Holtek HT66F20 - Page 120

Rev. 2.50 120 June 22, 2017 Rev. 2.50 121 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
PWM Output Mode
Toselectthismode,bitsTnM1andTnM0intheTMnC1registershouldbesetto10respectively.
ThePWMfunctionwithintheTMisusefulforapplicationswhichrequirefunctionssuchasmotor
control,heatingcontrol,illuminationcontroletc.Byprovidingasignaloffixedfrequencybut
ofvaryingdutycycleontheTMoutputpin,asquarewaveACwaveformcanbegeneratedwith
varyingequivalentDCRMSvalues.
AsboththeperiodanddutycycleofthePWMwaveformcanbecontrolled,thechoiceofgenerated
waveformisextremelyflexible.InthePWMmode,theTnCCLRbithasnoeffectonthePWM
operation.BothoftheCCRAandCCRPregistersareusedtogeneratethePWMwaveform,one
registerisusedtocleartheinternalcounterandthuscontrolthePWMwaveformfrequency,while
theotheroneisusedtocontrolthedutycycle.Whichregisterisusedtocontroleitherfrequency
ordutycycleisdeterminedusingtheTnDPXbitintheTMnC1register.ThePWMwaveform
frequencyanddutycyclecanthereforebecontrolledbythevaluesintheCCRAandCCRPregisters.
Aninterruptag,oneforeachoftheCCRAandCCRP,willbegeneratedwhenacomparematch
occursfromeitherComparatorAorComparatorP.TheTnOCbitintheTMnC1registerisusedto
selecttherequiredpolarityofthePWMwaveformwhilethetwoTnIO1andTnIO0bitsareusedto
enablethePWMoutputortoforcetheTMoutputpintoaxedhighorlowlevel.TheTnPOLbitis
usedtoreversethepolarityofthePWMoutputwaveform.
• CTM, PWM Mode, Edge-aligned Mode, TnDPX=0
CCRP 001b 010b 011b 100b 101b 110b 111b 000b
Period
128 256 384 512 640 768 896 1024
Duty CCRA
Iff
SYS
=16MHz,TMclocksourceisf
SYS
/4,CCRP=100bandCCRA=128,
TheCTMPWMoutputfrequency=(f
SYS
/4)/512=f
SYS
/2048=7.8125kHz,duty=128/512=25%.
IftheDutyvaluedenedbytheCCRAregisterisequaltoorgreaterthanthePeriodvalue,thenthe
PWMoutputdutyis100%.
• CTM, PWM Mode, Edge-aligned Mode, TnDPX=1
CCRP 001b 010b 011b 100b 101b 110b 111b 000b
Period CCRA
Duty 128 256 384 512 640 768 896 1024
ThePWMoutputperiodisdeterminedbytheCCRAregistervaluetogetherwiththeTMclockwhile
thePWMdutycycleisdenedbytheCCRPregistervalue.