文献翻译——电锅炉温度系统

第1页外文文献资料Electricboilertemperaturesystem1.MCUAmicrocontroller(orMCU)isacomputer-on-a-chip.Itisatypeofmicroprocessoremphasizingself-sufficiencyandcost-effectiveness,incontrasttoageneral-purposemicroprocessor(thekindusedinaPC).Themajorityofcomputersystemsinusetodayareembeddedinothermachinery,suchastelephones,clocks,appliances,vehicles,andinfrastructure.Anembeddedsystemusuallyhasminimalrequirementsformemoryandprogramlengthandmayrequiresimplebutunusualinput/outputsystems.Forexample,mostembeddedsystemslackkeyboards,screens,disks,printers,orotherrecognizableI/Odevicesofapersonalcomputer.Theymaycontrolelectricmotors,relaysorvoltages,andreadswitches,variableresistorsorotherelectronicdevices.Often,theonlyI/Odevicereadablebyahumanisasinglelight-emittingdiode,andseverecostorpowerconstraintscaneveneliminatethat.Incontrasttogeneral-purposeCPUs,microcontrollersdonothaveanaddressbusoradatabus,becausetheyintegratealltheRAMandnon-volatilememoryonthesamechipastheCPU.Becausetheyneedfewerpins,thechipcanbeplacedinamuchsmaller,cheaperpackage.Integratingthememoryandotherperipheralsonasinglechipandtestingthemasaunitincreasesthecostofthatchip,butoftenresultsindecreasednetcostoftheembeddedsystemasawhole.(EvenifthecostofaCPUthathasintegratedperipheralsisslightlymorethanthecostofaCPU+externalperipherals,havingfewerchipstypicallyallowsasmallerandcheapercircuitboard,andreducesthelaborrequiredtoassembleandtestthecircuitboard).Thistrendleadstodesign.Amicrocontrollerisasingleintegratedcircuit,commonlywiththefollowingfeatures:第2页centralprocessingunit-rangingfromsmallandsimple4-bitprocessorstosophisticated32-or64-bitprocessorsinput/outputinterfacessuchasserialports(UARTs)otherserialcommunicationsinterfaceslikeIC,SerialPeripheralInterfaceandControllerAreaNetworkforsysteminterconnectperipheralssuchastimersandwatchdogRAMfordatastorageROM,EPROM,EEPROMorFlashmemoryforprogramstorageclockgenerator-oftenanoscillatorforaquartztimingcrystal,resonatororRCcircuitmanyincludeanalog-to-digitalconvertersThisintegrationdrasticallyreducesthenumberofchipsandtheamountofwiringandPCBspacethatwouldbeneededtoproduceequivalentsystemsusingseparatechipsandhaveprovedtobehighlypopularinembeddedsystemssincetheirintroductioninthe1970s.SomemicrocontrollerscanaffordtouseaHarvardarchitecture:separatememorybusesforinstructionsanddata,allowingaccessestotakeplaceconcurrently.Thedecisionofwhichperipheraltointegrateisoftendifficult.TheMicrocontrollervendorsoftentradeoperatingfrequenciesandsystemdesignflexibilityagainsttime-to-marketrequirementsfromtheircustomersandoveralllowersystemcost.Manufacturershavetobalancetheneedtominimizethechipsizeagainstadditionalfunctionality.Microcontrollerarchitecturesareavailablefrommanydifferentvendorsinsomanyvarietiesthateachinstructionsetarchitecturecouldrightlybelongtoacategoryoftheirown.Chiefamongthesearethe8051,Z80andARMderivatives.citationneededAmicrocontroller(alsoMCUorC)isafunctionalcomputersystem-on-a-chip.Itcontainsaprocessorcore,memory,andprogrammableinput/outputperipherals.MicrocontrollersincludeanintegratedCPU,memory(asmallamountofRAM,programmemory,orboth)andperipheralscapableofinputandoutput.Itemphasizeshighintegration,incontrasttoamicroprocessorwhichonlycontainsaCPU(thekindusedinaPC).Inadditiontotheusualarithmeticandlogicelementsofageneralpurposemicroprocessor,themicrocontroller第3页integratesadditionalelementssuchasread-writememoryfordatastorage,read-onlymemoryforprogramstorage,Flashmemoryforpermanentdatastorage,peripherals,andinput/outputinterfaces.Atclockspeedsofaslittleas32KHz,microcontrollersoftenoperateatverylowspeedcomparedtomicroprocessors,butthisisadequatefortypicalapplications.Theyconsumerelativelylittlepower(milliwattsorevenmicrowatts),andwillgenerallyhavetheabilitytoretainfunctionalitywhilewaitingforaneventsuchasabuttonpressorinterrupt.Powerconsumptionwhilesleeping(CPUclockandperipheralsdisabled)maybejustnanowatts,makingthemidealforlowpowerandlonglastingbatteryapplications.Microcontrollersareusedinautomaticallycontrolledproductsanddevices,suchasautomobileenginecontrolsystems,remotecontrols,officemachines,appliances,powertools,andtoys.Byreducingthesize,cost,andpowerconsumptioncomparedtoadesignusingaseparatemicroprocessor,memory,andinput/outputdevices,microcontrollersmakeiteconomicaltoelectronicallycontrolmanymoreprocesses.Themajorityofcomputersystemsinusetodayareembeddedinothermachinery,suchasautomobiles,telephones,appliances,andperipheralsforcomputersystems.Thesearecalledembeddedsystems.Whilesomeembeddedsystemsareverysophisticated,manyhaveminimalrequirementsformemoryandprogramlength,withnooperatingsystem,andlowsoftwarecomplexity.Typicalinputandoutputdevicesincludeswitches,relays,solenoids,LEDs,smallorcustomLCDdisplays,radiofrequencydevices,andsensorsfordatasuchastemperature,humidity,lightleveletc.Embeddedsystemsusuallyhavenokeyboard,screen,disks,printers,orotherrecognizableI/Odevicesofapersonalcomputer,andmaylackhumaninteractiondevicesofanykind.Itismandatorythatmicrocontrollersproviderealtimeresponsetoeventsintheembeddedsystemtheyarecontrolling.Whencertaineventsoccur,aninterruptsystemcansignaltheprocessortosuspendprocessingthecurrentinstructionsequenceandtobeginaninterruptserviceroutine(ISR).TheISRwillperformanyprocessingrequiredbasedonthesourceoftheinterruptbeforereturningtotheoriginalinstructionsequence.Possibleinterrupt第4页sourcesaredevicedependent,andoftenincludeeventssuchasaninternaltimeroverflow,completingananalogtodigitalconversion,alogiclevelchangeonaninputsuchasfromabuttonbeingpressed,anddatareceivedonacommunicationlink.Wherepowerconsumptionisimportantasinbatteryoperateddevices,interruptsmayalsowakeamicrocontrollerfromalowpowersleepstatewheretheprocessorishalteduntilrequiredtodosomethingbyaperipheralevent.Microcontrollerprogramsmustfitintheavailableon-chipprogrammemory,sinceitwouldbecostlytoprovideasystemwithexternal,expandable,memory.Compilersandassemblylanguageareusedtoturnhigh-levellanguageprogramsintoacompactmachinecodeforstorageinthemicrocontrollersmemory.Dependingonthedevice,theprogrammemorymaybepermanent,read-onlymemorythatcanonlybeprogrammedatthefactory,orprogrammemorymaybefield-alterableflashorerasableread-onlymemory.Sinceembeddedprocessorsareusuallyusedtocontroldevices,theysometimesneedtoacceptinputfromthedevicetheyarecontrolling.Thisisthepurposeoftheanalogtodigitalconverter.Sinceprocessorsarebuilttointerpretandprocessdigitaldata,i.e.1sand0s,theywontbeabletodoanythingwiththeanalogsignalsthatmaybebeingsenttoitbyadevice.Sotheanalogtodigitalconverterisusedtoconverttheincomingdataintoaformthattheprocessorcanrecognize.Thereisalsoadigitaltoanalogconverterthatallowstheprocessortosenddatatothedeviceitiscontrolling.Inadditiontotheconverters,manyembeddedmicroprocessorsincludeavarietyoftimersaswell.OneofthemostcommontypesoftimersistheProgrammableIntervalTimer,orPITforshort.APITjustcountsdownfromsomevaluetozero.Onceitreacheszero,itsendsaninterrupttotheprocessorindicatingthatithasfinishedcounting.Thisisusefulfordevicessuchasthermostats,whichperiodicallytestthetemperaturearoundthemtoseeiftheyneedtoturntheairconditioneron,theheateron,etc.TimeProcessingUnitorTPUforshort.Isessentiallyjustanothertimer,butmoresophisticated.Inadditiontocountingdown,theTPUcandetectinputevents,generateoutputevents,andotherusefuloperations.第5页DedicatedPulseWidthModulation(PWM)blockmakesitpossiblefortheCPUtocontrolpowerconverters,resistiveloads,motors,etc.,withoutusinglotsofCPUresourcesintighttimerloops.UniversalAsynchronousReceiver/Transmitter(UART)blockmakesitpossibletoreceiveandtransmitdataoveraseriallinewithverylittleloadontheCPU.ForthosewantingethernetonecanuseanexternalchiplikeCrystalSemiconductorCS8900A,RealtekRTL8019,orMicrochipENC28J60.Allofthemalloweasyinterfacingwithlowpincount.第6页中文翻译稿电锅炉温度系统1.单片机单片机即单片微型计算机，是把中央处理器、存储器、定时/计数器、输入输出接口都集成在一块集成电路芯片上的微型计算机。与应用在个人电脑中的通用型微处理器相比，它更强调自供应（不用外接硬件）和节约成本。它的最大优点是体积小，可放在仪表内部，但存储量小，输入输出接口简单，功能较低。由于其发展非常迅速，旧的单片机的定义已不能满足，所以在很多应用场合被称为范围更广的微控制器，但是目前在中国大陆仍多沿用“单片机”的称呼。绝大多数现在的单片机都是基于冯诺伊曼结构的，这种结构清楚地定义了嵌入式系统所必需的四个基本部分：一个中央处理器核心，程序存储器（只读存储器或者闪存）、数据存储器（随机存储器），一个或者更多的定时/计时器，还有用来与外围设备以及扩展资源进行通信的输入/输出端口所有这些都被集成在单个集成电路芯片上。说单片机与通用型中央处理单元芯片不同是因为前者一般很容易配合最小型的外部支持芯片制成工作计算机。这样就可以很容易的把单片机系统植入装置内部来控制装置了。近年来为了在指令和数据上使用不同的字宽，并提高处理器流水线速度，哈佛结构在微控制器和DSP也逐渐得到了广泛的应用。传统的微处理器是不允许这么做的。它要完成单片机的工作，就必须连接一些其他芯片。比如说，片上没有数据存储器，就必须要添加一些RAM的存储芯片，虽然所添加存储器的容量很灵活，但是至少还是要添加，另外还需要添加很多连线来传递芯片之间的数据。比如，一个典型的微控制器只需要一个时钟发生器和很少的RAM和ROM(或者EPROM,E2PROM)就可以在软件和晶振下工作了。同时，微控制器具有丰富的输入输出设备，像是模拟数字转换(ADC)，定时器，串口或者其他串行通讯接口(比如I2C，串行外围接口(SPI),控制器局域网)。通常，这些继承在内部的设备可以通过特殊的指令来操作。一些现代的微控制器支持一些内建的高级编程语言，比如BASIC语言。一个微控制器（也叫MCU）是一个微型计算芯片。它包含一个处理器、一第7页个内存（有少量的RAM，程序存储器，或两者兼而有之）和一个可编程输入/输出外设。它强调高度集成，而相比之下，一个微处理器只包含一个CPU（比如一台PC）。除了通常的算术和逻辑要素等一般用途的微处理器，微控制器还集成了更多的要素，如读写存储器的数据存储，只读存储器的存储程序，快闪记忆体的永久数据存储，外设，和输入/输出接口。在时钟频率只有32Mhz的情况下，微操作系统往往以非常低的速度相运行，但是这足够典型的应用。他们消耗较少的功率（毫瓦或什微），且具有保持功能，同时可以等待一个事件，如一个按钮的按下或中断。在睡眠状态时，CPU时钟和外设禁用，从而使它们适合用于低功耗和长期持久的电池应用。微控制器广泛应用于自动控制产品和设备，如汽车发动机控制系统，远程控制系统，办公室机器设备系统，家用电器，电动工具，和玩具等。通过降低尺寸，成本和能耗，设计使用单独的微处理器，内存和输入/输出设备，能够使微控制器控制更多的