MottZilla wrote:
I don't think the mapper files for the FPGA would be useful for a CPLD. However I think the source code (if that's the correct term) for those mapper files could be adapted for use in a CPLD.
Most mappers are not terribly complex. Sure there are ones that are alot more work though. For example any mapper with behaviors other than mapping memory like MMC2's CHR Bank Switching on certain PPU reads is a bit more tricky. Then mappers with IRQ generation like MMC3's scanline counter. Then you have mappers that provide extra sound channels and finally the beast that is MMC5 which does a million things compared to other mappers.
I think it's wrongly assumed by many that just because RetroZone doesn't offer repro PCBs for MMC3 or other mappers that it isn't possible or they would have trouble doing it. This is not true.
For that matter, anyone that can design a PCB and figure out how to design for a CPLD could make their own MMC3 production boards. In my opinion the hardest part of doing so would be getting IRQ behavior done. Or atleast done right. If you were going to produce anything other than bootlegs though, it might be in your interest to see about making an operationally compatible Scanline Counter IRQ but actually use a method that would not interfere with using Sprites from both sides of the Pattern Tables.
SkinnyV wrote:
Thanks for you reply, it was very informative! The mapper specific info is past my level though but it was till very interesting. CPLD and FPGA seem so fun to play around and I wish I could use them. I wonder how hard it is to start playing around with them but I figured you need to know how to program in order to do anything.
Also I suppose that RetroZone are not selling MMC3 repro board as most people would likely buy the board at a lower price and add the rom themself insted of buying the full game reproduction at full price...
This is really my goal with the NESDEV1 dev cart:
http://nesdev.com/bbs/viewtopic.php?t=7656&start=180
You're right about needing the source code MottZilla for anything from the powerpak to be useful for someone like us putting mappers onto a CPLD. The only one I know of currently is qbradq's source code for the FME-7. He posted it up on the wiki, but no ones had the hardware to test it out yet.
I want to make it so it's hardware is capable of replicating the MMC3 plus room for extras. I want it to be easy to program the CLPD via USB cord and free software. The idea is we could all share the source code on a wiki or somewhere that would allow people to use mappers others have created, modify someone else's work, or brew up your own complete mapper. But also allow quick programming of the "ROMS" for testing games on the console with similar hardware that would be used for repros.
It won't have MMC5 capabilities, because that would require a FPGA but a future version could.
It's challenging to get all the parts together as an individual especially if you're not learned up on hardware design which is the case for a lot of developers here. My goal is to make the hardware so the only thing to do to make it better is develop code that implements it and have everyone share