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毕业设计(论文)外文资料翻译系别：电子信息系专业：通信工程班级：B100308姓名：董又银学号：B10030802外文出处：HighWire Press附件： 1. 原文；2. 译文2014年03月外文翻译（英)DESIGNING A DIGITAL SYSTEM WITH VHDL The digital systems are complex ones,consisting of lots of components.As far as the automated design of such systems is concerned, methods for designing time reducing and limiting the complexity of the task are sought out and applied.A method of the kind is connected with the decomposition and hierarchy principles.The decomposition of the systems is realized in a way,which differentiates functionally independent modules.A digital system can be described as a module with inputs and/or outputs.The electrical values on the outputs are some function of the values on the inputs.One way of describing the function of a module is to describe how it is composed of sub-modules.Each of the sub-modules is an instance of some entity,and the ports of the instances are connected using signal s.This kind of description is called a structural description.In many cases,it is not suitable to describe the structure used.One element is a module,which is at the bottom of the hierarchy in other structures described.For example,if you are using store bought from IC IC package design a system,you do not need to describe the internal structure of the IC.In this case, the module performs the described function is required,without reference to its actual internal structure.This description is called the function or behavior description.Usually,for structural and behavioral description,either Verilog or VHDL is used.In this paper a designing with VHDL is presented.Here are exposed sequentially all the phases of the very digital system's designing.The main methods are also on show here.The project descriptions,types are presented.The stress is put on the use of VHDL for synthesis of structural and behavioral models.Here are presented several VHDL models of computer systems’ components.In digital systems design,and the design of complex systems,several commonly used methods:Top- down design , bottom- up designBottom- down approach in the design direction of the system is usually established from the start at the bottom,the preparation module design,formed by the assembly after the entire product.The advantage of this method is to use a functional block level to achieve a lowerlevel of the structure , process only error checking in the project during the simulation.Top-down design starts with the highest level of specification.Thereafter,the program is broken down into functional blocks,and the ratio of the input and output time may be specified.Functional model is through behavioral model or registration level model description,followed by a simulation.The advantages of this approach are:Standardized tasks easier to implement;Details need to deal with the structure,allowing the project to be checked at the institutional level;Without regard to its implementation,inspection items to complete.Allows for late design projects to choose technology.Since the most effective way is to use a top-down design and specify the order details the different levels of description summary description of the program.The next stage of digital systems design experience:the specification,features, physical design and manufacturing,testing.Through standardized product parameters to determine the correct goals.By function design,electronic design,the reference product specifications to develop the product functions and parameters.The behavior described in the stage of system solutions and conducted its entry and exit have been marked.In most cases,the use of VHDL pleting the main function of the function block(electrical)are designed to ually done by a detailed description of VHDL function blocks and checked by VHDL simulation.With the increasing complexity of the project,at the structural level,synthesis techniques need to be applied.Program contains the logic elements it needs to be a comprehensive description through VHDL language.Detailed description of such charge through the logic delay elements is the key method is specified,and defines the problem of time discrete signal.Physical design phase tightly dependent on technology.Deployment logic elements and definitions links between them(tracking) and common tasks are closely related.Under the conditions of implementation of programmable logic devices,you can use the CPLD or FPGA chip,the result then it means that the physical design of the resource profile design of the selected device.Test items represent some programmers use to provide:In between projects and norms remain moderate;mplementation of the technical aspects of the project selected.The progressive realization of the design process usually includes pre-designed part has been,until obtaining the desired targets.For the test,commonly used analog electrical design(product and its electrical parameters of the function)to carry out the task.Before choosing its actual hybrid module,analog behavioral level defines how the product will run. For behavioral patterns,you should use a hardware description language(vhdl language,Verilog language and other languages).Through simulation,at the level of the logical unit,from the basic logic elements "and not","NOR",converter and triggers to create a system,in order to identify its independence expected behavior.In functional tests, he delay is not related to or similar to all of them is the logic elements.After identification of the physical design error.The next step after the last procedure described topology:Check the specifications during the production process;Check the authenticity of the project.Are to be specified for the manufacturing process of each specification.The purpose of the project is to ensure the verification of the authenticity of the normal working of the prising:Identify the interconnection scheme;identify topological parasitic components.The design process,there are three types of design specifications can be used:behavior,structure,physical.Processing systems using behavioral description,the system is like a entrance and exit only"black box",regardless of its structure.The purpose is to ignore the redundant details,and is committed to a detailed description of the necessary features and specifications made products.At this stage,the use of HDL(hardware description language)-vhdl language,Verilog language and other languages.A description of the way the structure is defined as the way the system established.Here,the system configuration and the block to be processed is composed of their relationship,As well as a detailed description of the subsystem defined,is to provide its functionality and execution,and analysis of operating speed and charges.Schema can be used to describe the hardware description language , such as through electronic design.Design process and system description and specification details of its order conversion are closely linked.From the behavior description to the schema decomposition can achieve some level of the hierarchy.From the highest tothe lowest of these levels can be summarized as follows: the system level;functional level;logic level;plan level.The highest level of the system,the algorithm description of its function represented by the system behavior.These functions are performed in order to calculate the system architecture includes a microprocessor,memory,motherboard and other structural components.Lower levels of the system by Bolivia equation to describe the behavior of the system.Its implementation using logic elements and flip-flops.Once the entity has had its physical interface specified in the declaration,we can describe an entity or multiple architectures.Each module can be described as constituting a different view of the entity.Declaration defines the structure of the system will be used to describe the structural design of the project.Signal is used to connect the sub-module.The structure of the system can be described as a sub-module blocks.The module structure of a block unit,with its own interface,or connected to other blocks through the signal port.A signal allocation scheduler signal(or port)or more transactions.Main Unit VHDL behavioral description language is a process.When activating multiple processes at the same time,they are performed simultaneously.A process that can be used in a structure declaration or block.Statement can be used in the process is defined.A process that may include some signals given signal assignment statements,together constitute a signal driver.VHDL description write them in the design file.Then invoke the compiler analyze them and insert them into the library.Some VHDL language constructs can be included in the database were analyzed.These structures are called library units.Design files may contain some library unit.Behavioral model represents the functional interpretation of digital system design.Digital hardware device is considered a tight system.Its behavior is described as a series of operations . These actions will be applied within the database system.By creating behavioral VHDL model,describing the operation of the signal through the process and their interconnection.VHDL model is a means to reflect the structure of the project hierarchy.They establish the functional decomposition of a portion interconnected digital systems.These parts are shown as components and the interconnection between them through the signal.These signals are input, and can exit through the port assembly.Due to the increasing complexity of the project,on the logical schema element levelbecomes difficult,or even impossible.Therefore,a higher level of abstraction description should allow the best results,such as improved features,size and price.VHDL hardware description language is very suitable for this purpose,you can use the high-level behavioral description and a detailed description of the structure.VHDL language to develop specific programs to allow full functionality of the structure of the model can simulate,in order to assess its adequate specifications.Therefore,to ensure a higher quality project because errors and problems will soon be able to find at the start of the design process.外文翻译（中）VHDL实现数字系统的设计数字系统都是由复杂的大量组件组成的。