畢業(yè)設(shè)計(jì)工程中的微型計(jì)算機(jī)外文文獻(xiàn)

1、內(nèi)蒙古工業(yè)大學(xué)本科畢業(yè)設(shè)計(jì)說(shuō)明書(shū)Microcomputers in EngineeringSystems Using MicroprocessorsThe development of the microcomputer during the 1970s brought about a revolution in engineering design. The industrial revolution at the turn of the nineteenth century heralded the development machines which replaced physical

2、drudgery by the mechanical mean. A major engineering application of microcomputers is in process control. The provision is normally made for programming the microcomputer for the particular application.Electronic systems are used for handing information in the most general sense; This information ma

3、y be telephone conversation, instrument reading or a companys accounts, but in each case the same main types of operation are involved: the processing, storage and transmission of information. In conventional electronic design these operations are combined at the function level: for example a counte

4、r, whether electronic or mechanical, stores the current count and increments it by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to store and process numbers.Present d

5、ay microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different sections of the system. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived espe

6、cially 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 essentially the same basic design.In a microprocessor based system the processing will be performed in the microprocessor it

7、self. 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. It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based cloc

8、k because the time would be stored in the memory and incremented at regular intervals by the microprocessor. However, the software which defined the systems behavior would contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor a

9、nd its associated circuits allows it to be very flexible in use, since the system is defined almost entirely in software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when p

10、roducing software.Figure 1.1 illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine. The system is controlled in terms of the communication of information within the machine. The system is controlled by the microproce

11、ssor 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 MicrocomputerAlthough only one storage section has bee

12、n 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 computer memory is more like a filing cabinet in concept; information is stored in a set of numbered boxes and it is referenced by the serial number of

13、 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 necessarily the same order in which it was written, hence the expression ra

14、ndom 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 to hold the program which defines the behavior of a microprocessor based sy

15、stem. 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 equipment and are called programmable ROMs. The widely used programmable RO

16、Ms 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 light, which are called Electrically Erasable Programmable Read Only Memories

17、, EEPROMs.Microcomputer InterfaceA microcomputer interface converts information between two forms. Outside the microcomputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken

18、 down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps.This can be illustrated by means of an example such as that of Figure 1.2, which shows an interface between a microcomput

19、er and a transducer producing a continuously variable analog signal. Transducers often produce very small output requiring amplification, or they may generate signals in a form that needs to be converted again before being handled by the rest of the system. For example, many transducers have variabl

20、e resistance which must be converted to a voltage by a special circuit. This process of converting the transducer output into a voltage signal which can be connected to the rest of the system is called signal conditioning. In the example of Figure 1.2, the signal conditioning section translates the

21、range of voltage or current signals from the transducer to one which can be converted to digital form by an analog-to-digital converter.Fig.1.2 Input InterfaceAn analog-to-digital converter (ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one

22、 of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output s

23、ection of the microcomputer itself.The I/O section converts digital “on/off” voltage signals to a form which can be presented to the processor via the system buses. Here the state of each input line, whether it is “on” or “off”, is indicated by a corresponding “1” or “0”. In the analog inputs which

24、have been converted to digital form, the patterns of ones and zeros in the internal representation will form binary numbers corresponding to the quantity being converted.The “raw” numbers from the interface are limited by the design of the interface circuitry and they often require linearization and

25、 scaling to produce values suitable for use in the main program. For example, the interface might be used to convert temperatures in the range -20 to +50 degrees, but the numbers produced by an 8-bit converter will lie in the range 0 to 255. Obviously it is easier from the programmers point of view

26、to deal directly with temperature rather than to work out the equivalent of any given temperature in terms of the numbers produced by the ADC. Every time the interface is used to read a transducer, the same operations must be carried out to convert the input number into a more convenient form. Addit

27、ionally, the operation of some interfaces requires control signals to be passed between the microcomputer and components of the interface. For these reasons it is normal to use a subroutine to look after the detailed operation of the interface and carry out any scaling and/or linearization which mig

28、ht be needed.Output interfaces take a similar form (Fig 1.3), the obvious difference being that here the flow of information is in the opposite direction; it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of the

29、interface and performs the scaling numbers which may be needed for a digital-to-analog converter (DAC). This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is condit

30、ioned (usually amplified) to a form suitable for operating an actuator.Fig.1.3 Output Interface IN this project, it is used Pressure Transmitters and Speed Transmitters.Pressure and Pressure Transmitters Pressure arises when a force is applied over an area Provided the force is one Newton (N) and un

31、iformly over the area of one square meter(m2)，the pressure has been designated one Pascal(Pa=N/m2).Pressure is a universal processing condition. It is also a condition of life on this planet：we live at the bottom of an atmospheric ocean that extends upward for many miles. This mass of air has weight

32、，and this weight pressing downward causes atmospheric pressure. Water，a fundamental necessity of life，is supplied 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 facto

33、rs. The measurement and control of pressure，or lack of it-vacuum-in the typical process plant is critical.The working instruments in the plant usually include simple pressure gauges，precision recorders and indicators，and pneumatic and electronic pressure transmitters. A pressure transmitter makes a

34、pressure measurement and generates either a pneumatic or electrical signal output that is proportional to the pressure being sensed.In the process plant，it is impractical to locate the control instruments out in the place near the process. It is also true that most measurements are not easily transm

35、itted from some remote location. Pressure measurement is an exception，but if a high pressure of some dangerous chemical is to be indicated or recorded several hundred feet from the point of measurement，a hazard may be from the pressure or from the chemical carried.To eliminate this problem，a signal

36、transmission system was developed. This system is usually either pneumatic(air pressure)or electrical. Using the transmission system，it wilt be possible to install most of the indicating，recording，and control instruments in one location. This makes it practical for a minimum number of operators to r

37、un the plant efficiently.When a pneumatic transmission system is employed，the measurement signal is converted into pneumatic signal by the transmitter scaled from 0 to 100 percent of the measured value. This transmitter is mounted close to the point of measurement in the process. The transmitter out

38、putair pressure for a pneumatic transmitteris piped to the recording or control instrument. The standard output range for a pneumatic transmitter is 20 to 100kPa，which is almost universally used.When an electronic pressure transmitter is used，the pressure is converted to electrical signal that may b

39、e current or voltage. Its standard range is from 4 to 20mA DC for current signal or from 1 to 5V DC for voltage signal. Nowadays，another type of electrical signal. which is becoming common，is the digital or discrete signal. The use of instruments and control systems based on computers or microproces

40、sors is forcing increased use of this type of signal.Sometimes it is important for analysis to obtain the parameters that describe the sensor/transmitter behavior. The gain is fairly simple to obtain once the span is known. Consider an electronic pressure transmitter with a range of 0600kPa.The gain

41、 is defined as the change in output divided by the change in input. In this case，the output is electrical signal(420mA DC)and the input is process pressure(O600kPa).Thus the gainKr =(20mA-4mA)/(600kPa-0kPa)=16mA/600kPa=0.27mA/kPaSpeed transmitter Speed transmitter is usually used closed-speed magnet

42、ic circuit reluctance belt speed sensor, which by the induction gear, sensors teeth, with induction coil, such as magnets composed. When the sensor gear shaft and measured connection with rotational axis, the induction of the gear teeth on movement sensors, air-gap between the two gears in the size

43、of the cyclical changes, changes have caused reluctance principle of electromagnetic induction can be induced potential. If the gear teeth to Z, measured shaft equipped with pulleys, its diameter D, the belt speed of V, while According to this belt can be the speed. FOR this, the speed of strap can

44、be received. 工程中的微型計(jì)算機(jī)微處理器化系統(tǒng)20世紀(jì)70年代的微型計(jì)算機(jī)發(fā)展引起了工程的一場(chǎng)革命。在19世紀(jì)之初的工業(yè)革命宣布了用機(jī)械工具代替繁重的體力勞動(dòng)的機(jī)器有了進(jìn)步。微計(jì)算機(jī)的一個(gè)主要工程應(yīng)用是在過(guò)程控制中，裝置是按特定的應(yīng)用情況由微機(jī)編程實(shí)現(xiàn)。廣義地說(shuō)，電子系統(tǒng)是用于處理信息的，這種信息可以是電話(huà)交談、儀器讀數(shù)或企業(yè)帳戶(hù)，但是各種情況下都涉及相同的主要操作：信息處理、存儲(chǔ)和傳送。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(lái)的，例如計(jì)數(shù)器，無(wú)論是電子的還是機(jī)械的，都要存儲(chǔ)當(dāng)前值，并按要求將該值增1。諸如采用計(jì)數(shù)器的電子鐘之類(lèi)的任一系統(tǒng)要使其存儲(chǔ)和處理能力遍布整個(gè)系

45、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。當(dāng)前微處理器化系統(tǒng)與上述的常規(guī)方法不同，它將處理、存儲(chǔ)和傳輸三個(gè)功能分離形成不同的系統(tǒng)單元。這種形成三個(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(lái)的，并且是針對(duì)微計(jì)算機(jī)的設(shè)想。從此幾乎所有制成的計(jì)算機(jī)都是用這種結(jié)構(gòu)設(shè)計(jì)的，盡管包含寬廣的物理形式，從根本上來(lái)說(shuō)它們均是具有相同的基本設(shè)計(jì)。在微處理器化系統(tǒng)中，處理是由微處理器本身完成的。存儲(chǔ)是利用存儲(chǔ)器電路，而進(jìn)入和出自系統(tǒng)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)微處理器化時(shí)鐘中找出執(zhí)行計(jì)數(shù)功能的一個(gè)特殊硬件是不可能的，因?yàn)闀r(shí)間存儲(chǔ)在存儲(chǔ)器中，而在固定的時(shí)間間隔下由微處理器控

46、制增值。但是，規(guī)定系統(tǒng)運(yùn)轉(zhuǎn)過(guò)程的軟件包含實(shí)現(xiàn)計(jì)數(shù)器功能的單元。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(lái)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(guò)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(wèn)題。圖1.1 典型微計(jì)算機(jī)的三個(gè)部分圖1.1顯示出了微型計(jì)算機(jī)中這三個(gè)單元是如何按照機(jī)器中的信息通信方式而聯(lián)接起來(lái)的。該系統(tǒng)由微處理器控制，它管理自己與存儲(chǔ)器和輸入/輸出單元的信息傳輸。外部的連接與工程系統(tǒng)的其余部分（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，實(shí)際中有RAM和ROM兩種不同的存儲(chǔ)器被使用。由于概念上的計(jì)算機(jī)存儲(chǔ)

47、器更像一個(gè)公文柜，上述的“存儲(chǔ)器”一詞時(shí)非常不恰當(dāng)?shù)模恍畔⒋娣旁谝幌盗幸褬?biāo)號(hào)的“箱子”中，而且可按問(wèn)題由“箱子”的序列號(hào)進(jìn)行信息的參考定位。微計(jì)算機(jī)常使用RAM（隨機(jī)存取存儲(chǔ)器），在RAM中數(shù)據(jù)可被寫(xiě)入，并且在需要時(shí)可被再次讀出。這種數(shù)據(jù)能以任一所希望的次序從存儲(chǔ)器中讀出，不必按寫(xiě)入時(shí)的相同次序，所以有“隨機(jī)”存取存儲(chǔ)器。另一類(lèi)型ROM（只讀存儲(chǔ)器）用來(lái)保持不受微處理器影響的固定的信息標(biāo)本；這些標(biāo)本在電源切斷后不會(huì)丟失，并通常用來(lái)保存規(guī)定微處理器化系統(tǒng)運(yùn)轉(zhuǎn)過(guò)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(lái)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(guò)特殊

48、的設(shè)備由用戶(hù)編程，所以稱(chēng)為可編程ROM。被廣泛使用的可編程ROM可利用特殊紫外線(xiàn)燈擦除，并被稱(chēng)為EPROM，即可擦除可編程只讀存儲(chǔ)器的縮寫(xiě)。另有新類(lèi)型的器件不必用紫外線(xiàn)燈而用電擦除，所以稱(chēng)為電可擦除可編程只讀存儲(chǔ)器EEPROM。微機(jī)接口微機(jī)接口實(shí)現(xiàn)兩種信息形式的交換。在計(jì)算機(jī)之外，由電子系統(tǒng)所處理的信息以一種物理信號(hào)形式存在，但在程序中，它是用數(shù)字表示的。任一接口的功能都可分為以某種形式進(jìn)行數(shù)據(jù)變換的一些操作，所以外部和內(nèi)部形式的轉(zhuǎn)換是由許多步驟完成的。用圖1.2所示的情況為例加以說(shuō)明，圖中展示了微計(jì)算機(jī)和產(chǎn)生連續(xù)變化模擬信號(hào)的傳感器之間的接口。傳感器產(chǎn)生的信號(hào)常很小，需要放大，或者產(chǎn)生的信號(hào)

49、和形式被系統(tǒng)的其他部分處理之前需要再次轉(zhuǎn)換。舉例來(lái)說(shuō)，許多傳感器具有電阻變化，這必須由一專(zhuān)門(mén)電路轉(zhuǎn)換成電壓。這種將傳感器輸出轉(zhuǎn)換成電壓信號(hào)，并與系統(tǒng)的其他電路相連接的過(guò)程，稱(chēng)為信號(hào)調(diào)理。如圖1.2所示例子中，信號(hào)調(diào)理部分將源自傳感器的電壓或電流信號(hào)范圍轉(zhuǎn)換成可用模擬-數(shù)字轉(zhuǎn)換器變成數(shù)字形式的信號(hào)范圍。圖1.2 輸入接口一個(gè)模擬-數(shù)字轉(zhuǎn)換器（ADC）用來(lái)將連續(xù)變化信號(hào)變成相應(yīng)的數(shù)字量，這數(shù)字量可是可能的二進(jìn)制數(shù)值中的一固定值。如果傳感器輸出不是連續(xù)變化的，就不需模擬-數(shù)字轉(zhuǎn)換。這種情況下，信號(hào)調(diào)理單元必須將輸入信號(hào)變換成為另一信號(hào)，也可直接與接口的下一部分，即微計(jì)算機(jī)本身的輸入輸出單元相連接。輸入/輸出單元將數(shù)字“開(kāi)/關(guān)”電壓信號(hào)轉(zhuǎn)換成能通過(guò)系統(tǒng)總線(xiàn)傳送到計(jì)算機(jī)的信號(hào)形式。這里每一根線(xiàn)的狀態(tài)，無(wú)論是“開(kāi)”或是“關(guān)”，用相應(yīng)得“1”或“0”表示。對(duì)于已經(jīng)轉(zhuǎn)換成數(shù)字形式的模擬輸入量，內(nèi)