Developing a uPD1771C instruction-level CPU driver

[ReverendGumby]

I'm a week into developing an improved MAME driver for the NEC uPD1771C sound chip. (This chip is used by the Super Cassette Vision [scv] and Advanced Personal Computer [apc] machines.) I've been reverse-engineering the chip from a die shot, and saw an opportunity to contribute to this project before the knowledge left my head.

As the code stands today, it can run the -017 ROM from the SCV variant. The main improvement is that games that play ADPCM samples (e.g., Star Speeder) are now playable.

I will continue adding missing features, some of which might be useful on other ROM variants. Hopefully someone out there can help test them and give feedback.

Link to git repo: https://github.com/ReverendGumby/mame/tree/upd1771c-cpu