HT66F0176 datasheet(37/165 Pages) HOLTEK

37 / 165 page

Rev. 1.20

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HT66F0176

A/D Flash MCU with EEPROM

HT66F0176

A/D Flash MCU with EEPROM

Oscillators

Variousoscillatortypesoffertheuserawiderangeoffunctionsaccordingtotheirvariousapplication

requirements.Theflexiblefeaturesoftheoscillatorfunctionsensurethatthebestoptimisationcan

beachievedintermsofspeedandpowersaving.Oscillatorselectionsandoperationareselected

throughacombinationofconfigurationoptionsandrelevantcontrolregisters.

Oscillator Overview

Inadditiontobeingthesourceofthemainsystemclocktheoscillatorsalsoprovideclocksources

fortheWatchdogTimerandTimeBaseInterrupts.Externaloscillatorsrequiringsomeexternal

componentsaswellasfullyintegratedinternaloscillators,requiringnoexternalcomponents,are

providedtoformawiderangeofbothfastandslowsystemoscillators.Alloscillatoroptionsare

selectedthroughconfigurationoptions.Thehigherfrequencyoscillatorsprovidehigherperformance

butcarrywithitthedisadvantageofhigherpowerrequirements,whiletheoppositeisofcoursetrue

forthelowerfrequencyoscillators.Withthecapabilityofdynamicallyswitchingbetweenfastand

slowsystemclock,thedevicehastheflexibilitytooptimizetheperformance/powerratio,afeature

especiallyimportantinpowersensitiveportableapplications.

Type

Name

Frequency

Pins

Hi�h Speed External Crystal

HXT

400 kHz~20 MHz

OSC1/OSC2

Hi�h Speed Internal RC

HIRC

�/12/16 MHz

—

Low Speed External Crystal

LXT

32.�6� kHz

XT1/XT2

Low Speed Internal RC

LIRC

32 kHz

—

Oscillator Types

System Clock Configurations

Therearefourmethodsofgeneratingthesystemclock,twohighspeedoscillatorsandtwolow

speedoscillatorsforthedevice.Thehighspeedoscillatoristheexternalcrystal/ceramicoscillator,

HXT,andtheinternal8/12/16MHzRCoscillator,HIRC.Thetwolowspeedoscillatorsarethe

internal32kHzRCoscillator,LIRC,andtheexternal32.768kHzcrystaloscillator,LXT.Selecting

whethertheloworhighspeedoscillatorisusedasthesystemoscillatorisimplementedusingthe

HLCLKbitandCKS2~CKS0bitsintheSMODregisterandasthesystemclockcanbedynamically

selected.

Theactualsourceclockusedforeachofthehighandlowspeedoscillatorsischosenvia

configurationoptions.Thefrequencyoftheslowspeedorhighspeedsystemclockisalso

determinedusingtheHLCLKbitandCKS2~CKS0bitsintheSMODregister.Notethattwo

oscillatorselectionsmustbemadenamelyonehighspeedandonelowspeedsystemoscillators.Itis

notpossibletochooseano-oscillatorselectionforeitherthehighorlowspeedoscillator.TheOSC1

andOSC2pinsareusedtoconnecttheexternalcomponentsfortheexternalcrystal.

HT66F0176 Datasheet(PDF) 37 Page - Holtek Semiconductor Inc

HT66F0176 Datasheet(HTML) 37 Page - Holtek Semiconductor Inc

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