INES Mapper 077
iNES Mapper 077 is a singleton allocated for the game Napoleon Senki.
Registers: (** BUS CONFLICTS **)
---------------------------
$8000-FFFF: [CCCC PPPP]
C = CHR Reg (2k @ $0000)
P = PRG Reg (32k @ $8000)
CHR Setup:
---------------------------
CHR-RAM is fixed at $0800-$1FFF. CHR-ROM is swappable at $0000:
$0000-$07FF $0800-$0FFF $1000-$17FF $1800-$1FFF $2000-$27FF $2800-$2FFF $3000-$3FFF
+-----------+-----------+-----------+-----------+-----------+-------------+----------+
| $8000,ROM | {1},RAM | {2},RAM | {3},RAM | {0},RAM |Internal VRAM| Open Bus |
+-----------+-----------+-----------+-----------+-----------+-------------+----------+
When making an emulator, you do not need to care about the specific order of
the CHR-RAM banks: just provide 10KiB from $0800-$2FFF.
Two 74161s latch the 8 bits above.
A 74138 divides the PPU’s 16KiB of address space into eight 2KiB regions. One of these goes straight to the CHR ROM; another goes straight to the CIRAM.
A 74'21 (two 4-input AND gates) combines the other four outputs to generate a chip enable for the 8KiB RAM on the PPU.