Sonic 2's level select in Sonic 1

This guide was originally written by Esrael, though it was made for the Outdated disassembly by DRX, so credit also goes to Esrael.


This guide was designed for use with Snasm68k (v2.1D) =P


Firstly, make a back-up of all your current work.


Secondly, open sonic1.asm, and go to Title_ChkLevSel, replace it with:



Title_ChkLevSel:
tst.b ($FFFFFFE0).w; check if level select asm is on


beq.w PlayLevel; if not, play level


jmp Level_Select_Menu; Go to Sonic 2 Level Select


moveq #2,d0


bsr.w PalLoad2; load level select pallet


lea ($FFFFCC00).w,a1


moveq #0,d0


move.w #$DF,d1


rts



Then, go to endofrom, and before that, add the following lines:



s2_menuasm:
include 's2_menu.asm'



Now, open up _inc/Pallet Pointers.asm, and underneath



dc.l Pal_Ending
dc.w $FB00


dc.w $1F



add the following:



dc.l Menu_Palette; pallet address
dc.w $FB00 ; RAM address


dc.w $1F ; (pallet length / 2) - 1



Finally, extract this file into the same directory as sonic1.asm


------------


Some people not using Snasm68k get the following error:

Code:

SN 68k version 2.53



C:\USERS\INFINITI\DESKTOP\S1 - COPY\S2_MENU.ASM(125) : Error : Illegal value (64

416)

lea $fba0(a2),a2

Errors during pass 1 - pass 2 aborted

Assembly completed.

1 error(s) from 48844 lines in 0.17 seconds

Lightning's ROM Padder

So to fix that, go to line 125 in S2_MENU.ASM and replace



lea $FBA0(A2), A2


with

Code:

lea     $FFFFFBA0(A2), A2

Expect more guides as I learn more. =P

 

This is just awesome! But there is one thing, I can't get:

You know, the code under the jmp will be ignored, so why are you keep it there? Also, you just added the jmp line, so "replace" isn't the right word, it'll be much better, when you call it "Add this line (~the jmp line~) under the beq.w line and delete the code under it (to the rts)." or something like that.


Just a few ideas. =P

 

Yeah, i'm just a little lazy =P

 

Hello I have a small bug with soundtest


I play sound : 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13


bug at 14 I have : illagal instruction$9091A44B


Please help me and your tutorial is Great !!! B)


Sorry for Bad grammar Because i'm French

 

Hello again I resolved my problem


Just add a music in the slot 94

 

Wrong Topic huh? You know, you have to post in the "Sonic Specific Modification" forum. Split please.

 

Not really. With the level select, tends to come a sounds test too =P The person from what I see was having a problem with that but figured it out.

 

Heh, i wouldn't of noticed this since I already have music in the slot. Thanks for pointing it out Hyper b^_^d

 

*bump*


An asterisk is missing on the level select screen, however it can be rectified by going to Menu_Clear_Act_x in s2_menu.asm and uncommenting the 2 lines after dbra D1, Menu_Clear_Act_x:



lea $FFFFFF10(A2), A2
move.w #$001A, (A2) ; Load "*"



I added FFFF before FF10 in case it provided incompatibilities with ASM68K.

 

A few weeks ago someone was testing my hack on real hardware and helped me at fixing some bugs to make it work. However, then he said (something like this):


"The S2 Level Select screen gives you an illegal instruction, but you can just press C to skip that. Not a big problem."


Well right, not a big problem, but it still annoys me. So I decided to look through Esrael's code another time to find the problem, and I found it! Here's a simple guide:


1. Open the file (s2_menu.asm) and make a search for Inicializa o contador das animações do menu (I don't know what the hell that means, but I think it's the easiest way to find that line.)


You should see this:



;-------------------------------------------------------------------------------
move.w #$0000,($FFFFF7B8).w ; Inicializa os quadros das animações do menu


move.w #$0000,($FFFFF7B9).w ; Inicializa o contador das animações do menu


jsr Dynamic_Menu ; Chama a rotina de animação


;-------------------------------------------------------------------------------



You don't need much ASM knowledge to understand what's wrong here, but I'll explain the bug anyway: You can't clear odd RAM adresses using words or longwords (well, at least not on real hardware and some emulators).



move.w #$0000,($FFFFF7B9).w ; Inicializa o contador das animações do menu


This line causes the error.


2. To fix that you can simply replace those two move.w lines with a single clr.l line, for example this:



;-------------------------------------------------------------------------------
clr.l ($FFFFF7B8).w ; clear RAM adresses $F7B8 to $F7BA


; move.w #$0000,($FFFFF7B8).w ; Inicializa os quadros das animações do menu


; move.w #$0000,($FFFFF7B9).w ; Inicializa o contador das animações do menu


jsr Dynamic_Menu ; Chama a rotina de animação


;-------------------------------------------------------------------------------



After that the bug should be gone and the S2 screen should completly work with real hardware.


(Also, please don't tell me there are smarter/alternate ways, cause I know that myself.)

 

It means to Start the counter for the menu animations.

 

I shall bump, but just thought I'd let everyone know that the link in OP is broken making this guide..not work. :>

 

Yeah, I noticed. I don't have the original files either. (Though, I did recreate it, but it's now heavily modified, so that's no good for this guide).


Though you can download Esrael's version, which is made for his disassembly, it just requires pointing subroutines to their sonic 1 equivalents, and it's a small, easy, good way to learn.

 

I mirrored all the forum tutorials on the main site for exactly this reason. Fixed the link at the top too.


http://sonicresearch.org/tut_archive/Sonic...iles/s2menu.rar

 

This Tutorial Is Amazing And Is Easy To Modify It In ASM Greetings !!!