Casio’s FX-CG, or Prizm, is a rather interesting device, and the programmers over on Cemetech seem to have found it worthwhile to make the Prizm do their bidding in software.
The Prizm device itself is based around some sort of SuperH core,
identified at times in the system software as a SH7305 a “SH7780 or
7780 is not an
exact device, though, and it’s likely a licensed
core in a Casio ASIC. Whatever the case, GCC targeted for sh and compiling
without the FPU (-m4a-nofpu) and in big-endian mode (-mb) seems to work on the
Between Jonimus and myself (with input from other users on what configurations will work), we’ve assembled a GCC-based toolchain targeting the Prizm. Jon put together a cross-compiler for sh with some supporting scripts, while I contributed a linker script and runtime initialization routine (crt0), both of which were adapted from Kristaba’s work.
With that, we can build binaries targetting sh and linked such that they’ll run on the Prizm, but that alone isn’t very useful. Jon also created libfxcg, a library providing access to the syscalls on the platform. Finally, I created mkg3a, a tool to pack the raw binaries output by the linker into the g3a files accepted by the device.
Rumor has it the whole set of tools works. I haven’t been able to verify that myself since I don’t have a Prizm of my own, but it’s all out there. Tarballs of the whole package are over on Jon’s site, for anyone interested.