HT45F65 datasheet(138/231 Pages) HOLTEK

138 / 231 page

Rev. 1.60

138

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Rev. 1.60

139

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HT45F65/HT45F66/HT45F67

Glucose Meter 8-Bit Flash MCU

Capture Input Mode

Toselectthismode,bitsT1AM1,T1AM0andT1BM1,T1BM0intheTM1C1andTM1C2registers

shouldbesetto01respectively.Thismodeenablesexternalsignalstocaptureandstorethe

presentvalueoftheinternalcounterandcanthereforebeusedforapplicationssuchaspulsewidth

measurements.TheexternalsignalissuppliedontheTP1AandTP1B_0,TP1B_1,TP1B_2pins,

whoseactiveedgecanbeeitherarisingedge,afallingedgeorbothrisingandfallingedges;the

activeedgetransitiontypeisselectedusingtheT1AIO1,T1AIO0andT1BIO1,T1BIO0bitsinthe

TM1C1andTM1C2registers.ThecounterisstartedwhentheT1ONbitchangesfromlowtohigh

whichisinitiatedusingtheapplicationprogram.

WhentherequirededgetransitionappearsontheTP1AandTP1B_0,TP1B_1,TP1B_2pinsthe

presentvalueinthecounterwillbelatchedintotheCCRAandCCRBregistersandaTMinterrupt

generated.IrrespectiveofwhateventsoccurontheTP1AandTP1B_0,TP1B_1,TP1B_2pins

thecounterwillcontinuetofreerununtiltheT1ONbitchangesfromhightolow.WhenaCCRP

comparematchoccursthecounterwillresetbacktozero;inthiswaytheCCRPvaluecanbeused

tocontrolthemaximumcountervalue.WhenaCCRPcomparematchoccursfromComparatorP,

aTMinterruptwillalsobegenerated.Countingthenumberofoverflowinterruptsignalsfromthe

CCRPcanbeausefulmethodinmeasuringlongpulsewidths.TheT1AIO1,T1AIO0andT1BIO1,

T1BIO0bitscanselecttheactivetriggeredgeontheTP1AandTP1B_0,TP1B_1,TP1B_2pins

tobearisingedge,fallingedgeorbothedgetypes.IftheT1AIO1,T1AIO0andT1BIO1,T1BIO0

bitsarebothsethigh,thennocaptureoperationwilltakeplaceirrespectiveofwhathappensonthe

TP1AandTP1B_0,TP1B_1,TP1B_2pins,howeveritmustbenotedthatthecounterwillcontinue

torun.

AstheTP1AandTP1B_0,TP1B_1,TP1B_2pinsarepinsharedwithotherfunctions,caremust

betakeniftheTMisintheCaptureInputMode.Thisisbecauseifthepinissetupasanoutput,

thenanytransitionsonthispinmaycauseaninputcaptureoperationtobeexecuted.TheT1CCLR,

T1AOC,T1BOC,T1APOLandT1BPOLbitsarenotusedinthismode.

HT45F65 Datasheet(PDF) 138 Page - Holtek Semiconductor Inc