| Company | varies (homebrew) |
| Complexity | CPLD |
| Boards | unknown (homebrew) |
| PRG ROM capacity | 1024K |
| PRG ROM window | 4K |
| PRG RAM capacity | None |
| CHR capacity | 8K |
| CHR window | n/a |
| Nametable mirroring | Fixed H or V, controlled by solder pads |
| Bus conflicts | Not applicable |
| IRQ | No |
| Audio | No |
| iNES mappers | 031 |
iNES Mapper 031 represents a mapper created to facilitate cartridge compilations of NSF music. It implements a common subset of the features used by NSFs.
PRG-ROM is bankswitched in 8 x 4 kB banks from $8000-FFFF. These are controlled by registers at $5FF8-$5FFF like the NSF mapper. The high bank at $F000-FFFF is initialized to the last bank at power-on.
There is no CHR banking, so it is recommended to use 8 kB CHR-RAM with this mapper.
As with BNROM and UxROM, there is no mirroring, CHR bank, or IRQ control; this mapper has hardwired H or V mirroring.
Examples:
address data
15 bit 0 7 bit 0
------------------- ---------
0101 .... .... .AAA PPPP PPPP
||| |||| ||||
||| ++++-++++- Select 4 kB PRG ROM bank at slot specified by write address.
+++------------ Specify 4 kB bank slot at: $8000 + (AAA * $1000)
The canonical write position for these registers is $5FF8-$5FFF, as used in NSFs.
At power on, the register at $5FFF is set to $FF. Startup code should be placed in the last bank. There is no change to this register on reset.
Cartridges:
Categories: Mappers using $4020-$5FFF, INES Mappers, CPLD mappers