【正文】 its with stronger real strenght, it is also use to design ASIC. The VHDL mainly useds for the structure, behavior which describes numerical system, function with addition to implying many languages sentence which have a hardware characteristic, VHDL languages forms and description style and sentence construction are very similar at general calculator deluxe procedure structure characteristics is an engineering design, or call that the design entity(can be a ponent, an electric circuit mold piece or a system) is divided into exterior(or call but part, and port) with inner part(or call to can39。t see part), since involve internal function and calculate way of entity to plete part to 1 designed entity to define exterior interface after, once it internal development pletion after, other designs can directly adjust to use this kind of will design entity to be divided into a little bit basic VHDL system that is a VHDL system inside the concept of outside part design design of a little bit basic and other hardware describe the language pare and the VHDL has a following characteristics:The function is strong and the design be VHDL has the function strong language structure, can describe a plicated logic control with the simple and direct and explicit source has a multilayer design description function, in multiple layers thin turn, finally directly born electric circuit class VHDL supports synchronous electric circuit, difference39。s tread electric circuit with random the design of electric circuit, this be the other hardware description although the language can39。t pare VHDL still supports various design method, since support from the bottom upward design, support again from the design of crest declivity。Since the support mold piece turns a design, support layer39。s turn a design again. Support extensively and be easy to a the VHDL has already bee IEEE standard the norm of hardware description language, most EDA tools almost support VHDL currently, this is VHDL of further expansion with extensively applied lay the design process of the hardware electric circuit, the main design document is the source code which writes with the VHDL, the VHDL easily reads with the structure turn, so be easy to a modification design. The strong system hardware describes VHDL has a multilayer design description function, since can describe system class electric circuit, can describe door class electric circuit description since can adopt a behavior description, deposit a machine to deliver description or structure description, can also adopt the hybrid description of threes , VHDL support is inertial to delay and deliver to delay, can also accurately build up hardware electric circuit support prepare definite of with from definition of data type, bring hardware description a bigger freedom degree, make design the personnel can expediently establish the system model of high time. The independence is at the design of spare part, have nothing to do with the 39。t need to consider a choice pletion the spare part of design first while designing a personnel to carry on a design with the VHDL, can concentrate energy to carry on design of excellent the design description plete after, can carry out its function with various different spare part structure. Very strong transplantation VHDL is a kind of hardware description for standardize language, the same of design description can be support by the different tool and make to design to describe of the transplantation make possible. Be easy to a share and reply to VHDL adoption can build up various mold piece that can again make use of according to the design method of canned in advance design or use to design a medium backup mold a piece before and depositted these to the database in, can be in laterly of the design carry on replying to use, can make the design result be design the personnel39。s to carry on exchanges and share, decrease hardware electric circuit design. (1) pared with other hardware description languages, the VHDL have stronger behavior description ability, e to a decision him to bee a system design realm the best hardware a description language strong behavior description ability is to avert from concrete spare part structure and describe and design important assurance of largescale electronics system from the logic behavior. (2) the VHDL be abundant of imitate true language sentence and database function, make in any big system of the design can inspect a function possibility of design the system in early days, can carry on imitating true emulation to the design at any time. (3) the ability and procedure structure of the behavior description with lexical VHDL e to a decision the deposition that he has to support a largescale design with have already have design of again make use of the market demanding largescale system efficiently, the pletion of the high speed has to include many people the several generation hair set even together and abreast works and then can carry out. (4) for use the design of an assurance of VHDL pletion, can make use of EDA tool to carry on logic prehensive with excellent turn, and auto of the VHDL describe the design change into the door class net form.(5) the description of VHDL to design have opposite and independent, the design can not understand the structure of hardware and need not manage the target spare part that the end design carry out, either is what, but carry on an independent design.EDA的發(fā)展及VHDL的應(yīng)用20世紀(jì)90年代，國際上電子和計算機(jī)技術(shù)較先進(jìn)的國家，一直在積極探索新的電子電路設(shè)計方法，并在設(shè)計方法、工具等方面進(jìn)行了徹底的變革，而且取得了巨大成功。在電子技術(shù)設(shè)計領(lǐng)域，可編程邏輯器件（如CPLD、FPGA）的應(yīng)用，已得到廣泛的普及，這些器件為數(shù)字系統(tǒng)的設(shè)計帶來了極大的靈活性。這些器件可以通過軟件編程而對其硬件結(jié)構(gòu)和工作方式進(jìn)行重構(gòu)，從而使得硬件的設(shè)計可以如同軟件設(shè)計那樣方便快捷。這一切極大地改變了傳統(tǒng)的數(shù)字系統(tǒng)設(shè)計方法、設(shè)計過程和設(shè)計觀念，促進(jìn)了EDA技術(shù)的迅速發(fā)展。EDA是電子設(shè)計自動化的縮寫，在20世紀(jì)90年代初從計算機(jī)輔助設(shè)計、計算機(jī)輔助制造、計算機(jī)輔助測試和計算機(jī)輔助工程的概念發(fā)展而來的。EDA技術(shù)就是以計算機(jī)為工具，設(shè)計者在EDA軟件平臺上，用硬件描述語言HDL完成設(shè)計文件，然后由計算機(jī)自動地完成邏輯編譯、化簡、分割、綜合、優(yōu)化、布局、布線和仿真，直至對于特定目標(biāo)芯片的適配編譯、邏輯映射和編程下載等工作。EDA技術(shù)的出現(xiàn)，極大地提高了電路設(shè)計的效率和可操作性，減輕了設(shè)計者的勞動強(qiáng)度。利用EDA工具，電子設(shè)計師可以從概念、算法、協(xié)議