Updates:
9/3/2000 Header added, bit numbering section rewritten
The most recent copy of this document can be obtained from the Tower of Bab-Il
(http://minitrue.weyland-yutani.net/tower/index.html).
This document uses normal bit order (bit 0 is the least significant bit).
All text documents, including this one, were written and maintained with the
MSDOS edit.com program, and are meant to be viewed with a fixed-width font.
All numbers on this page are in hexadecimal unless stated otherwise (such as
by being written out in words). All data addresses in these documents take the
form of offsets into the ROM file, including the header added by game back-up
units, which is 200 bytes long. When working with headerless ROMs, subtract
200 from all such addresses. Code addresses are written in the form XX:XXXX,
which reflect the actual values of the program bank and program counter
registers (and therefore do not include the header).
Two schemes of bit numbering are used here: "normal" and "reverse". At the
beginning of each document it is indicated which is used (if the document
specifies any bit numbers at all). In the "normal" bit numbering scheme, the
bits are numbered from least significant to most significant, starting with 0.
In the "reverse" bit numbering scheme, bits are numbered from most
significant to least significant, starting with 0.
During execution of most FF2 code, the A register is 8 bits wide and the X and
Y registers are 16 bits wide. The D register is always 0, allowing the
accumulator to be cleared with a simple TDC instruction (the code does this a
LOT). The DB register is usually 7E, pointing into WRAM, unless hardware
registers are to be accessed.
Please be aware that two different versions of the FF2 ROM were produced; the
information contained on this page pertains to version 1.0 (known to Game
Genie owners as version "A").