HT66F20 datasheet(257/298 Pages) HOLTEK

257 / 298 page

Rev. 1.90

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Rev. 1.90

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HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit MCU with EEPROM

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Enhanced A/D Flash Type 8-Bit MCU with EEPROM

Managing Receiver Errors

SeveraltypesofreceptionerrorscanoccurwithintheUARTmodule,thefollowingsectiondescribes

thevarioustypesandhowtheyaremanagedbytheUART.

• OverrunError–OERRflag

TheRXRregisteriscomposedofafourbytedeepFIFOdatabuffer,wherefourbytescanbeheld

intheFIFOregister,whilea5thbytecancontinuetobereceived.Beforethe5thbytehasbeen

entirelyshiftedin,thedatashouldbereadfromtheRXRregister.Ifthisisnotdone,theoverrun

errorflagOERRwillbeconsequentlyindicated.

Intheeventofanoverrunerroroccurring,thefollowingwillhappen:

♦

TheOERRflagintheUSRregisterwillbeset.

♦

TheRXRcontentswillnotbelost.

♦

Theshiftregisterwillbeoverwritten.

♦

AninterruptwillbegeneratediftheRIEbitisset.

TheOERRflagcanbeclearedbyanaccesstotheUSRregisterfollowedbyareadtotheRXR

• NoiseError–NFflag

Over-samplingisusedfordatarecoverytoidentifyvalidincomingdataandnoise.Ifnoiseis

detectedwithinaframe,thefollowingwilloccur:

♦

Thereadonlynoiseflag,NF,intheUSRregisterwillbesetontherisingedgeoftheRXIFbit.

♦

DatawillbetransferredfromtheshiftregistertotheRXRregister.

♦

Nointerruptwillbegenerated.HoweverthisbitrisesatthesametimeastheRXIFbitwhich

itselfgeneratesaninterrupt.

NotethattheNFflagisresetbyaUSRregisterreadoperationfollowedbyanRXRregisterread

operation.

• FramingError–FERRflag

Thereadonlyframingerrorflag,FERR,intheUSRregister,issetifazeroisdetectedinsteadof

stopbits.Iftwostopbitsareselected,bothstopbitsmustbehigh.OtherwisetheFERRflagwill

beset.TheFERRflagisbufferedalongwiththereceiveddataandisclearedinanyreset.

• ParityError–PERRflag

Thereadonlyparityerrorflag,PERR,intheUSRregister,issetiftheparityofthereceived

wordisincorrect.Thiserrorflagisonlyapplicableiftheparityfunctionisenabled,PREN=1,and

iftheparitytype,oddoreven,isselected.ThereadonlyPERRflagisbufferedalongwiththe

receiveddatabytes.Itisclearedonanyreset,itshouldbenotedthattheFERRandPERRflags

arebufferedalongwiththecorrespondingwordandshouldbereadbeforereadingthedataword.

HT66F20 Datasheet(PDF) 257 Page - Holtek Semiconductor Inc

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