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EarthBound Zero/RAM map: Difference between revisions

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{{rammap|game=EarthBound Zero}}
#REDIRECT [[EarthBound Beginnings/RAM map]]
 
=RAM=
 
{|border="1" cellpadding="1"
!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?
|-
|0x0047 || Combat state. 00: Not in combat.  All else correspond to which enemy group is being fought.
|-
|0x0060 || HP target value for stat increase during level up
|-
|0x00A0 || Which direction is Ninten moving: 88: Standing still. 00: U. 01: U-R. 2: R. 3: R-D. 04: D. 5: D-L. 6: L. 7: L-U.
|-
|0x00D9 || Controller 1 button data. [0]: Right. [1]: Left. [2]: Down. [3]: Up. [4]: Start. [5]: Select. [6]: B. [7]: A.
|-
|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
|}
 
===Coordinates===
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`):
 
<pre>
# 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))
</pre>
 
=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:
<pre>
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"))
</pre>
* 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 [[EarthBound Zero:Ally data|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 [[#Ally state|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?)
{{Internal Data|game=EarthBound Zero}}

Latest revision as of 12:20, 16 April 2025

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