User:Zzo38/Mapper D

This mapper is designed to be possible to write a game that can run on both this mapper and the MMC5, even though most of the features of MMC5 aren't needed.

Registers

There are two (write-only) registers, and the address of the registers is as follows:

[..01 .... .... .?..]

Where the question mark selects the register.

Register 0 is the RAM bank register. All the bits are used to select a 8K RAM bank at $6000-$7FFF. (Assume 64K RAM if the NES 2.0 header isn't present.)

Register 1 is the ROM bank register. All bits except for the highest and lowest bit select a 16K ROM bank at $8000-$BFFF.

The last PRG ROM bank is fixed at $C000-$FFFF.

There will be bus conflicts if you write the register using the addresses which are in the ROM, so don't do that.