User:Zzo38/Mapper G

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Revision as of 01:21, 20 January 2014 by Zzo38 (talk | contribs) (Created page with "Category:GNROM-like mappers This is a generic GNROM-like mapper. The NES 2.0 header is required for its use. There must be at most one of CHR-ROM, CHR-non-battery-RA...")
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This is a generic GNROM-like mapper. The NES 2.0 header is required for its use.

There must be at most one of CHR-ROM, CHR-non-battery-RAM, CHR-battery-RAM. There also must be at most one of PRG-non-battery-RAM and PRG-battery-RAM. If no CHR ROM/RAM is present, then CIRAM is used, similar to iNES Mapper 218, but without the one-screen modes.

PRG RAM can be mapped at $6000-$7FFF if it exists. If there is more than 8K, the CHR bank numbers are used to select PRG RAM banks (in addition to CHR banks, if applicable; it doesn't matter if one is more than the other or less or equal).

The high bit of the submapper number (bit3) is used to designate whether PRG or CHR is shifted (PRG if set, CHR if cleared); the other is starting the low bit on the right side.

The low three bits of a submapper number tells how much it is shifted by, from zero to seven. It is possible to overlap. If it overflows on the left then it wraps around.

Submapper 0 is reserved and should not be used.

Example:

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