HT67F488 datasheet(125/171 Pages) HOLTEK

125 / 171 page

Rev. 1.60

1�5

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

Managing Receiver Errors

SeveraltypesofreceptionerrorscanoccurwithintheUARTmodule,thefollowingsectiondescribes

thevarioustypesandhowtheyaremanagedbytheUART.

Overrun Error – OERR Flag

TheRXRregisteriscomposedofatwobytedeepFIFOdatabuffer,wheretwobytescanbeheld

intheFIFOregister,whileathirdbytecancontinuetobereceived.Beforethisthirdbytehasbeen

entirelyshiftedin,thedatashouldbereadfromtheRXRregister.Ifthisisnotdone,theoverrun

errorflagOERRwillbeconsequentlyindicated.

Intheeventofanoverrunerroroccurring,thefollowingwillhappen:

• TheOERRflagintheUSRregisterwillbeset.

• TheRXRcontentswillnotbelost.

• Theshiftregisterwillbeoverwritten.

• AninterruptwillbegeneratediftheRIEbitisset.

TheOERRflagcanbeclearedbyanaccesstotheUSRregisterfollowedbyareadtotheRXR

Noise Error – NF Flag

Over-samplingisusedfordatarecoverytoidentifyvalidincomingdataandnoise.Ifnoiseis

detectedwithinaframethefollowingwilloccur:

• Thereadonlynoiseflag,NF,intheUSRregisterwillbesetontherisingedgeoftheRXIFbit.

• DatawillbetransferredfromtheShiftregistertotheRXRregister.

• Nointerruptwillbegenerated.HoweverthisbitrisesatthesametimeastheRXIFbitwhich

itselfgeneratesaninterrupt.

NotethattheNFflagisresetbyaUSRregisterreadoperationfollowedbyanRXRregisterread

operation.

Framing Error – FERR Flag

Thereadonlyframingerrorflag,FERR,intheUSRregister,issetifazeroisdetectedinsteadof

stopbits.Iftwostopbitsareselected,bothstopbitsmustbehigh,otherwisetheFERRflagwillbe

set.TheFERRflagisbufferedalongwiththereceiveddataandisclearedonanyreset.

Parity Error – PERR Flag

Thereadonlyparityerrorflag,PERR,intheUSRregister,issetiftheparityofthereceivedwordis

incorrect.Thiserrorflagisonlyapplicableiftheparityisenabled,PREN=1,andiftheparitytype,

oddorevenisselected.ThereadonlyPERRflagisbufferedalongwiththereceiveddatabytes.Itis

clearedonanyreset.ItshouldbenotedthattheFERRandPERRflagsarebufferedalongwiththe

correspondingwordandshouldbereadbeforereadingthedataword.

HT67F488 Datasheet(PDF) 125 Page - Holtek Semiconductor Inc