HT67F488 datasheet(99/171 Pages) HOLTEK

99 / 171 page

Rev. 1.60

�ove��e� �� 016

HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

AN 0

AN 9

VB GE N

Bu ff er

PB4 /V RE F

VD D

VR EF S

V RE F

12 -b i t A DC

Ba n dga p

Re fe r enc e

Vo lt ag e

In put V ol ta ge

AC S4 ~A CS 0

V BG

A/D Input Structure

Summary of A/D Conversion Steps

ThefollowingsummarisestheindividualstepsthatshouldbeexecutedinordertoimplementanA/D

conversionprocess.

• Step1

SelecttherequiredA/DconversionclockbycorrectlyprogrammingbitsADCK2~ADCK0inthe

ADCR1register.

• Step2

EnabletheA/DbyclearingtheADOFFbitintheADCR0registertozero.

• Step3

SelectwhichchannelistobeconnectedtotheinternalA/Dconverterbycorrectlyprogramming

theACS4~ACS0bitswhicharealsocontainedintheADCR1andADCR0registers.

• Step4

SelectwhichpinsaretobeusedasA/Dinputsandconfigurethembycorrectlyprogrammingthe

ACE9~ACE0bitsintheACERHandACERLregisters.

• Step5

Iftheinterruptsaretobeused,theinterruptcontrolregistersmustbecorrectlyconfiguredto

ensuretheA/Dconverterinterruptfunctionisactive.Themasterinterruptcontrolbit,EMI,and

theA/Dconverterinterruptbit,ADE,mustbothbesethightodothis.

• Step6

TheanalogtodigitalconversionprocesscannowbeinitialisedbysettingtheSTARTbitin

theADCR0registerfromlowtohighandthenlowagain.Notethatthisbitshouldhavebeen

originallyclearedtozero.

• Step7

Tocheckwhentheanalogtodigitalconversionprocessiscomplete,theEOCBbitintheADCR0

registercanbepolled.Theconversionprocessiscompletewhenthisbitgoeslow.Whenthis

occurstheA/DdataregistersADRLandADRHcanbereadtoobtaintheconversionvalue.Asan

alternativemethod,iftheinterruptsareenabledandthestackisnotfull,theprogramcanwaitfor

anA/Dinterrupttooccur.

Note:Whencheckingfortheendoftheconversionprocess,ifthemethodofpollingtheEOCBbit

intheADCR0registerisused,theinterruptenablestepabovecanbeomitted.

Theaccompanyingdiagramshowsgraphicallythevariousstagesinvolvedinananalogtodigital

conversionprocessanditsassociatedtiming.AfteranA/Dconversionprocesshasbeeninitiated

bytheapplicationprogram,themicrocontrollerinternalhardwarewillbegintocarryoutthe

conversion,duringwhichtimetheprogramcancontinuewithotherfunctions.Thetimetakenforthe

A/Dconversionis16tADCKwheretADCKisequaltotheA/Dclockperiod.

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