VHDL and Verilog? HDL are high level description languages for system and circuit design. These languages support various abstraction levels of design， including architecture-specific design. At the higher levels， these languages can be used for system design without regard to a specific technology. To create a functional design， you only need to consider a specific target technology. However， to achieve optimal performance and area from your target device， you must become familiar with the architecture of the device and then code your design for that architecture. Efficient， standard HDL code is essential for creating good designs. The structure of the design is a direct result of the structure of the HDL code. Additionally， standard HDL code allows designs to be reused in other designs or by other HDL designers. This document provides the preferred coding styles for the Actel architecture. The information is reference material with instructions to optimize your HDL code for the Actel architecture. Examples in both VHDL and Verilog code are provided to illustrate these coding styles and to help implement the code into your design. For further information about HDL coding styles， synthesis methodology， or application notes， please visit Actel’s web site at the following URL： http://www.actel.com/