Physical Save Chip

64 Kbit EEPROM, 8,192 bytes total. In DeSmuME set save type to “EEPROM 64 Kbit”.

EEPROM Map

Slot n offset = 0x03E8 + n * 0x7D0 (decimal: 1000 + n * 2000).

Checksum Algorithm

Fletcher-32 variant seeded at 0xFFFF. Used for the header block and the Wi-Fi block.

function checksum(bytes, length):
    s1 = 0xFFFF
    s2 = 0xFFFF
    n  = length >> 1          // process 16-bit halfwords LE
    while n > 0:
        chunk = min(n, 360)
        n -= chunk
        for each halfword hw in next chunk:
            s1 += hw
            s2 += s1
        s1 = (s1 >> 16) + (s1 & 0xFFFF)   // fold carry
        s2 = (s2 >> 16) + (s2 & 0xFFFF)
    s1 = (s1 >> 16) + (s1 & 0xFFFF)       // final fold
    s2 = (s2 >> 16) + (s2 & 0xFFFF)
    return s1 | (s2 << 16)

0xFFFFFFFF means the block was never written (blank EEPROM). A mismatch between stored and computed value means corruption; the game reinitialises the block.

Header checksum covers bytes 4-335 and is stored at bytes 0-3.

Save Header (336 bytes at 0x0000)

Written atomically to EEPROM whenever any slot is saved.

The scene name is the short text shown under the slot name on the save selection screen. Header bytes 216-263 overlay gameState[1000..1047] in RAM directly.

Slot Data (2,000 bytes per slot)

The slot is a packed snapshot of the relevant in-RAM game state, compressed from the 327,680-byte in-RAM structure on save and expanded back on load.

Puzzle flag byte (slot offset 12 + puzzle_id)

Main story puzzles are IDs 1-135. IDs 136-199 are Wi-Fi / weekly download slots. ID 0 and 200-255 are unused.

Total picarats are not stored in the save file. They are computed at save time from the puzzle table using base values stored in ROM.

Wi-Fi / Secret Data (116 bytes at 0x1B58)

A checksum of 0xFFFFFFFF means this block has never been written. The Wi-Fi state is shared across all three save slots.

Conventions

• All multi-byte integers are little-endian.
• All strings are Shift-JIS, null-terminated, zero-padded to their field size.
• The magic string ATAMFIREBELLNY is ASCII (14 bytes + 2 null bytes = 16 bytes total).