User`s guide

Rev. 1.10 32 November 14, 2014 Rev. 1.10 33 November 14, 2014
HT66FW2230
Wireless Charger A/D Flash 8-Bit MCU
Operating Modes and System Clocks
Presentdayapplicationsrequirethattheirmicrocontrollershavehighperformancebutoftenstill
demandthattheyconsumeaslittlepoweraspossible,conictingrequirementsthatareespecially
trueinbatterypoweredportableapplications.Thefastclocksrequiredforhighperformancewill
bytheirnatureincreasecurrentconsumptionandofcoursevice-versa,lowerspeedclocksreduce
currentconsumption.AsHoltekhasprovidedthisdevicewithbothhighandlowspeedclock
sourcesandthemeanstoswitchbetweenthemdynamically,theusercanoptimisetheoperationof
theirmicrocontrollertoachievethebestperformance/powerratio.
System Clocks
ThedevicehasmanydifferentclocksourcesforboththeCPUandperipheralfunctionoperation.By
providingtheuserwithawiderangeofclockselectionsusingregisterprogramming,aclocksystem
canbeconguredtoobtainmaximumapplicationperformance.
Themainsystemclock,cancomefromeitherahighfrequency,f
H
,orlowfrequency,f
SUB
,source,
andisselectedusingtheCKS2~CKS0bitsintheSCCregister.Thehighspeedsystemclockcanbe
sourcedfromeitheranHXTorHIRCoscillatorbyconguringtheFHSbit.Thelowspeedsystem
clocksourcecanbesourcedfromtheLIRCoscillator.Theotherchoice,whichisadividedversion
ofthehighspeedsystemoscillatorhasarangeoff
H
/2~f
H
/64.
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
System Clock Congurations
Note:Whenthesystemclocksourcef
SYS
isswitchedtof
SUB
fromf
H
,thehighspeedoscillationwill
stoptoconservethepowerorcontinuetooscillatetoprovidetheclocksource,f
H
~f
H
/64,for
peripheralcircuittouse,whichisdeterminedbyconguringthecorrespondinghighspeed
oscillatorenablecontrolbit.