單片機(jī)控制系統(tǒng)外文翻譯

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1、 Microcomputer Systems Electronic systems are used for handing information in the most general sense; this information may be telephone conversation, instrument read or a company’s accounts, but in each case the same main type of operation are involved: the processing, storage and transmission o

2、f information. in conventional electronic design these operations are combined at the function level; for example a counter, whether electronic or mechanical, stores the current and increments it by one as required. A system such as an electronic clock which employs counters has its storage and proc

3、essing capabilities spread throughout the system because each counter is able to store and process numbers. Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different section of the sy

4、stem. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of ess

5、entially the same basic design. In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output(I/O) circuits.

6、 It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However, the software which defined the system’s behavior would

7、contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely software. The design process is largely one of software enginee

8、ring, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software. The figure1.1 illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine

9、. The system is controlled by the microprocessor which supervises the transfer of information between itself and the memory and input/output sections. The external connections relate to the rest (that is, the non-computer part) of the engineering system. Fig.1.1 Three Sections of a Typical

10、 Microcomputer Although only one storage section has been shown in the diagram, in practice two distinct types of memory RAM and ROM are used. In each case, the word ‘memory’ is rather inappropriate since a computers memory is more like a filing cabinet in concept; information is stored in a set of

11、 numbered ‘boxes’ and it is referenced by the serial number of the ‘box’ in question. Microcomputers use RAM (Random Access Memory) into which data can be written and from which data can be read again when needed. This data can be read back from the memory in any sequence desired, and not nec

12、essarily the same order in which it was written, hence the expression ‘random’ access memory. Another type of ROM (Read Only Memory) is used to hold fixed patterns of information which cannot be affected by the microprocessor; these patterns are not lost when power is removed and are normally used t

13、o hold the program which defines the behavior of a microprocessor based system. ROMs can be read like RAMs, but unlike RAMs they cannot be used to store variable information. Some ROMs have their data patterns put in during manufacture, while others are programmable by the user by means of special e

14、quipment and are called programmable ROMs. The widely used programmable ROMs are erasable by means of special ultraviolet lamps and are referred to as EPROMs, short for Erasable Programmable Read Only Memories. Other new types of device can be erased electrically without the need for ultraviolet lig

15、ht, which are called Electrically Erasable Programmable Read Only Memories, EEPROMs. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while oth

16、ers are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit qu

17、ite complex operations to be carried out without directly involving the main microprocessor. The microprocessor , memory and input/output circuit may all be contained on the same integrated circuit provided that the application does not require too much program or data storage . This is usually the

18、 case in low-cost application such as the controllers used in microwave ovens and automatic washing machines . The use of single package allows considerable cost savings to e made when articles are manufactured in large quantities . As technology develops , more and more powerful processors and larg

19、er and larger amounts of memory are being incorporated into single chip microcomputers with resulting saving in assembly costs in the final products . For the foreseeable future , however , it will continue to be necessary to interconnect a number of integrated circuits to make a microcomputer whene

20、ver larger amounts of storage or input/output are required. Another major engineering application of microcomputers is in process control. Here the presence of the microcomputer is usually more apparent to the user because provision is normally made for programming the microcomputer for the particu

21、lar application. In process control applications the benefits lf fitting the entire system on to single chip are usually outweighed by the high design cost involved, because this sort lf equipment is produced in smaller quantities. Moreover, process controllers are usually more complicated so that i

22、t is more difficult to make them as single integrated circuits. Two approaches are possible; the controller can be implemented as a general-purpose microcomputer rather like a more robust version lf a hobby computer, or as a ‘packaged’ system, signed for replacing controllers based on older technolo

23、gies such as electromagnetic relays. In the former case the system would probably be programmed in conventional programming languages such as the ones to9 be introduced later, while in the other case a special-purpose language might be used, for example one which allowed the function of the controll

24、er to be described in terms of relay interconnections, In either case programs can be stored in RAM, which allows them to be altered to suit changes in application, but this makes the overall system vulnerable to loss lf power unless batteries are used to ensure continuity of supply. Alternatively p

25、rograms can be stored in ROM, in which case they virtually become part of the electronic ‘hardware’ and are often referred to as firmware. More sophisticated process controllers require minicomputers for their implementation, although the use of large scale integrated circuits ‘the distinction bet

26、ween mini and microcomputers, Products and process controllers of various kinds represent the majority of present-day microcomputer applications, the exact figures depending on one’s interpretation of the word ‘product’. Virtually all engineering and scientific uses of microcomputers can be assigned

27、 to one or other of these categories. But in the system we most study Pressure and Pressure Transmitters. Pressure arises when a force is applied over an area. Provided the force is one Newton and uniformly over the area of one square meters, the pressure has been designated one Pascal. Pressure is

28、a universal processing condition. It is also a condition of life on the planet: we live at the bottom of an atmospheric ocean that extends upward for many miles. This mass of air has weight, and this weight pressing downward causes atmospheric pressure. Water, a fundamental necessity of life, is sup

29、plied to most of us under pressure. In the typical process plant, pressure influences boiling point temperatures, condensing point temperatures, process efficiency, costs, and other important factors. The measurement and control of pressure or lack of it-vacuum-in the typical process plant is critic

30、al. 單片機(jī)控制系統(tǒng) 廣義地說，微型計(jì)算機(jī)控制系統(tǒng)（單片機(jī)控制系統(tǒng)）是用于處理信息的，這種被用于處理的信息可以是電話交談，也可以是儀器的讀數(shù)或者是一個(gè)企業(yè)的帳戶，但是各種情況下都涉及到相同的主要操作：信息的處理、信息的存儲(chǔ)和信息的傳遞。在常規(guī)的電子設(shè)計(jì)中，這些操作都是以功能平臺(tái)方式組合起來的，例如計(jì)數(shù)器，無論是電子計(jì)數(shù)器還是機(jī)械計(jì)數(shù)器，都要存儲(chǔ)當(dāng)前的數(shù)值，并且按要求將該數(shù)值增加1。一個(gè)系統(tǒng)例如采用計(jì)數(shù)器的電子鐘之類的任一系統(tǒng)要使其存儲(chǔ)和處理能力遍布整個(gè)系統(tǒng)，因?yàn)槊總€(gè)計(jì)數(shù)器都能存儲(chǔ)和處理一些數(shù)字。 現(xiàn)如今，以微處理器為基礎(chǔ)的系統(tǒng)從常規(guī)的處理方法中分離了出來，它

31、將信息的處理，信息的存儲(chǔ)和信息的傳輸三個(gè)功能分離形成不同的系統(tǒng)單元。這種主要將系統(tǒng)分成三個(gè)主要單元的分離方法是馮-諾依曼在20世紀(jì)40年代所設(shè)想出來的，并且是針對(duì)微計(jì)算機(jī)的設(shè)想。從此以后基本上所有制成的計(jì)算機(jī)都是用這種結(jié)構(gòu)設(shè)計(jì)的，盡管他們包含著寬廣的物理形式與物理結(jié)構(gòu)，但從根本上來說他們均是具有相同基本設(shè)計(jì)的計(jì)算機(jī)。 在以微處理器為基礎(chǔ)的系統(tǒng)中，處理是由以微處理器為基礎(chǔ)的系統(tǒng)自身完成的。存儲(chǔ)是利用存儲(chǔ)器電路，而從系統(tǒng)中輸入和輸出的信息傳輸則是利用特定的輸入/輸出（I/O）電路。要在一個(gè)以微處理器為基礎(chǔ)的時(shí)鐘中找出執(zhí)行具有計(jì)數(shù)功能的一個(gè)特殊的硬件組成部分是不可能的，因?yàn)闀r(shí)間存儲(chǔ)在存儲(chǔ)器中，而在

32、固定的時(shí)間間隔下由微處理器控制增值。但是，規(guī)定系統(tǒng)運(yùn)轉(zhuǎn)過程的軟件卻規(guī)定了包含實(shí)現(xiàn)計(jì)數(shù)器計(jì)數(shù)功能的單元部分。由于系統(tǒng)幾乎完全由軟件所定義，所以對(duì)微處理器結(jié)構(gòu)和其輔助電路這種看起來非常抽象的處理方法使其在應(yīng)用時(shí)非常靈活。這種設(shè)計(jì)過程主要是軟件工程，而且在生產(chǎn)軟件時(shí)，就會(huì)遇到產(chǎn)生于常規(guī)工程中相似的構(gòu)造和維護(hù)問題。 圖1.1 微型計(jì)算機(jī)的三個(gè)組成部分 圖1.1顯示出了微型計(jì)算機(jī)中這三個(gè)單元在一個(gè)微處理器控制系統(tǒng)中是如何按照機(jī)器中的信息通信方式而聯(lián)接起來的。該系統(tǒng)由微處理器控制，微處理器能夠?qū)ζ渥陨淼拇鎯?chǔ)器和輸入/輸出單元的信息傳輸進(jìn)行管理。外部的連接部分與工程系統(tǒng)中的其余部分（

33、即非計(jì)算機(jī)部分）有關(guān)。 盡管圖中顯示的只有一個(gè)存儲(chǔ)單元，但是在實(shí)際中卻有RAM和ROM兩種不同的存儲(chǔ)器被使用。在每一種情況下，由于概念上的計(jì)算機(jī)存儲(chǔ)器更像一個(gè)公文柜，上述的“存儲(chǔ)器”一詞是非常不恰當(dāng)?shù)模恍畔⒈淮娣旁谝幌盗幸褦?shù)字標(biāo)記過的的“箱子”中，而且可以按照問題由“箱子”的序列號(hào)進(jìn)行相關(guān)信息的參考定位。 微計(jì)算機(jī)控制系統(tǒng)經(jīng)常使用RAM（隨機(jī)存取存儲(chǔ)器），在RAM中，數(shù)據(jù)可以被寫入，并且在需要的時(shí)候，可以被再次讀出。這種數(shù)據(jù)能以任意一種所希望的次序從存儲(chǔ)器中讀出，而不必按照寫入時(shí)的相同次序讀出，所以有“隨機(jī)”存取存儲(chǔ)器。另一類型ROM（只讀存儲(chǔ)器）是用來保持信息的，它們是不受微處理器影響的

34、固定的信息標(biāo)本；這些信息在電源切斷后不會(huì)丟失，并通常用來保存規(guī)定微處理器化系統(tǒng)運(yùn)轉(zhuǎn)過程的程序。ROM可像RAM一樣被讀取，但與RAM不一樣的是不能用來存儲(chǔ)可變的信息。有些ROM在制造時(shí)將其數(shù)據(jù)標(biāo)本放入，而另外的則可通過特殊的設(shè)備由用戶編程，所以稱為可編程ROM。被廣泛使用的可編程ROM可利用特殊紫外線燈察除，并被成為EPROM，即可察除可編程只讀存儲(chǔ)器的縮寫。另有新類型的期器件不必用紫外線燈而用電察除，所以稱為電可察除可編程只讀存儲(chǔ)器EEPROM。 微處理器在程序控制下處理數(shù)據(jù)，并控制流向和來自存儲(chǔ)器和輸入/輸出裝置的信息流。有些輸入/輸出裝置是通用型的，而另外一些則是設(shè)計(jì)來控制如磁

35、盤驅(qū)動(dòng)器的特殊硬件，或控制傳給其他計(jì)算機(jī)的信息傳輸。大多數(shù)類型的I/O裝置在某種程度下可編程，允許不同形式的操作，而有些則包含特殊用途微處理器的I/O裝置不用主微處理器的直接干預(yù)，就可實(shí)施非常復(fù)雜的操作。 假如應(yīng)用中不需要太多的程序和數(shù)據(jù)存儲(chǔ)量，微處理器、存儲(chǔ)器和輸入/輸出可全被包含在同一集成電路中。這通常是低成本應(yīng)用情況，例如用于微波爐和自動(dòng)洗衣機(jī)的控制器。當(dāng)商品被大量地生產(chǎn)時(shí)，這種單一芯片的使用就可節(jié)省相當(dāng)大的成本。當(dāng)技術(shù)進(jìn)一步發(fā)展，更強(qiáng)更強(qiáng)的處理器和更大更大數(shù)量的存儲(chǔ)器被包含形成單片微型計(jì)算機(jī)，結(jié)果使最終產(chǎn)品的裝配成本得以節(jié)省。但是在可預(yù)見的未來，當(dāng)需要大量的存儲(chǔ)器或輸入/輸出

36、時(shí)，還是有必要繼續(xù)將許多集成電路相互聯(lián)結(jié)起來，形成微計(jì)算機(jī)。 微計(jì)算機(jī)的另一主要工程應(yīng)用是在過程控制中。這是，由于裝置是按特定的應(yīng)用情況由微機(jī)編程實(shí)現(xiàn)的，對(duì)用戶來說微計(jì)算機(jī)的存在通常就更加明顯。在過程控制應(yīng)用中，由于這種設(shè)備以較少的數(shù)量生產(chǎn)，將整個(gè)系統(tǒng)安裝在單個(gè)芯片上所獲取的利益常比不上所涉及的高設(shè)計(jì)成本。而且，過程控制器通常更為復(fù)雜，所以要將他們做成單獨(dú)的集成電路就更為困難?？刹捎脙煞N處理，將控制器做成一種通用的微計(jì)算機(jī)，正像較強(qiáng)版本的業(yè)余計(jì)算機(jī)那樣；或者做成“包裹”式系統(tǒng)，按照像電磁繼電器那樣的較老式的技術(shù)進(jìn)行設(shè)計(jì)，來取代控制器。對(duì)前一種情況，系統(tǒng)可以用常規(guī)的編程語(yǔ)言來編程，正如

37、以后要介紹的語(yǔ)言那樣；而另一種情況，可采用特殊用途的語(yǔ)言，例如那種使控制器功能按照繼電器相互連接的方法進(jìn)行描述。兩種情況下，序均能存于RAM，這讓程序能按應(yīng)用情況變化時(shí)進(jìn)行相應(yīng)的變化，但是這使得總系統(tǒng)易受掉電影響而工作不正常，除非使用電池保證供電連續(xù)性。另一種選擇是將程序在ROM中，這樣他們就變成電子“硬件”的一部分并常被稱為“固件”。 盡管大規(guī)模集成電路的應(yīng)用使小型和微型計(jì)算機(jī)的差別變得“模糊”，更復(fù)雜的過程控制器需要小型計(jì)算機(jī)實(shí)現(xiàn)他們的過程。各種類型的產(chǎn)品和過程控制器代表了當(dāng)今微計(jì)算機(jī)應(yīng)用的廣泛性，而具體的結(jié)構(gòu)取決于對(duì)“產(chǎn)品”一詞的解釋。實(shí)際上，計(jì)算機(jī)的所有工程和科學(xué)上的應(yīng)用都能指定來進(jìn)行這些種類的某一或某些工作。而在這個(gè)系統(tǒng)中，我們主要學(xué)習(xí)壓力和壓力變送器，當(dāng)某一力加到某一面積上，就形成壓力，假如這力是1牛頓均勻地加在1平方米的面積上，這壓力被定義為1帕斯卡。壓力是一種普遍的工藝狀態(tài)，它也是這個(gè)星球上的一個(gè)生活條件：我們生活在向上延伸許多英里的大氣海洋的底部?？諝馕镔|(zhì)是有重量的，而且這種下壓的重量形成大氣壓。水，是生活的必需品，也是在壓力之下提供給我們中的大多數(shù)人。在典型的過程工廠中，壓力影響沸點(diǎn)溫度、凝固點(diǎn)溫度、過程效率、消耗和其他重要因數(shù)。壓力的測(cè)量和控制，或者壓力的不足—真空，在典型的過程控制中是極為重要的。 7