电源注意事项

Whenpoweringupanymicrocontrolleritisnecessary

forthepowersupplyvoltagetotraversevoltageranges,

wherethedeviceisnotguaranteedtooperate,before

thepowersupplyvoltagereachesitsfinalstate.Since

somecircuitsonthedevice(logic)willstartoperatingat

voltagelevelslowerthanothercircuitsonthechip

(memory),thedevicemaypower-upinanunknown

state.Toguaranteethatthedevicestartsupinaknown

state,itmustcontainapower-upresetcircuit.

PIC16C5Xmicrocontrollersareequippedwithon-chip

Power-onResetcircuitry,whicheliminatestheneedfor

externalresetlogic.Thiscircuitwillfunctioninmost

power-upsituationswhereV

DD

risetimeisfastenough

(50msorless).Thisapplicationnotedescribesthetyp-

icalpower-upsequenceforPIC16C5X

microcontrollers.Methodsofassuringreseton

power-upandafterabrown-outarediscussedandsim-

ple,low-costexternalsolutionsarediscussedfor

power-upsituationswherethePIC16C5X’sinternalcir-

cuitrycannotprovidethereset.AN522Power-upConsiderationsresetcircuitryisshowninFigure1.Onpower-up,theAuthor:SumitMitraresetlatchandthestart-uptimerareresettoappropri-MicrochipTechnologyInc.atestatesbythePower-onReset(POR).Thestart-uptimerwillbegincountingonceitdetectsMCLRtobehigh(i.e.,externalchipresetgo