HT45FM2C datasheet(48/171 Pages) HOLTEK

48 / 171 page

Rev. 1.10

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Rev. 1.10

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HT45FM2C

Brushless DC Motor Flash Type 8-Bit MCU

HT45FM2C

Brushless DC Motor Flash Type 8-Bit MCU

Preliminar�

Watchdog Timer Operation

NotethattheWatchdogTimerfunctionisalwaysenabled.TheWatchdogTimeroperatesby

providingadeviceresetwhenitstimeroverflows.Thismeansthatintheapplicationprogramand

duringnormaloperationtheuserhastostrategicallycleartheWatchdogTimerbeforeitoverflows

topreventtheWatchdogTimerfromexecutingareset.Thisisdoneusingtheclearwatchdog

instruction.Iftheprogrammalfunctionsforwhateverreason,jumpstoanunkownlocation,orenters

anendlessloop,theseclearinstructionswillnotbeexecutedinthecorrectmanner,inwhichcasethe

WatchdogTimerwilloverflowandresetthedevice.Therearefivebits,WE4~WE0,intheWDTC

registertoofferacontroloftheWatchdogTimer.IfWE4~WE0bitsaresettoaspecificvalueof

"10101"or"01010",theWDTisalwayenable.AnyothervaluesforthesebitswillkeeptheMCU

reset.

Undernormalprogramoperation,aWatchdogTimertime-outwillinitialiseadeviceresetandset

thestatusbitTO.However,ifthesystemisintheSLEEPorIDLEMode,whenaWatchdogTimer

time-outoccurs,theTObitinthestatusregisterwillbesetandonlytheProgramCounterandStack

Pointerwillbereset.ThreemethodscanbeadoptedtoclearthecontentsoftheWatchdogTimer.The

firstisanexternalhardwarereset,thesecondisusingtheWatchdogTimersoftwareclearinstruction

andthethirdisviaaHALTinstruction.

TocleartheWatchdogTimeristousethesingle“CLRWDT”instruction.Asimpleexecutionof

"CLRWDT"willcleartheWDT.

11- st age Di vi der

f S

WD T Ti me out

WS [2 :0 ]=

8- to -1 M UX

CL R WD T

CL R

WS 2~ WS 0

(f s/ 2 1 ~ f S /2 11 )

L IR C

7- st age Di vi der

000: 2 8 /f S

001: 2 10 /f S

010: 2 12 /f S

011 : 2 14 /f S

100: 2 15 /f S

101 : 2 16 /f S

110: 2 17 /f S

111 : 2 18 /f S

Watchdog Timer

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