在ICSP TM架构系统监控

Semiconductormanufacturershavedesignedseveral

typesofcircuitsupervisorswithvaryingtypesoffunc-

tionalityoverthepastfewyears.Somesupervisors

incorporatewatchdogfeaturesaswellascomplexfunc-

tions,suchasprogrammablethresholdlevels.Asit

turnsout,mostsystemsupervisordatasheetsaddress

typicalsupervisorfunctionsrelatedtoPower-onReset,

power-down,andbrown-outconditions.Inorderto

serveawidecustomerbase,semiconductormanufac-

turersshouldalsoaddresssystemsupervisors

designedintosystemswheremicrocontrollers(MCUs)

andprogrammablelogicdevices(PLDs)arepro-

grammedin-circuit.ProgrammingPICmicro

®

micro-

controllersinthisfashionisknownasIn-CircuitSerial

Programming

TM

(ICSP

TM

),whichcanbeimplemented

foravarietyofreasons,includingfieldupgrades.MAN820SystemSupervisorsinICSPTMArchitecturesAuthor:KenDietzCIRCUITRYBACKGROUNDMicrochipTechnologyInc.MCP120OutputStageAsimplifiedschematicfortheMCP120outputstageisshowninFigure1.Nominally,theoutputstageoftheMCP120canhandlesinkinglessthan1mAofcurrentINTRODUCTIONinahighimpedancestat