And what about the software guys and gals?

Actually, the software fraternity is the primary target of this book, because the techniques described allow software-centric engineers to take advantage of the massive amount of parallelism inherent in a dedicated hardware implementation while still using a software development methodology.

Perhaps not surprisingly, the majority of software development engineers writing C code for digital signal processing (DSP) and embedded applications tend to regard "raw hardware" in the form of an FPGA with anything ranging from trepidation (on a good day) to outright loathing. But fear not, my braves, because "there's nothing to fear but fear itself," as my dear old dad used to say.

In the case of someone tasked with creating a DSP application, for example, the majority of DSP code first sees the light of day in C. As horrendous as it seems, once the algorithms have been verified at this level of abstraction, a large proportion of the code gets rewritten and "tweaked" in assembly code in a desperate attempt to achieve the required performance. This manual translation is, of course, both painful and time-consuming.

The bigger problem is that the DSP code will eventually be run on a general-purpose microprocessor or a dedicated DSP device. Both of these realizations are inherently slow, because they are based on a classical von Neuman architecture, which requires them to

• Fetch an instruction

• Fetch a piece of data

• Fetch another piece of data

• Perform an operation

• Store the result

  :

• Do the same thing all over again

Now, consider a typical DSP-like function along these lines:

y = (a * b) + (c * d) + (e * f) + (g * h);

If you run this through a DSP chip, it will take a substantial number of operations and clock cycles to execute. Now consider an equivalent dedicated hardware implementation in an FPGA, in which all of the multiplications are performed in parallel without the need to fetch and decode the instructions. This results in orders-of-magnitude speed improvement.

Thus, one of the purposes of this book is to show you how to take your C code representation and use it to "program" an FPGA to implement your algorithms directly in hardware.

These techniques are not limited to DSP applications; they are also of interest to embedded applications developers in general. The concepts described in this book allow you to view all or part of an FPGA as being "just another programmable core." The difference is that, instead of running your code on an embedded (soft or hard) microprocessor core, you can now decide to implement appropriate portions of the code directly in hardware to achieve phenomenal increases in performance.