And I forgot to mention earlier about saving on this cart, it is intended that PRG-ROM is used for save data. Battery-backed SRAM may be faster to write, but the bad part is how easily the data gets corrupted, without using a real NVRAM controller. I've only found one cheap IC that is simply an NVRAM controller, but it's long out of production - most newer ICs that handle it cost too much because they include a lot of other features (like real time clock, CPU reset generator, watchdog timer). First time I made it to Chaos in Final Fantasy, my dog's tail hit the NES which erased my save (real life watchdog reset?), I think using FlashROM can put a stop to crap like that. Just don't bump it WHILE it's saving, but in practice you would probably want to keep 2 copies in memory, to revert to a backup if the first has failed.
Since the sector size for the Flash is 4kB, that means you can program individual bytes in whatever order you want (you could leave $FF "blank" bytes in your data and fill them in later, for example), but when you erase, it is done in 4kB-sized blocks. On the original Squeedo design it was 64kB sectors, that was a little inconvenient for NES, heheh. But, in theory a game saving to flash could be 128kB, and have 384kB of saved data! Who knows what for, but it may be a good way to write a live level editor on the NES or other stuff.
Since the flash endurance question usually comes up too, here is the calculation for that - 100k erase cycles - a player could save 10 times a day, every day, for 27 years straight. Use 2 sectors for saving and it's 54 years, and so on.
Yeah Famicom exp port is really close to be being a normal DA15 connector, but I don't think they can be bought without the metal flange. At least it's not something totally alien like the NES exp port.Good to hear about the famicom thingy. I forgot about the attached controllers so you cannot use it for debugging (except with an AV famicom) and the expansion port is different.