LOGO files are optional structured files to create custom CD loading animations.
The system ROM loads one of these files according to the console's nationality setting at address $120000 if present in the CD's root. The possible file names are LOGO_E.PRG, LOGO_U.PRG, and LOGO_J.PRG.
The files must not be larger than 2048 bytes.
(known values: $0000, $0001, $0003)
The 8 low bits are stored to $11C817 by the system ROM.
No other bits seem to be checked by the system ROM.
The above is true on the first IPL load only. Some games have different in-game loading graphics that do not follow the above. More information is needed on how these work (SAMSHO4 for example).
|2+4||Longword||Absolute data start address (Starting from $120000)|
Fix tiles data
- Offset (longword) $4000 = tile $200
- Size (longword) $4000 = $200 tiles
- Tile data...
Like the regular fix graphics format, but byteswapped.
- Palette number (word), the loading bar seems to use palette 0, so don't use it. Remember that fix tiles can only use the 16 first palettes.
- 16 words of color data.
- Fix address where to start mapping ($7102 is good)
- Width in tiles (word) $18
- Height in tiles (word) $0B
- Tile numbers/palettes...
Mapped left to right, top to down.
Animation map data
All values are words
- Fix map address where to start drawing ($7102 is good)
- Width in tiles
- Height in tiles
- Number of frames in animation
- Animation speed (in frames)
- Raw tile numbers/palettes as in the fix map...
Using LOGO files for in-game loading
By default the system ROM will always use the initial LOGO file during in game loading sequences. It is possible to change this by loading a new data over the logo information at $120000. How this gets loaded is not yet confirmed but its suspected that games request the data to be loaded as it would any other data given there is not need for 'LOGO' to be in the file name in this situation. It may also be possible the system ROM looks out for data being loaded into this region before drawing.
The ability to change the default progress bar (handled by the system ROM) is also available. The system ROM places the start address of its code to handle progress bar drawing at $11C80C. This code is then always called via 'MOVEA.L 0x11C80C,A0', 'JSR(A0)'. To use a custom progress bar simply place the start address of your custom progress bar code at $11C80C. Current progress bar state is held at address $10F691. Your code should handle all elements of drawing the progress bar.
It appears games plant their custom progress bar code into the default LOGO file as well as any further files that get loaded to this range. Below is the routine used by Samurai Shodown IV as seen in file 'JL_ST1.PRG' once in RAM. The main game program code places 0x120086 to $11C80C
120086 4EF9 0012 4AD0 JMP 0x124AD0
124AD0 4DF9 003C 0000 LEA 0x3C0000,A6 124AD6 41F9 0012 4B00 LEA 0x124B00,A0 124ADC 1239 0010 F691 MOVE.B 0x10F691,D1 124AE2 0241 00F0 ANDI.W #0xF0,D1 124AE6 D0C1 ADDA.W D1,A0 124AE8 203C 719B A200 MOVE.L #0x719BA200,D0 124AEE 7E0F MOVEQ #0xF,D7 124AF0 1018 MOVE.B (A0)+,D0 124AF2 2C80 MOVE.L D0,(A6) 124AF4 0680 0020 0000 ADDI.L #0x200000,D0 124AFA 51CF FFF4 DBF D7,*-0xA [0xC00422] 124AFE 4E75 RTS