Breath of Fire II/ROM map

The following article is a ROM map for Breath of Fire II.

The following ROM data was obtained from an old Gamefaqs thread (link) by a user called StarryKnights.

Characters starting information

Initial data for the game's characters. Information block starts at x00:087C ($C0:087C) and ends at x00:0D3B ($C0:0D3B) (Assuming no header). 
Each entry is 64 bytes long.  This data follows the RAM PC data setup from the RAM map, though, much of this start up data goes unused.

Layout:

01-04: Character Name
05: Unused (In-game compared to RAM, setting this value to 20 would make the PC sprite into Valerie)
06: Unused (PC Status)
07: Character's PC Number
    00 - Ryu
    01 - Bow
    02 - Rand
    03 - Katt
    04 - Nina
    05 - Jean
    06 - Sten
    07 - Spar
    08 - Bleu
    09 - Kid Ryu
    0A - Kid Bow (Zombie in battle)

08: Initial level
09-10: Unused (Current health)
11-12: Initial Max HP
13-14: Unused (Current AP)
15-16: Initial Max AP
17: Shaman Form
18: Initial Strength
19: Initial Stamina
20-21: Initial Agility
22: Initial Condition
23-24: Initial Weapon (Value 11 tells the game that you have a weapon equipped)
25-26: Initial Shield (Value 21 tells the game that you have a piece of armor equipped)
27-28: Initial Armor (Value 21 tells the game that you have a piece of armor equipped)
29-30: Initial Helmet(Value 21 tells the game that you have a piece of armor equipped)
31-32: Initial Accessory 1 (Although set to 00 00 on most characters, this is bugged as you're not supposed to be able to unequip 'nothing')
33-34: Initial Accessory 2 (Although set to 00 00 on most characters, this is bugged as you're not supposed to be able to unequip 'nothing')
35-36: Unused (Current Attack)
37-38: Unused (Current Defense)
39-40: Unused (Current Vigor)
41: Unused (Current Wisdom)
42-43: Unused (Current Luck)
44: Initial Guts
45: Initial Wisdom Base
46: Initial Luck Base
47-49: Initial EXP
50-64: Unused


Starting PC Stats tables
----
x00:087C - Ryu Starting Stats (UNUSED! Kid Ryu is what the states are based off of.)
x00:08BC - Bow Starting Stats (UNUSED! Kid Bow is what the states are based off of.)
x00:08FC - Rand Starting Stats
x00:093C - Katt Starting Stats
x00:097C - Nina Starting Stats
x00:09BC - Jean Starting Stats
x00:09FC - Sten Starting Stats
x00:0A3C - Spar Starting Stats
x00:0A7C - Deis Starting Stats

x00:0ABC - Kid Ryu Starting Stats (Carries over to Adult Ryu)
x00:0AFC - Kid Bow Starting Stats (Carries over to Adult Bow)

x00:0B3C - Bow Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0B7C - Rand Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0BBC - Katt Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0BFC - Nina Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0C3C - Jean Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0C7C - Sten Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0CBC - Spar Starting Stats (Character Intro) [UNUSED IN ENGLISH]
x00:0CFC - Ryu Starting Stats (Character Intro) [UNUSED IN ENGLISH]



Starting Spells (All values here start with "A9 xx". Edit the "xx" portion only!)
----
Rand:
x00:04F7 ;Cure1 
x00:04FD ;CurePSN 
x00:0503 ;Set spell learn flag

Nina:
x00:0509 ;Tornado 
x00:050F ;Thunder 
x00:0515 ;Cold 
x00:051B ;Spark 
x00:0521 ;Set spell learn flag

Jean:
x00:0527 ;Ag-Up
x00:052D ;Set spell learn flag

Sten:
x00:0533 ;Spark 
x00:0539 ;Set spell learn flag

Spar:
x00:053F ;Cold 
x00:0545 ;Cure1 
x00:054B ;Ag-Down 
x00:0551 ;Pwr. Down 
x00:0557 ;Def. Down 
x00:055D ;Hush 
x00:0563 ;Ag-Up 
x00:0569 ;Set spell learn flag

Deis:
x00:056F ;Sonic Boom 
x00:0575 ;Bomb 
x00:057B ;Flame 
x00:0581 ;Freeze 
x00:0587 ;Death 
x00:058D ;Ag-Down 
x00:0593 ;Pwr. Down 
x00:0599 ;Def. Down 
x00:059F ;Ag-Up 
x00:05A5 ;Def-Up 
x00:05AB ;Atk-Up 
x00:05B1 ;Sap 
x00:05B7 ;Drain 
x00:05BD ;Exit 
x00:05C3 ;Warp 
x00:05C9 ;Set spell learn flag 
x00:05CB

Stat gain tables

Stat Gain Tables:
----
These cover levels 2-99 for every single character.

Hex offset (HiROM Address)
x0571B0 - x055DF0 ($C5:71B0 - $C5:5DF0)

4 bytes, split into 8 half-bytes in this order with a max increase of '15 (F)' per stat: 

Byte 1: HP, AP
Byte 2: Strength, Stamina
Byte 3: Unused, Agility
Byte 4: Wisdom, Luck

Almost every character seems to have extra level gains for levels they don't join at. These are not used at all due to the initial data. 
Also, it seems Bleu's stats uses the Monster Table as her level up data so she doesn't have her 'own' to modify without some serious stat table moving.

x0571B0 - x057338: Ryu Stat Gain
x057338 - x0574C0: Bow Stat Gain
x0574C0 - x057648: Rand Stat Gain
x057648 - x0577D0: Katt Stat Gain
x0577D0 - x057958: Nina Stat Gain
x057958 - x057AE0: Jean Stat Gain
x057AE0 - x057C68: Sten Stat Gain
x057C68 - x057DF0: Spar Stat Gain

x057DF0 - x057F78: Bleu Stat Gain [THIS IS THE MONSTER ENTRY TABLE! DO NOT MODIFY THIS! This is how the original game does it as Bleu was haphazardly put in!]

Guts gain upon level is consistently the same for every level up.  Each PC's gain starts at: 
x018FE5 ($818FE5)

Spell gains table

Pointers: 5AA00-5AA011

5AA12-5AADE

Pairs of bytes. First is for level the spell is gained on, the second is the spell gained. 00 terminates.

Enemy information

Enemy Stats:
----
x05:9000 - 05:A8FF (C5:9000 - C5:A8FF)


Byte Listing
----
01-08: Enemy Name
09-10: Max HP
11-12: Max AP
13: Luck
14-15: Attack
16-17: Defense
18-19: Agility
20: ???, copied to monster RAM + 0x68
21-22: Experience
23-24: Zenny
25: Item set
26: ???, Copied to monster RAM 0x5D
27: Drop Rate. It is also used as another monster stat @ monster RAM + 0x50
28: ???, copied to monster RAM 0x52
29: ???, copied to monster RAM 0x51
30: ???, copied to monster RAM 0x54
31-32: ???


Enemy Battle Backgrounds:
----
x055561 - 0x05----: Battle backgrounds for enemy groups? [Must use values 00 or BB+] [This has not fully been deciphered.]

For detailed information on how drop rates and item sets work, check out Ben Siron's handbook that explains many of the game's mechanics: link

Spell Info Table

584F0-58A20

Each spell is 16 bytes long
Bytes 1-8: Spell Name.
Bytes 9 and 10: Spell cost.
Bytes 11 and 12: These are tricky, the first 15 bits are used for a description pointer, and the
most significant bit appears to be used on spells with beneficial effects(Cure, Antdt, Renew, Etc).
Byte 13: Spell element. These elements are set by bits and are, in order: Ability down, fire, lightning,
       ice/water, wind, unknown/unused, earth, physical/non-elemental.
Byte 14: Targeting and special switches.
 Bit 1: Unknown. used only on the spell 8.0.
 Bit 2: By default, will cast on opposing party.
 Bit 3: Unknown. Used on Dispell, Recover, IdiotLzr, Hunt, and Whodini.
 Bit 4: Usable outside of battle.
 Bit 5: Usable during battle.
 Bit 6: Auto-confirm spell. This is more used more for spells that target an entire party.
 Bit 7: Auto target opposing party.
 Bit 8: Sets the spell to show green numbers. This will not make a spell heal, but will cause 0 damage,
       and shows green numbers.
Byte 15: Other switches. Most of this byte has unknown usages, but these are known effects.
 Bits 1-4: These bits have an unknown effect.
 Bit 5: used as a trigger effect, used specifically on G.Drgn when it's first learned and Anfini during Deathevn.
 Bit 6: unknown, but is used in various spells
 Bit 7: set to consume all of the users AP and is only used in Ryu's dragon spells. This also changes the
       animation Ryu uses when casting, and will crash if it is changed. This does not change how much AP is actually
       used when casting the spell.
 Bit 8: set when the spell requires a check against the characters mood.
Byte 16: When a spell requires a mood check, this is the value a characters mood must be before using.

Item Info Table

Byte Listing
----
01-08: Item name
09-10: Item cost
11-12: Item description pointer, and similar to spell's description, the most significant bit is set for beneficial effects, when an item can be used as such.

13: Targeting and special switches. these switches appear to be exactly the same as said byte in the spells
14: Who can equip this item, if possible. each bit represents different characters with Nina and Bleu sharing bits.
15: Attack power for weapons, and defense power for armor. 
16: This has a number of uses depending on what item it is being used for. 
    For unequippable items and weapons, it appears to identify what spells are cast when an item is used. 
    For armors, the least significant 6 bits are used for armor weight, which allows for a max weight of 63.

    For values 0x00 to 0x3F, items get equipped into the armor slot with a weight assigned by the bit.
    For values 0x40 to 0x7F, items get equipped into the shield slot.
    For values 0x80 to 0xBF, items get equipped into the helmet slot.
    For values 0xC0 to 0xFF, items becomes unequippable.

Experience Tables

56680-571AF

Each level is 3 bytes each and starts at level 2.

All characters have individual experience tables except for Bleu, who shares Nina's table.

Each character table is 294 bytes long (98 levels * 3 bytes each).

The experience tables for individual characters are in the same order as the are in the 
ROM character information, so Ryu first, then Bow, Rand, Katt, Nina/Bleu, Jean, Sten, and Spar.

Shop data

3FA60-3FBBF

Shops use item slot numbers for what items to sell and is terminated by a value of 00.

The ROM uses 3FA60 when referencing the shop data, but the data appears to start around 3FAC9
and appears to mostly be in numerical order, by item slot number.

Game Script

The game script starts at 290000 and continues to 2CADA4, but this data uses simple compression.
with it's data starting at 22D000 through 22D531, and the actual pointer data starting at 22DE00.
22DDF2 through 22DDF7 contain values of when to switch banks, 2 bytes each.

The data itself is mostly ASCII coding, with some special formatting.

Music Data

Some data may be missing but these offsets are noted for setting music. (BacuraFF)

x00AF80 - x00B0B3 - Indoor Map Music
x00C0F0 - x00C13D - Event/Boss Battle Music

Each seem to be one byte each.

Some events forcefully change music and that is not included.

Monster Formation Data

Defines what enemies are in and how they are displayed on screen. Some of this data also interferes with the level up data.
Formation Data:
----
x05:7DF0 - 0x5:84EF 

Bytes (7 each)
----
01: Enemy formation - Doesn't appear to do anything except move enemies around the screen
02 - 07: Enemy pointer

Overworld mob formation pointers

Defines which enemies can be run into from your location on the overworld
Map Data:
----
x05:5460 - x5:5550

Note: Max value on overworld is naturally 0x3F

Map Portal Data

Defines where a portal is, and where it takes you, and some special switches
Portal Data:
----
x05:1800 - x05:48F4? (Might be shorter)

Bytes (variable bytes)
----
01: Which map these portals belong to
02: How many portals are in this map

Each portal is 7 bytes as
01: Source X map position
02: Source Y map position
03: Destination X map position
04: Destination Y map position
05: Destination map pointer
06: Special switches/values used for loading
07: More switches/values

RNG

The random number generator (RNG) is used in the game anywhere variance is required
Here it is, disassembled in it's glory, and how it works:

;Random Number Generator. Entry point is JSL
$C0/648B 08          PHP                  
$C0/648C C2 20       REP #$20             
$C0/648E AD D6 00    LDA $00D6  [$81:00D6]
$C0/6491 0A          ASL A                
$C0/6492 0A          ASL A                
$C0/6493 18          CLC                  
$C0/6494 6D D6 00    ADC $00D6  [$81:00D6]
$C0/6497 EB          XBA                  
$C0/6498 E2 20       SEP #$20             
$C0/649A 8D D7 00    STA $00D7  [$81:00D7]
$C0/649D 18          CLC                  
$C0/649E 6D D6 00    ADC $00D6  [$81:00D6]
$C0/64A1 8D D6 00    STA $00D6  [$81:00D6]
$C0/64A4 28          PLP                  
$C0/64A5 6B          RTL                  

What it does (just the math):

Load 7E00D6
Multiply by 5
Switch high and low bits
Set 8-bit register
Store into 7E00D7(High Byte of D6)
Add original D6 (Low byte only)

The function then reads/mutates A for the result