BS85B12-3/BS85C20-3/BS85C20-5
Touch Key Flash MCU with LCD/LED Driver
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Operating Mode Switching
Theꢀdeviceꢀcanꢀswitchꢀbetweenꢀoperatingꢀmodesꢀdynamicallyꢀallowingꢀtheꢀuserꢀtoꢀselectꢀtheꢀbestꢀ
performance/powerꢀratioꢀforꢀtheꢀpresentꢀtaskꢀinꢀhand.ꢀInꢀthisꢀwayꢀmicrocontrollerꢀoperationsꢀthatꢀ
doꢀnotꢀrequireꢀhighꢀperformanceꢀcanꢀbeꢀexecutedꢀusingꢀslowerꢀclocksꢀthusꢀrequiringꢀlessꢀoperatingꢀ
currentꢀandꢀprolongingꢀbatteryꢀlifeꢀinꢀportableꢀapplications.
Inꢀsimpleꢀterms,ꢀModeꢀSwitchingꢀbetweenꢀtheꢀNORMALꢀModeꢀandꢀSLOWꢀModeꢀisꢀexecutedꢀ
usingꢀtheꢀHLCLKꢀbitꢀandꢀCKS2~CKS0ꢀbitsꢀinꢀtheꢀSMODꢀregisterꢀwhileꢀModeꢀSwitchingꢀfromꢀtheꢀ
NORMAL/SLOWꢀModesꢀtoꢀtheꢀSLEEP/IDLEꢀModesꢀisꢀexecutedꢀviaꢀtheꢀHALTꢀinstruction.ꢀWhenꢀ
aꢀHALTꢀinstructionꢀisꢀexecuted,ꢀwhetherꢀtheꢀdeviceꢀentersꢀtheꢀIDLEꢀModeꢀorꢀtheꢀSLEEPꢀModeꢀisꢀ
determinedꢀbyꢀtheꢀconditionꢀofꢀtheꢀIDLENꢀbitꢀinꢀtheꢀSMODꢀregisterꢀandꢀFSYSONꢀinꢀtheꢀWDTCꢀ
register.
WhenꢀtheꢀHLCLKꢀbitꢀswitchesꢀtoꢀaꢀlowꢀlevel,ꢀwhichꢀimpliesꢀthatꢀclockꢀsourceꢀisꢀswitchedꢀfromꢀ
theꢀhighꢀspeedꢀclockꢀsource,ꢀfHIRC,ꢀtoꢀtheꢀclockꢀsource,ꢀfHIRC/2~fHIRC/64ꢀorꢀfLIRC.ꢀIfꢀtheꢀclockꢀisꢀfromꢀ
fHIRC,ꢀtheꢀhighꢀspeedꢀclockꢀsourceꢀwillꢀstopꢀrunningꢀtoꢀconserveꢀpower.ꢀWhenꢀthisꢀhappensꢀitꢀmustꢀbeꢀ
notedꢀthatꢀtheꢀfHIRC/16ꢀandꢀfHIRC/64ꢀinternalꢀclockꢀsourcesꢀwillꢀalsoꢀstopꢀrunning.ꢀTheꢀaccompanyingꢀ
flowchartꢀshowsꢀwhatꢀhappensꢀwhenꢀtheꢀdeviceꢀmovesꢀbetweenꢀtheꢀvariousꢀoperatingꢀmodes.
Rev. 1.20
48
�ꢀꢁꢀst 10ꢂ 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
