Preface

This is a book about software programming for FPGAs. To be more specific, this book is about using parallel programming techniques in combination with the C language to create FPGA-accelerated software applications.

We have written this book to help bridge the gapthe great chasm, in factthat exists between software development methods and philosophies, and the methods and philosophies of FPGA-based digital design. We understand that as a result we may be writing for two quite different audiences: software application developers and digital hardware designers.

For software engineers, our goal is to present FPGAs as software-programmable computing resources. We hope to show that these devices, when programmed using appropriate methods, are not so different from other non-traditional computing platforms, such as DSPs. We will show, through example, that software development methods and software languages can be used in a practical way to create FPGA-based, high-performance computing applications, without a deep knowledge of hardware design.

For hardware designers our intent is similar, but with a caveat: we are not trying to replace your existing methods of design or suggest that the methods and tools described in this book represent a "next wave" of hardware engineering. After all, if you are an FPGA designer using VHDL or Verilog to create complex electronic systems, the title of this book, Practical FPGA Programming in C, may sound like an oxymoron. How can C, a software programming language, be a practical way to describe digital electronic hardware? The truth is, sometimes the explicit and precise descriptions offered by hardware description languages (HDLs) are essential to achieve designs goals. But, as you'll see, this explicit control over hardware is not always necessary. In the same way that you might first write software in C and then recode key portions in assembler, hardware designers can benefit from tools that allow them to mix high-level and low-level descriptions as needed to meet design goals as quickly as possible. Even when the entire hardware design will be eventually be recoded with a lower-level HDL, high-level design languages allow hardware engineers to rapidly explore the design space and create working prototypes.

So for you, the experienced hardware engineer, we'll state right up front that we agree with you. We do not believe that C and C++ (as used by legions of programmers worldwide) are practical replacements for VHDL, Verilog, or any other HDL. And we agree with you that C and C++ may not play a leading, or perhaps even significant, role as a design entry language for general-purpose ASIC and FPGA design, at least not as we know such design today. Nevertheless, we believe there is a place for C-based design in a hardware design flow. Still not convinced? Stay with us for a moment, and we'll explain.