Holtek HT66F30 - Page 247

Rev. 2.50 246 June 22, 2017 Rev. 2.50 247 June 22, 2017
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
UCR3 register
TheUCR3registeristhelastoftheUARTcontrolregistersandcontrolsthesoftwareresetoperation
oftheUARTmodule.TheonlyoneavailablebitnamedURSTintheUARTcontrolregisterUCR3
istheUARTsoftwareresetcontrolbit.Whenthisbitisequalto0,theUARToperatesnormally.
Ifthisbitisequalto1,thewholeUARTmodulewillbereset.Whenthissituationoccurs,the
transmitterandreceiverwillbereset.TheUARTregistersincludingthestatusregisterandcontrol
registerswillkeepthePORstatesshownintheaboveUARTregisterstableaftertheresetcondition
occurs.
Bit 7 6 5 4 3 2 1 0
Name URST — — — — — — —
R/W R/W — — — — — — —
POR 0 — — — — — — —
Bit7 URST:UARTsoftwarereset
0:Noaction
1:UARTresetoccurs
Bit6~0 Unimplemented,readas“0”
Baud Rate Generator
Tosetupthespeedoftheserialdatacommunication,theUARTfunctioncontainsitsowndedicated
baudrategenerator.Thebaudrateiscontrolledbyitsowninternalfreerunning8-bittimer,the
periodofwhichisdeterminedbytwofactors.Therstoftheseisthevalueplacedinthebaudrate
registerBRGandthesecondisthevalueoftheBRGHbitwiththecontrolregisterUCR2.The
BRGHbitdecidesifthebaudrategeneratoristobeusedinahighspeedmodeorlowspeedmode,
whichinturndeterminestheformulathatisusedtocalculatethebaudrate.ThevalueNintheBRG
registerwhichisusedinthefollowingbaudratecalculationformuladeterminesthedivisionfactor.
NotethatNisthedecimalvalueplacedintheBRGregisterandhasarangeofbetween0and255.
UCR2 BRGH Bit 0 1
Baud Rate (BR)
f
CLKI
[64 (N+1)]
f
CLKI
[16 (N+1)]
ByprogrammingtheBRGHbitwhichallowsselectionoftherelatedformulaandprogrammingthe
requiredvalueintheBRGregister,therequiredbaudratecanbesetup.Notethatbecausetheactual
baudrateisdeterminedusingadiscretevalue,N,placedintheBRGregister,therewillbeanerror
associatedbetweentheactualandrequestedvalue.ThefollowingexampleshowshowtheBRG
registervalueNandtheerrorvaluecanbecalculated.