BS85B12-3/BS85C20-3/BS85C20-5
Touch Key Flash MCU with LCD/LED Driver
PWM Output Mode
Toꢀselectꢀthisꢀmode,ꢀbitsꢀTnM1ꢀandꢀTnM0ꢀinꢀtheꢀTMnC1ꢀregisterꢀshouldꢀbeꢀsetꢀtoꢀ10ꢀrespectively.ꢀ
TheꢀPWMꢀfunctionꢀwithinꢀtheꢀTMꢀisꢀusefulꢀforꢀapplicationsꢀwhichꢀrequireꢀfunctionsꢀsuchꢀasꢀmotorꢀ
control,ꢀheatingꢀcontrol,ꢀilluminationꢀcontrolꢀetc.ꢀByꢀprovidingꢀaꢀsignalꢀofꢀfixedꢀfrequencyꢀbutꢀ
ofꢀvaryingꢀdutyꢀcycleꢀonꢀtheꢀTMꢀoutputꢀpin,ꢀaꢀsquareꢀwaveꢀACꢀwaveformꢀcanꢀbeꢀgeneratedꢀwithꢀ
varyingꢀequivalentꢀDCꢀRMSꢀvalues.
AsꢀbothꢀtheꢀperiodꢀandꢀdutyꢀcycleꢀofꢀtheꢀPWMꢀwaveformꢀcanꢀbeꢀcontrolled,ꢀtheꢀchoiceꢀofꢀgeneratedꢀ
waveformꢀisꢀextremelyꢀflexible.ꢀInꢀtheꢀPWMꢀmode,ꢀtheꢀTnCCLRꢀbitꢀhasꢀnoꢀeffectꢀonꢀtheꢀPWMꢀ
operation.ꢀBothꢀofꢀtheꢀCCRAꢀandꢀCCRPꢀregistersꢀareꢀusedꢀtoꢀgenerateꢀtheꢀPWMꢀwaveform,ꢀoneꢀ
registerꢀisꢀusedꢀtoꢀclearꢀtheꢀinternalꢀcounterꢀandꢀthusꢀcontrolꢀtheꢀPWMꢀwaveformꢀfrequency,ꢀwhileꢀ
theꢀotherꢀoneꢀisꢀusedꢀtoꢀcontrolꢀtheꢀdutyꢀcycle.ꢀWhichꢀregisterꢀisꢀusedꢀtoꢀcontrolꢀeitherꢀfrequencyꢀ
orꢀdutyꢀcycleꢀisꢀdeterminedꢀusingꢀtheꢀTnDPXꢀbitꢀinꢀtheꢀTMnC1ꢀregister.ꢀTheꢀPWMꢀwaveformꢀ
frequencyꢀandꢀdutyꢀcycleꢀcanꢀthereforeꢀbeꢀcontrolledꢀbyꢀtheꢀvaluesꢀinꢀtheꢀCCRAꢀandꢀCCRPꢀregisters.
Anꢀinterruptꢀflag,ꢀoneꢀforꢀeachꢀofꢀtheꢀCCRAꢀandꢀCCRP,ꢀwillꢀbeꢀgeneratedꢀwhenꢀaꢀcompareꢀmatchꢀ
occursꢀfromꢀeitherꢀComparatorꢀAꢀorꢀComparatorꢀP.ꢀTheꢀTnOCꢀbitꢀinꢀtheꢀTMnC1ꢀregisterꢀisꢀusedꢀtoꢀ
selectꢀtheꢀrequiredꢀpolarityꢀofꢀtheꢀPWMꢀwaveformꢀwhileꢀtheꢀtwoꢀTnIO1ꢀandꢀTnIO0ꢀbitsꢀareꢀusedꢀtoꢀ
enableꢀtheꢀPWMꢀoutputꢀorꢀtoꢀforceꢀtheꢀTMꢀoutputꢀpinꢀtoꢀaꢀfixedꢀhighꢀorꢀlowꢀlevel.ꢀTheꢀTnPOLꢀbitꢀisꢀ
usedꢀtoꢀreverseꢀtheꢀpolarityꢀofꢀtheꢀPWMꢀoutputꢀwaveform.
STM, PWM Mode, Edge-aligned Mode, TnDPX=0
CCRP
Period
Dꢀty
001b
010b
011b
100b
101b
110b
111b
000b
128
256
384
512
640
768
896
1024
CCR�
IfꢀfSYSꢀ=ꢀ16MHz,ꢀTMꢀclockꢀsourceꢀisꢀfSYS/4,ꢀCCRPꢀ=ꢀ100bꢀandꢀCCRAꢀ=128,
TheꢀSTMꢀPWMꢀoutputꢀfrequencyꢀ=ꢀ(fSYS/4)ꢀ/ꢀ512ꢀ=ꢀfSYS/2048ꢀ=ꢀ7.8125ꢀkHz,ꢀdutyꢀ=ꢀ128/512ꢀ=ꢀ25%.
IfꢀtheꢀDutyꢀvalueꢀdefinedꢀbyꢀtheꢀCCRAꢀregisterꢀisꢀequalꢀtoꢀorꢀgreaterꢀthanꢀtheꢀPeriodꢀvalue,ꢀthenꢀtheꢀ
PWMꢀoutputꢀdutyꢀisꢀ100%.
STM, PWM Mode, Edge-aligned Mode, TnDPX=1
CCRP
Period
Dꢀty
001b
010b
011b
100b
101b
110b
111b
000b
CCR�
128
256
384
512
640
768
896
1024
TheꢀPWMꢀoutputꢀperiodꢀisꢀdeterminedꢀbyꢀtheꢀCCRAꢀregisterꢀvalueꢀtogetherꢀwithꢀtheꢀTMꢀclockꢀ
whileꢀtheꢀPWMꢀdutyꢀcycleꢀisꢀdefinedꢀbyꢀtheꢀCCRPꢀregisterꢀvalue.
Rev. 1.20
89
�ꢀꢁꢀst 10ꢂ 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
