【正文】 ellent 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 database(Library).These 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 in 20 centuries, calculator assistance manufacturing(CAM), calculator assistance test(CAT) and calculator lend support to the concept of engineering(CAE) a development since EDA technique is to take calculator as tool, design at EDA software terrace up, use the hardware description language HDL pletion a design a document, then is of oneself pleted logic to edit and translate, turn Chien, partitioned by the calculator, prehensive, excellent turn, set up, cloth line with imitate really, until for particular target chip of proper go together with to edit and translate, the logic reflect to shoot with plait distance download etc. EDA technical emergence, biggest raised efficiency and maneuverability of electric circuit design, eased to design of labor strength. These spare parts can pass a software plait a distance but as to it39。s hardware structure and work the way carry on heavy Gou and make thus the design of hardware can like software design so convenient all these biggest changed a traditional numerical method, design process of the system design and design idea and promoted the EDA technical quick development. The EDA is an electronics design automation(the Automation of the Electronic Design) of abbreviation, design(CAD) from the calculator assistance at the beginning of 9039。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 wi