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嵌入式系统概述. 宋健建 南京大学软件学院 2004/12/21. 内容. 什么是嵌入式系统 嵌入式系统的历史和发展 嵌入式系统的组成 嵌入式系统的特点 嵌入式系统软件开发. 1. What are embedded systems?. Definition: Embedded system : any device that includes a programmable computer but is not itself a general-purpose computer.

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slide1

嵌入式系统概述

宋健建

南京大学软件学院

2004/12/21

slide2
内容
  • 什么是嵌入式系统
  • 嵌入式系统的历史和发展
  • 嵌入式系统的组成
  • 嵌入式系统的特点
  • 嵌入式系统软件开发
1 what are embedded systems
1. What are embedded systems?
  • Definition:
    • Embedded system: any device that includes a programmable computer but is not itself a general-purpose computer.
  • Take advantage of application characteristics to optimize the design:
    • don’t need all the general-purpose bells and whistles.
a more detailed definition
A More Detailed Definition
  • 国内一般定义
    • 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。
    • 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 computer
Embedding a computer

output

analog

input

CPU

analog

mem

embedded

computer

examples
Examples
  • Personal digital assistant (PDA).
  • Printer.
  • Cell phone.
  • Automobile: engine, brakes, dash, etc.
  • Television.
  • Household appliances.
  • PC keyboard (scans keys).
reference interpretation 1
Reference Interpretation (1)
  • An "embedded system" is any computer system or computing device that performs a dedicated function or is designed for use with a specific embedded software application.
  • Embedded 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
Reference Interpretation (2)
  • A specialized computer 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 operating system, but many are so specialized that the entire logic can be implemented as a single program.
reference interpretation 3
Reference Interpretation(3)
  • 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。
    • 芯片级嵌入- 含程序或算法的处理器
    • 模块级嵌入- 系统中的某个核心模块板
    • 系统级嵌入- 主计算机系统
slide10
1.2 嵌入式系统历史和发展
  • 1971年代单片微处理器问世,它标志着嵌入式系统的开端。
  • 从4个方面了解嵌入式系统历史
    • 硬件
    • 软件
    • 代表产品
    • 系统结构
slide11
嵌入式硬件的历史
  • 1971年Intel 4004, 4位微处理器
  • TI, TMS1000, 4位微控制器
    • ROM, RAM, CPU + I/O port
  • 1980年Intel MCS-51, 8位微控制器
  • 16位, 32位微处理器…
  • 1990’s, DSP
    • TMS320C30
slide12
嵌入式处理器的分类和术语(1)
  • 微控制器(MCU:Micro-Controller Unit)
    • 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。
    • Intel 8051
  • 微处理器(MPU:Micro-Processor Unit)
    • 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。
    • ARM系列,MIPS
slide13
嵌入式处理器的分类和术语(2)
  • 数字信号处理器(DSP: Digital Signal Processor)
    • 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。
    • TI TMS320C30
  • ->片上系统(System-on-Chip, SoC)
    • 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。
    • Intel PCA架构;PXA 255
microprocessor varieties
Microprocessor varieties
  • Microcontroller: includes I/O devices, on-board memory.
  • Digital signal processor (DSP): microprocessor optimized for digital signal processing.
  • Typical embedded word sizes: 8-bit, 16-bit, 32-bit.
slide15
嵌入式软件的历史
  • 监控程序
  • 操作系统
    • 1981, 嵌入式实时内核 VTRX32
    • 1990’s, QNX-4
    • pSOS, VxWorks, Palm OS, WinCE, Embedded Linux, LynxOS, uCOS, Nucleus…
slide16
硬件系统

4位单片机

8位单片机/ 16位单片机

32位专用微处理器

32位DSP微处理器

SoC

SoPC

软件系统

实时监控程序

专用系统

通用系统

嵌入式系统结构演变
ia embedded system
IA & Embedded System
  • Information Appliance
    • An 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 distinguishing feature of information appliance is the ability to share information among themselves. (Don Norman)
ia embedded system cont d
IA & Embedded System (cont’d)
  • 信息电器的核心就是嵌入式系统
  • 信息电器的成本取决于嵌入式系统的成本
  • 信息电器的使用性能取决于嵌入式系统的软件
  • 信息电器的发展方向决定着嵌入式系统的发展方向
slide20
硬件

嵌入式处理器

各种类型存储器

模拟电路及电源

接口控制器及接插件

软件

实时操作系统(RTOS)

板级支持包(BSP)

设备驱动(Device Driver)

协议栈(Protocol Stack)

应用程序(Application)

软件硬件基本要素
slide21
嵌入式处理器的分类
  • 微控制器(MPU)
  • 微处理器(MCU)
  • 数字信号处理器(DSP)
  • 片上系统(SoC)
slide22
存储设备
  • ROM
    • PROM,EPROM,EEPROM
    • Flash ROM
      • Flash在嵌入式系统中的两种作用(boot ROM、hard disk)
  • RAM
    • SRAM
    • DRAM
embedded linux
Embedded Linux
  • Basic components:
    • Boot loader
    • Linux kernel
  • Further:
    • Hardware drivers
    • Application programs
    • File systems based on ROM or RAM
    • TCP/IP stack
    • GUI
slide31
嵌入式操作系统
  • 需要操作系统的场合
    • 多任务
    • 方便的用户界面
    • 网络功能
    • 升级和二次开发
  • 嵌入式操作系统的基本功能
    • 多任务调度
    • 内存管理
    • 硬件资源管理
slide32
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。

技术集成

软硬件集成,计算机和网络通信集成

有实时约束

一般采用实时操作系统

有功耗约束

软件通常没有系统和应用的区别,软件固化。

系统内核小

高可靠性

资源比PC少得多

嵌入式系统需要专用的开发工具

非垄断市场

1.5 嵌入式系统的特点
characteristics of embedded systems
Characteristics of embedded systems
  • Sophisticated functionality.
  • Real-time operation.
  • Low manufacturing cost.
  • Low power.
  • Designed to tight deadlines by small teams.
functional complexity
Functional complexity
  • Often have to run sophisticated algorithms or multiple algorithms.
    • Cell phone, laser printer.
  • Often provide sophisticated user interfaces.
real time operation
Real-time operation
  • Must finish operations by deadlines.
    • Hard real time: missing deadline causes failure.
    • Soft real time: missing deadline results in degraded performance.
  • Many systems are multi-rate: must handle operations at widely varying rates.
non functional requirements
Non-functional requirements
  • Many embedded systems are mass-market items that must have low manufacturing costs.
    • Limited memory, microprocessor power, etc.
  • Power consumption is critical in battery-powered devices.
    • Excessive power consumption increases system cost even in wall-powered devices.
design teams
Design teams
  • Often designed by a small team of designers.
  • Often must meet tight deadlines.
    • 6 month market window is common.
    • Can’t miss back-to-school window for calculator.
slide38
1.6 嵌入式系统软件开发
  • 编程语言
    • 汇编、C、Java…
    • 交叉编译器(cross compiler)
      • 在一种机器(host)上为另一种机器(target)生成代码的编译程序
slide40
代码的下载与调试

开发平台

下载代码

返回调试信息

目标平台

slide41
嵌入式系统调试的方法
  • LED
  • Simulator
  • ICE (In-Circuit Emulator)
  • 基于JTAG的Embedded ICE
  • Angel
simulator
Simulator
  • Simulator (模拟器)
    • 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,
  • 特点
    • 简单可行
    • 缺乏在线调试功能和实时仿真功能
    • 仅能模拟目标处理器,无法模拟处理器有关I/O的功能
    • 常作为初步基本调试工具
slide43
ICE
  • ICE: In-Circuit Emulator
    • 传统用于测试印刷电路板的方法。
    • ICE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,就可以监测CPU芯片各条引线上的逻辑电平。
    • 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 ice
Embedded ICE
  • Embedded ICE: 一组调试寄存器
    • IBCR (Instruction Break Control Register)
    • DBAR (Data Break Address Register)
  • JTAG接口
    • JTAG(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。
  • ARM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。
angel
Angel
  • Angel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。
  • 功能
    • Debug。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。
    • 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。
    • 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。
    • 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,也可根据操作需要在不同处理器模式中运行。
    • 具有中断功能。从而能实现调试、通信和管理等操作的要求。
embedded system design
Embedded System Design
  • Top-down design:
    • start from most abstract description;
    • work to most detailed.
  • Bottom-up design:
    • work from small components to big system.
  • Real design uses both techniques.
levels of abstraction
Levels of abstraction

requirements

specification

architecture

component

design

system

integration

example gps moving map
Example: GPS moving map
  • Requirements
  • Specification
  • Architecture
  • Component design
  • System integration
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