Holtek HT66F002 - Oscillator; Oscillator Overview; System Clock Configurations

Rev. 1.71 36 April 11, 2017 Rev. 1.71 37 April 11, 2017
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
HT66F002/HT66F0025/HT66F003/HT66F004
Cost-Effective A/D Flash MCU with EEPROM
Oscillator
Variousoscillatoroptionsoffertheuserawiderangeoffunctionsaccordingtotheirvarious
applicationrequirements.Theflexiblefeaturesoftheoscillatorfunctionsensurethatthebest
optimisationcanbeachievedintermsofspeedandpowersaving.Oscillatorselectionsandoperation
areselectedthroughregisters.
Oscillator Overview
Inadditiontobeingthesourceofthemainsystemclocktheoscillatorsalsoprovideclocksources
fortheWatchdogTimerandTimeBaseInterrupts.Twofullyintegratedinternaloscillators,requiring
noexternalcomponents,areprovidedtoformawiderangeofbothfastandslowsystemoscillators.
Thehigherfrequencyoscillatorprovideshigherperformancebutcarrywithitthedisadvantageof
higherpowerrequirements,whiletheoppositeisofcoursetrueforthelowerfrequencyoscillator.
Withthecapabilityofdynamicallyswitchingbetweenfastandslowsystemclock,thesedevices
havetheexibilitytooptimizetheperformance/powerratio,afeatureespeciallyimportantinpower
sensitiveportableapplications.
Type Name Freq.
Internal High Speed RC HIRC 8MHz
Internal Low Speed RC LIRC 32kHz
Oscillator Types
System Clock Congurations
Therearetwomethodsofgeneratingthesystemclock,ahighspeedoscillatorandalowspeed
oscillator.Thehighspeedoscillatoristheinternal8MHzRCoscillator.Thelowspeedoscillatoris
theinternal32kHzRCoscillator.Selectingwhethertheloworhighspeedoscillatorisusedasthe
systemoscillatorisimplementedusingtheHLCLKbitandCKS2~CKS0bitsintheSMODregister
andasthesystemclockcanbedynamicallyselected.
HIRC
Prescaler
f
H
LIRC
Low Speed Oscillation
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
HLCLK
CKS2~CKS0 bits
f
SYS
f
L
High Speed Oscillation
System Clock Congurations