The Testbench

Methodology Manual For FPGA-Based Prototyping Is Win-Win

In design automation, methodology counts for a lot. Methodology is, loosely put, how to do things. There are right ways to do things and there are wrong ways. Methodology miscues in EDA flows can end up costing you large sums of money, especially when they are made early in the design process. Conversely, correct methodologies can not only save money but also greatly enhance the making of it. Again, this applies even more so in the earliest stages of the process; decisions made then cost a lot more to correct later if they prove wrong.

This is why a new methodology for FPGA-based prototyping, produced jointly by Synopsys and Xilinx, is an important piece of news. Methodologies like this are usually a win-win situation. The vendors do not produce them strictly out of the goodness of their hearts, of course. Their hope is that with a clearly defined methodology that involves Synopsys tools and Xilinx silicon, designers will be inclined to gravitate toward their products and away from those of other vendors for whose products there is a less clearly delineated methodology.

Thus do the vendors win, but so do their customers by virtue of a means of avoiding those early methodology miscues. FPGA-based prototyping is becoming a critical aspect of design flows, fueled by the growing complexity of systems and the importance of software as a differentiator. No one can afford to wait until silicon is available to debug software. It has been estimated that in a given system-level design project, there are 100 or more software bugs for every hardware bug. This amplifies the need for a system-level platform for early joint test and debug of how the hardware and software and there is no better way to do this than on FPGAs.

Synopsys and Xilinx's FPGA-based Prototyping Methodology Manual (FPMM) is the product of three authors, Doug Amos and René Richter of Synopsys and Austin Lesea of Xilinx. Corporate contributors included Freescale Semiconductors, LSI, STMicroelectronics, and Texas Instruments, among others. A 40-member review council oversaw the material.

As it stands, FPGA-based prototyping certainly has many advantages for pre-silicon validation of embedded software. You gain real-time interfaces, cycle-accurate simulation, and high speed. It's a great platform for working out the kinks in a multicore implementation. The prototypes are portable and easily replicated.

However, there are disadvantages too. One is the need for FPGA expertise that may or may not be available. Another is that a given design often must be partitioned across several FPGAs, making it difficult to achieve real-world SoC speeds. Debug is difficult. RTL must be available, and not only that, but the RTL ideally should be optimized for FPGA implementation.

How can we improve on this state of affairs? That's where a methodology based on proven best practices comes in. The point of "best practices" is, of course, the avoidance of procedures that produce less successful results. Ultimately, the goal is to arrive at procedural improvements that lend themselves to what Synopsys and Xilinx term "design for prototyping." The most successful teams, the manual asserts, are those who integrate the prototypers with the RTL designers. Moreover, at larger companies it's not uncommon to find multiple teams engaged in prototyping on the same project. It is incumbent upon them to all use the same platform to avoid waste and encourage reuse.

The FPMM is available in book format; as with Synopsys' previous methodology manuals, it's self-published by Synopsys Press. In 500 pages and 15 chapters, the book begins with an introduction to FPGA-based prototyping, moving on to its benefits and currently available tools. From there it moves through the design of a prototyping flow, a treatment of the classic build-vs.-buy decision, and extensive how-to chapters. It concludes with a look at the future of prototyping.

An important aspect of the FPMM is an extensive online component. This is where Synopsys and Xilinx hope to continue the conversation between prototypers worldwide and to establish a forum for information exchange as well as a repository of best practices going forward. The book is a free download, or printed copies can be purchased through online retailers.

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