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《基于ADuC812的HART协议通信电路板硬件设计(毕业论文)》由会员上传分享,免费在线阅读,更多相关内容在工程资料-天天文库。
1、现场总线是目前国际上过程控制领域的一个热点,通过现场总线数字通信技术可以延伸到现场级仪表,给控制体系带来一场革命。考虑到我国目前传统的基于4〜20mA的模拟设备仍然广泛的应用于工业控制,为满足从模拟到全数字的过渡HART协议应运而生。该协议基于Bell202通信标准,在4〜20mA的模拟信号上叠加不同的频率信号来传送数字信号。其特点是在现有的模拟信号传输线上实现数字信号通信,属于模拟系统向数字系统转变过程屮的过渡产品,由于这项技术属于承前启后的研究,所以,在当前的过渡时期具有较强的市场竞争能力,得到了较快发展。本文主要讨论HARTI
2、*议通信模块的硬件相关方面的设计。首先,论文对HART协议做了较全面的分析。HART协议采用ISO/OSI简化模型,ISO/OSI分为七个功能层,HART协议只用了第一、二、七层即物理层、数据链路层和应用层。其屮物理层规定了信号的传输方式以及信号屯平等内容,数据链路层规定了设备类型以及数据传输帧格式,应用层规定了HART协议的各种命令及响应码。其次,论文以HARTI办议为通信标准,提岀了通信板的硕件设计的总体方法。论文在介绍了HART协议的基础上着重研究了硬件设计,硬件上较为详尽的介绍了齐个组成模块一一微处理器模块、电流环模块、调制
3、解调器模块的功能和实现方法。关键词:现场总线;HART协议;通信模块;ADuC812单片机AbstractNowadays,fieldbustechniquebecameveryimportantintheworldofprocesscontroLthroughwhichdigitalcommunicationisusedtofieldsinstruments,thisleadstoarevolutiontocontrolsystems.However,4〜20mAanalogsignalinstrumentsalsehaveala
4、rgeapplicationinindustry,theHARTcommunicationprotocol一atransitionalprotocolduringtransitionfromanalogsystemtodigitalsystem—emergesasthetimesrequire.BasedonBell202communicationstandards,HARTprotocoltransferdatawithdifferentfrequencysignalsandpluswithanalogsignalsof4〜20m
5、A.Itischaracteristicthatrealizesdigitalcommunicationinthetransmissionofanalogsignalsjthasstrongcompetitioninthisinterimperiodandgrowsquicklybecauseofthistechnologybelongstoresearchoflinkbetweentheprecedingandthefollowing・Inthispaper,itmainlyfocusesonHARTprotocolcommuni
6、cationmodulehardware-relatedaspectsofthedesign.Firstly,thethesisdoesafairlycomprehensiveanalysisoftheHARTprotocol,itadoptapredigestedmodeofOSI/ISOinwhichhavesevenfunctionallayers,onlythreelayershavebeenusedinHARTprotocol.PhysicalLayerspecifiesthetransmittalmannerofsign
7、alandvoltageofsignal,DataLinkLayerspecifiesthedevicetypeandformatofdatatransmit,CommandLayerspecifiesallkindsofHARTcommandandreoponsecodes・AtthebasisofHARTprotocoljtfocusedonstudyinghardwaredesign.Secondly,beingbaseduponHARTprotocol,theOverallapproachaboutHardwareDesig
8、nofcommunicationcircuitboardisintroduced,thedetailedhardwareareintroduced,includingthesingle-chipmicrocomputermodule,