外文翻譯--嵌入式系統(tǒng)與rtos

1、<p><b>　　外文資料翻譯</b></p><p>　　Embedded systems and RTOS</p><p>　　One of the more surprising developments of the last few decades has been the ascendance of computers to a positio

2、n of prevalence in human affairs. Today there are more computers in our homes and offices than there are people who live and work in them. Yet many of these computers are not recognized as such by their users. In this ch

3、apter, we'll explain what embedded systems are and where they are found. We will also introduce the subject of embedded programming and discuss what makes it a unique </p><p>　　1. What Is an Embedded Sys

4、tem?</p><p>　　An embedded system is a combination of computer hardware and softwareand perhaps additional parts, either mechanical or electronicdesigned to perform a dedicated function. A good example is the

5、 microwave oven. Almost every household has one, and tens of millions of them are used every day, but very few people realize that a computer processor and software are involved in the preparation of their lunch or dinne

6、r.</p><p>　　The design of an embedded system to perform a dedicated function is in direct contrast to that of the personal computer. It too is comprised of computer hardware and software and mechanical compo

7、nents (disk drives, for example). However, a personal computer is not designed to perform a specific function. Rather, it is able to do many different things. Many people use the term general-purpose computer to make thi

8、s distinction clear. As shipped, a general-purpose computer is a blank slate; the man</p><p>　　Frequently, an embedded system is a component within some larger system. For example, modern cars and trucks con

9、tain many embedded systems. One embedded system controls the antilock brakes, another monitors and controls the vehicle's emissions, and a third displays information on the dashboard. Some luxury car manufacturers ha

10、ve even touted the number of processors (often more than 60, including one in each headlight) in advertisements. In most cases, automotive embedded systems are connected by</p><p>　　It is important to point

11、out that a general-purpose computer interfaces to numerous embedded systems. For example, a typical computer has a keyboard and mouse, each of which is an embedded system. These peripherals each contain a processor and s

12、oftware and is designed to perform a specific function. Another example is a modem, which is designed to send and receive digital data over an analog telephone line; that's all it does. And the specific function of o

13、ther peripherals can each be summarized</p><p>　　The existence of the processor and software in an embedded system may be unnoticed by a user of the device. Such is the case for a microwave oven, MP3 player,

14、 or alarm clock. In some cases, it would even be possible to build a functionally equivalent device that does not contain the processor and software. This could be done by replacing the processor-software combination wit

15、h a custom integrated circuit (IC) that performs the same functions in hardware. However, the processor and software combi</p><p>　　2. History and Future</p><p>　　Given the definition of embedde

16、d systems presented earlier in this chapter, the first such systems could not possibly have appeared before 1971. That was the year Intel introduced the world's first single-chip microprocessor. This chip, the 4004,

17、was designed for use in a line of business calculators produced by the Japanese company Busicom. In 1969, Busicom asked Intel to design a set of custom integrated circuits, one for each of its new calculator models. The

18、4004 was Intel's response. Rather</p><p>　　The microprocessor was an overnight success, and its use increased steadily over the next decade. Early embedded applications included unmanned space probes, co

19、mputerized traffic lights, and aircraft flight control systems. In the 1980s and 1990s, embedded systems quietly rode the waves of the microcomputer age and brought microprocessors into every part of our personal and pro

20、fessional lives. Most of the electronic devices in our kitchens (bread machines, food processors, and microwave ovens), </p><p>　　It seems inevitable that the number of embedded systems will continue to incr

21、ease rapidly. Already there are promising new embedded devices that have enormous market potential: light switches and thermostats that are networked together and can be controlled wirelessly by a central computer, intel

22、ligent air-bag systems that don't inflate when children or small adults are present, medical monitoring devices that can notify a doctor if a patient's physiological conditions are at critical levels, an</p>

23、;<p>　　3. Real-Time Systems</p><p>　　One subclass of embedded systems deserves an introduction at this point. A real-time system has timing constraints. The function of a real-time system is thus part

24、ly specified in terms of its ability to make certain calculations or decisions in a timely manner. These important calculations or activities have deadlines for completion.</p><p>　　The crucial distinction a

25、mong real-time systems lies in what happens if a deadline is missed. For example, if the real-time system is part of an airplane's flight control system, the lives of the passengers and crew may be endangered by a si

26、ngle missed deadline. However, if instead the system is involved in satellite communication, the damage could be limited to a single corrupt data packet (which may or may not have catastrophic consequences depending on t

27、he application and error recovery schem</p><p>　　嵌入式系統(tǒng)與RTOS</p><p>　　最近幾十年里最令人驚訝的事，莫過(guò)于計(jì)算機(jī)逐漸占據(jù)了人類(lèi)生活的主要地位。今天在我們的家里和辦公室里，計(jì)算機(jī)的數(shù)量要比使用它們來(lái)生活和工作的人還要多，只是這些計(jì)算機(jī)里有很大一部分我們沒(méi)有意識(shí)到它們的存在罷了。</p><p>　　

28、在這里，我將說(shuō)明什么是嵌人式系統(tǒng)，以及可以在哪里找到它們。同附會(huì)介紹一下嵌人式編程的主題，說(shuō)明一下為什么本書(shū)采用C 和C++語(yǔ)言講述，另外簡(jiǎn)單介紹一下示例中所用到的硬件環(huán)境。</p><p>　　1. 什么是嵌入式系統(tǒng)</p><p>　　一個(gè)嵌入式系統(tǒng)(embedded system)就是一個(gè)計(jì)算機(jī)硬件和軟件的集合體，也許還包括其他一些機(jī)械部件，它是為完成某種特定的功能而設(shè)計(jì)的。一個(gè)很好

29、的例子就是微波爐。幾乎每個(gè)家庭都有一臺(tái)，并且每天都有上千萬(wàn)臺(tái)微波爐在被人們使用著，但是很少有人意識(shí)到有處理器和軟件在幫助他們做飯。</p><p>　　這和家里的個(gè)人計(jì)算機(jī)形成了鮮明的對(duì)比。同樣是由計(jì)算機(jī)硬件和軟件，還有機(jī)械部件(比如硬盤(pán))組成的，個(gè)人計(jì)算機(jī)卻不是用來(lái)完成某個(gè)特定功能的。相反它可以做各種不同的事情。很多人用通用計(jì)算機(jī)來(lái)區(qū)分這一點(diǎn)。在發(fā)貨的時(shí)候，通用計(jì)算機(jī)就像一塊沒(méi)有字的黑板，制造商并不知道用戶要拿

30、它來(lái)做什么。一個(gè)用戶可能會(huì)用它來(lái)做文件服務(wù)器。另一個(gè)只用來(lái)玩游戲，還有一位可能會(huì)用它來(lái)寫(xiě)下一部偉大的美國(guó)小說(shuō)。</p><p>　　而嵌入式系統(tǒng)常常是一些更大的系統(tǒng)中的一個(gè)組成部分。比如，現(xiàn)代的轎車(chē)或卡車(chē)?yán)锞桶撕芏嗲度耸较到y(tǒng)。一個(gè)嵌人式系統(tǒng)會(huì)被用來(lái)控制防剎車(chē)鎖死，另一個(gè)監(jiān)控車(chē)輛的氣體排放情況，還有一個(gè)用來(lái)在儀表板上顯示信息。雖然不是必需的，但在某些情況下，這些嵌人式系統(tǒng)會(huì)通過(guò)某種通信網(wǎng)絡(luò)互相連起來(lái)。</

31、p><p>　　為了不至于混淆你的思路，有必要指出，通用計(jì)算機(jī)本身就是由很多嵌入式系統(tǒng)組成的。比如，我的電腦包含了鍵盤(pán)、鼠標(biāo)、顯示卡、調(diào)制解調(diào)器、硬盤(pán)、軟盤(pán)和聲卡，它們中的每一樣都是一個(gè)嵌入式系統(tǒng)。每個(gè)設(shè)備都包含處理器和相應(yīng)的軟件來(lái)完成特定的功能。比如凋制解調(diào)器就是用來(lái)在模擬電話線上收發(fā)數(shù)字信號(hào)用的。正是如此，所有其他的設(shè)備也都能歸納出這么一句話來(lái)。</p><p>　　如果一個(gè)嵌入式系統(tǒng)設(shè)計(jì)

32、得很完善，那么它的使用者完全可以忽略它內(nèi)部的處理器和軟件的存在。微波爐、錄像機(jī)和報(bào)時(shí)鬧鐘就是很好的例子。在某些情況下，用同樣的功能的定制集成電路硬件來(lái)代替上面所說(shuō)的處理器和軟件，也能做出具有同樣功能的設(shè)備來(lái)。不過(guò)，如果真是這樣用純粹的硬件來(lái)設(shè)計(jì)的話，在靈活性上就會(huì)喪失不少了，改幾行軟件怎么說(shuō)也要比重新設(shè)計(jì)一塊硬件電路來(lái)得方便和便宜。</p><p><b>　　2. 過(guò)去和將來(lái)</b><

33、;/p><p>　　本章開(kāi)頭定義的嵌人式系統(tǒng)的第一個(gè)產(chǎn)品直到 1971 年以后才出現(xiàn)。這一年，Intel 發(fā)布了世界上第一塊微處理器，4004，主要被日本的Busicom 公司用來(lái)生產(chǎn)商用計(jì)算器。1969 年，Busicom 請(qǐng)Intel 為他們的每一種新式計(jì)算器分別設(shè)計(jì)一種定制的集成電路，Intel 則拿出了4004。Intel 沒(méi)有為每一種計(jì)算器分別進(jìn)行設(shè)計(jì)，而是設(shè)計(jì)了一種可以用在所有型號(hào)上的通用電路。這個(gè)通用處

34、理器被設(shè)計(jì)來(lái)讀取存在外部存儲(chǔ)芯片里的一系列指令(軟件)。Intel 的想法是通過(guò)軟件的設(shè)計(jì)可以為每一種計(jì)算器提供各自的特性。</p><p>　　這種微處理器在一夜之間就成功了，并且在以后的十年中獲得了廣泛的應(yīng)用。早期的嵌入式應(yīng)用包括無(wú)人空間探測(cè)器、計(jì)算機(jī)控制的交通信號(hào)燈以及航空燈光控制系統(tǒng)。在整個(gè)80 年代，嵌人式系統(tǒng)靜悄悄地統(tǒng)治著微處理器時(shí)代，并把微處理器帶人了我們個(gè)人和職業(yè)生活的每一個(gè)角落。裝有嵌人式系統(tǒng)的

35、電子設(shè)備已經(jīng)充斥了我們的廚房(烤面包機(jī)、食物處理機(jī)、微波爐)、臥室(電視、音響、遙控器)和工作場(chǎng)所(傳真機(jī)、尋呼機(jī)、激光打印機(jī)、點(diǎn)鈔機(jī)和信用卡讀卡機(jī))。</p><p>　　嵌入式系統(tǒng)的數(shù)量看起來(lái)肯定會(huì)繼續(xù)迅速增長(zhǎng)。已經(jīng)有很多具有巨大市場(chǎng)潛力的新的嵌入式設(shè)備了：可以被中央計(jì)算機(jī)控制的調(diào)光器和恒溫器、當(dāng)小孩子或矮個(gè)子的人在的時(shí)候不會(huì)充氣的智能氣囊、掌上電子記事簿和個(gè)人數(shù)字助(PDA)、數(shù)碼照相機(jī)和儀表導(dǎo)航系統(tǒng)。很明

36、顯，掌握一定技能并且愿意從事下一代嵌入式系統(tǒng)設(shè)計(jì)的人將會(huì)獲得很多的機(jī)會(huì)。</p><p><b>　　3. 實(shí)時(shí)系統(tǒng)</b></p><p>　　現(xiàn)在很有必要介紹一下嵌入式系統(tǒng)的一個(gè)子集。按照通常的定義，實(shí)時(shí)系統(tǒng)(real-time system)就是有一定時(shí)間約束的計(jì)算機(jī)系統(tǒng)。換句話說(shuō)，實(shí)時(shí)系統(tǒng)可以部分地從及時(shí)完成計(jì)算或判斷的能力來(lái)辨別。這些重要的計(jì)算有完成的明確期

37、限，并且，對(duì)實(shí)際應(yīng)用來(lái)說(shuō)，一個(gè)延期的反應(yīng)就像一個(gè)錯(cuò)誤的結(jié)果一樣糟糕。</p><p>　　如果一旦延期會(huì)產(chǎn)生什么結(jié)果，是至關(guān)重要的問(wèn)題。例如，如果一個(gè)實(shí)時(shí)系統(tǒng)是飛機(jī)飛行控制系統(tǒng)的一部分，那么一個(gè)延期的計(jì)算就可能會(huì)使乘客和機(jī)組人員的生命受到威脅。而把這個(gè)系統(tǒng)用在衛(wèi)星通信環(huán)境下，危害也許可以限制在僅僅一個(gè)損壞的數(shù)據(jù)包。在更嚴(yán)格的情況下，很可能這個(gè)時(shí)間期限是“硬性”需求的，也就是說(shuō)，這個(gè)系統(tǒng)是個(gè)“硬”實(shí)時(shí)系統(tǒng)，和它對(duì)應(yīng)