INES Mapper 143

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GoodNES, Nestopia, and Санчез say that iNES Mapper 143 is “just NROM games [with] a pathetic form of copy protection in them.” Games include Dancing Blocks and Magical Mathematics.

The functional description is consistent with a 74138 and a 74368.

Reads from these addresses produce this output:

A:[010. ...1 ..DD DDDD] -> [xxii iiii]
               || ||||      |||| ||||
               ++-++++------||++-++++-- reads provide the logical inversion of DDDDDD in the bits iiiiii
                            ++--------- open bus

Nestopia additionally implies that at least Dancing Blocks relies extensively on the values of uninitialized memory, and so manually sets the emulated famiclone's 2K of internal RAM to a different pattern than Nestopia's default.