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1、外文文献及译文 学院：电气与控制工程学院 班级：测控技术与仪器1002班 姓名： 学号： 指导老师：Thesingle-chipmicrocomputeristheculminationofboththedevelopmentofthedigitalcomputerandtheintegratedcircuitarguablythetowmostsignificantinventionsofthe20thcentury.Thesetowtypesofarchitecturearefoundinsingle-chipmicrocomputer.Someemploythesplitprogram/
2、datamemoryoftheHarvardarchitecture,othersfollowthephilosophy,widelyadaptedforgeneral-purposecomputersandmicroprocessors,ofmakingnologicaldistinctionbetweenprogramanddatamemoryasinthePrincetonarchitecture.Ingeneraltermsasingle-chipmicrocomputerischaracterizedbytheincorporationofalltheunitsofacomputer
3、intoasingledevice.ROMisusuallyforthepermanent,non-volatilestorageofanapplicationsprogram.Manymicrocomputersandmicrocontrollersareintendedforhigh-volumeapplicationsandhencetheeconomicalmanufactureofthedevicesrequiresthatthecontentsoftheprogrammemorybecommittedpermanentlyduringthemanufactureofchips.Cl
4、early,thisimpliesarigorousapproachtoROMcodedevelopmentsincechangescannotbemadeaftermanufacture.Thisdevelopmentprocessmayinvolveemulationusingasophisticateddevelopmentsystemwithahardwareemulationcapabilityaswellastheuseofpowerfulsoftwaretools.SomemanufacturersprovideadditionalROMoptionsbyincludingint
5、heirrangedeviceswith(orintendedforusewith)userprogrammablememory.Thesimplestoftheseisusuallydevicewhichcanoperateinamicroprocessormodebyusingsomeoftheinput/outputlinesasanaddressanddatabusforaccessingexternalmemory.Thistypeofdevicecanbehavefunctionallyasthesinglechipmicrocomputerfromwhichitisderived
6、albeitwithrestrictedI/Oandamodifiedexternalcircuit.TheuseoftheseROMlessdevicesiscommoneveninproductioncircuitswherethevolumedoesnotjustifythedevelopmentcostsofcustomon-chipROM;therecanstillbeasignificantsavinginI/Oandotherchipscomparedtoaconventionalmicroprocessorbasedcircuit.Moreexactreplacementfor
7、ROMdevicescanbeobtainedintheformofvariantswithpiggy-backEPROM(ErasableprogrammableROM)socketsordeviceswithEPROMinsteadofROM.ThesedevicesarenaturallymoreexpensivethanequivalentROMdevice,butdoprovidecompletecircuitequivalents.EPROMbaseddevicesarealsoextremelyattractiveforlow-volumeapplicationswherethe
8、yprovidetheadvantagesofasingle-chipdevice,intermsofon-chipI/O,etc.,withtheconvenienceofflexibleuserprogrammability.TheCPUismuchlikethatofanymicroprocessor.Manyapplicationsofmicrocomputersandmicrocontrollersinvolvethehandlingofbinary-codeddecimal(BCD)data(fornumericaldisplays,forexample),henceitiscom
9、montofindthattheCPUiswelladaptedtohandlingthistypeofdata.Itisalsocommontofindgoodfacilitiesfortesting,settingandresettingindividualbitsofmemoryorI/Osincemanycontrollerapplicationsinvolvetheturningonandoffofsingleoutputlinesorthereadingthesingleline.Theselinesarereadilyinterfacedtotwo-statedevicessuc
10、hasswitches,thermostats,solid-staterelays,valves,motor,etc.Parallelinputandoutputschemesvarysomewhatindifferentmicrocomputer;inmostamechanismisprovidedtoatleastallowsomeflexibilityofchoosingwhichpinsareoutputsandwhichareinputs.Thismayapplytoallorsomeoftheports.SomeI/Olinesaresuitablefordirectinterfa
11、cingto,forexample,fluorescentdisplays,orcanprovidesufficientcurrenttomakeinterfacingothercomponentsstraightforward.SomedevicesallowanI/Oporttobeconfiguredasasystembustoallowoff-chipmemoryandI/Oexpansion.Thisfacilityispotentiallyusefulasaproductrangedevelops,sincesuccessiveenhancementsmaybecometoobig
12、foron-chipmemoryanditisundesirablenottobuildontheexistingsoftwarebase.Serialcommunicationwithterminaldevicesiscommonmeansofprovidingalinkusingasmallnumberoflines.Thissortofcommunicationcanalsobeexploitedforinterfacingspecialfunctionchipsorlinkingseveralmicrocomputerstogether.Boththecommonasynchronou
13、ssynchronouscommunicationschemesrequireprotocolsthatprovideframing(startandstop)information.ThiscanbeimplementedasahardwarefacilityorU(S)ART(Universal(synchronous)asynchronousreceiver/transmitter)relievingtheprocessor(andtheapplicationsprogrammer)ofthislow-level,time-consuming,detail.tismerelynecess
14、arytoselectedabaud-rateandpossiblyotheroptions(numberofstopbits,parity,etc.)andload(orreadfrom)theserialtransmitter(orreceiver)buffer.Serializationofthedataintheappropriateformatisthenhandledbythehardwarecircuit.TheDS18B20digitalthermometerprovides9-bitto12-bitCelsiustemperaturemeasurementsandhasana
15、larmfunctionwithnonvolatileuser-programmableupperandlowertriggerpoints.TheDS18B20communicatesovera1-Wirebusthatbydefinitionrequiresonlyonedataline(andground)forcommunicationwithacentralmicroprocessor.Ithasanoperatingtemperaturerangeof-55Cto+125Candisaccurateto0.5Covertherangeof-10Cto+85C.Inaddition,
16、theDS18B20canderivepowerdirectlyfromthedataline(“parasitepower”),eliminatingtheneedforanexternalpowersupply.EachDS18B20hasaunique64-bitserialcode,whichallowsmultipleDS18B20stofunctiononthesame1-Wirebus.Thus,itissimpletouseonemicroprocessortocontrolmanyDS18B20sdistributedoveralargearea.Applicationsth
17、atcanbenefitfromthisfeatureincludeHVACenvironmentalcontrols,temperaturemonitoringsystemsinsidebuildings,equipment,ormachinery,andprocessmonitoringandcontrolsystems.TheDS18B20canbepoweredbyanexternalsupplyontheVDDpin,oritcanoperatein“parasitepower”mode,whichallowstheDS18B20tofunctionwithoutalocalexte
18、rnalsupply.Parasitepowerisveryusefulforapplicationsthatrequireremotetemperaturesensingorthatareveryspaceconstrained.Figure1showstheDS18B20sparasite-powercontrolcircuitry,which“steals”powerfromthe1-WirebusviatheDQpinwhenthebusishigh.ThestolenchargepowerstheDS18B20whilethebusishigh,andsomeofthechargei
19、sstoredontheparasitepowercapacitor(CPP)toprovidepowerwhenthebusislow.WhentheDS18B20isusedinparasitepowermode,theVDDpinmustbeconnectedtoground.Inparasitepowermode,the1-WirebusandCPPcanprovidesufficientcurrenttotheDS18B20formostoperationsaslongasthespecifiedtimingandvoltagerequirementsaremet(seetheDCE
20、lectricalCharacteristicsandACElectricalCharacteristics).However,whentheDS18B20isperformingtemperatureconversionsorcopyingdatafromthescratchpadmemorytoEEPROM,theoperatingcurrentcanbeashighas1.5mA.Thiscurrentcancauseanunacceptablevoltagedropacrosstheweak1-Wirepullupresistorandismorecurrentthancanbesup
21、pliedbyCPP.ToassurethattheDS18B20hassufficientsupplycurrent,itisnecessarytoprovideastrongpulluponthe1-WirebuswhenevertemperatureconversionsaretakingplaceordataisbeingcopiedfromthescratchpadtoEEPROM.ThiscanbeaccomplishedbyusingaMOSFETtopullthebusdirectlytotherailasshowninFigure4.The1-Wirebusmustbeswi
22、tchedtothe strongpullupwithin10s(max) afteraConvert T44horCopyScratchpad48hCommandisissued,andthebusmustbeheldhighbythepullupforthedurationoftheconversion(tCONV)ordatatransfer(tWR=10ms).Nootheractivitycantakeplaceonthe1-Wirebuswhilethepullupisenabled.TheDS18B20canalsobepoweredbytheconventionalmethod
23、ofconnectinganexternalpowersupplytotheVDDpin,asshowninFigure5.TheadvantageofthismethodisthattheMOSFETpullupisnotrequired,andthe1-Wirebusisfreetocarryothertrafficduringthetemperatureconversiontime.Theuseofparasitepowerisnotrecommendedfortemperaturesabove+100CsincetheDS18B20maynotbeabletosustaincommun
24、icationsduetothehigherleakagecurrentsthatcanexistatthesetemperatures.Forapplicationsinwhichsuchtemperaturesarelikely,itisstronglyrecommendedthattheDS18B20bepoweredbyanexternalpowersupply.InsomesituationsthebusmastermaynotknowwhethertheDS18B20sonthebusareparasitepoweredorpoweredbyexternalsupplies.The
25、masterneedsthisinformationtodetermineifthestrongbuspullupshouldbeusedduringtemperatureconversions.Togetthisinformation,themastercanissueaSkipROMCChcommandfollowedbyaReadPowerSupplyB4hcommandfollowedbya“readtimeslot”.Duringthereadtimeslot,parasitepoweredDS18B20swillpullthebuslow,andexternallypoweredD
26、S18B20swillletthebusremainhigh.Ifthebusispulledlow,themasterknowsthatitmustsupplythestrongpulluponthe1-Wirebusduringtemperatureconversions.Whenyousetouttoselectatemperaturesensor,youarenolongerlimitedtoeitherananalogoutputoradigitaloutputdevice.Thereisnowabroadselectionofsensortypes,oneofwhichshould
27、matchyoursystemsneeds.Untilrecently,allthetemperaturesensorsonthemarketprovidedanalogoutputs.Thermistors,RTDs,andthermocoupleswerefollowedbyanotheranalog-outputdevice,thesilicontemperaturesensor.Inmostapplications,unfortunately,theseanalog-outputdevicesrequireacomparator,anADC,oranamplifierattheirou
28、tputtomakethemuseful.Thus,whenhigherlevelsofintegrationbecamefeasible,temperaturesensorswithdigitalinterfacesbecameavailable.TheseICsaresoldinavarietyofforms,fromsimpledevicesthatsignalwhenaspecifictemperaturehasbeenexceededtothosethatreportbothremoteandlocaltemperatureswhileprovidingwarningsatprogr
29、ammedtemperaturesettings.Thechoicenowisntsimplybetweenanalog-outputanddigital-outputsensors;thereisabroadrangeofsensortypesfromwhichtochoose.TheDS18B20DigitalThermometerprovides9to12-bit(configurable)temperaturereadingswhichindicatethetemperatureofthedevice.Informationissentto/fromtheDS18B20overa1-W
30、ireinterface,sothatonlyonewire(andground)needstobeconnectedfromacentralmicroprocessortoaDS18B20.Powerforreading,writing,andperformingtemperatureconversionscanbederivedfromthedatalineitselfwithnoneedforanexternalpowersource.BecauseeachDS18B20containsauniquesiliconserialnumber,multipleDS18B20scanexist
31、onthesame1-Wirebus.Thisallowsforplacingtemperaturesensorsinmanydifferentplaces.ApplicationswherethisfeatureisusefulincludeHVACenvironmentalcontrols,sensingtemperaturesinsidebuildings,equipmentormachinery,andprocessmonitoringandcontrol.TheblockdiagramofFigure1showsthemajorcomponentsoftheDS18B20.TheDS
32、18B20hasfourmaindatacomponents:1)64-bitlaserROM,2)temperaturesensor,3)nonvolatiletemperaturealarmtriggersTHandTL,and4)aconfigurationregister.Thedevicederivesitspowerfromthe1-Wirecommunicationlinebystoringenergyonaninternalcapacitorduringperiodsoftimewhenthesignallineishighandcontinuestooperateoffthi
33、spowersourceduringthelowtimesofthe1-Wirelineuntilitreturnshightoreplenishtheparasite(capacitor)supply.Asanalternative,theDS18B20mayalsobepoweredfromanexternal3V-5.5Vsupply.CommunicationtotheDS18B20isviaa1-Wireport.Withthe1-Wireport,thememoryandcontrolfunctionswillnotbeavailablebeforetheROMfunctionpr
34、otocolhasbeenestablished.ThemastermustfirstprovideoneoffiveROMfunctioncommands:1)ReadROM,2)MatchROM,3)SearchROM,4)SkipROM,or5)AlarmSearch.Thesecommandsoperateonthe64-bitlaserROMportionofeachdeviceandcansingleoutaspecificdeviceifmanyarepresentonthe1-Wirelineaswellasindicatetothebusmasterhowmanyandwha
35、ttypesofdevicesarepresent.AfteraROMfunctionsequencehasbeensuccessfullyexecuted,thememoryandcontrolfunctionsareaccessibleandthemastermaythenprovideanyoneofthesixmemoryandcontrolfunctioncommands. 单片机是数字计算机的开发和集成电路20世纪可以说是拖最显著的发明之大成体系结构，这些纤维束类型被发现在单芯片微型计算机。一些采用了哈佛结构的分割程序/数据存储器，别人遵守的理念，广泛适用于通用计算机和微处理器，使
36、得程序和数据存储器之间没有逻辑的区别在普林斯顿体系结构。笼统的单芯片微型计算机，其特征在于通过计算机的所有单位纳入一个单一的设备。 ROM是通常的永久性的，非应用程序的易失性存储器。不少微机和单片机用于大批量应用，因此，经济的设备制造要求的程序存储器的内容是在制造期间永久性的刻录在芯片中，这意味着严谨的方法，因为修改ROM代码不能制造之后发展。这一发展过程可能涉及仿真,使用硬件仿真功能以及强大的软件工具使用先进的开发系统。一些制造商在其提供的设备包括的范围（或拟使用）用户可编程内存.其中最简单的通常是设备能够运行于微处理器模式通过使用一些输入/输出作为地址线额外的ROM选项和数据总线访问外部内
37、存.这种类型的设备可以表现为单芯片微型计算机尽管有限制的I/O和外部修改这些设备的电路.小内存装置的应用是非常普遍的在永久性内存的制造中;但仍然可以在我节省大量成本I/O和其它芯片相比，传统的基于微处理器电路.更准确的ROM设备更换，可在与形式变种背驮式EPROM（可擦除可编程只读存储器）插座或存储器，而不是ROM器件。这些器件自然价格比同等ROM设备贵，但不提供完整的等效电路.EPROM的设备也非常有吸引力对于低容量应用中，他们提供的单芯片器件的优势，在以下方面的板载I/O等，在灵活的用户可编程带来的便利。CPU是很象微型电子计算机和微控制器的任何微电脑.许多微电脑和微控制器涉及到二进制编码
38、(十进制处理（BCD）的数据为例）数字显示，因而，常常可以发现该CPU是很适合处理这种类型的数据。对设施良好与否进行的测试，设置和重置单个位的内存或I/O控制器的应用程序，也是常见的因为许多涉及打开和关闭的单输出线或在单线.这些线很容易连接到二进制的设备，如开关，恒温器，固态继电器，阀门，电机等。并行输入和输出的计划有所不同，在不同的微机，在大多数设立一个机制，至少选择让其中一些引脚输出，一些引脚输如是非常灵活的。这可能适用于所有或端口.有些I/O线直接连接到适当的设备，例如，荧光显示器，也可以提供足够的电流，使接口和其他设备直接相连.一些设备允许一个I/O端口,其他组件将作为系统总线配置为允
39、许片外存储器和I/O扩展。这个设施是潜在有用的一个产品系列的发展，因为连续增强可能成为太上存储器，这是不可取的，不是建立在现有的软件基础上的。串行通信是指与终端设备的链接使用少量的通讯线.这种通讯也可利用特殊的接口连接功能芯片使几个微型机连在一起。双方共同异步同步通信方案要求的规则提供成帧（启动和停止）的信息。这可以作为一个硬件设施或U（拧）艺术（通用执行（同步）异步接收器/发送器）减轻处理器（和应用程序）的这种低层次的确费时.它也只需要选择一个波特率及其他可能的选择（停止位，奇偶校验等）和负载号码（或读取），串行发送器（或接收）的缓冲器.进行适当的格式的数据串行处理，然后由硬件电路完成。该D
40、S18B20数字温度计提供9位至12位摄氏温度测量，并与非易失性用户可编程上下触发点报警功能。 DS18B20的通信通过一个1-Wire总线，按照定义，只需要一个数据线（和地线）与中央微处理器通信。它具有-55C至+125C的工作温度范围，精确到0.5C在-10C至+85C。此外，DS18B20可以直接从数据线（“寄生电源”）获得电力，省去了外部电源。每个DS18B20都有一个唯一的64位序列码，它允许多个DS18B20s到相同的1-Wire总线上运行。因此，它是简单的使用一个微处理器来控制分布在大面积上许多DS18B20s。应用可以受益于这个功能包括HVAC环境控制，建筑物内部的温度监测系统
41、，设备或机械，过程监测和控制系统。该DS18B20可以通过在VDD引脚上的外部电源供电，也可以在“寄生供电”模式，它允许DS18B20来没有本地外部电源正常工作。寄生电源是用于需要远程温度传感或应用程序非常有用非常空间受限。图1显示了DS18B20的寄生功率控制电路，其中“偷”的力量从1-Wire总线通过DQ针时总线高。失窃的主管权力的DS18B20在总线处于高，一些电荷存储在寄生电源电容（CPP）提供电源时，总线低。当DS18B20采用的是寄生供电模式，VDD引脚必须连接到地面。在寄生供电模式，在1-Wire总线和CPP能够提供足够的电流，以DS18B20的大多数操作，只要满足指定的时间和电
42、压要求（见DC电气特性和AC电气特性）。然而，DS18B20从暂存存储器进行温度转换或复制数据时，EEPROM时，工作电流可高达1.5毫安。该电流可能会造成整个弱1-Wire上拉电阻不可接受的电压降，是更多的电流比可通过CPP提供。为了确保DS18B20的有足够的电源电流，就必须提供1-Wire总线强上拉每当温度转换正在发生或数据被复制暂存器到EEPROM中。这可以通过使用一个MOSFET直接拉路公交车到铁路如图4来完成。一个转换T 44H或复制暂存器后的1-Wire总线必须切换到的10s内强上拉（最大） 48小时命令发出，而总线必须转换（tCONV时间）或数据传输（TWR = 10ms）的持续时间高举的上拉。而拉启用没有其他活动可以采取的1-Wire总线上的地方。该DS18B20也可通过连接外部电源为VDD端子，如图5的传统方法提供动力。这种方法的优点是，不需要在MOSFET上拉，并在1-Wire总线空闲时，以过程中的温度转换时间进行其它流量。不建议使用寄生电源的温度高于100C，因为DS18B20可能无法维持通讯由于能够在这些温度下存在较高的漏电流