HT45F12
8-Bit Flash MCU with Op Amps & Comparators
Operating Modes and System Clocks
Presentꢀdayꢀapplicationsꢀrequireꢀthatꢀtheirꢀmicrocontrollersꢀhaveꢀhighꢀperformanceꢀbutꢀoftenꢀstillꢀ
demandꢀthatꢀtheyꢀconsumeꢀasꢀlittleꢀpowerꢀasꢀpossible,ꢀconflictingꢀrequirementsꢀthatꢀareꢀespeciallyꢀ
trueꢀinꢀbatteryꢀpoweredꢀportableꢀapplications.ꢀTheꢀfastꢀclocksꢀrequiredꢀforꢀhighꢀperformanceꢀwillꢀ
byꢀtheirꢀnatureꢀincreaseꢀcurrentꢀconsumptionꢀandꢀofꢀcourseꢀvice-versa,ꢀlowerꢀspeedꢀclocksꢀreduceꢀ
currentꢀconsumption.ꢀAsꢀHoltekꢀhasꢀprovidedꢀtheꢀdeviceꢀwithꢀbothꢀhighꢀandꢀlowꢀspeedꢀclockꢀsourcesꢀ
andꢀtheꢀmeansꢀtoꢀswitchꢀbetweenꢀthemꢀdynamically,ꢀtheꢀuserꢀcanꢀoptimiseꢀtheꢀoperationꢀofꢀtheirꢀ
microcontrollerꢀtoꢀachieveꢀtheꢀbestꢀperformance/powerꢀratio.
System Clocks
TheꢀdeviceꢀhasꢀmanyꢀdifferentꢀclockꢀsourcesꢀforꢀbothꢀtheꢀCPUꢀandꢀperipheralꢀfunctionꢀoperation.ꢀ
Byꢀprovidingꢀtheꢀuserꢀwithꢀaꢀwideꢀrangeꢀofꢀclockꢀoptionsꢀusingꢀconfigurationꢀoptionsꢀandꢀregisterꢀ
programming,ꢀaꢀclockꢀsystemꢀcanꢀbeꢀconfiguredꢀtoꢀobtainꢀmaximumꢀapplicationꢀperformance.
Theꢀmainꢀsystemꢀclock,ꢀcanꢀcomeꢀfromꢀeitherꢀaꢀhighꢀfrequency,ꢀfH,ꢀorꢀlowꢀfrequency,ꢀfL,ꢀsource,ꢀ
andꢀisꢀselectedꢀusingꢀtheꢀHLCLKꢀbitꢀandꢀLCKS2~LCKS0ꢀbitsꢀinꢀtheꢀSYSMODꢀregister.ꢀTheꢀhighꢀ
speedꢀsystemꢀclockꢀcanꢀbeꢀsourcedꢀfromꢀeitherꢀanꢀHXT,ꢀERC,ꢀECꢀorꢀHIRCꢀoscillator,ꢀselectedꢀviaꢀaꢀ
configurationꢀoption.ꢀTheꢀlowꢀspeedꢀsystemꢀclockꢀsourceꢀcanꢀbeꢀsourcedꢀfromꢀinternalꢀclockꢀLIRC.ꢀ
Theꢀotherꢀchoice,ꢀwhichꢀisꢀaꢀdividedꢀversionꢀofꢀtheꢀhighꢀspeedꢀsystemꢀoscillatorꢀhasꢀaꢀrangeꢀofꢀ
fH/2~fH/64.
System Operation Modes
Thereꢀareꢀsixꢀdifferentꢀmodesꢀofꢀoperationꢀforꢀtheꢀmicrocontroller,ꢀeachꢀoneꢀwithꢀitsꢀownꢀ
specialꢀcharacteristicsꢀandꢀwhichꢀcanꢀbeꢀchosenꢀaccordingꢀtoꢀtheꢀspecificꢀperformanceꢀandꢀ
powerꢀrequirementsꢀofꢀtheꢀapplication.Thereꢀareꢀtwoꢀmodesꢀallowingꢀnormalꢀoperationꢀofꢀtheꢀ
microcontroller,ꢀtheꢀNORMALꢀModeꢀandꢀSLOWꢀMode.Theꢀremainingꢀfourꢀmodes,ꢀtheꢀSLEEP0,ꢀ
SLEEP1,ꢀIDLE0ꢀandꢀIDLE1ꢀModeꢀareꢀusedꢀwhenꢀtheꢀmicrocontrollerꢀCPUꢀisꢀswitchedꢀoffꢀtoꢀ
conserveꢀpower.
Rev. 0.00
3ꢅ
�eꢀteꢁꢂeꢃ ꢄꢅꢆ ꢄ01ꢄ
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
