ROM Hack Etrian Odyssey 3 Drowned City: Making cheat codes, questions on RAM + share what's done so far

demonata

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Just noticed that no$gba debugger is free already, so I picked it up and try to do something I wanted to.
There are quite a few codes for the JP version that changes game mechanics instead of in-game values,
and making the US version is my target.

So far my first US code is working great:
1st skill of a class is not restricted to main class anymore (can be selected in subclass skill list)
020A6C84 E1A00000

Now I'm working on my 2nd one, and needs some advice:
I want to create a code in US version like this one,
(JP version) item sell price multiplier (XX=03 will become 3 times)
020001E0 E3A040XX
020001E4 E0000490
020001E8 E8BD8010
020B5BE4 EAFD297D

I looked into the JP-ver. memory to see what these addresses are...
For the first 3 lines (also showing 1 line above/below here),
I have no idea what these are, and so far I cannot trigger break point on them, or find similar pattern in US version.
020001DC 64234507 strvst r4,[r3],-507h
020001E0 DE42641A movle p4,2,c2,c10,0,r6
020001E4 3A7A759F bcc 3E9D868h
020001E8 8ABAFD00 bhi 0EBF5F0h
020001EC BA392F23 blt 2E4BE80h

For the last address 020B5BE4, I found that it's part of the logic that runs when I 1st enter sell items menu
020B5BCC E5900008 ldr r0,[r0,8h]
020B5BD0 EBFD8A25 bl 201846Ch
020B5BD4 E1A01000 mov r1, r0
020B5BD8 E59F0014 ldr r0,=3ECCCCCDh
020B5BDC EBFD8A34 bl 20184B4h
020B5BE0 EBFD89F2 bl 20183B0h
020B5BE4 E8BD8010 pop r4,r15

After applying the JP code to JP-ver. of game, basically 020B5BE4 routes to the above 3,
which do the inflation math and the original pop instruction.
020001E0 E3A04003 mov r4,3h<=multiply by 3 as example
020001E4 E0000490 mul r0,r0,r4
020001E8 E8BD8010 pop r4,r15
020B5BE4 EAFD297D b 20001E0h

For US version, I'm able to locate the same set of logic running when I enter sell menu, location:
020B0458 E8BD8010 pop r4,r15

But for the first 3 lines, I really don't know what to do with them....
Are these address safe to be overwritten by this code (i.e. useless address???)

FYI I have zero knowledge about assembly level programming :)
++If there is a better place to ask about these, please let me know what forum it is, thx
 
Last edited by demonata,

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