We currently have dumps of both 68HC05 microcontrollers used on a Mono-II CD-i motherboard, one of SERVO, one of SLAVE. SERVO apparently controls the mechanics in the CD drive itself, and SLAVE manages the front panel and a few other miscellaneous tasks.
I'm banking on the idea that by emulating the two 68HC05s properly as well as their hookups, then the cdimono2 driver should boot far enough that we can figure out if there are any remaining issues in the DSP56k core that it uses for audio.
In the meantime, I'm tasking myself with coming up with a C-like decompilation of the 68HC05 programs. I'm starting on SERVO, and will post updates as I figure out more and more of the program code.
Here's what I've got so far: https://gist.github.com/MooglyGuy/4a0276e66c36e2ad8c4842c3b0b8c749