INES Mapper 117

iNES Mapper 117 is used for Crayon Shin-Chan (Ch) and San Guo Zhi 4 - Chi Bi Feng Yun by Future Media.

Banks

• CPU $8000-$9FFF: 8 KB switchable PRG ROM bank.
• CPU $A000-$BFFF: 8 KB switchable PRG ROM bank.
• CPU $C000-$DFFF: 8 KB switchable PRG ROM bank.
• CPU $E000-$FFFF: 8 KB PRG ROM bank, fixed to the last bank.

• PPU $0000-$03FF: 1 KB switchable CHR ROM bank.
• PPU $0400-$07FF: 1 KB switchable CHR ROM bank.
• PPU $0800-$0BFF: 1 KB switchable CHR ROM bank.
• PPU $0C00-$0FFF: 1 KB switchable CHR ROM bank.
• PPU $1000-$13FF: 1 KB switchable CHR ROM bank.
• PPU $1400-$17FF: 1 KB switchable CHR ROM bank.
• PPU $1800-$1BFF: 1 KB switchable CHR ROM bank.
• PPU $1C00-$1FFF: 1 KB switchable CHR ROM bank.

Registers

$8000/$8001/$8002
7  bit  0
---- ----
PPPP PPPP
|||| ||||
++++-++++- swaps 8 KB PRG ROM bank at CPU $8000/$A000/$C000.

$A000/$A001/$A002/$A003/$A004/$A005/$A006/$A007
7  bit  0
---- ----
CCCC CCCC
|||| ||||
++++-++++- swaps 1 KB CHR ROM bank at PPU $400*(address AND 7).

$A008/$A009/$A00A/$A00B/$A00C/$A00D/$A00E/$A00F
* Unknown, writes should be ignored.

$C000/$C001/$C002
* Any write to these registers sets the IRQ counter AND latch to the value written.
* IRQs are also acknowledged.

$E000
7  bit  0
---- ----
xxxx xxxI
        |
        +-- IRQ enable/disable.

IRQ operation

• The IRQ counter value MINUS $14 (?) selects a PPU scanline to trigger an IRQ.
• If the IRQ counter matches the scanline number, and IRQs are enabled, and the latched value isn't zero, an IRQ is triggered. The counter is set to zero.