User`s guide

Rev. 1.10 30 November 14, 2014 Rev. 1.10 31 November 14, 2014
HT66FW2230
Wireless Charger A/D Flash 8-Bit MCU
Oscillator
Variousoscillatorcongurations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the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.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oscillatorsprovidehigherperformancebutcarrywithitthedisadvantageof
higherpowerrequirements,whiletheoppositeisofcoursetrueforthelowerfrequencyoscillators.
Withthecapabilityofdynamicallyswitchingbetweenfastandslowsystemclock,thedevicehasthe
exibilitytooptimizetheperformance/powerratio,afeatureespeciallyimportantinpowersensitive
portableapplications.
Type Name Freq.
External Crystal HXT 20MHz
Internal High Speed RC HIRC 20MHz
Internal Low Speed RC LIRC 32kHz
Oscillator Types
System Clock Congurations
Therearethreemethodsofgeneratingthesystemclock,twohighspeedoscillatorsandalow
speedoscillator.Thehighspeedoscillatorsaretheexternal20MHzcrystalandinternal20MHzRC
oscillators.Thelowspeedoscillatoristheinternal32kHz(LIRC)oscillator.Selectingwhetherthe
loworhighspeedoscillatorisusedasthesystemoscillatorisimplementedusingtheFHSbitand
CKS2~CKS0bitsintheSCCregisterandasthesystemclockcanbedynamicallyselected.
Theactualsourceclockusedforthehighspeedandthelowspeedoscillatorsischosenviaregister.
Notethattwooscillatorselectionsmustbemadenamelyonehighspeedandonelowspeedsystem
oscillators.Itisnotpossibletochooseano-oscillatorselectionforeitherthehighorlowspeed
oscillator.
HXT
HIRC
f
H
LIRC
High Speed
Oscillation
Low Speed
Oscillation
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
FHS
CKS2~CKS0
f
SYS
f
SUB
MCD
Reset
MCD
f
SUB
HXTEN
HIRCEN
Prescaler