The art of FPGA construction

Gina R. Smith

January 06, 2008

Gina R. SmithJanuary 06, 2008

Working with FPGAs isn't intimidating when you know the basic techniques and options.

Over the last several years, the use of FPGAs has greatly increased in military and commercial products. They can be found in primary and secondary surveillance radar, satellite communication, automotive, manufacturing, and many other types of products. While the FPGA development process is second nature to embedded systems designers experienced in implementing digital designs on an FPGA, it can be confusing and difficult for the rest of us. Good communication is important when technical leads, supervisors, managers, or systems engineers interface with FPGA designers.

The key to good communication is having an understanding of the development process. A solid understanding will help you comprehend and extract relevant information for status reports, define schedule tasks, and allocate appropriate resources and time. There have been many times when my FPGA knowledge has allowed me to detect and correct errors, such as wrong part numbers or misuse of terms and terminology found in requirements and other documents.

Regardless of your final product, FPGA designers must follow the same basic process. The FPGA development stages are design, simulation, synthesis, and implementation, as shown in Figure 1. The design process involves converting the requirements into a format that represents the desired digital function(s). Common design formats are schematic capture, hardware description language (HDL), or a combination of the two. While each method has its advantages and disadvantages, HDLs generally offer the greatest design flexibility.

Schematic capture
Schematic capture, the graphical depiction of a digital design, shows the actual interconnection between each logic gate that produces the desired output function(s). Many of these logic-gate symbols involve proprietary information making them available to the designer only through the specific vendor's component library. Schematic capture designs that mainly consist of proprietary symbols make the design unrecognizable by competitors' FPGA development tools. The proprietary nature of this type of design makes it vendor dependent, and the entire design process must be repeated if a different vendor is used.

Examples of schematic capture tools are Viewlogic's ViewDraw and HDL's EASE. The main advantage of schematic capture is that the graphical representation is easy to understand. However, its major drawback is an increase in cost and time to reproduce a design for different vendors due to the design's proprietary nature.

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