自動化專業(yè)可參考的外文文獻.doc

1外文原文 A: Fundamentals of Single-chip Microcomputer The single-chip microcomputer is the culmination of both the development of the digital computer and the integrated circuit arguably the tow most significant inventions of the 20th century 1. These tow types of architecture are found in single-chip microcomputer. Some employ the split program/data memory of the Harvard architecture, shown in Fig.3-5A-1, others follow the philosophy, widely adapted for general-purpose computers and microprocessors, of making no logical distinction between program and data memory as in the Princeton architecture, shown in Fig.3-5A-2. In general terms a single-chip microcomputer is characterized by the incorporation of all the units of a computer into a single device, as shown in Fig3-5A-3.ProgrammemoryInput&Outputunit CPUDatamemory Fig.3-5A-1 A Harvard typeInput&Outputunit CPUmemory Fig.3-5A-2. A conventional Princeton computerTimer/Counter SystemclockExternalTimingcomponentsSerial I/O ROM Reset Prarallel I/O RAM Interrupts CPU Power Fig3-5A-3. Principal features of a microcomputer Read only memory (ROM).ROM is usually for the permanent, non-volatile storage of an applications program .Many microcomputers and microcontrollers are intended for high-volume applications and hence the economical manufacture of the devices requires that the contents of the program memory be committed permanently during the manufacture of chips . Clearly, this implies a rigorous approach to ROM code development since changes cannot be made after manufacture .This development process may involve emulation using a sophisticated development system with a hardware emulation capability as well as the use of powerful software tools. Some manufacturers provide additional ROM options by including in their range devices with (or intended for use with) user programmable memory. The simplest of these is usually device which can operate in a microprocessor mode by using some of the input/output lines as an address and data bus for accessing external memory. This type of device can behave functionally as the single chip microcomputer from which it is derived albeit with restricted I/O and a modified external circuit. The use of these ROMless devices is common even in production circuits where the volume does not justify the development costs of custom on-chip ROM2;there can still be a significant saving in I/O and other chips compared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with piggy-back EPROM(Erasable programmable ROM )sockets or devices with EPROM instead of ROM 。These devices are naturally more expensive than equivalent ROM device, but do provide complete circuit equivalents. EPROM based devices are also extremely attractive for low-volume applications where they provide the advantages of a single-chip device, in terms of on-chip I/O, etc. ,with the convenience of flexible user programmability. Random access memory (RAM).RAM is for the storage of working variables and data used during program execution. The size of this memory varies with device type but it has the same characteristic width (4,8,16 bits etc.) as the processor ,Special function registers, such as stack pointer or timer register are often logically incorporated into the RAM area. It is also common in Harard type microcomputers to treat the RAM area as a collection of register; it is unnecessary to make distinction between RAM and processor register as is done in the case of a microprocessor system since RAM and registers are not usually physically separated in a microcomputer .Central processing unit (CPU).The CPU is much like that of any microprocessor. Many applications of microcomputers and microcontrollers involve the handling of binary-coded decimal (BCD) data (for numerical displays, for example) ,hence it is common to find that the CPU is well adapted to handling this type of data .It is also common to find good facilities for testing, setting and resetting individual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to two-state devices such as switches, thermostats, solid-state relays, valves, motor, etc.Parallel input/output. Parallel input and output schemes vary somewhat in different microcomputer; in most a mechanism is provided to at least allow some flexibility of choosing which pins are outputs and which are inputs. This may apply to all or some of the ports. Some I/O lines are suitable for direct interfacing to, for example, fluorescent displays, or can provide sufficient current to make interfacing other components straightforward. Some devices allow an I/O port to be configured as a system bus to allow off-chip memory and I/O expansion. This facility is potentially useful as a product range develops, since successive enhancements may become too big for on-chip memory and it is undesirable not to build on the existing software base.Serial input/output .Serial communication with terminal devices is common means of providing a link using a small number of lines. This sort of communication can also be exploited for interfacing special function chips or linking several microcomputers together .Both the common asynchronous synchronous communication schemes require protocols that provide framing (start and stop) information .This can be implemented as a hardware facility or U(S)ART(Universal(synchronous) asynchronous receiver/transmitter) relieving the processor (and the applications programmer) of this low-level, time-consuming, detail. t is merely necessary to selected a baud-rate and possibly other options (number of stop bits, parity, etc.) and load (or read from) the serial transmitter (or receiver) buffer. Serialization of the data in the appropriate format is then handled by the hardware circuit.Timing/counter facilities. Many application of single-chip microcomputers require accurate evaluation of elapsed real time .This can be determined by careful assessment of the execution time of each branch in a program but this rapidly becomes inefficient for all but simplest programs .The preferred approach is to use timer circuit that can independently count precise time increments and generate an interrupt after a preset time has elapsed .This type of timer is usually arranged to be reloadable with the required count .The timer then decrements this value producing an interrupt or setting a flag when the counter reaches zero. Better timers then have the ability to automatically reload the initial count value. This relieves the programmer of the responsibility of reloading the counter and assessing elapsed time before the timer restarted ,which otherwise wound be necessary if continuous precisely timed interrupts were required (as in a clock ,for example).Sometimes associated with timer is an event counter. With this facility there is usually a special input pin ,that can drive the counter directly. Timing components. The clock circuitry of most microcomputers requires only simple timing components. If maximum performance is required,a crystal must be used to ensure the maximum clock frequency is approached but not exceeded. Many clock circuits also work with a resistor and capacitor as low-cost timing components or can be driven from an external source. This latter arrangement is useful is external synchronization of the microcomputer is required. WORDS AND TERMSculmination n.頂點 spilt adj.分離的volatile n. 易變的commit v.保證albeit conj.雖然custom adj.定制的variant adj.不同的piggy-back adj.背負式的socket n. 插座B:PLC1PLCs (programmable logical controller) face ever more complex challenges these days . Where once they quietly replaced relays and gave an occasional report to a corporate mainframe, they are now grouped into cells, given new job and new languages, and are forced to compete against a growing array of control products. For this years annual PLC technology update ,we queried PLC makers on these topics and more .Programming languages Higher level PLC programming languages have been around for some time ,but lately their popularity has mushrooming. As Raymond Leveille, vice president & general manager, Siemens Energy &Automation .inc; Programmable controls are being used for more and more sophisticated operations, languages other than ladder logic become more practical, efficient, and powerful. For example, its very difficult to write a trigonometric function using ladder logic .Languages gaining acceptance include Boolean, control system flowcharting, and such function chart languages as Graphcet and its variation .And theres increasing interest in languages like C and BASIC.PLCs in process controlThus far, PLCs have not been used extensively for continuous process control .Will this continue? The feeling that Ive gotten, says Ken Jannotta, manger, product planning, series One and Series Six product ,at GE Fanuc North America ,is that PLCs will be used in the process industry but not necessarily for process control.Several vendors -obviously betting that the opposite will happen -have introduced PLCs optimized for process application .Rich Ryan, manger, commercial marketing, Allen-bradley Programmable Controls Div., cites PLCss increasing use such industries as food ,chemicals ,and petroleum. Ryan feels there are two types of applications in which theyre appropriate. one, he says, is where the size of the process control system thats being automated doesnt justify DCSdistributed control system.With the starting price tags of chose products being relatively high, a programmable controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system.Bill Barkovitz, president of Triconex, predicts that all future controllers that come out in the process control system business will embrace a lot of more PLC technology and a lot more PLC functionality than they ever did before .Communications and MAPCommunications are vital to an individual automation cell and to be automated factory as a whole. Weve heard a lot about MAP in the last few years ,and a lot of companies have jumped on the bandwagon.2Many, however, were disappointed when a fully-defined and completed MAP specification didnt appear immediately .Says Larry Komarek: Right now, MAP is still a moving target for the manufacturers, a specification that is not final .Presently, for example. people are introducing products to meet the MAP2.1standard .Yet2.1-based products will be obsolete when the new standard for MAP3.0 is introduced.Because of this, many PLC vendors are holding off on full MAP implementations. Omron, for example, has an ongoing MAP-compatibility program;3but Frank Newburn, vice president of Omrons Industrial Division ,reports that because of the lack of a firm definition ,Omrons PLCs dont yet talk to MAP.Since its unlikely that an individual PLC would talk to broad MAP anyway, makers are concentrating on proprietary networks. According to Sal Provanzano, users fear that if they do get on board and vendors withdraw from MAP, theyll be the ones left holding a communications structure thats not supported.Universal I/OWhile there are concerns about the lack of compatible communications between PLCs from different vendors, the connection at the other end-the I/O-is even more fragmented .With rare exceptions, I/O is still proprietary .Yet there are those who feel that I/O will eventually become more universal .GE Fanuc is hoping to do that with its Genius smart I/O line. The independent I/O makers are pulling in the same direction. Many say that I/O is such a high-value item that PLC makers will always want to keep it proprietary .As Ken Jannotta, says: The I/O is going to be a disproportionate amount of the hardware sale. Certainly each PLC vendor is going to try to protect that. For that reason, he says, PLC makers wont begin selling universal I/O system from other vendor. if we start selling that kind of product, says jannotta, what do we manufacture?With more intelligent I/O appearing, Sal Provanzano feels this will lead to more differentiation among I/O from different makers. Where the I/O becomes extremely intelligent and becomes part of the system, he says, it really is hard to define which is the I/O and which is CPU. It really CPU, if you will, is equally integrated into the system as the I/O.Connecting PLC I/O to PCsWhile different PLCs probably will continue to use proprietary I/O, several vendors make it possible to connect5 their I/O to IBM PC-compatible equipment. Alle-bradeley, Could, and Cincinnati Milacron already have, and rumor has it that GE is planning something along these same lines .4Bill Ketelhut, manage of product planning at GE Fanuc North America ,sees this sort of thing as alternative to universal I/O.I think the trend ,instead of toward universal I/O, will be multiple host interface , he says .Jodie Glore ,director of marking, Square D Automation Products, Views it as another indication that PLCs are, and have been for some time, industrial computers.PLCs VS PCsIf the IBM 7552, the Action Instruments BC22,and other computers are appearing on the factory floor, wont this mean new competition for PLCs? Rich Ryan: There are some control functions that are better jobs for computers. Programmable controllers have been forced to fit into those applications. Yet, the majority of vendors we surveyed dont like the PC invasion will pose a problem for them .Most said that PLCs and PCs are enough apart in architecture that they will usually do the control. They dont feel that PCs will take jobs from PLCs just because PLC I/O modules can now be connected to PCs; they believe this simply means that PLCs and PCs will be able to share the same data.There are inherent architectural differences between a general purpose computer, says Rich Ryan, and a programmable controller .There are hardware constructs built into almost every manufactures programmable controller today that customize the hardware to run ladder logic and to solve machine code. One fundamental difference he cites is called state of the machine .Ryan: When you shut the machine off, or interrupt the cycle, or you jump to another spot in the cycle, programmable controllers inherently remember the state of the machine: what the timers were, what the counters were ,what the states of all the latches were .Computers dont inherently do that. WORDS AND TERMSbet v.確信optimized n.優(yōu)化程序corporate adj.共同的mushroom v.迅速發(fā)展trigonometric function 三角函數(shù)vendor n.廠商tag n.標簽smart adj.智能型的compatible adj.兼容的1、 外文資料翻譯譯文單片機基礎(chǔ)單片機是電腦和集成電路發(fā)展的巔峰，有據(jù)可查的是他們也是20世紀最有意義的兩大發(fā)明。 這兩種特性在單片機中得到了充分的體現(xiàn)。一些廠家用這兩種特性區(qū)分程序內(nèi)存和數(shù)據(jù)內(nèi)存在硬件中的特性，如圖3-5A-1，依據(jù)同樣的原理廣泛的適用于一般目的的電腦和微電腦，一些廠家在程序內(nèi)存和數(shù)據(jù)內(nèi)存之間不區(qū)分的像Princeton特性，展示如圖3-5A-2.只讀存貯器(ROM). ROM是通常的永久性的，非應(yīng)用程序的易失性存儲器。不少微機和單片機用于大批量應(yīng)用，因此，經(jīng)濟的設(shè)備制造要求的程序存儲器的內(nèi)容是在制造期間永久性的刻錄在芯片中，這意味著嚴謹?shù)姆椒ǎ驗樾薷腞OM代碼不能制造之后發(fā)展。這一發(fā)展過程可能涉及仿真,使用硬件仿真功能以及強大的軟件工具使用先進的開發(fā)系統(tǒng)。一些制造商在其提供的設(shè)備包括的范圍（或擬使用）用戶可編程內(nèi)存.其中最簡單的通常是設(shè)備能夠運行于微處理器模式通過使用一些輸入/輸出作為地址線額外的ROM選項和數(shù)據(jù)總線訪問外部內(nèi)存.這種類型的設(shè)備可以表現(xiàn)為單芯片微型計算機盡管有限制的I / O和外部修改這些設(shè)備的電路.小內(nèi)存裝置的應(yīng)用是非常普遍的在永久性內(nèi)存的制造中 2;但仍然可以在我節(jié)省大量成本I/ O和其它芯片相比，傳統(tǒng)的基于微處理器電路.更準確的ROM設(shè)備更換，可在與形式變種背馱式EPROM（可擦除可編程只讀存儲器）插座或存儲器，而不是ROM器件。這些器件自然價格比同等ROM設(shè)備貴，但不提供完整的等效電路.EPROM的設(shè)備也非常有吸引力對于低容量應(yīng)用中，他們提供的單芯片器件的優(yōu)勢，在以下方面的板載I / O等，在靈活的用戶可編程帶來的便利。 隨機存取存儲器（RAM）。RAM用于變量和工作在程序使用該存儲器的執(zhí)行.隨數(shù)據(jù)存儲設(shè)備的大小不同類型而有所不同，但具有相同的特征寬度（4,8,16 比特等）作為處理器。特殊功能寄存器，如棧指針或定時器寄存器，往往邏輯納入內(nèi)存區(qū)域.它也在型微電腦的硬件中做集中內(nèi)存，它是不必要的區(qū)分內(nèi)存和處理器之間的區(qū)別在通常不物理上分開的微機中。中央處理單元（CPU）。CPU是很象微型電子計算機和微控制器的任何微電腦.許多微電腦和微控制器涉及到二進制編碼(十進制處理（BCD）的數(shù)據(jù)為例）數(shù)字顯示，因而，常常可以發(fā)現(xiàn)該CPU是很適合處理這種類型的數(shù)據(jù)。對設(shè)施良好與否進行的測試，設(shè)置和重置單個位的內(nèi)存或I / O控制器的應(yīng)用程序，也是常見的因為許多涉及打開和關(guān)閉的單輸出線或在單線.這些線很容易連接到二進制的設(shè)備，如開關(guān)，恒溫器，固態(tài)繼電器，閥門，電機等 并行輸入/ 輸出.并行輸入和輸出的計劃有所不同，在不同的微機，在大多數(shù)設(shè)立一個機制，至少選擇讓其中一些引腳輸出，一些引腳輸如是非常靈活的。這可能適用于所有或端口.有些I / O線直接連接到適當?shù)脑O(shè)備，例如，熒光顯示器，也可以提供足夠的電流，使接口和其他設(shè)備直接相連.一些設(shè)備允許一個I / O端口,其他組件將作為系統(tǒng)總線配置為允許片外存儲器和I / O擴展。這個設(shè)施是潛在有用的一個產(chǎn)品系列的發(fā)展，因為連續(xù)增強可能成為太上存儲器，這是不可取的，不是建立在現(xiàn)有的軟件基礎(chǔ)上的。 串行輸入/輸出。串行通信是指與終端設(shè)備的鏈接使用少量的通訊線.這種通訊也可利用特殊的接口連接功能芯片使幾個微型機連在一起。雙方共同異步同步通信方案要求的規(guī)則提供成幀（啟動和停止）的信息。這可以作為一個硬件設(shè)施或U（擰）藝術(shù)（通用執(zhí)行（同步）異步接收器/發(fā)送器）減輕處理器（和應(yīng)用程序）的這種低層次的確費時.它也只需要選擇一個波特率及其他可能的選擇（停止位，奇偶校驗等）和負載號碼（或讀?。?，串行發(fā)送器（或接收）的緩沖器.進行適當?shù)母袷降臄?shù)據(jù)串行處理，然后由硬件電路完成。 定時/計數(shù)器設(shè)施。許多應(yīng)用的單片機需要對過去的真實時間準確的評價。這可以由每個程序中的執(zhí)行時間分支認真評估，但除最簡單的程序外，他的工作效率不高。首選方法是使用計時器電路，能獨立計算精確的時間增量，并生成一個預設(shè)的時間后中斷的時間。這種類型的定時器通常在所要求的數(shù)量可重載中應(yīng)用。計時器然后減少此值產(chǎn)生中斷或設(shè)置標記時，計數(shù)器到達零.更好的計時器有自動加載初始值的功能。這將緩解重新加載計數(shù)器和評估所用的時間，計時器重新啟動之前這是必要的。有時候與定時器相關(guān)的是一個事件計數(shù)器。這個設(shè)備通常有一個特殊的輸入引腳，可直接驅(qū)動計數(shù)器。定時元件。大多數(shù)微型計算機時鐘電路只需要簡單的計時元件.如果要求最高性能，必須使用晶體以確保最大時鐘頻率接近，但不會超出。許多時鐘電路，還具有電阻和低電容工作成本定時元件，也可以從外部源驅(qū)動。這后一種安排是有用的在微機外部同步是必需的時候。 B:PLC1今天的PLC（可編程邏輯控制器）將面對日益復雜的挑戰(zhàn)。一旦他們悄悄地取代繼電器，偶爾向主機報告，如果他們將他們比作細胞，賦予新的工作和新的語言，將被迫和大量的控制產(chǎn)品競爭。對于今年的年度PLC技術(shù)的更新，我們對PLC的制造商會就這些主題提出更多問題.編程語言更高水平的PLC編程語言已經(jīng)推行有一段時間了，但最近的流行，如雨后春筍般。正如雷蒙德萊韋耶，副總裁兼總經(jīng)理，西門子能源和自動化公司，可編程控制正在為更復雜的操作使用，梯形邏輯比語言變得更加實際，有效和強大的。舉例來說，很難寫三角函數(shù)使用梯形邏輯?！罢Z言為人們所接受，包括布爾，控制系統(tǒng)流程圖，這種