Computer-assisted design continues to become a more powerful tool in digital and analog circuit design, especially using programmable integrated circuits. The different types and manufacturers of such devices fall into two main classes field programmable gate arrays (FPGAs) and field programmable analog arrays (FPAAs).

We will focus on digital circuits (FPGAs) using the most general process of design. However, the approach works well on all of the rest of the commercial CAD tools and can be applied to the analog devices (FPAAs) as well. C.A.

OVERVIEW

The use of CAD tools for programming digital circuits has dramatically increased the reusability, processing power, and reliability of digitally designed components. Currently field programmable gate array (FPGA) chips use very high-speed integrated circuits hardware description language (VHDL) to take advantage of these CAD tools in the programming of chips at the lowest gate level. VHDL has become an industry standard language, which is regulated by the Institute of Electrical and Electronic Engineers (IEEE). It is similar, with many conceptual changes described later in this section, to any other programming language (e.g., C, C++, visual basic). The companies that manufacture FPGA devices have software packages that can compile VHDL code that can be simulated or burned to a chip.

One of the potential benefits to VHDL over chip-depended software is the capability to migrate from one chip manufacturer to another. VHDL is an industrial standard language, therefore the software for each chip manufacture...