Holtek HT66F30 - Page 71

Rev. 2.50 70 June 22, 2017 Rev. 2.50 71 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
• RESPin
AstheresetpinissharedwithPB.0,theresetfunctionmustbeselectedusingaconguration
option.AlthoughthemicrocontrollerhasaninternalRCresetfunction,iftheVDDpowersupply
risetimeisnotfastenoughordoesnotstabilisequicklyatpower-on,theinternalresetfunction
maybeincapableofprovidingproperresetoperation.Forthisreasonitisrecommendedthatan
externalRCnetworkisconnectedtotheRESpin,whoseadditionaltimedelaywillensurethatthe
RESpinremainslowforanextendedperiodtoallowthepowersupplytostabilise.Duringthis
timedelay,normaloperationofthemicrocontrollerwillbeinhibited.AftertheRESlinereaches
acertainvoltagevalue,theresetdelaytimet
RSTD
isinvokedtoprovideanextradelaytimeafter
whichthemicrocontrollerwillbeginnormaloperation.TheabbreviationSSTinthefigures
standsforSystemStart-upTimer.
FormostapplicationsaresistorconnectedbetweenVDDandtheRESpinandacapacitor
connectedbetweenVSSandtheRESpinwillprovideasuitableexternalresetcircuit.Any
wiringconnectedtotheRESpinshouldbekeptasshortaspossibletominimiseanystraynoise
interference.
ForapplicationsthatoperatewithinanenvironmentwheremorenoiseispresenttheEnhanced
ResetCircuitshownisrecommended.
















 



Note:*ItisrecommendedthatthiscomponentisaddedforaddedESDprotection.
**Itisrecommendedthatthiscomponentisaddedinenvironmentswherepower
linenoiseissignicant.
Extern RES Circuit
MoreinformationregardingexternalresetcircuitsislocatedinApplicationNoteHA0075Eon
theHoltekwebsite.
PullingtheRESPinlowusingexternalhardwarewillalsoexecuteadevicereset.Inthiscase,as
inthecaseofotherresets,theProgramCounterwillresettozeroandprogramexecutioninitiated
fromthispoint.

    




     
Note: t
RSTD
ispower-ondelay,typicaltime=100ms
RES Reset Timing Chart