Table of Contents
C compilers
SunPlus released sources for the C compiler. It doesn't include the assembler and is based on GCC 2.95 so quite hard to compile: https://github.com/vsmile-dev/unsp-gcc
µ'nSP IDE is the official IDE for the CPU used. It can still be downloaded from GeneralPlus website - local copy
Assemblers
XASM is the original assembler provided by the µ'nSP IDE
naken_asm has support for µ'nSP and provides a standard include file for SPG200 registers.
Work in progress patch to add µ'nSP support in vasm. There are problems in vasm handling the pure 16-bit CPU, I have asked the vasm developers for help solving that.
This early homebrew experiment took an interesting approach of not using an assembler at all.
Emulators
MAME has good support for the V.Smile.
Unununium is a standalone emulator, but is known to have some bugs.