Originally Posted by hap
I added a driver for the COP400 handhelds, see: http://git.redump.net/mame/tree/src/mess/drivers/hh_cop400.c

Lightfight is fully playable. Entex Space Invader and Mattel Funtronics Jacks are responsive and do some stuff right, but are very buggy overall.

I think the MCU emulation core is not perfect yet. I did fix some small bugs there(eg. Space Invader didn't boot at all at first), but I don't know enough of COP400 (yet) though to see where the problems are.
COP400 emulation core is here: http://git.redump.net/mame/tree/src/emu/cpu/cop400
Cool! I'm confident of all 3 of those dumps, since I did them electronically and compared hundreds (thousands even) of dumps of each chip. But there are probably a few bits wrong in Plus One since I dumped it visually. I'm going to clean the die in nitric acid and take more pics. Funtronics Red Light Green Light is on the way, and I bet it uses a COP410L, too.

When I used unidasm on the Entex Space Invader code, it didn't work quite right because the COP444L has a 2K address space. There might be other little differences between the 3 different COP chips used in those games.