HT67F488 datasheet(120/171 Pages) HOLTEK

120 / 171 page

Rev. 1.60

1�0

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HT67F488/HT67F489

TinyPowerTM A/D Flash MCU with LCD & EEPROM

Calculating the Register and Error Values

Foraclockfrequencyof4MHz,andwithBRGHsetto“0”determinetheBRGregistervalueN,the

actualbaudrateandtheerrorvalueforadesiredbaudrateof4800.

FromtheabovetablethedesiredbaudrateBR=fSYS/[64(N+1)]

Re-arrangingthisequationgivesN=[fSYS/(BR×64)]-1

GivingavalueforN=[4000000/(4800×64)]-1=12.0208

Toobtaintheclosestvalue,adecimalvalueof12shouldbeplacedintotheBRGregister.Thisgives

anactualorcalculatedbaudratevalueofBR=4000000/[64×(12+1)]=4808

Thereforetheerrorisequalto(4808-4800)/4800=0.16%

ThefollowingtableshowsactualvaluesofbaudrateanderrorvaluesforthetwovaluesofBRGH.

Baud Rate

K/BPS

fSYS=8MHz

Baud Rates for BRGH=0

Baud Rates for BRGH=1

BRG

Kbaud

Error (%)

BRG

Kbaud

Error (%)

0.3

—

1.�

103

1.�0�

0.16

—

�.4

�.404

0.16

�07

�.404

0.16

4.8

�5

4.808

0.16

103

4.808

0.16

9.6

1�

9.615

0.16

9.615

0.16

19.�

17.8857

-6.99

�5

19.�31

0.16

38.4

�

41.667

8.51

1�

38.46�

0.16

57.6

6�.500

8.51

55.556

-3.55

115.�

1�5

8.51

1�5

8.51

�50

—

�50

Baud Rates and Error Values

UART Setup and Control

Fordatatransfer,theUARTfunctionutilizesanon-return-to-zero,morecommonlyknownasNRZ,

format.Thisiscomposedofonestartbit,eightorninedatabits,andoneortwostopbits.Parity

issupportedbytheUARThardware,andcanbesetuptobeeven,oddornoparity.Forthemost

commondataformat,8databitsalongwithnoparityandonestopbit,denotedas8,N,1,isused

asthedefaultsetting,whichisthesettingatpower-on.Thenumberofdatabitsandstopbits,along

withtheparity,aresetupbyprogrammingthecorrespondingBNO,PRT,PREN,andSTOPSbits

intheUCR1register.Thebaudrateusedtotransmitandreceivedataissetupusingtheinternal

8-bitbaudrategenerator,whilethedataistransmittedandreceivedLSBfirst.AlthoughtheUART

transmitterandreceiverarefunctionallyindependent,theybothusethesamedataformatandbaud

rate.Inallcasesstopbitswillbeusedfordatatransmission.

HT67F488 Datasheet(PDF) 120 Page - Holtek Semiconductor Inc

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