FPGA-based system-on-chip platforms are the etch-a-sketches of embedded design.  You can quickly sketch out your embedded computing system, use it, and easily erase and re-construct it in place as design changes are required.  Need a different peripheral?  No problem, just reprogram it.  Need to change a protocol – another simple hardware and software modification.  Want to use a different processor core – or an additional one?  Just drop it in and re-program the chip.  Your same board keeps right on working.

Actel is the alternative FPGA supplier.  On the FPGA vendor playground, their technology would be the ones with the punk hairdos, tattoos, and piercings, while the other FPGAs ran around in their matching crew-cuts, polo shirts, and jeans.  Actel has chosen non-volatile technologies such as flash and antifuse for thier FPGAs, compared with the industry standard SRAM-type implementation.  As a result, their FPGAs tend to be stingy with power, minimize the part count (as in – one), and have reasonable performance and density.

Flash–based FPGAs are usually a process node or two behind SRAM on the technology curve, however, and that tends to mean lower-density devices than other manufacturers supply.  Flash-based devices have only recently reached density levels where it is practical to construct an entire system-on-chip platform on a single device.  In response to that milestone, Actel has added a plethora of processors, peripherals, software, and design tools to their offering to facilitate the construction of embedded system-on-chip designs on their flash-based FPGAs.  Their ProASIC3, Fusion, and Igloo devices all have the capabilities to support the inclusion of soft-core embedded processors into their FPGA programmable fabric.

Unlike many of the FPGA suppliers, Actel has chosen to go primarily with industry-standard processor architectures such as ARM rather than introducing their own new proprietary architectures.  In their recent processor roadmap announcement, Actel now boasts a lineup of both 8-bit microcontrollers and 32-bit RTOS-ready RISC cores.

Starting at the high end, you can plop down Actel’s version of the ubiquitous ARM7 processor – CoreMP7.  Actel’s licensing of the ARM processor cores is unique and simple – only a specially-licensed version of Actel’s chips can accept the ARM cores, and the royalties are pre-paid as part of the cost of the device.  The 32-bit ARM core can connect with a variety of peripherals via the AMBA bus, which provides wide-ranging IP interoperability. 

Actel also offers a version of the Gaisler Research LEON3 32-bit processor core, which is based on the SPARC V8 architecture.  The LEON3 core is popular in high-reliability applications such as military and aerospace – markets where Actel has always maintained a strong presence with their high-rel antifuse FPGAs. 

On the 8-bit side, Actel has long offered support for soft-core embedded versions of the venerable 8051 processor – a magnet for legacy board-based embedded systems wanting to integrate into a lower-cost, lower-power, smaller form-factor single-chip solution.

Actel’s Core8051 and Core8051s are both compatible with the instruction set of the 8051 microcontroller and preserve the three conventional 8051 software memory spaces, allowing the use of standard compilers.  Even implemented as soft-core FPGA blocks, both versions are significantly faster (Actel claims more than 30X faster) than legacy 8051 processors.  The “s” version is smaller, giving up a few of the more area-expensive capabilities in exchange for a smaller footprint on the FPGA.  The combination of these compatibilities means that it is fairly straightforward to migrate legacy 8051 applications to an FPGA-based SOC – dramatically lowering costs and improving performance.

Moving down the size scale we find Actel’s new, tiny, CoreABC.  CoreABC uses a miserly 241 tiles in the FPGA fabric, and it is intended primarily for programmable-controller applications requiring a small number of executions, very fast execution, and extremely small form factor.  CoreABC is actually a soft-configurable state machine, requiring no on-chip memory and connectable via the advanced peripheral bus (APB) interface.  The core is free to use, and according to Actel it uses only $0.10 worth of FPGA fabric.  CoreABC is delivered as part of Actel’s CoreConsole 1.2.1.   

CoreConsole is Actel’s processor system hardware development toolkit.  It is Actel’s cockpit for embedded system creation and configuration.  From CoreConsole, you choose processor, bus, peripherals and other IP.  You can use IP provided by Actel and their partners (some of which require separate licenses) or add your own SPIRIT-compliant IP to the library.  The output of CoreConsole is RTL with protected IP included as black-boxes.  CoreConsole also generates system and IP test benches to get your verification and debug process jump-started.

Using CoreABC is a fairly straightforward process.  Its robust GUI requires virtually no training, and you can stitch together a system in minutes (even if you’re an out-of-practice ex-engineer journalist).  The already comprehensive IP library is still growing, and the system provides easy access to both free and licensed/protected IP blocks.

On the software side, CoreConsole’s counterpart is called “SoftConsole”.  SoftConsole uses an Eclipse-based IDE and provides C/C++ programming and debug for Actel’s 8051 and ARM offerings.  It also includes an FS2 in-circuit debugger that facilitates software debug directly on the target FPGA platform.  SoftConsole supports RTOS, including µC/OS and µClinux – the embedded microcontroller flavor of the popular open-source operating system.  It also supports a variety of stacks such as TCP/IP, USB, and IPMI. 

Actel has partnered with a number of third parties to provide the necessary tools, IP, RTOS, APIs, and drivers to make their embedded platform offering credible.  The result is an end-to-end embedded design platform where processors, peripherals, memory, OS, and software can all be integrated as single-chip systems on reprogrammable FPGAs.  Because the cost of system-capable FPGAs has dropped significantly in the past few years, an FPGA-based platform is even a viable option for higher-volume cost-sensitive applications.  The time-to-market, time-in-market, and system flexibility advantages can be truly compelling when compared to fixed-hardware solutions. 

Actel’s range of FPGA platforms includes one-time programmable antifuse devices for high-reliability applications as well as reprogrammable flash devices.  Over the past few years, their flash offering has expanded to include flash FPGAs, ARM-core enabled flash FPGAs, mixed-signal analog/digital flash FPGAs, and, most recently, low-power flash FPGAs suitable even for handheld, battery-powered applications.  The combination of these hardware platforms with the ready availability of a comprehensive set of embedded platform IP make an interesting alternative option for many system designs.