8x8 Tiles mapping for monsters of FF3us, written by Lord J, Feb. 2000
lord_j@hotmail.com, http://www.angelfire.com/pq/jumparound/index.html


We will assume that you already have decoded your 8x8 pixels tiles at 
offset 0x297200 (3 and/or 4 colors bmps). These tiles forms a very 
long string of 8x8 pixels tiles. Lets experiment with the guard bitmap, 
wich tiles starts this string. We can approximate the size of this 
specific bitmap with a snapshot and any good bitmap editor. The 
resulting size is 32 pixels of width, and 48 pixels of length (or 4x6 
tiles).

We will represent a 8x8 pixels tile by this character: #

One might expect the guard bitmap to be mapped like so:
         ####
         ####
         ####
         ####
         ####
         ####

In fact, the tiles are mapped this way; to the right, the binary 
result of the 'mapping':
         ###-----   ==> E0
         ####----   ==> F0
         ####----   ==> F0
         ####----   ==> F0
         -###----   ==> 70
         ###-----   ==> E0
         --------   ==> 00
         --------   ==> 00
                         `-----> a string of eight bytes
                              

Where a `-' is a blank tile, not picked in the tiles string.


This allows reduction of tile use: empty tiles do not clog up
the ROM. It is a primitive, but effective form of compression.

So, instead of using a 4x6 tiles stencil, a standard 8x8 stencil
is used, and the tile mapping is done by a seperate bank.

The big bitmaps (bosses like Atma) uses 16x16 tiles stencil,
we dispose of 48 different maps, following the 128 8x8 stencils
(consult pointers meaning at the end).
Each string will need 32 bytes instead of 8.


Descr.: 2 Pointers
Base: 12AA20
Length: 4 bytes or 2 words
A824: Small stencils index (absolute: 0x12AA24)
      Reminder: small stencils are 8 bytes long, and the next pointer
                indicates that 128 of these stencils are used.
AC24: Big stencils index (absolute: 0x12AA24 + (AC24 - A824))
      Reminder: big stencils are 32 bytes long, 


Descr.: Tile mapping for monsters
Base: 12AA24
Length: 8 for the first bank, then 16 for the second bank
Number of strings: 128 for the first bank, 48 for the second
Note: The first 2 words are pointers, relative to the maps (A824 & AC24 ???)


Analysis on Guard bitmap (0x297200)
Mapping:
E0 F0 F0 F0 70 E0 00 00 (0x12AA24)