EarthBound Zero/RAM map

The following article is a RAM map for EarthBound Zero.

RAM

RAM	Purpose
0x0006	Part of an instruction for "copy protection". $E5 on checksum failure. $00 to bypass. "Correct"/non-hack value unknown.
0x0015	Used for assigning area to objects?
0x0060	HP target value for stat increase during level up
0x0611	Looks like the first EXP byte, but changing it even mid-battle will result in insta-death. Anti-cheat?
0x0818-B	The X and Y coordinates, stored strangely; see below

The coordinates in RAM to not correspond to coordinates in the rest of the game. To convert it, run this Python code (in this example, bytes $818-B are `80 19 C0 2D`):

# replace with the values from the RAM
ram_x = 0x8019
ram_y = 0xc02d

byte0, byte1 = ram_x.to_bytes(2, "little")
byte2, byte3 = ram_y.to_bytes(2, "little")

real_x = ((byte0 << 8) | (byte1 & 0xC0)) >> 2
real_y = ((byte2 << 8) - 0x1e00 | (byte3 & 0xC0)) >> 2

print((real_x, real_y))

SRAM (save data)

Entire SRAM

There are multiple saves throughout the save RAM, three for the saved data and one for the last save. The last save is the one that was saved last, and unless an error occurred during saving, should be identical to the save slot that was last saved.

Save RAM

• 0000-13FF: Unknown
• 1400-16FF: Last save
• 1700-19FF: Save slot 1
• 1A00-1CFF: Save slot 2
• 1D00-1FFF: Save slot 3

Saves

Each save has this format:

Slot metadata

The 2-byte checksum is calculated by subtracting each byte after it (0x300 for each save, so 0x29E bytes to subtract), then running it through mod 0x10000. Here is an example Python program that verifies it:

def calculate_checksum(handle, slot = 0): # 0 = last save
    handle.seek(0x1400 + slot * 0x300)
    ram_checksum = int.from_bytes(handle.read(2), "little") # read the checksum from the RAM

    # calculate it manually
    calculated_checksum = 0x0
    for number in range(0x300 - 0x2):
        calculated_checksum = (calculated_checksum - int.from_bytes(handle.read(2), "little")) % 0x100 ** 2 # this is ran for each byte other then the checksum

    assert ram_checksum == calculated_checksum, "checksum is invalid" # throw an error if the checksum doesn't match
    return calculated_checksum
calculate_checksum(open("file.sav", "rb"))

• 1400-1401: Checksum
• 1402: Slot number

  $B0 for slot 1, $B1 for slot 2 and $B2 for slot 3

• 1403: Slot state

  Normally $7E, deleted slots are $00. It's possible to recover an accidentally deleted save slot by changing this back

Main data

• 1404-1407: Position
• 1408-140B: Current party members

  Each number corresponds to an ally in Ally data, 0 means empty and skips to the next value

• 140C-140F: Last save position

  Right before showing the XP needed to level up for each character (during Dad's phone call), the game copies the position to this address, meaning that this is always the position you were when you last phoned Dad (regardless of whether you saved or not); changing it doesn't affect the position when loading the save

• 1410-1411: Current money
• 1412-1414: Money in bank
• 1415-141F: Unknown
• 1420-1430: Your name (the player name, not Ninten's name)
• 1431-143F: Unknown

Ally status

This is documented below.

• 1440-147F: Ninten
• 1480-14BF: Ana
• 14C0-14FF: Lloyd
• 1500-153F: Teddy
• 1540-157F: Pippi
• 1580-15BF: EVE
• 15C0-15FF: Flying Man

Other

• 1600-1688: Unknown
• 1689-1983: Favorite food name
• 1984-16AF: Unknown
• 16B0-16CF: Items in storage
• 16D0-16FF: Unknown

Ally state

Each ally's state is stored at a place corresponding to the character, see the above section

• 00: Unknown (unused?)
• 01: Status condition
  • Bit 0: Cold
  • Bit 1: Poisoned
  • Bit 2: Puzzled
  • Bit 3: Confused
  • Bit 4: Sleeping
  • Bit 5: Paralyzed
  • Bit 6: Stone
  • Bit 7: Unconscious (can be applied even when HP isn't at 0)
• 02: Unknown
• 03-04: Max HP
• 05-06: Max PP
• 07-08: Offense
• 09-0A: Defense
• 0B: Fight
• 0C: Speed
• 0D: Wisdom
• 0E: Strength
• 0F: Force
• 10: Level
• 11-13: Experience
• 14-15: Current HP
• 16-17: Current PP
• 18-19: Unknown
• 20-27: Items
• 28: Weapon
• 29: Coin
• 2A: Ring
• 2B: Pendant
• 30-37: Learned PSI
• 38-3E: Name
• 3F: Unknown (unused?)