jsgroth
commented
3 weeks ago The HuC-3 ROM/RAM banking and RTC are now emulated, which is enough for Robopon to work.
The following features of this mapper are not currently emulated:
- The speaker built into the cartridge and the associated tone generator
- The IR sensor built into the cartridge
- Some sort of alarm/event functionality related to the RTC that is not well-documented (or maybe just not well-understood)
The mapper byte in the header is $FE which is Hudson's custom HuC-3 mapper, not currently emulated: https://gbdev.io/pandocs/HuC3.html
This seems to be the only HuC-3 (or HuC-1) game that released outside of Japan.
The ROM/RAM banking looks trivial to emulate (it's basically the same as MBC3/MBC5), but this mapper has a real-time clock with a much more complex command/communication protocol than the MBC3 RTC. There's also a builtin speaker with a tone generator that doesn't seem to be well-understood/documented - this GBDev thread suggests that the tone generator behavior comes from a microcontroller program ROM that likely varies between different HuC-3 cartridges.
I'm probably not going to try to emulate the speaker/tone generator but the rest of this mapper seems doable.