Executive summary: If you need an extremely efficient datapath and the flexibility of a programmable solution, you should check out Target's ASIP tools. 

The full scoop: Remember the story of the Goldilocks and the three bears?   Papa bear’s porridge was too hot, and mama bear’s porridge was too cold.  Goldilocks needed a third, in-between option… and baby bear’s porridge was just right!

Sometimes DSP hardware is like that.  Microprocessors are flexible but relatively inefficient.  A custom-designed, hard-wired datapath is efficient but inflexible.  Sometimes you need something in between—and that’s when you want an ASIP (Application Specific Processor).

The ASIP universe.  Image courtesy of Target Compiler Technologies.

ASIPs are like the baby bear of the processor world.  As the name suggests, ASIPs are specialized for a specific application, but they retain the programmability of a microprocessor.  The level of specialization in an ASIP can be modest—e.g., a general-purpose DSP can be considered an ASIP—or the ASIP can be highly tailored to an application.

ASIPs are sometimes sold as off-the-shelf chips, or you can design your own.  In either case, there’s a good chance you’ll use technology from Target Compiler Technologies. Target provides tools that make it easier to design and program ASIPs.

Target uses a language-based approach lets you design any kind of processor you want.  For example, you can define the native datatype to be a 12-bit complex number.  (NXP did just that with the CoolFlux DSP.)  This approach gives you more flexibility than you get with customizable processors like the Tensilica Xtensa 8.  Tensilica gives you a pre-defined architecture that you can customize by selecting check-box options and/or writing your own custom extensions.  Tensilica processors can be heavily customized, but you can’t modify the basic architecture.  This limitation has an upside, though: the basic architecture and check-box options are all pre-verified and worry-free, so it is easy to crank out a working processor.

Target’s language-based approach may not be as easy as using Tensilica's check-box options, but is way easier than writing hand-coded RTL.   (And this is the relevant comparison if you need a fully-custom datapath.)  With Target’s tools, the processor description is written a high-level processor modeling language called nML.  This language lets you write and change the architecture description with impressive speed.  For example, one of the company’s new hires was able to write a JPEG encoder in just 23 days.  At the same time, the language gives you a high degree of control over the data path, allowing you to achieve near-RTL efficiency.

The Target tool flow. Image courtesy of Target Compiler Technologies.

Programming your processor is also relatively straightforward.  Algorithms are written in ISO C with some C++ extensions and fed to an architecture-aware compiler.  (Target’s tools generate a custom compiler for your architecture.)  This is where Target gets its biggest advantage over RTL—if you write your own RTL, you’ll have to write your own compiler, use assembly code, etc.  Since development cycles are now dominated by software development, the lack of a compiler  is a major problem for hand-coded RTL.

One of the Target’s other points that it does not charge any royalties—just buy the tools and you’re done.  This is another contrast to Tensilica, which charges royalties for every chip you ship.

Bottom line: So are Target’s tools just right for you?  If you only need efficiency or programmability--but not both--the answer is probably no.  But if you need an extremely efficient datapath and the flexibility of a programmable solution, the answer is likely to be yes.  Target has lots of big-name licensees like NXP, TI, and ST, so if you chose Target’s tools you will be in good company.