外文翻譯微型計(jì)算機(jī)控制系統(tǒng)單片機(jī)控制系統(tǒng)

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1、外文翻譯--微型計(jì)算機(jī)控制系統(tǒng)（單片機(jī)控制系統(tǒng)） 外文原文 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

2、are involved: the processing, storage and transmission of 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 electron

3、ic 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 day microprocessor based systems depart from this conventional approach by separating the three functions of processing, st

4、orage, and transmission into different section of the system. 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

5、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 itself. The storage will be by means of memory circuits and the communication of information into and out of the system

6、 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 clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However,

7、 the software which defined the system’s behavior would 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 softwar

8、e. 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 producing software. The figure1.1 illustrates how these three sections within a microcomputer are connected in term

9、s of the communication of information within the machine. 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 engineeri

10、ng system. Fig.1.1 Three Sections of a Typical 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 cabin

11、et in concept; information is stored in a set of 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

12、 the memory in any sequence desired, and not necessarily 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 lo

13、st when power is removed and are normally used to 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 ar

14、e programmable by the user by means of special equipment 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 e

15、lectrically without the need for ultraviolet light, 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/ou

16、tput devices are general-purpose types while others 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 cont

17、ain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some

18、input/output devices are general-purpose types while others 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 actua

19、lly contain special-purpose microprocessors to permit quite 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 re

20、quire too much program or data storage . This is usually the 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 tech

21、nology develops , more and more powerful processors and larger 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

22、 number of integrated circuits to make a microcomputer whenever 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 nor

23、mally made for programming the microcomputer for the particular 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

24、, process controllers are usually more complicated so that it 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’ syst

25、em, signed for replacing controllers based on older technologies 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

26、, for example one which allowed the function of the controller 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 batter

27、ies are used to ensure continuity of supply. Alternatively programs 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 u

28、se lf large scale integrated circuits ‘the distinction between 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 enginee

29、ring and scientific uses of microcomputers can be assigned 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

30、meters, the pressure has been designated one Pascal. Pressure is 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 atm

31、ospheric 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 factors. The measurement and control of pre

32、ssure 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 pressure measurement and generates

33、 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 transmitted from some remote location

34、. 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 transmission system was de

35、veloped. This system is usually either pneumatic or electrical. And control instruments in one location. This makes it practical for a minimum number of operators to run the plant efficiently. When a pneumatic transmission system is employed, the measurement signal is converted into pneumatic signa

36、l by the transmitter scaled from 0 to 100 percent of the measurement value. This transmitter is mounted close to the point of measurement in the process. The transmitter output-air pressure for a pneumatic transmitter-is piped to the recording or control instrument. The standard output range for a p

37、neumatic 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 be current or voltage. Its standard range is from 4 to 20mA DC for current signal or from 1 to 5V DC for voltage signal. N

38、owadays, another type of electrical signal, which is becoming common, is the digital or discrete signal. The use of instruments and control systems based on computer or forcing increased use of this type of signal. Sometimes it is important for analysis to obtain the parameters that describe the se

39、nsor/transmitter behavior. The gain is fairly simple to obtain once the span is known. Consider an electronic pressure transmitter with a range of 0～600kPa.The gain is defined as the change in output divided by the change in input. In this case, the output is electrical signal 4～20mA DC and the

40、input is process pressure 0～600kPa . Thus the gain. Beside we must measure Temperature Temperature measurement is important in industrial control, as direct indications of system or product state and as indirect indications of such factors as reaction rates, energy flow, turbine efficiency, and lub

41、ricant quality. Present temperature scales have been in use for about 200 years, the earliest instruments were based on the thermal expansion of gases and liquids. Such filled systems are still employed, although many other types of instruments are available. Representative temperature sensors inclu

42、de: filled thermal systems, liquid-in-glass thermometers, thermocouples, resistance temperature detectors, thermostats, bimetallic devices, optical and radiation pyrometers and temperature-sensitive paints. Advantages of electrical systems include high accuracy and sensitivity, practicality of swi

43、tching or scanning several measurements points, larger distances possible between measuring elements and controllers, replacement of components rather than complete system , fast response, and ability to measure higher temperature. Among the electrical temperature sensors, thermocouples and resistan

44、ce temperature detectors are most widely used. Description The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory PEROM . The device is manufactured using Atmel’s high-density nonvolatile memory technology and is co

45、mpatible with the industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful micr

46、ocomputer which provides a highly-flexible and cost-effective solution to many embedded control applications. Function characteristic The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interr

47、upt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters

48、, serial port and interrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset. Pin Description VCC：Supply voltage. GND：Ground. Port 0： Port 0 is an 8-bit open-drain bi-direc

49、tional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0

50、has internal pullups.Port 0 also receives the code bytes during Flash programming,and outputs the code bytes during programverification. External pullups are required during programverification. Port 1 Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers

51、 can sink/source four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 1 pins that are externally being pulled low will source current IIL because of the internal pullups.Port 1 also receives the low-order address

52、bytes during Flash programming and verification. Port 2 Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,

53、Port 2 pins that are externally being pulled low will source current, because of the internal pullups.Port 2 emits the high-order address byte during fetches from external program memory and during accesses to external data memory that use 16-bit addresses. In this application, it uses strong intern

54、al pullupswhen emitting 1s. During accesses to external data memory that use 8-bit addresses, Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals during Flash programming and verification. Port 3 Port 3 is an 8-b

55、it bi-directional I/O port with internal pullups.The Port 3 output buffers can sink/source four TTL inputs.When 1s are written to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current IIL b

56、ecause of the pullups.Port 3 also serves the functions of various special features of the AT89C51 as listed below: Port 3 also receives some control signals for Flash programming and verification. RST Reset input. A high on this pin for two machine cycles while the oscillator is running re

57、sets the device. ALE/PROG Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input PROG during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency,

58、 and may be used for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory. If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction

59、. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode. PSEN Program Store Enable is the read strobe to external program memory.When the AT89C51 is executing code from external program memory, PSEN is activated

60、 twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. EA/VPP External Access Enable. EA must be strapped to GND in order to enable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, ho

61、wever, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage VPP during Flash programming, for parts that require12-volt VPP. XTAL1 Input to the invert

62、ing oscillator amplifier and input to the internal clock operating circuit. XTAL2 Output from the inverting oscillator amplifier. Oscillator Characteristics XTAL1 and XTAL2 are the input and output, respectively,of an inverting amplifier which can be configured for use as an on-chip oscill

63、ator, as shown in Figure 1.Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown in Figure 2.There are no requirements on the duty cycle of the external clock signal, since the inpu

64、t to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and imum voltage high and low time specifications must be observed. 中文譯文 微型計(jì)算機(jī)控制系統(tǒng) 廣義地說，是用于處理信息的，這種信息可以是電話交談，儀器讀數(shù)或企業(yè)帳戶，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，無論是電子還是機(jī)械，都要存儲(chǔ)當(dāng)前，按要求將該增1。

65、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。 系統(tǒng)，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，從根本上來說他們均是具有相同基本設(shè)計(jì)。 在系統(tǒng)中，處理是由系統(tǒng)完成的。存儲(chǔ)是利用存儲(chǔ)器電路，而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制增值

66、。但是，規(guī)定系統(tǒng)運(yùn)轉(zhuǎn)過程的軟件包含實(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)接起來的。該系統(tǒng)由微處理器控制，微處理器存儲(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)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)?；信息存放在一系列已的“箱子”中，而且可問題由“箱子”的序列號(hào)進(jìn)行信息的參考定位。 微計(jì)算機(jī)使用RAM（隨機(jī)存取存儲(chǔ)器），在RAM中數(shù)據(jù)被寫入，并且在需要被再次讀出。這種數(shù)據(jù)能以所希望的次序從存儲(chǔ)器中讀出，不必寫入時(shí)的相同次序，所以有“隨機(jī)”存取存儲(chǔ)器。另一類型ROM（只讀存儲(chǔ)器）用來保持不受微處理器影響的固定的信息標(biāo)本；這些在電源切斷后不會(huì)丟失，并