HT67F488 datasheet(121/171 Pages) HOLTEK

121 / 171 page

Rev. 1.60

1�1

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

Enabling/Disabling the UART

Thebasicon/offfunctionoftheinternalUARTfunctioniscontrolledusingtheUARTENbitinthe

UCR1register.IftheUARTEN,TXENandRXENbitsareset,thenthesetwoUARTpinswillact

asnormalTXoutputpinandRXinputpinrespectively.IfnodataisbeingtransmittedontheTX

pin,thenitwilldefaulttoalogichighvalue.

ClearingtheUARTENbitwilldisabletheTXandRXpinsandallowthesetwopinstobeusedas

normalI/Oorotherpin-sharedfunctionalpins.WhentheUARTfunctionisdisabledthebufferwill

beresettoanemptycondition,atthesametimediscardinganyremainingresidualdata.Disabling

theUARTwillalsoresettheerrorandstatusflagswithbitsTXEN,RXEN,TXBRK,RXIF,OERR,

FERR,PERRandNFbeingclearedwhilebitsTIDLE,TXIFandRIDLEwillbeset.Theremaining

controlbitsintheUCR1,UCR2andBRGregisterswillremainunaffected.IftheUARTENbitin

theUCR1registerisclearedwhiletheUARTisactive,thenallpendingtransmissionsandreceptions

willbeimmediatelysuspendedandtheUARTwillberesettoaconditionasdefinedabove.Ifthe

UARTisthensubsequentlyre-enabled,itwillrestartagaininthesameconfiguration.

Data, Parity and Stop bit Selection

Theformatofthedatatobetransferrediscomposedofvariousfactorssuchasdatabitlength,

parityon/off,paritytype,addressbitsandthenumberofstopbits.Thesefactorsaredeterminedby

thesetupofvariousbitswithintheUCR1register.TheBNObitcontrolsthenumberofdatabits

whichcanbesettoeither8or9,thePRTbitcontrolsthechoiceofoddorevenparity,thePREN

bitcontrolstheparityon/offfunctionandtheSTOPSbitdecideswhetheroneortwostopbitsareto

beused.Thefollowingtableshowsvariousformatsfordatatransmission.Theaddressbitidentifies

theframeasanaddresscharacter.Thenumberofstopbits,whichcanbeeitheroneortwo,is

independentofthedatalength.

Start Bit

Data Bits

Address Bits

Parity Bits

Stop Bit

Example of 8-bit Data Formats

Example of 9-bit Data Formats

Transmitter Receiver Data Format

Thefollowingdiagramshowsthetransmitandreceivewaveformsforboth8-bitand9-bitdata

formats.

St ar t B it

Bi t 0

Bi t 1

Bi t 2

Bi t 3

Bi t 4

Bi t 5

Bi t 6

Bi t 7

St op B it

Ne xt

St ar t

Bi t

Pa ri ty B it

8- Bi t Da ta F or ma t

St ar t B it

Bi t 0

Bi t 1

Bi t 2

Bi t 3

Bi t 4

Bi t 5

Bi t 6

Bi t 7

St op B it

Ne xt

St ar t

Bi t

Pa ri ty B it

9- Bi t Da ta F or ma t

Bi t 8

HT67F488 Datasheet(PDF) 121 Page - Holtek Semiconductor Inc

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