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You have SNES_RST as an input to the FPGA and you're not doing anything with it. Should this be an output to the cart and set low (assuming it's active high)?
What does SNES_ADDR(15) do?
And what actually sets SNES_ADDR on your board/cart? Is there software somewhere else that does this?
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The RST line I was trying with different code versions, to try and use it as a output_enable on the SNES lines. It didn't make a difference, so I commented it out (not shown in the code I pasted, my mistake).
SNES_ADDR(15) is a variable address that is only used (for the most part) when a game is accessed via HIROM mode. My test game is not HIROM, so A15 is not used. This instead routes FLASH pins A15-A21 to SNES pins A16-A22, which is needed for my test game to work. This also answers your last part, this address information is handled by the software in the ROM file.
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