Menu HDMA Colors

thanks to Chickenlump and JLukas

General Information[edit]

Chrono Trigger[edit]

I couldn't find the HDMA color menu in the ROM for the dialog boxes for the locations, I assume it's generated somehow, and not read from a hardcoded table. The menu HDMA colors are in the ROM easily editable, and I was hoping that the dialog boxes would be similar. Sooooo... I found the routines, and cheated the game into reading my own table I created in some freespace.  :lee:

First up, the Menu HDMA colors:

Menu HDMA color loading
$C2/86DD   08    PHP   
$C2/86DE   8B    PHB   
$C2/86DF   C2 30   REP #$30   
$C2/86E1   A2 71 87   LDX #$8771     //8771 = C28771(ROM Address for HDMA Color table for menu)    
$C2/86E4   A0 E9 9D   LDY #$9DE9     //9DE9 = 7E9DE9(RAM Address for HDMA Color Table for menu)   
$C2/86E7   A9 1F 00   LDA #$001F     //1F = 30 bytes to copy
$C2/86EA   54 7E C2   MVN 7E C2

The 30 byte table is located at C28771 in the ROM.

02 E8 02 E7 02 E6 02 E5 02 E4 02 E3 02 E2 02 E1
02 E0 82 E1 82 E2 82 E3 82 E4 82 E5 82 E6 82 E7

The first row is the top half of the colors, the second row is the bottom half of the colors. Change the color and direction of the colors. The bytes seem to go as DirectionByte then ColorByte. So if you just want to change the colors only, leave the 02's and 82's alone.

The menu was easy. The dialog boxes, I had to make my own table for. The game generates a table at 7F1538 and copies it to 7F1600. The dialog boxes need both tables, and both are exactly the same. I copied the table in RAM and moved it to some freespace in the ROM.

$FD/D5C5   A2 38 15   LDX #$1538   //First table
$FD/D5C8   A0 00 16   LDY #$1600   //Second table
$FD/D5CB   A9 FF 00   LDA #$00FF   
$FD/D5CE   54 7F 7F   MVN 7F 7F   
$FD/D5D1   E2 20            SEP #$20   
$FD/D5D3   60               RTS   

At FDD5C5, I changed to

20 79 67 60

This jumps to my modified routine in some freespace.

The address for my routine is FD6779.
At FD6779, my new code is

A2 99 66 A0 38 15 A9 FF 00 54 7F FD A2 99 66 A0
00 16 A9 FF 00 54 7F FD E2 20 60

This loads my custom table from some freespace in the ROM.

The new table is right above the new code.

The table address is FD6699. This table you can modify to change the colors of the gradient, the direction of the gradient, etc..

Here is my custom table, pasted at FD6699:

01 A8 01 A8 01 A8 01 A8 01 A8 01 A7 01 A7 01 A7
01 A7 01 A7 01 A6 01 A6 01 A6 01 A6 01 A6 01 A5
01 A5 01 A5 01 A5 01 A5 01 A4 01 A4 01 A4 01 A4
01 A4 01 A3 01 A3 01 A3 01 A3 01 A3 01 A2 01 A2
01 A2 01 A2 01 A2 01 A1 01 A1 01 A1 01 A1 01 A1
81 A0 81 A0 81 A0 81 A0 81 A0 81 A1 81 A1 81 A1
81 A1 81 A1 81 A2 81 A2 81 A2 81 A2 81 A2 81 A3
81 A3 81 A3 81 A3 81 A3 81 A4 81 A4 81 A4 81 A4
81 A4 81 A5 81 A5 81 A5 81 A5 81 A5 81 A6 81 A6
81 A6 81 A6 81 A6 81 A7 81 A7 81 A7 81 A7 81 A7
81 A8 81 A8 81 A8 81 A8 81 A8 81 A9 81 A9 81 A9
81 A9 81 A9

I can't really recommend using this for your hacks just yet, as TF will probably overwrite it. The Menu HDMA table you can overwrite and change without worry though. This is just something I was scratching my head over for awhile, even if I had to cheat to get my own colors on there.

Hmm, I just had a look at this. You're right, the HDMA colors are generated instead of using a table. In fact, the routine is directly above the first table/second table copy routine posted above. After examining the pattern you used for your custom table, I came up with the following. Enter these PAR codes on a fresh, unmodified CT:


Look familiar?  :D

FDD55A-FDD57F is the routine for the first color/top half

FDD599-FDD5B2 is the routine for the second color/bottom half

The only part I'm not sure on is what FDD580-FDD598 is doing. It has something to do with how the two colors blend in the middle of the textbox. The value at FDD58C should probably be set to the same value FDD57B and FDD59A are using.

I was pretty sure that's what the whole routine did, but couldn't quite wrap my head around it. I certainly needed some more ASM experience, so I thought I'd come back to this. It's fun changing the way the game works.

The MVN command is quite useful, copying large chunks of data from ROM to RAM, and RAM to RAM.

I suppose they wrote the routine to generate that table to save 255 bytes that would have been taken up by the table, but looking at how much freespace and junk is left in the final ROM, it doesn't appear to have mattered much.

The overworld select minimap also uses a generated table, copied twice in RAM, one after the other. It's quite a huge table. I'll pinpoint it's routine later tonight.

From: Modification