NES 2.0 Mapper 263 is used for an MMC3 clone with scrambled mapper address and data bits. Its UNIF board name is UNL-KOF97. It is used for two games by Rex Soft:
A12 is used for the MMC3's A0:
Mask: $F000
Mapper 263 Regular MMC3 address address ---------- ------------ 8000 8000 9000 8001 A000 A000 B000 A001 C000 C000 D000 C001 E000 E000 F000 E001
The data written to the MMC3 clone has the following bit order compared to a regular MMC3:
Written bit 76543210
--------
Actual bit 76243051
Which means that to get from the written data to the actual data, the following operation must be performed:
Val =(Val &0xD8) | ((Val &0x20) >>4) | ((Val &4) <<3) | ((Val &2) >>1) | ((Val &1) <<2);
Categories: MMC3-like mappers