Game file format

From Sp305x wiki

Game files (.BIN ending) are special executable files supported by some of the mp4 players. See the List of units "support .BIN" column.

A game-file consists of 2 parts: the 128-byte header and the actual executable code:

.bin game file format overview

header	executable code
128 bytes	remaining bytes

Header

Values taken from Mp4-pong header.

byte 0 to 11 (12 bytes)

header/file info?
'NGame1.0'								?
0x4e	0x47	0x61	0x6d	0x65	0x31	0x2e	0x30	0x80	0x00	0x00	0x00

byte 12 to 27 (16 bytes, string, zero terminated)

unknown
...	0x00

byte 28 to 43 (16 bytes, string, zero terminated)

"SPCA556" ?
0x53	0x50	0x43	0x41	0x35	0x35	0x36	0x00

byte 44 to 75 (32 bytes, string, zero terminated)

name of the game
...	0x00

byte 76 to 107 (32 bytes, string, zero terminated)

maker of the game
...	0x00

byte 108 to 127 (20 bytes)

unknown / flags? (e.g. screen rotation)

0x03

0x05

0x03

0x00

0x02

0x00

0x01

0x00

0x00

0x31

0x30

0x30

0x39

0x59

0x00

0x00

0x40

0x00

0x40

0x00

Executable code

Code from here is copied from nand/SD to RAM at position 0x24C00000. Then the game is called as a subroutine with entry point 0x24C00000. Returning to the os happens using a standard mov pc,lr-instruction. The code the game consists of is standard little-endian ARM9 machine code. It can call OS-calls to ask the OS to do stuff like play music, get keys, etc.