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