INES Mapper 143

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iNES Mapper 143 denotes an NROM circuit board with a simple form of protection:

  • Dancing Blocks
  • Magical Mathematics (NTSC version only)

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 console's 2K of internal RAM to a different pattern than Nestopia's default.