INES Mapper 143
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.