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Author Topic: [GBA] Need some help editing a tiled background (Can't find offset)  (Read 1624 times)


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Hey guys I need some help with my first graphical mod.
I'm working on a simple mod for "Megaman Battle Network"
 where I change the pause screen from
This--> TO:  ->
I've been following some guides and I've made sure the image is index, and I made a pallet file for it.
But, I run into trouble when most the guide just straight up tell you the offset for the specific game.
Since as a pretty much non-existent modding scene, I could not find any offsets.
I've checked other guides, (that where more for sprites), and they'd say, use yy-chr/nlz-gba/unlz-gba.tlp/GBA GE/TM/TilEd/CrystalTile to search your rom for the tiles/ sprites manually.
And I've tried every single one. I've found a few sprites, but not the tiles, when using tm/yy-chr, I found some thing that 'might' be the right thing, but  the tiles are so small that even with the proper pallte it's almost impossible to say for sure.
The last thing I tried was looking it up from vba,
I went into the map viewer to see where the background is in memory, and I found the memory address:

IT says the map base starts at:  0x0600E000 and ends at 0x0600E7fe
with a size of 254x254

So I dumped that entire section of the ram,
While I could not find the whole thing in my rom, Quite a bit of it was, and it was in order too!
Left: ROM ---Right: Memory Dump

I tried going to the start of this shared data in the tile viewers, but all it showed was garbled pixels.

Is there any other way for me to locate and edit this tiled background?


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Re: [GBA] Need some help editing a tiled background (Can't find offset)
« Reply #1 on: September 17, 2017, 08:32:34 am »
There are a few places which delve into megaman battle network as their thing out there (if you can find where that rockman bn 4.5 translation was happening it might get you somewhere), perhaps not to the extent of some other games but more than most. I will assume for now that your ability to search is up to the task though.

Sounds like you may want to take your first graphical mod as far as learning tracing, though you already have many of the steps done (sounds like you already have data in the ROM, and it does not look compressed either) so you can skip some of the tedium in place of putting a break on read on the relevant part of the ROM section. With that in place you can follow what happens on its way to the VRAM, either with an eye to doing what it does or simply subverting the map and eventual VRAM data reads to your own location in the ROM. It may be that you can smack crystaltile2 hard enough after all that (it is probably the best at tackling random game with mapped BG type affairs but that is not high praise as most of that is trickle backwards from the far superior DS options) and the tracing is irrelevant but if not then you have the info and either way you are in good stead for when you next have to trace in anger. is my usual suggestion for a my first tracing session document (especially for graphics) but I might say try to adapt what it says for no$gba, the debug version of which is better and free these days.

Otherwise that should be doable. Plenty have ran into memory trouble on the GBA and DS playing with BG and mapped images but the complexity does not look too much greater and you may even be able to claw some back if you don't need that quasi gradient effect going on.

Also that would be 256xsomething. The 254 is the overflow value rather than the "tile" size, though if it is a mapped image then it might be back to what could be 8x8 tiles there.

Alas I am not in a terribly good way right now or I might have a little prod at this myself.

Keep it up -- the vast majority of posts like this I help with would have thrown their hands up long before they thought to take the VRAM data and have a little searching session in the ROM.


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Re: [GBA] Need some help editing a tiled background (Can't find offset)
« Reply #2 on: September 18, 2017, 12:03:21 am »
Thanks! that should help a lot!