===============================================================================
Game: Lufia & The Fortress of Doom (SNES)
Author: Vegetaman
Document: SRAM Locations
Originally written for posting on romhacking.net (RHDN) and my personal site.
Copyright (C) 2011 Vegetaman
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3
or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU
Free Documentation License".
===============================================================================
===============================================================================
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Table of Contents:
--------------------
I. Introduction
II. SRAM Divisions
III. The Checksum Algorithm
IV. SRAM Location Meanings
V. Item List
VI. Magic List
VII. Revision History
VIII. Contact Information
IX. Other Notes
X. Special Thanks
===============================================================================
----------------
I. Introduction
----------------
Hello, I am Vegetaman, and this is my SRAM guide to Lufia & The Fortress of
Doom for SNES. In it, I will discuss how the SRAM is broken up for this game,
as well as the different save slots. I will also talk about how the checksum
algorithm works to verify good data, and show you how to figure out what
items you have in your inventory and what magic you are able to cast (or, what
value you would need to put into the SRAM to give yourself that item or that
magic ability -- including some dummied out items and spells!). I will also
briefly cover binary and hexadecimal to decimal. This entire document is the
parallel effort of my SRAM editor I created for this game, as it contains all
the documentation that was necessary to go about programming that project. I
also included a discussion on binary, hexadecimal, and decimal numbers in the
IX. OTHER NOTES section of this document, just in case you wanted a refresher
or it is new to you. These are just the things I have discovered about the
SRAM while making my editor progam -- but I am working on expanding the scope
of that to discover what every byte of SRAM in each save slot does, so I would
appreciate any help or assisstance that you can give!
===============================================================================
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II. SRAM Divisions
-------------------
The SRAM for Lufia & The Fortress of Doom is approximately 8192 bytes long, or
in HEX 0x2000 (see IX. OTHER NOTES for more information about HEX numbers).
Now, that 0x2000 bytes of SRAM is divided up into 3 "save slots" that are
approximately 0x800 bytes in length (that's 2048 bytes in decmial notation).
With the final fourth of SRAM seemingly just loaded with the value "E5".
That means the four slots are located at:
SLOT 00: 0x000
SLOT 01: 0x800
SLOT 02: 0x1000
EXTRA SPACE: 0x1800
On an interesting note though, where the fourth save slot would be, the SRAM
file I was working with says "Estpolis Biography Neverland Co.". A perfect
32 bytes starting at SRAM location 0x1800.
===============================================================================
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III. The Checksum Algorithm
----------------------------
Special thanks to KingMike from RHDN for supplying me with this assembler code
that contains the checksum algorithm for Lufia & The Fortress of Doom:
$00/9429 A0 FC 03 LDY #$03FC A:0070 X:616E Y:0000
$00/942C A6 1F LDX $1F [$00:001F] A:0070 X:616E Y:03FC
$00/942E A9 02 65 LDA #$6502 A:0070 X:0000 Y:03FC
$00/9431 18 CLC A:6502 X:0000 Y:03FC
$00/9432 7D 08 00 ADC $0008,x[$70:0008] A:6502 X:0000 Y:03FC
$00/9435 E8 INX A:4AE7 X:0000 Y:03FC
$00/9436 E8 INX A:4AE7 X:0001 Y:03FC
$00/9437 88 DEY A:4AE7 X:0002 Y:03FC
$00/9438 D0 F7 BNE $F7 [$9431] A:4AE7 X:0002 Y:03FB
$00/943A AA TAX A:592C X:07F8 Y:0000
$00/943B 7A PLY A:592C X:592C Y:0000
$00/943C AB PLB A:592C X:592C Y:0000
$00/943D 28 PLP A:592C X:592C Y:0000
$00/943E 60 RTS A:592C X:592C Y:0000
The first 8 bytes of each save slot file are used to serve two purposes:
1. The first six bytes contain the save slot number (SLOT00, SLOT01, SLOT02).
2. The next two bytes contain the calculated checksum value.
The checksum is calculated by starting with the first memory location after
the calculated checksum value, and going forth until the next save slot
location. So, you have three slots that break down as such in SRAM:
0x000 - 0x007: File00XX (where XX is the checksum value for 0x008 - 0x7FF)
0x008 - 0x7FF <- The actual save slot data that gets added up for the checksum
that gets stored at 0x006 and 0x007
0x800 - 0x807: File01XX (where XX is the checksum value for 0x808 - 0xFFF)
0x808 - 0xFFF <- The actual save slot data that gets added up for the checksum
that gets stored at 0x806 and 0x807
0x1000 - 0x1007: File02XX (where XX is the checksum value for 0x1008 - 0x17FF)
0x1008 - 0x17FF <- The actual save slot data that gets added up for the
checksum that gets stored at 0x1006 and 0x1007
0x1800 - 0x1FFF <- Unused data bank
To calculate the checksum for each save slot, you start with the first offset
in your save slot, and add up the little endian 16-bit numbers.
So, say for SLOT00, your first 16 bytes looked like this:
46 69 6C 65 30 30 E8 63 01 04 E5 E5 E5 E5 E5 E5
So, your first four bytes: "46 69 6c 65", are the HEX equivalent of the word
"File" (if you don't believe me, look up the ASCII character table, and find
that hex values 0x41 - 0x5A are upper case characters and hex 0x61 - 0x7A are
lower case characters of the alphabet [A-Z and a-z respectively]).
Then, your next two bytes: "30 30", are the HEX equivalent of the printable
ASCII characters 00 (the ASCII table defines hex values 0x30 - 0x39 as the
textual representations of the characters 0 - 9).
Now we come to the little endian checksum part, which can be complicated, so
please bear with me:
Then, the next two bytes are what your checksum is currently calculated as.
Since it is a 16 byte value, to get your checksum as a decimal number, you
take the first number, "0xE8", and convert it to a decimal -- 232. Now, you
take the second number, "0x63", and convert it to a decimal -- 99.
But! Before you can add these two numbers together, you have multiply 99 by
256, since the number that exists there would actually be 0x6300. Anyway, 99
times 256 is 25344. Then you add 232 to that, and you get: 25576. That is your
checksum value.
Why did I show you that complicated method? Because, we're dealing with little
endian encoding. That means that "0x63" is your high order byte, and "0xE8" is
your low order byte. The 16 bit value that is your checksum is not 0xE863, but
it is actually 0x63E8. This little tidbit of information becomes important when
we start going through the save slot to compute the checksum.
Now, if we were to start computing the checksum for this save slot, we would
begin after the checksum bytes with the first "0x01". This is the low order
byte, so the decimal equivalent here is 1. Now, we take the high order byte,
which is "0x04". Remember, this is just like saying "0x0400" for the purposes
of computing a checksum. So, convert the byte to a decimal -- in this case, 4,
and then multiply it by 256 -- 1024; before adding back in 1. So, your first
value in your checksum is 1025. You will continue in this manner until you
reach the end of that save slot.
Except, there is a caveat: what happens when your checksum value goes over
0xFFFF (the biggest 16-bit number, aka. 65535). Well, your counter technically
rolls back over to 0, and starts counting up again -- and you just throw
away the extra.
So you've added up your save slot and you find out that it still doesn't match
the two bytes at the end of "File00"? Well, that's why the assembler code up
above was important -- it not only told us how the checksum algorithm works,
but it also told us the base value to begin the checksum calculation off of.
In this case, it is 6502. You can either start with this value from the onset,
or you can add it on as the last step in the process, but regardless, the
value this yields will be the two bytes that get stored away as your checksum
for this save slot. Then you just have to rinse and repeat this process for
the next two save slots! (by the way, 6502 is a decimal value -- not in hex).
If you decide you want to make modifications to the hex file but do not want
to calculate the checksum by hand -- I have an SRAM editor program that will
crunch the data for you.
===============================================================================
---------------------------
IV. SRAM Location Meanings
---------------------------
As I discussed earlier, the SRAM is divided into four logical blocks:
0x0000 - 0x07FF <- Save Slot File 0
0x0800 - 0x0FFF <- Save Slot File 1
0x1000 - 0x17FF <- Save Slot File 2
0x1800 - 0x1FFF <- Unused Space
So, I will be doing this document based on the offsets for the first save slot,
also known as File00. If you want to know the appropriate location for the
data you are looking for in File01 or File02, you just have to add either
0x800 to the number for File 1, or 0x1000 to the number for File 2.
NOTE: If I do not know what the data at a particular SRAM location holds, I
will just be skipping over it. This document is still a work in progress,
and if you have any light to shed on these other SRAM locations -- please
scroll down to the Contact Info section and give me a buzz ASAP!
With that being said, let us look at the SRAM for File00 (and don't forget that
these values are stored in little endian format):
0x000 - 0x005 -> "FILE0?" where 0 is the ? for this file location in SRAM.
0x006 - 0x007 -> The 16 bit little endian checksum we discussed in the previous
section of this document.
0x113 - 0x116 -> 5 bytes for the Hero's name plus a null terminator (0x00).
0x119 - 0x11E -> 5 bytes for the Hero's name a second time plus a 0x00.
0x11F - 0x124 -> 5 bytes for Lufia's name (once she joins) plus a 0x00.
0x125 - 0x12A -> 5 bytes for Aguro's name (once he joins) plus a 0x00.
0x12B - 0x12F -> 5 bytes for Jerin's name (once she joins) plus a 0x00.
0x131 -> This byte says how many party members you currently have.
0x132 - 0x134 -> Three bytes that contain the amount of gold your party has.
0x13E - 0x1B5 -> 120 bytes that hold the item information, which breaks down
as follows into byte pairs:
Items: You get a maximum of 5 pages of items, with 12 items a page,
for a maximum of 60 items. The way the data is stored is that
the first byte of the pair identifies what the item is (see
V. ITEM LIST for more info on that), while the second byte of
the pair identifies the quantity of that item that you have.
0x1B6 -> Hero's Level
0x1B7 -> Lufia's Level
0x1B8 -> Aguro's Level
0x1B9 -> Jerin's Level
0x1C6 - 0x1C7 -> Hero's HP
0x1C8 - 0x1C9 -> Lufia's HP
0x1CA - 0x1CB -> Aguro's HP
0x1CC - 0x1CC -> Jerin's HP
0x1CE - 0x1CF -> Hero's MP
0x1D0 - 0x1D1 -> Lufia's MP
0x1D2 - 0x1D2 -> Aguro's MP
0x1D3 - 0x1D4 -> Jerin's MP
0x1D6 - 0x1F5 -> Hero's Magic Spells (32 bytes for 32 spells)
0x1F6 - 0x215 -> Lufia's Magic Spells (32 bytes for 32 spells)
0x216 - 0x235 -> Jerin's Magic Spells (32 bytes for 32 spells)
Magic: You have a maximum amount of space for spells of 32 bytes. However,
the way that magic works is that the spell listing must end with a
call to 0x00 for "END OF LIST". Otherwise, if you use up all 32 slots
in Hero's Magic list, he will also have every spell of Lufia's in his
spell casting ability as well! And likewise, if you fill up all 32 of
Lufia's spells, you can spill over into Jerin's territory. And if you
fill up Jerin's... Well, you'll probably crash something, but just
beware if you go to edit the game in this manner. Though with this
method, you can actually give your Hero EVERY spell in the game when
the team consists of only you and Lufia! Also, notice that there is
no space reserved for Aguro to have magic, so you cannot just give
him some spells to let him cast away.
0x307 -> Hero's Equipped Weapon
0x308 -> Lufia's Equipped Weapon
0x309 -> Aguro's Equipped Weapon
0x30A -> Jerin's Equipped Weapon
0x30B -> Hero's Equipped Armor
0x30C -> Lufia's Equipped Armor
0x30D -> Aguro's Equipped Armor
0x30E -> Jerin's Equipped Armor
0x30F -> Hero's Equipped Shield
0x310 -> Lufia's Equipped Shield
0x311 -> Aguro's Equipped Shield
0x312 -> Jerin's Equipped Shield
0x313 -> Hero's Equipped Helm
0x314 -> Lufia's Equipped Helm
0x315 -> Aguro's Equipped Helm
0x316 -> Jerin's Equipped Helm
0x317 -> Hero's Equipped Shoes
0x318 -> Lufia's Equipped Shoes
0x319 -> Aguro's Equipped Shoes
0x31A -> Jerin's Equipped Shoes
0x31B -> Hero's Equipped Ring
0x31C -> Lufia's Equipped Ring
0x31D -> Aguro's Equipped Ring
0x31E -> Jerin's Equipped Ring
===============================================================================
-------------
V. Item List
-------------
The whole section in the SRAM locations about inventory data does no real good
unless you can decipher just exactly what item it is that is stored in that
location -- so, I give you the hex codes for items you can obtain (and some
dummy items that you should not be able to obtain and that don't seem to do
anything even if you hex edit the game to give you the items).
ITEM NAME HEX NUMBER DECIMAL NUMBER
|---------------|--------------|-----------------|
Empty Slot 00 0
Knife 01 1
Club 02 2
Mace 03 3
Dagger 04 4
Long Knife 05 5
Short Sword 06 6
Rod 07 7
Gladius 08 8
Glass Robe 09 9
Brone Sword 0A 10
Staff 0B 11
Scimitar 0C 12
Rapier 0D 13
Long Sword 0E 14
Long Staff 0F 15
Axe 10 16
Spear 11 17
Morning Star 12 18
Catwhip 13 19
Battle Axe 14 20
Hammer Rod 15 21
Trident 16 22
Silver Rod 17 23
Silver Sword 18 24
Buster Sword 19 25
Zircon Rod 1A 26
Great Axe 1B 27
Grand Blade 1C 28
Zircon Axe 1D 29
Zircon Sword 1E 30
Broad Sword 1F 31 (cursed)
Broad Rod 20 32 (cursed)
Luck Blade 21 33 (cursed)
Gloom Pick 22 34 (cursed)
Dual Blade 23 35
Dress 24 36
Cloth 25 37
Cloth Armor 26 38
Robe 27 39
Tan Armor 28 40
Tan Robe 29 41
Light Armor 2A 42
Light Robe 2B 43
Chain Mail 2C 44
Chain Cloth 2D 45
Plate Cloth 2E 46
Brone Armor 2F 47
Quilted Silk 30 48
Half Mail 31 49
Brone Robe 32 50
Silver Armor 33 51
Silver Robe 34 52
Plate Mail 35 53
Zircon Robe 36 54
Zircon Armor 37 55
Clear Silk 38 56
Bracelet 39 57
Tan Shield 3A 58
Wood Shield 3B 59
Buckler 3C 60
Wood Wrist 3D 61
Kite Shield 3E 62
Round Shield 3F 63
Round Wrist 40 64
Brone Shield 41 65
Tower Shield 42 66
Large Shield 43 67
Silver Wrist 44 68
Silver Plate 45 69
Zircon Wrist 46 70
Zircon Plate 47 71
Cloth Helm 48 72
Tan Helm 49 73
Hair Band 4A 74
Wood Helm 4B 75
Glass Cap 4C 76
Brone Helm 4D 77
Red Beret 4E 78
Iron Helm 4F 79
Plate Cap 50 80
Plate Helm 51 81
Glass Beret 52 82
Silver Helm 53 83
Sakret 54 84
Zircon Beret 55 85
Zircon Helm 56 86
Sandal 57 87
Cloth Shoes 58 88
Tan Shoes 59 89
Spike Shoes 5A 90
Heeled Shoes 5B 91
Wind Shoes 5C 92
Wind Heels 5D 93
Knife Shoes 5E 94
Needle Heels 5F 95
Sonic Shoes 60 96
Sonic Heels 61 97
Sword Shoes 62 98
Cat Heels 63 99
Mach Shoes 64 100
Mach Heels 65 101
Power Ring 66 102
HiPower Ring 67 103
Daze Ring 68 104
Hi Daze Ring 69 105
Mind Ring 6A 106
Sonic Ring 6B 107
Mach Ring 6C 108
Undead Ring 6D 109
Ghost Ring 6E 110
Dragon Ring 6F 111
Sea Ring 70 112
Fly Ring 71 113
Water Ring 72 114
Fire Ring 73 115
Ice Ring 74 116
Electro Ring 75 117
Flash Ring 76 118
Flame Ring 77 119
Water Ring 78 120
Blast Ring 79 121
Frost Ring 7A 122
Might Armor 7B 123
Might Shield 7C 124
Might Helmet 7D 125
Gloom Ring 7E 126
Gloom Voice 7F 127
Dummy 80 128
Brone Breast 81 129
Carbo Sword 82 130
Carbo Plate 83 131
Carbo Shield 84 132
Carbo Helm 85 133
Carbo Cap 86 134
Gloom Guard 87 135
Diamond Ring 88 136
Engage Ring 89 137
Monster Ring 8A 138
Blue Ring 8B 139
Yellow Ring 8C 140
Red Ring 8D 141
Purple Ring 8E 142
Green Ring 8F 143
White Ring 90 144
Black Ring 91 145
Heavy Ring 92 146
Wave Ring 93 147
Potion 94 148
Hi Potion 95 149
Ex Potion 96 150
Hi Magic 97 151
Ex Magic 98 152
Antidote 99 153
Sweet Water 9A 154
Foul Water 9B 155
Awaken 9C 156
Stone Cure 9D 157
Mystery Pin 9E 158
Shriek 9F 159
Swing Wing A0 160
Magic Guard A1 161
Power Gourd A2 162
Mind Gourd A3 163
Power Potion A4 164
Spell Potion A5 165
Speed Potion A6 166
Mind Potion A7 167
Great Potion A8 168
Float A9 169
Smoke Ball AA 170
Arror AB 171
Mid Arrow AC 172
Big Arrow AD 173
Arrows AE 174
Hi Arrows AF 175
Ex Arrows B0 176
Dragon Arrows B1 177
Sleep Arrow B2 178
Puzzle Arrow B3 179
Stun Arrow B4 180
Gloom Arrow B5 181
Bomb B6 182
Hi Bomb B7 183
Ex Bomb B8 184
Miracle B9 185
Revive BA 186
Pear Cider BB 187
Sour Cider BC 188
Lime Cider BD 189
Plum Cider BE 190
Apple Cider BF 191
Hair Band C0 192
Brooch C1 193
Earring C2 194
Necklace C3 195
Stuffed Bear C4 196
Stuffed Dog C5 197
Stuffed Pig C6 198
Emerald C7 199
Opal C8 200
Goblet C9 201
Ear Tip CA 202
Empty Bottle CB 203
Gown CC 204
Ribbon CD 205
Fry Pan CE 206
Small Knife CF 207
Pot D0 208
Chop Block D1 209
Apron D2 210
Dragon Egg D3 211
Crown D4 212
Secret Map D5 213
Miracle Gem D6 214
Silver Wick D7 215
Royal Statue D8 216
Silver Tarot D9 217
Golden Pawn DA 218
Crown Jewels DB 219
Wind Flute DC 220
Escape DD 221
Magic Jar DE 222
Dragon Tooth DF 223
Grilled Newt E0 224
Poison Pin E1 225
Might Sword E2 226
Straw Doll E3 227
Long Nail E4 228
Bomb E5 229
Alumina E6 230
Power Oil E7 231
Elven Bow E8 232
Artea's Bow E9 233
Might Bow EA 234
Dummy EB 235
Dummy EC 236
Dummy ED 237
Dummy EE 238
Free Door EF 239
Sheran Key F0 240
Letter F1 241
Dais Key F2 242
Shrine Key F3 243
Pirate Key F4 244
Light Key F5 245
Oil Key F6 246
Green Jade F7 247
Red Sapphire F8 248
Blue Jade F9 249
Purple Newt FA 250
Glasdar Key FB 251
Magic Flavor FC 252
Fairy Kiss FD 253
Not Used FE 254
Not Used FF 255
|---------------|--------------|-----------------|
Note that there is some oddity in this list, such as two items named "Bomb",
and at least 5 "Dummy" items, and then there's "Free Door" on top of that.
Not only that, but several of these items, such as "Sheran Key", go into your
Scenario page, not your item list. But, I digress -- you can add them in to
your SRAM file anyway.
===============================================================================
---------------
VI. Magic List
---------------
When you are reading through the magic section of the SRAM data, use this data
to decode (or modify) what you are reading [again, see section IX. Other Notes
for information about how HEX numbers work]:
MAGIC NAME HEX NUMBER DECIMAL NUMBER
|-------------|--------------|-----------------|
END OF LIST 00 0
Flash 01 1
Bolt 02 2
Thunder 03 3
Spark 04 4
Flame 05 5
vulcan 06 6
Dew 07 7
Water 08 8
Flood 09 9
Bang 0A 10
Blast 0B 11
Sunder 0C 12
Frost 0D 13
Blizzard 0E 14
Glacier 0F 15
Perish 10 16
Succumb 11 17
Drowsy 12 18
Fright 13 19
Drain 14 20
Dread 15 21
Deflect 16 22
Bounce 17 23
Absorb 18 24
Fake 19 25
Trick 1A 26
Confuse 1B 27
Bravery 1C 28
Courage 1D 29
Shield 1E 30
Protect 1F 31
Mirror 20 32
Statue 21 33
Strong 22 34
Stronger 23 35
Champion 24 36
Boost 25 37
Valor 26 38
Poison 27 39
Stun 28 40
Dead 29 41
Rally 2A 42
Stone 2B 43
Waken 2C 44
Warp 2D 45
Escape 2E 46
Float 2F 47
Elf 30 48
Defake 31 49
Figual 32 50
Paraiz 33 51
Elegion 34 52
Elegi 35 53
Elegio 36 54
Absobl 37 55
|-------------|--------------|-----------------|
In case you do not recognize some of the last magic spells on that list, that
is because they must have been in there for test purposes. Without going too
much off topic, here is what it appears that these extra magic spells do:
Defake - Agility Down
Figual - Confuse
Paraiz - Paralyze
Elegion - Thunder Spell (all enemies)
Elegi - Flash Spell (all enemies)
Elegio - Bolt Spell (all enemies)
Absobl - Absorb Magic
The plus of some of these spells is that they cost only 1 or no MP at all to
cast, meaning you can give them to your low level party and completly rule
the entire game -- nevermind the great items you could give yourself as well.
===============================================================================
----------------------
VII. Revision History
----------------------
Version 0.5 - February 02, 2010
Version 1.0 - February 20, 2011 *CURRENT VERSION*
Currently working on for next update... Experience Offsets and Stat Offsets...
===============================================================================
--------------------------
VIII. Contact Information
--------------------------
You should be able to contact me via e-mail at: vegetaman@gmail.com
In leui of that, I post on the Lufia & The Fortress of Doom board over at
gamefaqs.com relatively frequently, so you can drop me a line there.
Also, there's a topic on RHDN devoted to Lufia you could check out:
http://www.romhacking.net/forum/index.php/topic,10287.0.html
And, failing that, you may be able to find new contact information, or new
information about projects I've got running, at my personal website:
https://sites.google.com/site/vegetaman/home
In case you were interested in my SRAM editor, you can pick it up from
links on my website (there's a readme to go along with it, as well):
https://sites.google.com/site/vegetaman/home/sramchecksum
===============================================================================
----------------
IX. Other Notes
----------------
Okay, a brief run through over how binary and hexadecimal are related and how
bits and bytes work and converting binary and hexadecimal to our human readable
base 10 decimal.
First! Computers store data as a series of 0s and 1s. Well, these 0s and 1s are
grouped into sets of 8 bits called a byte (a byte also can be said to consist
of two groups of 4 bits each, a left nibble/nybble and a right nibble/nybble,
which is a handy trick for something I will show you shortly). Anyway, binary
is a base 2 number system, so a byte will look like this:
_ _ _ _ _ _ _ _
128 64 32 16 8 4 2 1
Now, since it is base 2, you will see that from right to left:
2 to the 0 power is 1.
2 to the 1 power is 2.
2 to the 2 power is 4.
2 to the 3 power is 8.
2 to the 4 power is 16.
2 to the 5 power is 32.
2 to the 6 power is 64.
2 to the 7 power is 128.
All of these will sum up to one less than 2 to the 8 power, or 256.
So, if you have a 1 in that position, you add that value to the sum of the
byte, and if it is a 0, you do not. So, for example:
00001001 = 9 (since you have a 1 in the 1s spot, and a 1 in the 8 spot, and
8 + 1 = 9).
10010010 = 146 (since you would have 128 + 16 + 2, which is 146).
Now, there's something called hexadecimal, or HEX, which consists of base 16
numbers (and are usually signified by writing 0x before the number). The
numbers in HEX work like so:
0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 are all equal to what you think they are.
But, to get to 16, you have the addition of:
A = 10
B = 11
C = 12
D = 13
E = 14
F = 15
Now, to convert from hex to binary or binary to hex is the easiest thing in
the world, due to the 4 bit "nibbles" or "nybbles" I told you about earlier.
Take our earlier example of:
10010010
Now, split that into a left half and a right half:
1001 0010
Now, pretend -- just for a moment -- that these are two new binary values
that start out with 2 to the 0 power on the right and 2 to the 3 power on
the far left...
1001 = 9 0010 = 2
Okay, so now in hex, the value 10010010 would be 0x92 (or 92H). Simple, eh? It
works really quickly and is the simplest method I know. Try another example:
11110000 -> 1111 = 16 0000 = 0
Well, since 16 is F, and 0 is 0, the resulting value would be: 0xF0.
There's other cool things about binary, such as the fact that all the bits to
the right of a number add up to one less than itself. Again, for example:
01111111 = 127 decimal or 0x7F hexadecimal
Why? Because 64 + 32 + 16 + 8 + 4 + 2 + 1 = 127, which happens to be one less
than the value of the 2 to the 7th power, 128! But, I digress, this is a Lufia
SRAM guide, not an introduction to computers course...
So, on a final note, you may ask -- Why convert from hex to binary? Well,
namely because it makes it really easy to get to a decimal value, since binary
is pretty obvious. Also, you will need some understanding of how binary and
hexadecimal and decimal work together when you try to read a SRAM file in a
hex editor.
One final note on this front, when something takes more than one byte, you
just have to tack on the next batch of powers of 2.
1 byte = 256 possible values (Remind you of anything? Like... The
rupee counter on The Legend of Zelda
for NES?)
2 bytes = 65536 possible values (You will probably run across the number
65536 or 65535 a lot when playing SNES
games)
3 bytes = 16777215 possible values (I include this because it is the maximum
amount of gold that this game lets you
have)
So, if you have 2 bytes you need to convert to a decimal:
D3 E5
If it is little endian, you multiply the decimal value of E5 by 256 and add
it to the decimal value of D3. If it is big endian, you multiply the value of
D3 as a decimal by 256 and then add the decimal value of E5.
Same goes for if you increase it to three bytes:
42 F7 96
If it is little endian, you will covert all three of these numbers to decimal,
and multiply 96 by 65536 and multiply F7 by 256 and add those values up with
the decimal value of 42. If it is big endian, you multiply 42 by 65536, then
you multiply F7 by 256, and then you add those two values up with the decimal
value for 96 and that will give you your number. I'll tell you right now that
you may well wind up with some pointer math that deals with three bytes and
an offset (meaning a set value you need to start with to add the pointer to
to reference a location in memory), but I fear I am going out of the scope of
this document, so I will stop here...
It makes sense, right? 8-bit is 1 byte, 16-bit is 2 bytes, 32-bit is 4 bytes,
etc. etc. It seems like a lot of difficult math, but the more you use it, and
the more comfortable you get with it, it will become just like second nature.
I'll leave all the chat about assembly language to the pros. I do good just
being able to read it when coming out of a disassembler, honestly...
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X. Special Thanks
------------------
I have quite a list of people I would like to thank, so here it goes:
KingMike - The first person to set me off on this SRAM path, as you veered me
away from making just a save state evaluator and editor -- and not
only that, but you hunted down the checksum algorithm code for me,
without which this project would have never gotten off the ground!
DarkCecil - You were the first person to make me want to pick this project
up again after six months of activity and you had a lot of
great tidbits and ideas to share, especially when it came to
character EXP offsets and how everything worked in tandem.
Guktian Guk - Your e-mails made me re-examine my SRAM editor program and
discover about emulators wiping data on a save state load.
Jigglysaint - You too helped bring this project back to life, as well as
what will (hopefully) become a reference for the Lufia text
dictionary in the very near future.
Nightcrawler - You told me that doing this documentation as an aside from my
SRAM editor would be a good thing to share with the world.
creaothceann - Though a bit outside of the context of this SRAM guide, you
did show me what a proper SRAM editor should look like.
DarknessSavior - Thanks for being just generally a good supporter of my
several ongoing Lufia projects for over a year now.
John David Ratliff - Your great SRAM guides were a prototype or a starting
point for me. Also, you gave me the idea to throw a
GNU Free Public License or "copyleft" on this.
And lastly, thanks to all the good folks over at romhacking.net (RHDN) for
making all of this possible, as well as a few ardent supporters from gamefaqs!
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