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題 目: Fundamentals of Single-chip Microcomputer
院系名稱: 專業(yè)班級:
學生姓名: 學 號: 20
指導教師: 教師職稱:
附 件: 1.外文資料翻譯譯文;2.外文原文。
附件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)可查的是它們也是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)分程序存儲器和數(shù)據(jù)存儲器在硬件中的特性,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,像普林斯頓特性,展示如圖3-5A-2。
程序存儲器
輸入輸出單元
CPU
數(shù)據(jù)存儲器
Fig.3-5A-1 微機系統(tǒng)
輸入輸出單元
CPU
內(nèi)存
Fig.3-5A-2. 傳統(tǒng)的普林斯頓計算機
定時器/計時器
時鐘系統(tǒng)
外部定時組件
串行輸入輸出
程序存儲器
重啟
并行輸入輸出
數(shù)據(jù)存儲器
中斷
CPU
電源
Fig3-5A-3. 微型計算機的主要特點
只讀存貯器(ROM)
ROM是永久的、非應用程序的易失性存儲器。不少微機和單片機用于大批量應用。因此,經(jīng)濟的設(shè)備制造要求程序存儲器的內(nèi)容是在制造期間永久性的刻錄在芯片中,這意味著必須采用嚴謹?shù)姆椒?,因為ROM代碼不能在制造之后修改。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等先進的開發(fā)系統(tǒng)。
一些制造商在其提供的設(shè)備包括了用戶可編程內(nèi)存。其中最簡單的是設(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選項和訪問外部內(nèi)存的數(shù)據(jù)總線。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,但小內(nèi)存裝置在永久性內(nèi)存制造中的應用是非常普遍的。和其它芯片相比,單芯片微型計算機可以節(jié)省大量成本,可以有更方便的ROM設(shè)備更換,可在與EPROM(可擦除可編程只讀存儲器)插座或存儲器共同使用。
隨機存取存儲器(RAM)
RAM用于變量和工作在存儲器的程序。由于數(shù)據(jù)存儲設(shè)備的大小不同,RAM類型也有所不同,但具有相同的特征寬度(4,8,16 比特等)。特殊功能寄存器,如棧指針或定時器寄存器,往往在邏輯上被納入內(nèi)存區(qū)域。它也在微型電腦的硬件中做集中內(nèi)存,在非物理特性的微機中,它是沒必要區(qū)分內(nèi)存和處理器之間的區(qū)別。
中央處理單元(CPU)
CPU是象微型電子計算機和微控制器的微型電腦。許多微型電腦和微控制器涉及到二進制編碼,因而,常??梢园l(fā)現(xiàn)該CPU是很適合處理這種類型的數(shù)據(jù)。對設(shè)施進行良好與否的測試,設(shè)置和重置單個位的內(nèi)存或I / O控制器的應用程序,以及常見的許多涉及打開和關(guān)閉的單輸出線,這些都很容易使用到二進制設(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
并行輸入和輸出有所不同,在不同的微機中,大多數(shù)設(shè)立一個機制,至少選擇讓其中一些引腳輸出和一些引腳輸入,這可能適用于所有的端口和有些I / O線直接連接的設(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,比如一些設(shè)備只允許一個I / O端口,其他組件將作為系統(tǒng)總線配置的片外存儲器和I / O擴展。這個設(shè)施是一個產(chǎn)品系列的潛在發(fā)展,因為連續(xù)增強不是建立在現(xiàn)有的軟件基礎(chǔ)上的,因此這是不可取的。
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,這種通訊也可以利用特殊的接口連接功能芯片把幾個微型機連在一起。雙方按照異步同步通信方案要求的規(guī)則提供成幀的信息,這可以作為一個硬件設(shè)施必須的條件。它需要選擇一個波特率和負載號碼、有串行發(fā)送器的緩沖器,進行適當?shù)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
許多應用的單片機需要對過去真實時間進行準確的評價,這可以由每個程序中的執(zhí)行時間分支進行認真評估,經(jīng)常用于簡單的程序,因為它的工作效率不高。評估的首選方法是使用計時器電路,能獨立地計算精確的時間增量,并生成一個預設(shè)的中斷時間,這種類型的定時器通常可重載應用。當計時器產(chǎn)生中斷或設(shè)置標記時,計數(shù)器到達零(更好一點的計時器有自動加載初始值的功能),這將在計時器重新啟動之前減少重新加載計數(shù)器和評估的時間。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,如果要求比較高的性能,必須使用晶體以確保最大接近時鐘頻率。許多時鐘電路還具有計算電阻和低電容工作成本的定時元件,這必須從外部驅(qū)動,這種安排在微機外部同步時是非常有用的。
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?nèi)〈^電器,將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,我們將在PLC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,但最近才如雨后春筍般的流行起來。正如西門子能源和自動化公司副總裁兼總經(jīng)理雷蒙德萊韋耶所說,可編程控制更適合于復雜的操作,因為梯形邏輯使編程語言變得更加實際,更加有效和更加強大的。
PLC的過程控制
到目前為止,PLC并沒有大量用于連續(xù)過程控制,這種狀況會繼續(xù)下去嗎?“我感覺到了,PLC將用于過程工業(yè),但不一定是過程控制?!?Jannotta說。幾個供應商,顯然是把賭注押在已經(jīng)實行了PLC的應用優(yōu)化的過程,富瑞安的經(jīng)理Ryan認為PLC將越來越多地使用食品、化工、石化等行業(yè),在PLC的兩種類型應用程序中,第一種是過程控制系統(tǒng),它目前已經(jīng)隨著價格標簽開始發(fā)展。第二種是融入順序邏輯,在這方面批次控制循環(huán)的密切合作是最好的例子,在那里順序和維持過程變量是密切合作地交織在一起,使擁有一個可編程控制器的邏輯順序的好處遠遠超過了不具有分布式控制的系統(tǒng)。
Bill Barkovitz, Triconex的總統(tǒng),預言:“今后所有的控制器在過程控制系統(tǒng)的業(yè)務將引用更多的PLC技術(shù), PLC功能比以往任何時候都要多?!?
通信和規(guī)范
對自動化工廠來說,在整體上通信是至關(guān)重要的個人自動化單元。在過去數(shù)年我們聽說了許多公司都紛紛跟進的很多規(guī)范,但是,不少人失望的發(fā)現(xiàn)地圖規(guī)范并沒有立即出現(xiàn)。拉里科馬雷克說:“現(xiàn)在,規(guī)范仍然是一個不確定的目標,對于制造商規(guī)范沒有最終決定。目前,正在推出的產(chǎn)品樣本滿足MAP2.1標準,但是當新標準MAP3.0被引進后,以MAP2.1為基礎(chǔ)的產(chǎn)品將被淘汰”。
正因為如此,許多PLC廠商正在制定完整的規(guī)范。 例如Omron,擁有一個完整的兼容程序,但歐姆龍工業(yè)部副總裁弗蘭克紐伯恩在報告中說,歐姆龍公司的PLC定義還談不上規(guī)范。
由于不太可能將個人的PLC進行廣泛的交流,制造商更專注于專有的網(wǎng)絡(luò)。按照薩爾的說法,用戶擔心,如果他們不從規(guī)則上和供應商妥協(xié),他們將要增加對通信結(jié)構(gòu)的不支持程度。
通用的I / O
由于大多數(shù)PLC廠商在兼容問題上溝通不夠,在另一端連接的I / O問題,更是支離破碎。除了少數(shù)例外,I / O是仍然專有技術(shù),然而,誰都感覺到了I / O最終將成為普遍的。GE Fanuc的希望是做智能I / O線,I / O制造商都向同一方向進發(fā)。
許多人說,I / O是一個高價值項目, PLC制造商將永遠希望保持它的專有性。Jannotta說:“ I / O將在硬件銷售中不成比例,而每個PLC供應商都在試圖保護這一點,出于這個原因,PLC的制造商將不會開始銷售通用I / O和其他廠商的系統(tǒng),如果我們開始銷售該產(chǎn)品的實物,那我們還有什么可生產(chǎn)的?”
隨著更多智能I / O出現(xiàn),Provanzano認為在不同的制造商中間這將導致更多的分化?!澳睦锏腎 / O成為系統(tǒng)的一部分真的很難定義,哪些是I / O?哪些是CPU?隨著分布式的發(fā)展,如果你愿意,CPU也同樣可以納入作為I / O的系統(tǒng)”
PLC的 I / O和個人電腦的連接
雖然不同的PLC廠商可能會繼續(xù)用專有的I / O,但一些廠商使I / O連接到IBM PC這樣的兼容設(shè)備成為可能.Alle - bradeley和辛辛那提米拉克龍公司已經(jīng)擁有這項技術(shù),并有傳言說,通用的電氣計劃也將沿著同樣的思路。GE Fanuc北美的產(chǎn)品規(guī)劃經(jīng)理克特爾胡特認為“我想主機多個接口將有代替I/O的趨勢?!?
PLC VS電腦
如果IBM 7552,行動儀器BC22,和其他計算機出現(xiàn)在工廠,這是否就意味著不會對PLC產(chǎn)生新的競爭?富瑞恩說:“有一些控制功能可用于電腦,可編程程序控制器為了更好的工作已被迫適應這些應用?!比欢谖覀冋{(diào)查的廠商多數(shù)不認為“個人電腦入侵”將對他們產(chǎn)生問題。大多表示PLC和PC結(jié)構(gòu)上的差別決定他們有不同的作用,PC將主管通訊和管理,PLC則進行控制,他們相信這只是意味著,PLC和個人電腦將能夠共享相同的數(shù)據(jù)。
富瑞恩說:“通用的計算機內(nèi)在結(jié)構(gòu)不同,可編程控制器硬件結(jié)構(gòu)也已經(jīng)由單一制造商內(nèi)置到幾乎每一個制造商都可以生產(chǎn)的狀況。今天定制的硬件主要來運行梯形邏輯,解決機器代碼?!痹诟镜膮^(qū)別上,他引用了一個稱呼“機器狀態(tài)。富瑞安說:“當你關(guān)閉機器,或中斷周期,或跳轉(zhuǎn)到另一個周期,現(xiàn)場可編程控制器可以記得機器的狀態(tài):定時器狀態(tài)是什么?計數(shù)器狀態(tài)是什么?鎖存的狀態(tài)是什么?但計算機本身不這樣做,這就是計算機和可編程控制器的區(qū)別。”
附件2:外文原文(復印件)
外文出處
Automation Professional English Course
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 .
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.
Program
memory
Input&
Output
unit
CPU
Data
memory
Fig.3-5A-1 A Harvard type
Input&
Output
unit
CPU
memory
Fig.3-5A-2. A conventional Princeton computer
Timer/
Counter
System
clock
External
Timing
components
Serial 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 ROM;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 US 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.