标签: 系统监控

Semiconductormanufacturershavedesignedseveraltypesofcircuitsupervisorswithvaryingtypesoffunc-tionalityoverthepastfewyears.Somesupervisorsincorporatewatchdogfeaturesaswellascomplexfunc-tions,suchasprogrammablethresholdlevels.Asitturnsout,mostsystemsupervisordatasheetsaddresstypicalsupervisorfunctionsrelatedtoPower-onReset,power-down,andbrown-outconditions.Inordertoserveawidecustomerbase,semiconductormanufac-turersshouldalsoaddresssystemsupervisorsdesignedintosystemswheremicrocontrollers(MCUs)andprogrammablelogicdevices(PLDs)arepro-grammedin-circuit.ProgrammingPICmicro®micro-controllersinthisfashionisknownasIn-CircuitSerialProgrammingTM(ICSPTM),whichcanbeimplementedforavarietyofreasons,includingfieldupgrades.MAN820SystemSupervisorsinICSPTMArchitecturesAuthor:KenDietzCIRCUITRYBACKGROUNDMicrochipTechnologyInc.MCP120OutputStageAsimplifiedschematicfortheMCP120outputstageisshowninFigure1.Nominally,theoutputstageoftheMCP120canhandlesinkinglessthan1mAofcurrentINTRODUCTIONinahighimpedancestat……