Sega Master System Game Genie Op Codes?

[orcanaoftime]

Hi all,

I'm having a tough time finding the right value(s) to complete some Game Genie codes for the Sega Master System & Game Gear. Here's what I've been able to figure out so far:


After reading Whipon's great MESS tutorial, I'm using the Mess emulator to find (or use existing) PAR codes, then trying to make a Game Genie code out of that. So for example, the game Streets of Rage 2, the PAR code 00CCFF:03 is Infinite Lives.

The address 931F B7 is where the lives are stored. What I can't figure out are the last 2 digits I have to use to complete the code! I keep running into this problem every time I try to make a Game Genie code.

Another example is 00CCE7:27 for Infinite Health (Streets of Rage 2 - SMS). So the address is 9486 C9, but again, I can't figure out the last 2 digits.

[Mezmorize]

I hope someone answers.

Me and you both are in the same boat, if I can't figure one out, I just move on to the next game/code and try again.
Nearly all the ones Ive made so far simply use 00 (NOP) to make the line of coding do nothing instead of what it's supposed to do.

Edit:
I just tried the two above codes, with no luck also.

But, I made an Infinite Time code for Streets of Rage 2:
006-1F7-19E

I would guess that the coding says to decrease the number, but with NOP, it never decreases...

[Pugsy]

So for example, the game Streets of Rage 2, the PAR code 00CCFF:03 is Infinite Lives.

The address 931F B7 is where the lives are stored. What I can't figure out are the last 2 digits I have to use to complete the code! I keep running into this problem every time I try to make a Game Genie code.

When you use wp ccff,1,w you will find that it will stop at the address AFTER the memory has changed - changing 931F will achieve nothing. You need to reverse the previous instruction at 931C so change "ld a, (ix+$49)" to "ld (ix+$49),a"....so something along the lines of 931D 7E should work.

Another example is 00CCE7:27 for Infinite Health (Streets of Rage 2 - SMS). So the address is 9486 C9, but again, I can't figure out the last 2 digits.

Again, If you used wp cce7,1,w then you will find that it will stop at the address AFTER the memory has changed - changing 9486 will achieve nothing. Make the RTS (C9) happen earlier - try poking 9483 with C9

[Mezmorize]

Thanks for that info.

I don't fully understand every aspect yet, but I'm getting it more and more now.

I didn't realize that all the address listed in the top square were accessing the address.
Nor did I put together that the values on the right could be for more than one line of code.



Took me a while to understand what you were meaning by the asm stuff, but I now see in the pdf that Whipon linked the line of code.



Thanks a whole lot for the info! I'll 'get' it all someday...

[orcanaoftime]

Many thanks for that info Pugsy, it will help a lot. Thanks to you too Mezmorize for the SOR 2 code.



edit: Damn, this is hard. I can whip up an NES Game Genie code no problem, not with the SMS and GG.


Well, back to trying again...

[Mezmorize]

Using info I learned from you, I was able to make a code work when I normally couldn't.

Here's the image:


The game is Power Strike (1) for the Master System.
The RAM address is C416 and the ROM address 427A writes to the RAM address.
I paid more attention to the line of code directly above that ROM address and noticed that it says 'dec'.
(IX=C400+0x16=C416)

I figured I would try to replace the DEC with ADD and see what happens and it worked!
I changed the:
DEC (IX+N) [DD 35]
to the closest thing I could find
ADD A,(IX+N) [DD 86]

So the ROM code is:
354278:86 <-Unencrypted for Fusion
862-78B-3BE <-Game Genie

[Pugsy]

Replacing DEC with ADD will work, but it might have side effects. For instance if it was a lives counter it would end up higher than it was ever envisaged it would reach and could cause gfx glitches/crashing - eg. trying to display a number higher than 9 on a single digit counter. Also note if it was a lives counter you changed DEC to ADD with then you'd get 250 ish lives rather than infinite.

Instead of going 5,4,3,2,1 it would go 5,6,7,8,9......253,254,255,0

It's better to try to use an appropriate LD or alternatively get a earlier branch...so for instance from the picture you posted 425A C3 may have the desired effect.


The cleanest solution here may be to change 4277 dec (ix+$16) to jr $4280 (18 07) but that would of course use 2 pokes

[Mezmorize]

Thanks for the info. I'm starting to understand a little better now thanks to you.

I should have noted what the code is.
It's an invulnerability code where the plane doesn't blink, and enemies die when they hit you.

Edit:
And you were correct, the earlier branch did indeed work.
C32-5AB-C41