超大规模集成技术_翻译.doc

外文原文：VLSI TechnologyOne of the key inventions in the history of electronics，and in fact one of the most important inventions ever period，was the transistorIt was invented by Bell Laboratories in 1948In short，a transistor is a device that conducts a variable amount of electricity through it，depending on how much electricity is input to itIn other words，it is a digital switchHowever，unlike the vacuum tube，it is solid stateThis means that it doesnt change its physical form as it switchesThere are no moving parts in a transistorThe advantages of the transistor over the vacuum tube were enormousCompared to the old technology，transistors were much smaller， faster， and cheaper to manufactureThey were also far more reliable and used much 1ess powerThe transistor is what started the evolution of the modern computer industry in motionThe transistor was originally a single，discrete device，which you could p1ace individually into a circuit much like any otherToday，some special-purpose transistors are still used that wayWhat allowed the creation of modern processors was the invention of the integrated circuit，which is a group of transistors manufactured from a single piece of material and connected together internally，without extra wiringIntegrated circuits are also called ICs or chipsA special material is used to make these integrated circuitsWhile most materials either insulate from electrical flow (air，glass，wood) or conduct electricity readily(metals,water)，there are some that only conduct electricity a small amount。or only under certain conditionsThese are called semiconductorsThe most commonly used semiconductor is of course siliconBy careful chemical composition and arrangement，it is possible to create a very small transistor directly on a layer of silicon，using various technologies to manipulate the material into the correct formThese transistors are small，fast and reliable,and use relatively little powerThe first integrated circuit was invented in 1959 bv Texas Instruments.It contained just six transistors on a single semiconductor surface.After the invention of the integrated circuit，it took very little time to realize the tremendous benefits of miniaturizing and integrating larger numbers of transistors into the same integrated circuit.More transistors(switches) were required in order to implement more complicated functions.Miniaturization was the key to integrating together large numbers of transistors while increasing hardware speed and keeping power consumption and space requirements manageable.Large-scale integration(“LSI”)came to refer to the creation of integrated circuits that had previously been made from multiple discrete components.These devices typically contained hundreds of transistors.Early computers were made from many of these smaller ICs connected together on circuit boards.As time progressed after the invention of LSI integrated circuits，the technology improved and chips became smaller，faster and cheaper.Building on the success of earlier integration efforts，engineers learned to pack more and more logic into a single circuit.This effort became known as very large scale integration(VLSI).VLSI circuits can contain millions of transistors.Originally，the functions performed by a processor were implemented using several different logic chipsIntel was the first company to incorporate a11 of these logic components into a single chip.This was the first microprocessor，the 4004，introduced by Intel in 1971.All of todays processors are(highly advanced!)descendants of this original 4-bit CPU.Memory DevicesMemories can be made in mechanical，magnetic，optical，biological and electronic technologies.Examples of magnetic memories are tapes，floppy disks，hard drives and ferroelectric RAMs.Examples of optical memories are CDROMs，rewrittable CDs.Electronic memory is used extensively in computer equipment since it is the fastest available.For applications where speed is less important，magnetic and optical techno1ogies are often used.The flip-flop A filp-flop is basically a bi-state circuit in which eight a 0 or 1 state can resides.Because of its simplicity，the flip-flop is extremely fast.As a basic element，the flip-flop is used in digital circuits and ICs.A flip-flop will lose its state when the supply voltage is removed.Therefore，it is volatile.The register A register is a set of flip-flops in parallelTypically a register is 8，16，32 or 64 bits wide.Often a register is used to hold data，address pointers，etcA register is volatile and very fast just like the flipflop.SRAM(Static Random Access Memory) An SRAM is an array of addressable flip-flops.The array can be configured as such that the data comes out in single bit，4-bit，8 bit，and etc.format.SRAM is simple，fast and volatile just like the flip-flop，its basic memory cellSRAM can be found on microcontroller boards(either on or off the CPU chip)，where the amount of memory required is small and it will not pay off to build the extra interface circuitry for DRAMs.In addition，SRAM is often used as cache because of its high speed.SRAM comes in many speed classes，ranging from several ns for cache applications to 200ns for low power applications.SRAM exists in both bipolar and MOS technology.CMOS technology boasts the highest density and the lowest power consumptionFast cache memory can be constructed in BiCMOS technology，a hybrid technology that uses bipolar transistors for extra driveThe fastest SRAM memories are available in ECL(Emitter Coupled Logic)bipolar technology.Because of the high power consumption，the memory size is limited in this technology.A special case of SRAM memory is Content Addressable Memory(CAM).In this technology，the memory consists of an array of flip-flops，in which each row is connected to a data comparator.The memory is addressed by presenting data to it(not an address!).All comparators will then check simultaneously if their corresponding RAM register holds the same data.The CAM will respond with the address of the row(register)corresponding to the original dataThe main application for this technology is fast lookup tables.These are often used in network routers.DRAM(Dynamic Random Access Memory) The word“dynamic”indicates that the data is not held in a flip-flop but rather in a storage cell.The data in a storage cell must be refreshed(read out and re-written)regularly because of leakage.The refresh time interval is usually 4 to 64 msThe storage cell only requires one capacitor and one transistor，whereas a flip-flop connected in an array requires 6 transistorsIn trench capacitor memory technology，which is used in all modern DRAMs,the transistor is constructed above the capacitor so that the space on chip is ultimately minimizedFor this reason，DRAM technology has a lower cost per bit than SRAM technology.The disadvantage of the extra circuitry required for refreshing is easily offset by the lower price per bit when using large memory sizes.DRAM memory is，just like SRAM memory constructed as an array of memory cells.A major difference between SRAM and DRAM，however，lies in the addressing techniqueWith an SRAM，an address needs to be presented and the chip will respond with presenting the data of the memory cell at the output，or accepting the data at the input and write it into the addressed cell.With DRAM technology，this simple approach is impossible since addressing a row of data without rewriting it will destruct all data in the row because of the dynamic nature.ROM(Read Only Memory) ROMS are also called mask-ROMs or mask programmed ROMs.This is because a ROM needs to be programmed by setting its cells to either 0 or 1 at the time of manufacture.Usually the 0 or 1 is formed by the presence or absence of an aluminium lineThis aluminium pattern is defined by a lithographic mask used in one of the last steps of manufactureTherefore these devices are often called mask-ROMS.The advantage of ROM is that it can be manufactured at the lowest price in high volumes.Another advantage in some applications is that it is impossible to alter the data once the chips are made，and that no further programming and testing are requiredOn the other hand，if the data or code must be changed this can be a small disasterThe rest of the chips will end in the dustbin and new chips will have to be made.EEPROM(Electrically Erasable Programmable ROM) This means that the chip can be programmed like an EPROM，but can be erased electricallyAs a resuIt，no UV source is requiredEEPROMS can be erased on a byte-by-byte basis.VHDLVHDL, which stands for VHSIC(Very High Speed Integrated Circuit ) Hardware Description Language ,was developed in the early 1980s as a spin-off a high speed integrated circuit research project funded by the U.S. Department of Defenses. During the VHSIC program, researchers were confronted with the daunting task of describing circuits of enormous scale (for their time )and of engineers. With only gate-level design problems that involved multiple teams of engineers. With only gate-level design tools available, it soon became clear that betters, more structured design methods and tools would be needed.VHDL is a programming language that has been designed and optimized for describing the behavior of digital systems. VHDL has many features appropriate for describing the behavior of electronic components ranging from simple logic gates to complete microprocessors and custom chips .Features of VHDL allow electrical aspects of circuit behavior (such as rise and fall times of signals, delays through gates, and functional operation )to be precisely described. The resulting VHDL simulation models can then be used as building blocks in larger circuits (using schematics, block diagrams or system-level VHDL descriptions) for the purpose of simulation.VHDL is also a general-purpose programming language allow complex design concepts to be expressed as computer programs, VHDL allows the behavior of complex electronic circuits to be captured into a design system for automatic circuit synthesis or for system simulation. .Like Pascal, C and C+, VHDL includes features useful for structured design techniques, and offers a rich set of control and data representation features. Unlike these other programming languages, VHDL provides features allowing concurrent events to be described. This is important because the hardware described using VHDL is inherently concurrent in its operation.One of the most important applications of VHDL is to capture the performance specification for a circuit, in the form of what is commonly referred to as a test bench. Test benches are VHDL descriptions of circuit and corresponding expected outputs that verify the behavior of a circuit over time .Test benches should be an integral part of any VHDL project and should be created in tandem with other descriptions of the circuit.译文：超大规模集成技术晶体管是电子学发展史上的关键发明之一，它实际上也是人类历史上最重要的发明之一。1948年，贝尔实验室发明了晶体管。简单地讲，晶体管是一种依据输入电量大小而传导可变电量的器件。换言之，晶体管是一种数字开关。然而，和真空管不同，晶体管是“固态”的。“固态”的意思是当晶体管切换状态时，其物理形式不发生变化。晶体管中不存在可以移动的部分。和真空管相比，晶体管有巨大的优势。与以前的这种技术相比，晶体管(尺寸)小得多，(切换速度)快得多，生产成本低得多；晶体管的性能也更加可靠，而且耗费的能量也要少。晶体管(的发明)启动了计算机工业的蓬勃发展。最早的晶体管是分立器件。与其他分立器件一样，你可以单独地把它放置在某个电路中。今天，一些特殊用途的晶体管还是这样使用着。集成电路的发明为现代处理器的诞生创造了条件。集成电路就是一组用单片材料制造的、内部互联的(无外部连线)晶体管。集成电路则可称为IC或者芯片。制造集成电路需要使用一种特殊材料。尽管多数材料要么对电流绝缘(如空气、玻璃、木头)，要么很容易传导电流(如金属、水溶液)，但也有一些材料只传导少量电流，或者只在特定条件下传导电流。这些材料被称做半导体。最常用的半导体材料当然是硅了。这样的晶体管体积小、速度快、功能可靠，耗能也比较少。第一块集成电路是1959年由德州仪器公司发明的。它只含6个晶体管。集成电路发明后不久，人们很快就意识到了小型化和将大量晶体管集成到同一块集成电路的巨大好处。为了实现更复杂的功能就需要更多的晶体管(数字开关)。在提高硬件速度、控制功耗的同时，集成大量晶体管的关键技术就是小型化。大规模集成是指将先前多个分立部件构成的电路集成化。这些器件通常包含几百个晶体管。早期计算机就是将电路板上多片此类集成电路相互连接而成的。大规模集成电路发明后，集成技术随着时间的推移而提高，芯片也更小、更快、更便宜。在此前集成化努力成功的基础上，工程师们掌握了将越来越多逻辑集成到一个电路中的技术。这就是“超大规模集成”技术。超大规模集成电路能够包含数百万个晶体管。处理器完成的功能最早是由几个不同的逻辑芯片实现的。英特尔公司率先将所有这些部件集成到单个芯片中。这就是最早的微处理器1971年英特尔公司推出的4004。今天(非常先进)的处理器都是这个最早4位CPU的后代。存储器件存储器件可以用机械、磁、光、生物或电子技术制造。磁存储器件的例子有软盘、硬盘和铁电随机存储器。光技术存储器件有只读光盘和可写光盘。在计算机设备中，电子存储器件使用得很广泛。这是因为它是目前可以得到的速度最快的存储器件。在速度的重要性稍差的应用中，经常使用磁技术和光技术。今天，所有电子存储器既可以是独立的集成电路形式、独立的模块形式，也可作为集成电路的一部分。下表是一些电子存储器的概况。触发器 触发器是一种存储“O”或“1”的双态电路。由于触发器结构简单，所以其速度极快。触发器是数字电路和集成电路中的基本部件。由于电源电压去掉后，触发器原有的状态就失去了，因此它是“易失的”。寄存器 寄存器是一组并行触发器。寄存器的典型数据宽度为8位、16位、32位或者64位。寄存器常用于保存数据、地址指针等。和触发器一样，寄存器也是“易失”的，而且速度很快。静态随机存取存储器 SRAM是一种可寻址触发器阵列。该阵列可配置成1位、4位，8位等数据格式。它和它的基本存储单元触发器一样：结构简单、存取速度快、具有易失的特点。我们可以在微控器电路板当中(芯片内部或外部)找到它，因为在这些应用中所需的存储量不大，而且也不值得为了使用DRAM去构建额外的接口电路。此外，因其存取速度快也用做高速缓存。SRAM的速度等级很多：从高速缓存的几个纳秒到低功率应用的200纳秒。双极性技术的SRAM和MOS技术的SRAM现在都有。CMOS技术的优势在于密度最高、功耗最低。高速缓存可以使用BiCMOS技术构建；BiCMOS是一种混合技术，它使用双极性晶体管作为附加的驱动。采用ECL双极性技术的SRAM具有最快的速度。由于这种技术的功耗高，所以存储器容量受到限制。内容寻址存储器(CAM)是一种特殊的SRAM存储器。在这种技术中，构成存储器的触发器阵列中的每一行都和一个数据比较器相连。访问存储器的方式不是向其提供地址，而是向其提供数据。所有的数据比较器将同时检查其对应的寄存器是否保存着和该数据相同的数据。CAM将数据对应的行地址输出。该技术的主要用途是实现快速