down

condition.Topreventsuchawake-upfromoccurring,thetimerinterruptrequestflagshouldfirstbe

sethighbeforeissuingthe“HALT”instructiontoentertheSleepMode.

Timer Program Example

TheprogramshowshowtheTimer/EventCounterregistersaresetalongwithhowtheinterruptsare

enabledandmanaged.NotehowtheTimer/EventCounteristurnedon,bysettingbit4oftheTimer

ControlRegister.TheTimer/EventCountercanbeturnedoffinasimilarwaybyclearingthesame

bit.ThisexampleprogramsetstheTimer/EventCounterstobeinthetimermode,whichusesthe

internalsystemclockastheirclocksource.

PFD Programming Example

org 04h

; external interrupt vector

org 08h

; Timer/Event Counter interrupt vector

jmptmrint;jumpherewhenTimeroverflows

org 20h

; main program

; internal Timer interrupt routine

tmrint:

; Timer main program placed here

begin:

; set Timer registers

mov a,09bh

; set Timer preload value

mov tmr,a

mov a,081h

; set Timer control register

mov tmrc,a

; timer mode and prescaler set to /2

mov a, 0c0H

; select fSYSfortheTMRclocksource

mov wdtc, a

; set interrupt register

mov a,05h

; enable master interrupt and both timer interrupts

mov intc0,a

set tmrc.4

; start Timer

HT46R003B Datasheet(PDF) 41 Page - Holtek Semiconductor Inc

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