嵌入式系统概述-南京大学软件学院ppt课件

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1、嵌入式系统概述宋健建南京大学软件学院2004/02/10内容n什么是嵌入式系统n嵌入式系统的历史和发展n嵌入式系统的组成n嵌入式系统的特点n嵌入式系统软件开发1.What are embedded systems?nDefinition:nEmbedded system:any device that includes a programmable computer but is not itself a general-purpose computer.nTake advantage of application characteristics to optimize the design:

2、ndont need all the general-purpose bells and whistles.A More Detailed Definitionn国内一般定义n嵌入式系统是以应用为中心，以计算机技术为基础，并且软硬件可裁剪，适用于应用系统对功能、可靠性、成本、体积、功耗有严格要求的专用计算机系统。n一般由嵌入式微处理器、外围硬件设备、嵌入式操作系统以及用户应用程序等四个部分组成，用于实现对其他设备的控制、监视或管理等功能。Embedding a computerCPUmeminputoutputanaloganalogembeddedcomputerExamplesnPerso

3、nal digital assistant(PDA).nPrinter.nCell phone.nAutomobile:engine,brakes,dash,etc.nTelevision.nHousehold appliances.nPC keyboard(scans keys).Reference Interpretation(1)nAn embedded system is any computer system or computing device that performs a dedicated function or is designed for use with a spe

4、cific embedded software application.nEmbedded systems may use a ROM-based operating system or they may use a disk-based system,like a PC.But an embedded system is not usable as a commercially viable substitute for general purpose computers or devices.Reference Interpretation(2)nA specialized compute

5、r system that is part of a larger system or machine.Typically,an embedded system is housed on a single microprocessor board with the programs stored in ROM.Virtually all appliances that have a digital interface-watches,microwaves,VCRs,cars-utilize embedded systems.Some embedded systems include an op

6、erating system,but many are so specialized that the entire logic can be implemented as a single program.Reference Interpretation(3)n中国微机学会的定义：嵌入式系统是以嵌入式应用为目的的计算机系统，可以分为片级、板级、系统级。q芯片级嵌入 含程序或算法的处理器q模块级嵌入 系统中的某个核心模块板q系统级嵌入 主计算机系统1.2 嵌入式系统历史和发展n1971年代单片微处理器问世，它标志着嵌入式系统的开端。n从4个方面了解嵌入式系统历史n硬件n软件n代表产品n系统结构

7、嵌入式硬件的历史n1971年Intel 4004,4位微处理器nTI,TMS1000,4位微控制器nROM,RAM,CPU+I/O portn1980年Intel MCS-51,8位微控制器n16位,32位微处理器n1990s,DSPnTMS320C30嵌入式处理器的分类和术语(1)n微控制器(MCU：Micro-Controller Unit)n即单片机。早期比较流行的处理器，将整个计算机系统集成到一个芯片中，内部以某种微处理器为核心，并对ROM、RAM、总线、总线逻辑、定时器/计数器、I/O、串行口、A/D转换、D/A转换等必要外设加以集成。nIntel 8051n微处理器(MPU：Mic

8、ro-Processor Unit)n必须在电路板上完成嵌入式系统功能。将MPU和其必要外设装配在一起的电路板称为单板机。nARM系列，MIPS嵌入式处理器的分类和术语(2)n数字信号处理器(DSP:Digital Signal Processor)n对系统结构和指令进行特殊设计，使其适合于执行DSP算法，编译效率较高，指令执行速度也快。nTI TMS320C30n-片上系统(System-on-Chip,SoC)n将重要处理器的内核和各种外围的芯片器件整合在一起，进一步降低功耗。nIntel PCA架构；PXA 255Microprocessor varietiesnMicrocontrol

9、ler:includes I/O devices,on-board memory.nDigital signal processor(DSP):microprocessor optimized for digital signal processing.nTypical embedded word sizes:8-bit,16-bit,32-bit.嵌入式软件的历史n监控程序n操作系统n1981,嵌入式实时内核 VTRX32n1990s,QNX-4npSOS,VxWorks,Palm OS,WinCE,Embedded Linux,LynxOS,uCOS,Nucleus嵌入式系统结构演变n硬件

10、系统n4位单片机n8位单片机/16位单片机n32位专用微处理器n32位DSP微处理器nSoCnSoPCn软件系统n实时监控程序n专用系统n通用系统IA&Embedded SystemnInformation AppliancenAn appliance specializing in information:Knowledge,facts,graphics,images,video,or sound.An information appliance is designed to perform activity,such as music,photography,or writing.A di

11、stinguishing feature of information appliance is the ability to share information among themselves.(Don Norman)IA&Embedded System(contd)n信息电器的核心就是嵌入式系统n信息电器的成本取决于嵌入式系统的成本n信息电器的使用性能取决于嵌入式系统的软件n信息电器的发展方向决定着嵌入式系统的发展方向1.4 嵌入式系统的基本组成软件硬件基本要素硬件硬件n嵌入式处理器n各种类型存储器n模拟电路及电源n接口控制器及接插件软件软件n实时操作系统（RTOS）n板级支持包（BSP

12、）n设备驱动（Device Driver）n协议栈（Protocol Stack）n应用程序（Application）嵌入式处理器的分类n微控制器(MPU)n微处理器(MCU)n数字信号处理器(DSP)n片上系统(SoC)存储设备nROMnPROM，EPROM，EEPROMnFlash ROMnFlash在嵌入式系统中的两种作用(boot ROM、hard disk)nRAMnSRAMnDRAM典型的嵌入式系统硬件组成Chip Board CircuitCPU CoreExternal DevicesUSBLCDPenKeyboardIRDAOthersConnection for Debug

13、gingPortsResetCircuitOscillationCircuitPowerSupplyDMATimerPrescalerA/DI/O PortInterruptControlerConnectingDRAMConnectingSRAMConnectingFlashConnectingROMCPUBCUPXA255 Architecture USB Host controller PXA250 Application processor IrDA FF UART MMC/SD Card BT UART Touch Screen SPI to Touch Screen USB Cli

14、ent LCD Toshiba LTM04C380K SDRAM Flash Memory Boot ROM CPLD&Board level Registers Driver and Transceiver Compact Flash AC97 Codec CS4201 Audio Jack Debug Leds Accelerometer sensor HEX-encoding switches Expansion-card slot Power System Ethernet Controller 典型的嵌入式系统软件组成VxWorks Architecture工具软件，应用软件VxWo

15、rks LibrariesTCP/IPI/O SystemWind kernelBSPFile SystemSCSI DriverNetwork DriverHardware dependent SoftwareHardware dependent SoftwareEthernetControllerSerialControllerClockTimerSCSIControllerHardwareHardwareHardware Independent SoftwareHardware Independent SoftwareEmbedded LinuxnBasic components:nBo

16、ot loadernLinux kernelnFurther:nHardware driversnApplication programsnFile systems based on ROM or RAMnTCP/IP stacknGUI嵌入式操作系统n需要操作系统的场合n多任务n方便的用户界面n网络功能n升级和二次开发n嵌入式操作系统的基本功能n多任务调度n内存管理n硬件资源管理1.5 嵌入式系统的特点n专门用于特定任务嵌入式系统一般是专用系统，而PC是通用计算平台。n技术集成软硬件集成，计算机和网络通信集成n有实时约束一般采用实时操作系统n有功耗约束n软件通常没有系统和应用的区别，软件固化

17、。n系统内核小n高可靠性n资源比PC少得多n嵌入式系统需要专用的开发工具n非垄断市场Characteristics of embedded systemsnSophisticated functionality.nReal-time operation.nLow manufacturing cost.nLow power.nDesigned to tight deadlines by small teams.Functional complexitynOften have to run sophisticated algorithms or multiple algorithms.nCell

18、phone,laser printer.nOften provide sophisticated user interfaces.Real-time operationnMust finish operations by deadlines.nHard real time:missing deadline causes failure.nSoft real time:missing deadline results in degraded performance.nMany systems are multi-rate:must handle operations at widely vary

19、ing rates.Non-functional requirementsnMany embedded systems are mass-market items that must have low manufacturing costs.nLimited memory,microprocessor power,etc.nPower consumption is critical in battery-powered devices.nExcessive power consumption increases system cost even in wall-powered devices.

20、Design teamsnOften designed by a small team of designers.nOften must meet tight deadlines.n6 month market window is common.nCant miss back-to-school window for calculator.1.6 嵌入式系统软件开发n编程语言n汇编、C、Javan交叉编译器(cross compiler)n在一种机器(host)上为另一种机器(target)生成代码的编译程序开发流程代码的下载与调试开发平台目标平台下载代码返回调试信息嵌入式系统调试的方法nLE

21、DnSimulatornICE(In-Circuit Emulator)n基于JTAG的Embedded ICEnAngelSimulatornSimulator(模拟器)n完全基于主机的软件。在主机上模拟了目标机中处理器的功能和指令，n特点n简单可行 n缺乏在线调试功能和实时仿真功能n仅能模拟目标处理器，无法模拟处理器有关I/O的功能 n常作为初步基本调试工具ICEnICE:In-Circuit Emulatorn传统用于测试印刷电路板的方法。nICE是一种专用的设备，配有专用于特定CPU芯片的接头。将ICE的接头骑在CPU芯片上并加以固定，使它的每一条引线与CPU芯片上的对应引线接触，就可

22、以监测CPU芯片各条引线上的逻辑电平。n由于集成电路的集成度不断提高，芯片的引脚不断增加；此外,为了缩小体积常常采用表面贴装技术。因此，无法用常规的在线仿真的方式Embedded ICEnEmbedded ICE:一组调试寄存器nIBCR(Instruction Break Control Register)nDBAR(Data Break Address Register)nnJTAG接口nJTAG(Joint Test Action Group)制定了边界扫描标准，只需5根引脚就可以实现在线仿真的功能。nARM架构处理器内含嵌入式在线仿真宏单元，为JTAG调试提供相应的接口。同时，为了能达

23、到实时跟踪调试的功能，ARM架构处理器还内含嵌入式跟踪宏单元，通过逻辑分析仪来实现实时跟踪调试的功能。AngelnAngel是一组运行在目标机上的程序，可以接受主机上调试器发送的命令。n功能nDebug。接收和解释PC主机的调试命令，显示处理器、存储器和寄存器的状态，也可以通过未定义指令来设置断点。n支持Angel调试协议ADP(Angel Debug Protocol)，从而实现PC主机与目标机的串行或并行通信,也支持与目标板的网卡通信。n支持目标机中应用程序可使用主机PC上的标准C函数库。通过软中断SWI指令来实现。n具有多任务调度和处理器模式管理功能。能分配任务优先级并对任务进行管理,也

24、可根据操作需要在不同处理器模式中运行。n具有中断功能。从而能实现调试、通信和管理等操作的要求。ARM的调试系统Embedded System DesignnTop-down design:nstart from most abstract description;nwork to most detailed.nBottom-up design:nwork from small components to big system.nReal design uses both techniques.Levels of abstractionrequirementsspecificationarchitecturecomponentdesignsystemintegrationExample:GPS moving mapnRequirementsnSpecificationnArchitecture nComponent designnSystem integrationReview