A few questions about RAM usage

Ambil · Aug 16, 2005

I am writing some lines in the Sonic 1 dissasembly, and I need some information about it. So I want to some locations in the RAM, regarding:

The current X camera position.
The current Y camera position.
The current X Sonic position.
The current Y Sonic position.

Another information I need for my program is where the current input from the joypad are located, yet I had a look at drx's Assembly notes and checked it's at 0xFFF604.

Thank you for helping me.

~Ambil

Sonic 65 · Aug 16, 2005

$FFFFD008: Sonic's X position
$FFFFD00C: Sonic's Y position

Dunno where the camera position is, though.

LOst · Aug 16, 2005

$FFF700 Camera X
$FFF704 Camera Y

$FFF604 Input hold (Use this for button holds)
$FFF605 Input click (Use this for button clicks)

Sonic 65 · Aug 16, 2005

Here's a value list too:

F0 = Any button
80 = Start
01 = Up
02 = Down
04 = Left
06 = A
08 = Right
?? = B

When you want to check if a button is pressed, simply use the following code:

andi.b #$xx,($FFFFF605).w ; Check if xx is pressed
beq.w subroutine_before ; If not, go back...
[custom code here]

Same if you want to check if it's being held; just replace FFFFF605 with FFFFF604.

Aurochs · Aug 16, 2005

Sonic65 is way off.

Bitfield:

SACBRLDU

And that, I believe, is a standard across most Genesis games. Or, at least those developed by Sega. :P

Ambil · Aug 16, 2005

Thanks guys, but I have some things to say.

I wish to know what do address 0xFFF7CC store in the RAM.

And Sonic 65, that's a good idea, but now that I know the bits in the drx's guide,

The joypad output format:

Bit 7 - Start
Bit 6 - A button
Bit 5 - C button
Bit 4 - B button
Bit 3 - Right
Bit 2 - Left
Bit 1 - Down
Bit 0 - Up
Click to expand...

I guess the codes for the buttons would be:

Code (Text):

$80 - Start

$40 - A button

$20 - C button

$10 - B button

$08 - Right

$04 - Left

$02 - Down

$01 - Up

Example:

my_program:
andi.b #$11, ($FFFFF604).w ;test if B and Up are holded
bne.s _return_

(custom code)

_return_
rts

LOst · Aug 16, 2005

SACBRLDU

LOst · Aug 16, 2005

Ambil said:

I wish to know what do address 0xFFF7CC store in the RAM.
Click to expand...

$FFF7CC is a byte flag cleared when going into debug. If it isn't cleared, it will store the last keystrokes for Sonic in $FFF602

EDIT: Well, simply if it is set to something other than 00, it will stop Sonic from taking input. Nothing is really doing this in the game that I know of.

Ambil · Aug 16, 2005

Well, my program is completed (I think). I now wish to know where is the routine in the disassembly where the game is paused.

Note: I use drx's disassembly. It's quite useful, but I would like to grab Hivebrain's one, since I heard it's much nicer. Now that Hacking CulT is down, I can't download it, so anyone to do me this favour, please.

Tweaker · Aug 16, 2005

Hehe, you guys should read Saxman's S2 Guide more. It has all this shit in there.

Ambil · Aug 16, 2005

Tweaker said:

Hehe, you guys should read Saxman's S2 Guide more. It has all this shit in there.
Click to expand...

Regarding Sonic 1?

Hivebrain · Aug 17, 2005

LOst said:

Ambil said:

I wish to know what do address 0xFFF7CC store in the RAM.
Click to expand...

$FFF7CC is a byte flag cleared when going into debug. If it isn't cleared, it will store the last keystrokes for Sonic in $FFF602

EDIT: Well, simply if it is set to something other than 00, it will stop Sonic from taking input. Nothing is really doing this in the game that I know of.
Click to expand...

$FFFFF7CC is the "ending mode" flag, used during the ending sequence. If it's set to 01, then the controls are locked.

Tweaker · Aug 21, 2005

Ambil said:

Tweaker said:

Hehe, you guys should read Saxman's S2 Guide more. It has all this shit in there.
Click to expand...

Regarding Sonic 1?
Click to expand...

Yep. S2 was built off S1, and uses most of the same RAM locations. Besides that, the button format is universal.

A few questions about RAM usage

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