how to make master code for sega saturn?

[lee4]

how to make master code for sega saturn?

specify for capcom fighting games that never got USA release

[Helder]

Most games for the Saturn use these master codes which I updated here on the Wiki but I have some more info to add to that which I will post here.
Using C305 or C3?? (insert a value here) sets a jump to a location in memory that then call an RTE so it jumps back to the next instruction following the Master code address and as far as I can tell from looking at some games that area of code is around the Header of the game but 95% of all Saturn games use this area and is called constantly to memory and doesn't seem to affect game play or instructions that are vital to game play. Now the ?? in the C3?? I'm not entirely sure as to what it does or if it even makes a difference since all variables go to the same memory location that calls for the RTE instruction.

The 230B (thanks gedowski for bringing this to my attention) acts like a joker command that is set to the Reset Button on the console itself which is cool in my opinion and you can't reset the console with this Master Code variation. I haven't experiment with it too much but it does work and in that Street Fighter game it made me go past that Loading screen but Froze the game as soon as I hit the Reset Button. I assume it makes a jump to the same area the C3?? variation does once the condition (Reset Button pressed) and won't jump till the condition is met again. I will test other values to see if other buttons can be used.

The FFFF I assumed to not be a functioning code since I have tried one Megaman game that had that as it's Master code and the game never went past the Sega logo just like many other non functioning Master Codes (Seems some Capcom Games need to use this variation). Looking it it with a debugger it just says its an invalid instruction but this actually makes the hook and doesn't jump to the area of memory to the RTE (still need to verify this but its my assumption).

I'm sure other values do other things, but now for the other 5% of the other games that have no Master Code or that these don't work I have discovered that the games stops accessing that header area once the Sega Logo disappears and the actual game starts to load. The Master Code needs to load a hook at the Sega Logo and it has to be an address that is called throughout the game but here lies the problem to this: To hook an address you must over write the instruction with the one we plan on using (one of the 3 I just explained above) but sometimes these instructions are needed to make the game function properly so alot of trial and error is needed to test which address we can use with minor issues on actual hardware since an emulator will continue where real hardware might not.

[lee4]

Datel had article on the Sega Saturn Master Codes

First thing its talk about reset button hook.

http://web.archive.org/web/?http://www.datel.co.uk/saturn/satind.htm

Inside the their AR Flasher for Sega Saturn in the VERSION.TXT file,
states Master code with FFFF hook for version 1.90 or higher and can't use on lower versions.

http://web.archive.org/web/?http://www.datel.co.uk/binaries/sat_comm.zip

I still till today have no idea what the 2nd line is for

I can't find any info the B6 does neither.

[Hacc]

The Yabause Action Replay wiki has info on all of the commands.

These two threads have a bunch of useful info spread throughout the page (there should be a link to some Street Fighter hacks, too). You'll need to view some of the links via the Wayback Machine.

Thread 1
Thread 2

[Helder]

Finally some god damn info on that second line although I don't see how useful it is to modify as I have seen no ill effects on all games I have tested besides the custom Master code for Assault Leynos 2 but that has nothing to do with that second line. Good job Hacc and Lee4 on digging up info.