I've been dreaming up a design for a flash cart, and I've come up with a few questions which might affect the cost or possibility of actually building it.
My design currently has at its core a "magic box" which needs to be filled in with an actual component. I have it handling all connections between the NES cart bus and the various onboard ROMs and RAMs. If I added correctly, interfacing the cart bus with a 512KB PRG, 512KB CHR, and 8KB WRAM would require 119 (!!) I/O lines.
On to the actual questions:
1. Is there any kind of (cheap) programmable logic that loads its behavior from an external memory and has at least 119 I/O lines?
Do I really need that many I/O lines? Can I get away with multiplexing the buses somehow? If I get a chip with that many pins, I'll have to learn how to solder surface-mount by hand, which I've heard can be a pain.
2. Where can I find information on MMC/SD cards? From my searching, it seems that SD cards should support the older (and more open) MMC standard, but I haven't been able to find any documentation on interfacing with an MMC card.
3. Will I be able get my controller chip and the MMC/SD interface to work using only +5V and ground?
4. Where online can I get a few custom boards made? Is there any free PCB design software available? How many layers might I need for all of those I/O lines?
Thanks in advance to anyone who can help. I have this vision for my flash cart, but I don't have the knowledge to build it yet.
My design currently has at its core a "magic box" which needs to be filled in with an actual component. I have it handling all connections between the NES cart bus and the various onboard ROMs and RAMs. If I added correctly, interfacing the cart bus with a 512KB PRG, 512KB CHR, and 8KB WRAM would require 119 (!!) I/O lines.
On to the actual questions:
1. Is there any kind of (cheap) programmable logic that loads its behavior from an external memory and has at least 119 I/O lines?
Do I really need that many I/O lines? Can I get away with multiplexing the buses somehow? If I get a chip with that many pins, I'll have to learn how to solder surface-mount by hand, which I've heard can be a pain.
2. Where can I find information on MMC/SD cards? From my searching, it seems that SD cards should support the older (and more open) MMC standard, but I haven't been able to find any documentation on interfacing with an MMC card.
3. Will I be able get my controller chip and the MMC/SD interface to work using only +5V and ground?
4. Where online can I get a few custom boards made? Is there any free PCB design software available? How many layers might I need for all of those I/O lines?
Thanks in advance to anyone who can help. I have this vision for my flash cart, but I don't have the knowledge to build it yet.