GBA save file checksums?

[BlackShark]

Hello guys

Does anyone of you now where I can find the checksums of the GBA save files (especially Ruby, Saphire, Emerald)? And how can I calculate it?

I think it's located at 0x7042 but I'm not sure...

[evandixon]

I don't see any checksums (or any data) there in Sapphire or Emerald. If it works like it does in 4th and 5th gen games, there's a block of data with a checksum at the end. Try looking there, or where ever a seemingly random 4 byte sequence follows or precedes data. Change things in game and look for that kind of change. If it's like in Black and White, the checksum may be a CRC16-CCITT. Other users may be able to help you more, but if not, post where you think the checksums are and I'll see chat I can do. For all I know, it could be like Mystery Dungeon Explorers of Sky (where data is split into 4 byte "words", added together, and part of the result is the checksum).

[Edit] Oh, also look at Pokebox GBA (listed in this thread), because it should be able to fix the checksums for you, helping determine where they are.

[BlackShark]

I already found some information about gen 3 checksum on Bulbapedia (here). I didn't look hard enough...

Thank you anyway!

[Kaphotics]

If you want something concrete, here's a program from 2004 that fixes the checksums for R/S

https://dl.dropboxusercontent.com/u/12206225/PSavFixV2.zip

included is a readme on how to use it, and the source code.

How it calculates checksums:

int Chksum(int length, int *Data)
{
int Chk,i,tmp;
length = length>>2;
Chk=0;
for(i=0; i<length; i++)
	Chk += Data[i];

tmp = Chk>>16;
tmp +=Chk;

Chk = (tmp&0xFFFF);

return Chk;
}