Expand description
The OBC1 board — a simple sprite-object-controller ASIC (Metal Combat: Falcon’s Revenge).
OBC1 builds sprite (OAM) tables in its own dedicated 8 KiB RAM, which the game then DMAs to
PPU OAM. There is no on-chip program (no LLE, no chip-ROM dump) — it is a fixed hardware
register file over that RAM, so the board is functional the moment the cart loads
(docs/adr/0003 — nothing to silently degrade). Clean-room port of ares’ OBC1 component
(ISC): every register at $1FF0-$1FF7 (bus address & 0x1FFF) redirects through a movable
baseptr/address/shift cursor into the RAM; every other address is a plain RAM byte.
Bus window (ares board SHVC-2E3M-01/OBC1-LOROM-RAM, both LoROM): $00-3F,$80-BF:$6000- $7FFF and the mirror $70-71,$F0-F1:$6000-$7FFF,$E000-$FFFF, both masked to a repeating 8 KiB
window (addr & 0x1FFF) over the SAME dedicated RAM — never the cartridge’s own SRAM. ROM and
everything else delegates to the wrapped base board.
Structs§
- Obc1
Board - A LoROM cartridge carrying an OBC1.