【正文】 side wires are connected within this package between the semiconductor sandwich and pins that protrude from the package to make electrical contact with other parts of the intended circuit. Once you have several discrete transistors, digital logic can be built by directly wiring these ponents together. The circuit will function, but any substantial amount of digital logic will be very bulky, because several transistors are required to implement each of the various types of logic gates. At the time of the invention of the transistor in 1947 by John Bardeen, Walter Brattain, and William Shockley, the only way to assemble multiple transistors into a single circuit was to buy separate discrete transistors and wire them together. In 1959, Jack Kilby and Robert Noyce independently invented a means of fabricating multiple transistors on a single slab of semiconductor material. Their invention would e to be known as the integrated circuit, or IC, which is the foundation of our modern puterized world. An IC is so called because it integrates multiple transistors and diodes onto the same small semiconductor chip. Instead of having to solder individual wires between discrete ponents, an IC contains many small ponents that are already wired together in the desired topology to form a circuit. A typical IC, without its plastic or ceramic package, is a square or rectangular silicon die measuring from 2 to 15 mm on an edge. Depending on the level of technology used to manufacture the IC, there may be anywhere from a dozen to tens of millions of individual transistors on this small chip. This amazing density of electronic ponents indicates that the transistors and the wires that connect them are extremely small in size. Dimensions on an IC are measured in units of micrometers, with one micrometer (1mm) being one millionth of a meter. To serve as a reference point, a human hair is roughly 100mm in diameter. Some modern ICs contain ponents and wires that are measured in increments as small as ! Each year, researchers and engineers have been finding new ways to steadily reduce these feature sizes to pack more transistors into the same silicon area, as indicated in Figure . When an IC is designed and fabricated, it generally follows one of two main transistor technologies: bipolar or metaloxide semiconductor (MOS). Bipolar processes create BJTs, whereas MOS processes create FETs. Bipolar logic was more mon before the 1980s, but MOS technologies have since accounted the great majority of digital logic ICs. Nchannel FETs are fabricated in an NMOS process, and Pchannel FETs are fabricated in a PMOS process. In the 1980s, plementaryMOS, or CMOS, became the dominant process technology and remains so to this day. CMOS ICs incorporate both NMOS and PMOS transistors. Application Specific Integrated Circuit An applicationspecific integrated circuit (ASIC) is an integrated circuit (IC) customized for a particular use, rather than intended for generalpurpose use. For example, a chip designed solely to run a cell phone is an ASIC. In contrast, the 7400 series and 4000 series integrated circuits are logic building blocks that can be wired together for use in many different applications. As feature sizes have shrunk and design tools improved over the years, the maximum plexity (and hence functionality) possible in an ASIC has grown from 5,000 gates to over 100 ASICs often include entire 32bit processors, memory blocks including ROM, RAM, EEPROM, Flash and other large building blocks. Such an ASIC is often termed a SoC (SystemonChip). Designers of digital ASICs use a hardware description language (HDL), such as Verilog or VHDL, to describe the functionality of ASICs. Fieldprogrammable gate arrays (FPGA) are the modern day equivalent of 7400 series logic and a breadboard, containing programmable logic blocks and programmable interconnects that allow the same FPGA to be used in many different applications. For smaller designs and/or lower production volumes, FPGAs may be more cost effective than an ASIC design. The nonrecurring engineering cost (the cost to setup the factory to produce a particular ASIC) can run into hundreds of thousands of dollars. The general term application specific integrated circuit includes FPGAs, but most designers use ASIC only for nonfield programmable devices and make a distinction between ASIC and FPGAs.HistoryThe initial ASICs used gate array technology. Ferranti produced perhaps the first gatearray, the ULA (Unmitted Logic Array), around 1980. Customization occurred by varying the metal interconnect mask. ULAs had plexities of up to a few thousand gates. Later versions became more generalized, with different base dies customized by both metal and polysilicon layers. Some base dies include RAM elements.Standard cell designIn the mid 1980s a designer would choose an ASIC manufacturer and implement their design using the design tools available from the manufacturer. While third party design tools were available, there was not an effective link from the third party design tools to the layout and actual semiconductor process performance characteristics of the various ASIC designers ended up using factory specific tools to plete the implementation of their designs. A solution to this problem that also yielded a much higher density device was the implementation of Standard Cells. Every ASIC manufacturer could create functional blocks with known electrical characteristics, such as propagation delay, capacitance and inductance。我還要感謝我的同學(xué)，一個(gè)畢業(yè)設(shè)計(jì)中所需要了解和學(xué)會(huì)的知識(shí)有很多，一些我來不及學(xué)習(xí)的知識(shí)點(diǎn)通過對(duì)其熟悉的同學(xué)我才能很快的掌握。由于時(shí)間倉(cāng)促，再加上本人水平有限，雖然設(shè)計(jì)基本完成，但仍有很多不足甚至錯(cuò)誤之處，望各位老師能夠不吝賜教，加以斧正，謝謝！致謝 首先，我要向我的指導(dǎo)老師——孫虹老師表示衷心的感謝，感謝她一個(gè)學(xué)期的耐心指導(dǎo)，使得我從對(duì)畢業(yè)設(shè)計(jì)的茫然甚至擔(dān)憂到現(xiàn)在最終獨(dú)立完成。最后簡(jiǎn)單介紹和比較了生產(chǎn)實(shí)踐中液位控制使用的儀表過程控制方法和計(jì)算機(jī)過程控制方法。計(jì)算機(jī)控制系統(tǒng)除了擁有過程儀表控制的一般特點(diǎn)外，不需要人在生產(chǎn)現(xiàn)場(chǎng)，改善了勞動(dòng)條件，不用人工手動(dòng)操作，消除了人為因素；易于現(xiàn)代化管理和產(chǎn)品質(zhì)量分析；采用表格、圖形、曲線顯示直觀，并有輸出打印功能。計(jì)算機(jī)控制相對(duì)與儀表控制，其主要特點(diǎn)是：1）儀表控制系統(tǒng)中均使用模擬部件，而計(jì)算機(jī)控制系統(tǒng)除了檢測(cè)、變送裝置，執(zhí)行機(jī)構(gòu)等常用的模擬部件之外，其執(zhí)行控