The Game Genie ROM replacement was successful and now my Game Genie runs a bootloader at power, ready to communicate with the PC. From there the PC can run any code out of NES RAM.
The PC can write to Game Genie registers, and disable it so that the game plugged in (if any) is accessible. Its ROMs can be dumped, or code can be run out of NES RAM or any RAM on the cartridge, and use the cartridge mapper. Interrupt vectors can be routed to RAM, so that the running code can use IRQ and NMI. I'll have to make sure the romless program format works well with this, as this is the perfect way to run code on anything.
I desoldered the Game Genie ROM, soldered in a 28-pin socket, and used a 2732A 1KB EPROM as a replacement. Programming the EPROM was frustrating, since I lack a proper programmer and had to rig one up on a breadboard. Further, I don't have a UV eraser, and the EPROMs I had already had code on them, so I had to fit things into the unused spaces. Plus getting the bugs out of the writing routine caused even more garbage.
Once I've played around more with this I'll see about making a ROM that has the original Game Genie ROM as well as the bootloader (argh, after looking at the Game Genie ROM, there's no apparent free space in it). Thanks to clueless for the idea and posting the image of a Game Genie that caught my interest.
The PC can write to Game Genie registers, and disable it so that the game plugged in (if any) is accessible. Its ROMs can be dumped, or code can be run out of NES RAM or any RAM on the cartridge, and use the cartridge mapper. Interrupt vectors can be routed to RAM, so that the running code can use IRQ and NMI. I'll have to make sure the romless program format works well with this, as this is the perfect way to run code on anything.
I desoldered the Game Genie ROM, soldered in a 28-pin socket, and used a 2732A 1KB EPROM as a replacement. Programming the EPROM was frustrating, since I lack a proper programmer and had to rig one up on a breadboard. Further, I don't have a UV eraser, and the EPROMs I had already had code on them, so I had to fit things into the unused spaces. Plus getting the bugs out of the writing routine caused even more garbage.
Once I've played around more with this I'll see about making a ROM that has the original Game Genie ROM as well as the bootloader (argh, after looking at the Game Genie ROM, there's no apparent free space in it). Thanks to clueless for the idea and posting the image of a Game Genie that caught my interest.