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Topics - umaggot

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Programming / ARM/THUMB compared to 6502 ASM?
« on: May 14, 2011, 01:53:08 am »
I have a general question about ARM/THUMB hacking; it's mainly about getting started. Granted I've worked with ASM two years ago -- and fairly recently as well, GBA hacking seems to be a whole new ballpark. I usually use a combination of a cheat finder, debugger, and hex editor, not unlike what FCEUXDSP has. What I want to know is this: how could I apply the same principles -- ruling out addresses with a cheat finder, and then using a debugger to stop all of the action immediately when the address and function I'm looking for has been called, in VBA (or VBALink)?

For a game specific example, The Legend of Zelda: Four Swords for the GBA. I've been using the cheat finder to call out differences between when linked, and when unlinked -- specifically, in-game and after forcing a disconnect (in-game error screen). I haven't been using any specific numbers in the search. The problem is that I can't seem to find any specific address that calls for a link connection. I've tried checking for different address bit sizes as well, but I still end up with 0 entries by the time I'm done comparing. When I had only a handful of addresses that I saved from the search, I'd only managed to successfully find an "A button prompt" cheat (which tells you to press A on the title screen, but doesn't allow you to actually do so and enter the game). My goal is to make the game entirely single-player. If I had to take a guess, I would say that it has something to do with a multiplayer-specific call, that is made on the second VBA Link window. I don't claim to know exactly what I'm talking about, but just out of curiousity, if that were the case -- how would I work around it?

That should just about do it for questions, thank you for taking the time to read this.

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