Memory Layout

ROM Layout

There are 2 addressing modes:

• $800000-$BFFFFF is used in scripts, because it allows accessing RAM, ROM and Hardware without switching banks

  ROM $xx0000-$xx7FFF is inaccessible (memory-mapped hardware and WRAM) in this mode.

• $C0000-$FFFFFF is used for data (or code)

  ROM $FE0000-$FFFFFF is inaccessible (mapped to WRAM)
  and $xx8000-$xxFFFF may be occupied by scripts (in 80-BF addressing)

This means in major portions of the ROM, we have interleaved data/code and scripts with 0x8000 block size.

Reserved/used/added addresses

see Data Crystal for existing ROM map

• $b08000…$b0822a: relocated alchemy drops (alchemy_rando_drops.txt)
• $b08280…$b082??: trap item setup scripts (traps.txt)
• $b08300…$b0????: jukebox (jukebox.txt)
• $b0ff00…$b0ff83: sniffamizer drop setup scripts (1 per ingredient + iron bracer)
• $b18000…$b18950: gourdomizer drop values (gourds.h)
• $b18951…$b1dfff: gourdomizer added items/messages for looting (gourdomizer_drops.txt)
• $b1e000…$b1????: re-enter colosseum holding room code (colosseum.txt)
• $f00000…$f07fff: empty to allow 2p patch (code)
• $f10000…$f17fff: patches to engine (code, call/jmp here from engine):
  • $f10000: weapon/attack experience modifier
  • $??????: update call bead flags (see RAM Layout)
• $fd0000…2f: 48B seed and settings (for auto-tracking), will be copied to $7e2600…2f:
  • 8 bytes seed (64bit int in SNES byte order, so +0 is LSB, +7 is MSB)
  • 3 bytes ASCII version (e.g. 040)
  • 1 byte reserved 0
  • 1 byte flags (&1 = mystery, &0x80 = death link)
  • up to 35 bytes ASCII settings (null terminated)
• $fd0030…3f: reserved 0
• $fd0040…7f: 64B multiworld seed and slot, will be copied to $7e2640…7f:
  • 32 bytes UTF8 seed string (optional null termination)
  • 32 byte UTF8 slot name (optional null termination)
• $fd1000: ASM code patched into $c084a3 to support multiworld
• $fd1100: ASM for settings ROM->WRAM copy
• $fd8000: Script scheduled by ASM above to support multiworld
• $fd8100: Death Link script
• $fd8110: Screen Shake script
• $fd8150: Multiworld "clear state" script

RAM Layout

Reserved/used/added addresses

see Data Crystal for existing RAM map

• $7e2353: 8 new loot flags ("Queen's Key on Boy" in vanilla)

  Gauge:           &0x01 ^= 07d8 ← number to address in scripts
  Knight Basher:   &0x02 ^= 07d9
  First torso:     &0x04 ^= 07da
  Second torso:    &0x08 ^= 07db
  First arm prot:  &0x10 ^= 07dc
  Second arm prot: &0x20 ^= 07dd
  First helmet:    &0x40 ^= 07de
  Second hemlet:   &0x80 ^= 07df
  

• $7e225c: 3 bits added (unused in vanilla?)

  Aquagoth defeated: &0x08
  Volcano viper:     &0x10
  Monk defeated:     &0x20
  

• $7e227b: 1 bit changed

  Third torso:     &0x10 ^= 011c ← vanilla unreachable act3 chest
  

• $7e2531…32: will be used to extend market timer in v039 (unused trade good in vanilla)
• $7e2531…32: reserved for energy core fragments
• $7e2533…56: in use
• $7e2557…63: free
• $7e2564…6b: reserved (4 slot multiworld send queue; we'll most likely not use this)
• $7e256c…6d: 4 4bit enums to determine which call bead spells should be visible in the auto-tracker; FIXME: chaos will still have to read the mapping
• $7e256e…6f: will be used to extend market timer in v042?
• $7e2570…74: 35 bits = 5 bytes for alchemy checks (set when checking alchemist, order of vanilla spells, required for multiworld) in v040
• $7e2575…76: multiworld "expected item index" for resync
• $7e2577…7f: reserved for multiworld communication
  • 1B PC -> Game: Start transaction. Set to non-zero to schedule the script using the values below
  • 2B PC -> Game: Received item index (Game should ignore the item if != expected and PC should resync)
  • 2B PC -> Game: Amount
  • 2B PC -> Game: In-game Item ID (Game clears this when ready for the next and increments "last received item index")
  • 2B Game -> PC: reserved
• $7e2600…2f: will copy 48B from $fd0000…2f: Game seed and settings (auto-tracking; for RA with snes9x core)
• $7e2630…3f: 16B reserved
• $7e2640…7f: will copy 64B from $fd0040…7f: Multiworld seed and slot (for RA with snes9x core)

Possibly unused RAM

• $7e2557 to $7e2833 seems to be unused
• save file needs to grow by 7e2557-7e2533+whatever_we_need = 36+whatever_we_need to be used for flags
  • 7e2531-32 are unused, but already part of SRAM save/load
  • 36 bytes from 7e2533-56 are in use, but can probably be saved/restored to/from SRAM without side effects
  • see above for how we map added bytes
  • for now we reserve 32 bytes $7e2557…76, 19 bytes from the back occupied, 13 from front still free

Pending ROM Layout changes

• $b08000…$b082ff: alchemists' drops
• $b08300…$b80700: jukebox (musicmizer)
• $b1d200…???: special item drop setup scripts ("remote item")
• $b18951…???: extended item drops (now includes alchemy and boss drops)

SRAM

We allocate from back of the 8KB SRAM

• $a07ffe…$a07fff: Remote effect flag (1 = "DeathLink") (or $207ffe, SRAM $1ffe)