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1、Electricboilertemperaturesysteml.MCUAmicrocontroller(orMCU)isacomputer-on-a-chip.Itisatypeofmicroprocessoremphasizingself-sufficiencyandcost-effectiveness,incontrasttoageneral-purposemicroprocessor(thekindusedinaPC).Themajorityofcomputersystemsinusetodayareembeddedinothermachine
2、ry,suchastelephones,clocks,appliances,vehicles,andinfrastructure.Anembeddedsystemusuallyhasminimalrequirementsformemoryandprogramlengthandmayrequiresimplebutunusualinput/outputsystems.Forexample,mostembeddedsystemslackkeyboards,screens,disks,printers,orotherrecognizableI/Odevice
3、sofapersonalcompute匚Theymaycontrolelectricmotors,relaysorvoltages,andreadswitches,variableresistorsorotherelectronicdevices.Often,theonlyI/Odevicereadablebyahumanisasinglelight-emittingdiode,andseverecostorpowerconstraintscaneveneliminatethat.Incontrasttogeneral-purposeCPUs,micr
4、ocontrollersdonothaveanaddressbusoradatabus,becausetheyintegratealltheRAMandnon-volatilememoryonthesamechipastheCPU.Becausetheyneedfewerpins,thechipcanbeplacedinamuchsmaller,cheaperpackage.Integratingthememoryandotherperipheralsonasinglechipandtestingthemasaunitincreasesthecosto
5、fthatchip,butoftenresultsindecreasednetcostoftheembeddedsystemasawhole.(EvenifthecostofaCPUthathasintegratedperipheralsisslightlymorethanthecostofaCPU+externalperipherals,havingfewerchipstypicallyallowsasmallerandcheapercircuitboard,andreducesthelaborrequiredtoassembleandtestthe
6、circuitboard).Thistrendleadstodesign.Amicrocontrollerisasingleintegratedcircuit,commonlywiththefollowingfeatures:centralprocessingunit-rangingfromsmallandsimple4-bitprocessorstosophisticated32・or64-bitprocessorsinput/outputinterfacessuchasserialports(UARTs)otherserialcommunicati
7、onsinterfaceslikeI2C,SerialPeripheralInterfaceandControllerAreaNetworkforsysteminterconnectperipheralssuchastimersandwatchdogRAMfordatastorageROM,EPROM,EEPROMorFlashmemoryforprogramstorageclockgenerator-oftenanoscillatorforaquartztimingcrystal,resonatororRCcircuitmanyincludeanal
8、og-to-digitalconverters.Thisintegrationdrastica