A method I discovered hacking Genesis ROMS

[Whipon]

Well, you know, I like very much to hack Genesis ROMS to play them in a real Genesis with my Tototek's MD-PRO. So I wanted to be able to freely select weapons in Castlevania - Bloodlines.

Here's the result:

Joypad RAM Addresses:
Every Frame:
FF9060
FF930C

One Frame:
FF9061
FF930D

01,Up
02,Down
04,Left
08,Right

A,40
B,10
C,20
Start,80

Every Frame,
FF9064
FF930E

One Frame,
FF9065
FF930F

X,04
Y,02
Z,01

[B]00C4C6[/B]: 4EF9 0000 BC90 => 4EF9 [B]0005 1758[/B]


[B]0051758[/B]:
0051758:
4239 00FF 9C1D ;Set $FF9C1D to 0 to enable weapons;
0C39 0004 00FF 9065 ;Compare FF9065 (X,Y and Z read one frame address with 4 (X Value);
6616 ;If not equal branch to Always have 99 Lives;
5239 00FF 9C1F ;Add 1 to FF9C1F (Weapon Adress);
0C39 0009 00FF 9C1F ;Compare FF9C1F with 09;
6606 ;If not equal skip the next instruction;
4239 00FF 9C1F ;Clear FF9C1F;
(Values higher than 08 make the game freeze.
So this instruction will set it to 0 to avoid crashes)
13FC 0099 00FF FB2F ; Always have 99 Lives
13FC 0050 00FF 9C11 ; Infinite Health
13FC 0003 00FF 90DF ; Always have Powered Weapon
33FC 9900 00FF FB0E ; Always Have 98 Hearts
4EF9 0000 BC90 ;Jump to $BC90 (the replaced instruction at $[B]00C4C6[/B])

Everytime you press the X button your weapon changes to the next one.
It serves very well as an example to make similar hacks to other games to select an especific desired item in game.
The discover?. I didn't know that 3 buttons games have reads of the X,Y and Z buttons. I tought these buttons simply didn't exist in those games.

Well, I hope this one helps someone. It was very fun for me.
C U.

Whipon.

[scarface200729]

I suppose this would require more codes than the genesis game genie could handle. Good work tho.

[Whipon]

Of course n.n

Its not intended to be used with game genie. You can use it to play the game with an emulator, or to play it with a reprogrammable flash cart like Tototek's.
There's one more alternative:
Reprogrammable Genesis Cartridge
Have fun n_n.
Whipon.