Holy crap, man. This is tougher than NES text hacking.
I just want to make sure I understand what I'm actually looking at here.
If anyone here has tried to translate, or simply text hack Devil Children Black Book, you'll notice how the PPU instead of showing all text characters at all times, will dynamically change to whatever text characters are needed. Nah' mean? If not Devil Children, perhaps other GBC games use this method maybe?
I've done famicom translating before and I've never encountered a PPU as dynamic as this.
I'll show some example pictures below.
So, I'm just going to focus on the top row text.
Looking at the MAP, the first address with text is $99C1, and ends at $99D2.
Proceeding through text as well will always display the same bytes in that address stream (DC, DE, DF, etc).
What I'm interpreting this as (and I might be wrong), is that $99C1 - $99E1 is always a fixed value, which are the bytes:
DC DE DF E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED
Those bytes are fixed on $99C1-$99E1, but the value they're pulling from is not. Said "From" is the PPU, which is dynamically changing DC - ED's values.
You guys think crazy hacking is required to decipher this stuff?
Or maybe, within the rom, there's a set of bytes representing what gets applied into the PPU for specific text use? I never tried looking for that, and I'm not sure what the byte value of each character would be either.
Eh... Sorry if this explanation sucks. Truth be told, I don't really get it but I'd like to understand it I guess.