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DZ241电动汽车自动控制系统,毕业设计
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微处理器 1.1 前言 微处理器是一个电子电路，其功能相当于计算机的中央处理单元，提供计算的控制。微处理器也用于电子系统，例如计算机的打印机，汽车和喷气飞机等，微处理器是一类超大规模集成电路。集成电路是复杂的电子电路，它由印制在单个，细小和平整的半导体材料上的极其微小的元件组成。现代微处理器合并了多达 1 千万个晶体管，另外还有像电阻，二极管，电容和导线等其他元件，通通装进大约邮票大小的一块面积里。 一个微处理器由几个不同的部分组成，算术逻辑单元实现数字计算和逻辑推理判断；寄存器是存储器暂时信 息的特殊记忆区，就像便携本的功能一样；控制单元解释程序；总线承载出入芯片和计算机的数据信息；内存支持片上计算。更复杂的微处理器往往包含其他部件，例如特殊存储区，也叫高速缓存存储器，也可以加速微处理器对外部数据存储设备访问。新式微处理器是以 64 比特的总线宽度工作的，这就是说，可同时传输 64 位数据，它是一个二进制数，即用 1 和 0 表示的信息单位元。 计算机的晶振提供协调微处理器所有活动的时钟信号。最先进的微处理器的时钟频率是 300MHz，允许在每秒钟可以执行 10 亿个计算机指令。 1.2 计算机存储器 由于微处理器本身不能提供大量的存储空间去存储程序指令和数据，像字处理程序中的文本，就需要晶体管与微处理器结合当作存储元件使用。单独的存储集成电路称为随机访问存储器，它包括大量的晶体管，与微处理器结合在一起提供需要的存储空间。随机访问存储器分为：静态 RAM 在有电时可以保存信息，由于其操作速度快，通常被当作高速缓存存储器使用。另一类存储器是动态 RAM 比静态的速度慢，必须用电定期刷新，否则保持的信息将丢失。动态 RAM 比静态 RAM 有更高的效率，在大多数计算机中，动态 RAM 作为主要的存储单元。 1.3 微控制器 微控制器不是完整的计算机。它没有大容量的存储器，也没有能力键盘，游戏杆和鼠标等输入设备以及显示器和打印器和打印机等输出设备进行通信。微控制器是一个不同类型的集成电路，它是一个完整的片上计算机面包喊了具有特殊功能的基本微处理器的所有功能部件。视频游戏，录象机，汽车和其他机器都使用了微控制器。 1.4 半导体 所有的集成电路都是由半导体制造的，半导体的导电性能介于导体和非导体或绝缘体之间。硅是最通用的半导体材料。因为半导体的导电性能可以随着施加电压的改变而改变。由半导体制成的集体观可以像微开关那 样动作，在仅仅几纳秒的时间内可nts以切断和连接电流。晶体管的这种能力可以使计算机一秒钟执行上百万条单指令，也可以很快完成复杂的任务。 大多数半导体器件的基本组成有二极管， N 型和 P 型的连接或合并。“ N”型和“ P”型指的是经过掺杂的半导体材料，控制加入非常少量的硼或磷这样的杂质。这些半导体材料的连接处，而且仅发生在 P 区电压比 N 区高的情况下。这种情况下施加给二极管的电压叫正向偏置。施加相反的电压叫反向偏置，二极管没有电流通过。一个集成电路包含有几百万个 PN 结，而且每一个结服务与特定的目的。 P 区和 N 区的恰当布局 和偏置要求电流有正确的路径，确保整个芯片正确地工作。 1.5 晶体管 在微电子行业广泛使用的晶体管被称为金属氧化物半导体场效应管。它包含有两个 N 型区，被称为源极和漏极，在源极和漏极之间的 P 型区被称为沟道。在沟道上是一层很薄的不导电的二氧化硅，二氧化硅上面附的另一层叫做栅极。要使电流从源极流向漏极，必须在栅极加一个正偏压。这就使得栅极像一个控制开关，连通和关断MOS 场效应，构成一个逻辑门，在微处理器中传送数字 1 和 0。 1.6 微处理器的制造 制造微处理器采用的技术与制造其他集成电路使用的技术类 似，例如存储器芯片。微处理器通常具有比其他芯片更复杂的结构，而且微处理器的制造需要极其精细的技术。微处理器的经济制造需要批量生产。在硅晶片的表面，上百个的掩膜或电路模式被同时制造出来。微处理器是通过导电物质，绝缘物质和半导体物质的无数次沉积和清除过程制造的，每次一薄层，直到几百万个分离的步骤后，才制成一个复杂的“三明治”，它包含了微处理器的所有内部连线和电路。仅在硅晶体的外表面的部分被用于电子电路。加工处理的步骤包括衬基的制备，氧化，光刻，蚀刻，注入和薄膜沉积。 生产微处理器的第一步是制造超纯的硅基体，然后将所有圆晶体形状的硅切片磨成平滑的镜面。 几乎沉积在晶体的每一层都必须精确地按晶体管和其他电子元件的形状制备。通常这个处理过程叫做光刻，它类似于把晶片转换为一张摄像图片和投射一个电路图片在晶片上。晶片边面的叫防光剂或防腐蚀剂的涂层，当曝露在光线下将发生变化，这样使得它很容易溶解在规定的模板中。这些模板的尺寸只有 0.25 微米，因为最短的可见光的波长是大约 0.5 微米，短波长的紫外线才可以用于模板微小细节的溶解。光刻后，对晶片进行腐蚀，或者用化学药品进行湿腐蚀， 或者放在一个特别的装有等离子体腐蚀气体的密室中，出去抗蚀剂。 紧接着的步骤是离子注入，像硼和磷等杂质被掺入硅内，可以改变其导电性。完成这个过程需要电离硼或者磷原子，用离子注入机使用巨大的能量将它们推进晶片里，最后离子依次嵌入在晶片的表面中。 nts 用于构建微处理器的薄层被称做薄膜。这一过程的最后一步，是在一个等离子体溅射器中进行沉积的，生成一层薄膜。这可以用蒸发法，把涂料熔化，然后蒸发，使其涂覆在晶片中；也可以用化学气化沉积法，使涂料在低压或正常气压下，从气态浓缩在晶片中。在每种方法中，薄膜必须似 是高度纯净的，它的厚度必须控制在几个微米之内。 微处理器的结构如此小和精细以至于灰尘可以破坏整个掩模。因为生产微处理器车间的空气需要极好的过滤和没有任何灰尘，所以此车间被称为清洁车间。 今天最清洁的车间被定义为一类车间：它表明每立方英尺的空气中超过 0.12 m 微粒的最大数目。 1.7 微处理器的历史 第一个微处理器是 1971 年生产的英特尔 4004。它最初是为计算机开发的，但它是那个时代的革命，在这个 4 位微处理器上包含 2300 个晶体管，每秒钟可以执行将近 6 万个指令。第一个 8 位微处理器是 1972 年 开发的作为计算机终端的英特尔 8080，它包含 4500 个晶体管，每秒能够执行 20 万个指令。现代微处理器具有更大的容量和更高的速度。 1.8 未来技术 微处理器和集成电路的制造技术变革非常快。当前，最复杂的微处理器集成了将近 1000 万个晶体管。到 2000 年，先进的微处理器将期望达到可以集成 5000 万个晶体管，到 2010 年，将达到 80 亿个。 光刻技术也将改进。到 2000 年，最小元件的尺寸将小于 0.2 m。按这样的尺寸，即使最短的紫外线也可能达不到必须的精度。可能的选择包括使用非常窄的电子和离子束，或者使用超 短波长的 X 射线代替光刻技术。 未来的微处理器可能需要像分子束外延和扫描隧道显微检查这些技术作为其制造工具。分子束外延是半导体在超真空的密室里一次一个原子地培植，利用扫描隧道显微检查，都能够看到单个的原子，甚至以原子大小的精度对原子进行移动。 ntsMicroprocessor 1.Introduction Microprocessor is an electronic circuit that functions as the central processing unit (CPU) of a computer , providing computational control .Microprocessors are also used in other advanced electronic systems ,such as computer printers ,automobiles ,and jet airline .In 1995 about 4 billion microprocessors were produced worldwide . The microprocessor is one type of ultra-large-scale integrated circuit .Integrated circuits ,also known as microchips or chips ,are complex electronic circuits consisting of extremely tiny components formed on a single ,thin ,flat piece of material known as a semiconductor .Modern microprocessors incorporate as many as ten million transistors(which act as electronic amplifiers ,oscillators ,or ,most commonly, switches),in addition to other components such as resistors ,diodes ,capacitors ,and wires ,all packed into an area about the size of a postage stamp . A microprocessor consists of several different sections :the arithmetic/logic unit (ALU) performs calculations on numbers and makes logical decisions ;the registers are special memory locations for storing temporary information much as scratch pad does ;the control unit deciphers programs ;bused carry digital information throughout the chip and computer ;and local memory supports on-chip computation .More complex microprocessors often contain other sections ,such as sections of specialized memory ,called cache memory ,to speed up access to external data-storage devices .Modern microprocessors operate with bus widths of 64 bits ( binary digits ,or units of information represented as 1s and 0s ) ,meaning that 64 bits of data can be transferred at the same time . A crystal oscillator in the computer provides a clock signal to coordinate all activities of the microprocessor .The clock speed of the most advanced microprocessors is about 300 megahertz (MHz) about 300 million cycles per second-allowing about a billion computer instructions to be executed every second . 2 .Computer Memory Because the microprocessor alone cannot accommodate the large amount of memory required to store program instructions and data ,such as the text in a word-processing program ,transistors can be used as memory elements in combination with the microprocessor .Separate integrated circuits ,called random-access memory (RAM) chips ,which contain large numbers of transistors ,are used in conjunction with the microprocessor to provide the needed memory .There are different kinds of ntsrandom-access memory ,Static RAM (SRAM) holds information as long as power is turned on and is usually used as cache memory because it operates very quickly .Another type of memory ,dynamic RAM (DRAM) ,is slower than SRAM and must be periodically refreshed with electricity or the information it holds is lost .DRAM is more economical than SRAM and serves as the main memory element in most computers 3 .Microcontroller A microprocessor is not a complete computer .It does not contain large amounts of memory or have the ability to communicate with input devices ,such as keyboards ,joysticks ,and mice-or with output devices ,such as monitors and printers .A different kind of integrated circuit ,a microcontroller , is a complete computer on a chip ,containing all of the elements of the basic microprocessor along with other specialized functions .Microcontrollers are used in video games ,videocassette recorders (VCRs) automobiles ,and other machines . 4.Semiconductors All integrated circuits are fabricated from semiconductors ,substances whose ability to conduct electricity ranks between that of a conductor and that of a nonconductor ,or insulator .Silicon is the most common semiconductor material .Because the electrical conductivity of a semiconductor can change according to the voltage applied to it ,transistors made from semiconductors act like tiny switches that turn electrical concurrent on and off in just a few nanoseconds ( billionths of a second ) .This capability enables a computer to perform many millions of simple instructions each second and to complete complex tasks quickly . The basic building block of most semiconductor devices is the diode ,a junction ,or union ,of negative-type (n-type) and positive-type (p-type) materials .The terms n-type and p-type refer to conducting materials that have been doped-that is ,that have had their electrical properties altered by the controlled addition of very small quantities of impurities such as boron or phosphorus .In a diode ,current floes in only one direction :across the junction from the n-type material ,and then only when the p-type material is at a higher voltage than the n-type .The voltage applied to the diode to create this condition is called the forward bias ,the opposite voltage ,for which current will not flow ,is called the reverse bias ,An integrated circuit contains millions of p-n junctions ,each serving a specific purpose within the millions of electronic circuit elements .Proper placement and biasing of p- and n-type regions restrict the electrical current to the correct paths and ensure the operation of the entire chip . nts5.Transistors The transistor used most commonly in the microelectronics industry is called a metal-oxide-semiconductor field effect transistor (MOSFET) .it contains two n-type regions ,called the source and the drain ,with a p-type region in between them , called the channel .Over the channel is a thin layer of nonconductive silicon dioxide topped by another layer ,called the gate .For electrons to flow from the source to the drain ,a voltage (forward bias) must be applied to the gate .This cause the gate to act like a control switch ,turning the MOSFET on and creating a logic gate that transmits digital 1s and 0s throughout the microprocessor . 6.Construction of Microprocessors Microprocessors are fabricated using techniques similar to those used for other integrated circuits ,such as memory chips .Microprocessor generally have a more complex structure than do other chips ,and their manufacture requires extremely precise techniques .Economical manufacturing of microprocessors requires mass production .Several hundred dies ,or circuit patterns ,are created on the surface of a silicon wafer simultaneously .Microprocessors are constructed by a process of deposition and removal of conducting ,insulating ,and conducting material one thin layer at a time until ,after hundreds of separate steps ,a complex sandwich is constructed that contains all the interconnected circuitry of the microprocessor . only the outer surface of the silicon wafer-a layer about 10 microns (about 0.01mm/0.0004in ) thick ( about one-tenth the thickness of a human hair )is used for the electronic circuit .The processing steps include substrate creation ,oxidation ,lithography ,etching ,ion implantation ,and film deposition . The first step in producing a microprocessor is the creation of an ultra pure silicon substrate ,a silicon slice in the shape of a round wafer that is polished to a mirror like smoothness .At present ,the largest wafers used in industry are 200 mm (8 in) in diameter . In the oxidation step , an electrically no conducting layer ,called a dielectric ,is placed between each conductive layer on the wafer . The most important type of dielectric is silicon dioxide ,which is grown by exposing the silicon wafer to oxygen in a furnace at about 1000 . The oxygen combines with the silicon to form a thin layer of oxide about 75 angstroms deep ( an angstrom is one ten-billionth of a meter ) . Nearly every layer that is deposited on the wafer must be patterned accurately into the shape of the transistors and other electronic elements .Usually this is done in process known as photolithography ,which is analogous to transforming the wafer into a piece of ntsphotographic film and projecting a picture of the circuit on it . A coating on the surface of the wafer ,called the resist ,changes when exposed to light ,making it east to dissolve in a developing solution .These patterns are as small as 0.25 microns in size .because th shortest wavelength of visible light is about 005 microns ,Short-wave-length ultraviolet light must be used to resolve the tiny details of the patterns .After photolithography ,the wafer is etched-that is ,the resist is removed from the wafer either by chemicals ,in a process known as wet etching ,or by exposure to a corrosive gas , called a plasma , in a special vacuum chamber . In the next step of the process ,ion implantation ,impurities such as boron and phosphorus are introduced into the silicon to alter its conductivity .This is accomplished by ionizing the boron or phosphorus atoms ( stripping off one or two electrons ) and propelling them at the wafer with an ion implanter at very high energies . The ions become embedded in the surface of the wafer . The thin layers used to build up a microprocessor are referred to as films .In the final step of the process ,the films are deposited using sputters in which thin films are grown in a plasma ;by means of evaporation whereby the material is melted and then evaporated coating the wafer ;or by means of chemical-vapor deposition ,whereby the material condenses from a gas at low or atmospheric pressure .In each case ,the film must be of high purity and its thickness must be controlled within a small fraction of a micron . Microprocessor features are to small and precise that a single speck of dust can destroy an entire die .The rooms used for microprocessor creation are called clean rooms because the air in them is extremely well filtered and virtually free of dust .The purest of todays clean rooms are referred to as class 1 , indicating the maximum number of allowed particles larger than 0.12 micron in one cubic foot of air .( For comparison , a typical home is class one million or so ). History of the Microprocessor The first microprocessor was the Intel 4004 ,produced in 1971 Originally developed for a calculator ,and revolutionary for its time ,it contained 2,300 transistors on a 4-bit microprocessor that could perform only 60,000 operations per second .The first 8-bit microprocessor was the Intel8008 ,developed in 1972 to run computer terminals ,The Intel 8008 contains 3,300transistors .The first truly general-purpose microprocessor ,developed in 1974 , was the 8-bit Intel8080 ,which contained 4,500 transistors and could execute 200,000 instructions per second .Modern microprocessors have much greater capacity and speed .They include the Intel Pentium Pro ,containing nts5.5 million transistors ;the UltraSparc-II ,by Sun Microsystems ,containing 5.4 million transistors ;the PowerPC620 , developed jointly by Apple ,IBM ,and Motorola , and containing 7 million transistors ;and the Digital Equipment Corporations Alpha 21164A ,containing 9.3 million transistors . 8.Future Tech
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