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SCHG How-to

Difference between revisions of "Set up the Goggle Monitor to work with it"

From Sonic Retro

m (Made the new section more specific.)
(Added a GitHub adaption.)
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−
Did you know that there are 2 unused monitors in Sonic 1? The 'S' and 'Goggle' monitors. You can place and also destroy them, but nothing will happen. In the split is under "Obj2E_ChkS:" the code for the S monitor, but there is no code for the Goggle monitor! If you want to have that monitor to do something, you need to set it up first. It's not too hard, so I will explain it you step-by-step. (Bug fix added by Inferno Gear.)
+
Did you know that there are 2 unused monitors in Sonic 1? The 'S' and 'Goggle' monitors. You can place and also destroy them, but nothing will happen. In the split is under "Obj2E_ChkS:" the code for the S monitor, but there is no code for the Goggle monitor! If you want to have that monitor to do something, you need to set it up first. It's not too hard, so I will explain it you step-by-step. (Bug fix and GitHub adaption added by Inferno Gear.)
−
 
+
==Hivebrain disassembly ==
−
== Quick guide ==
+
=== Quick guide ===
 
I know there are many people who just want to rip off the code without learning because they think they have better things to do. For those people I took the time to make a simple copy/paste guide:
 
I know there are many people who just want to rip off the code without learning because they think they have better things to do. For those people I took the time to make a simple copy/paste guide:
  
Line 16: Line 16:
 
That was everything. If you are too dumb to add/understand this, then you weren't reading the real guide.
 
That was everything. If you are too dumb to add/understand this, then you weren't reading the real guide.
  
−
== Full guide ==
+
=== Full guide ===
 
This version tells you how to do this in detail, and very well explained. It's not more than what you can see in the quick version, but with comments and explanations you can learn something, so this one is recommended.
 
This version tells you how to do this in detail, and very well explained. It's not more than what you can see in the quick version, but with comments and explanations you can learn something, so this one is recommended.
  
Line 71: Line 71:
  
 
Obj2E_ChkGoggles:
 
Obj2E_ChkGoggles:
−
cmpi.b #7,d0 ; does monitor contain 'S'
 
 
bne Obj2E_ChkGoggles ; if not, branch to Goggle code
 
bne Obj2E_ChkGoggles ; if not, branch to Goggle code
  
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 
Obj2E_ChkEnd:
 
Obj2E_ChkEnd:
 
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
Line 117: Line 117:
 
rts</syntaxhighlight>
 
rts</syntaxhighlight>
  
−
== Example Code ==
+
=== Example Code ===
 
Although that code is perfect now, it still does nothing. Unless you already have plans to do something with it, you can use this very simple code, that gives infinite air in LZ.
 
Although that code is perfect now, it still does nothing. Unless you already have plans to do something with it, you can use this very simple code, that gives infinite air in LZ.
  
Line 145: Line 145:
 
...</syntaxhighlight>
 
...</syntaxhighlight>
  
−
== Fixing the infinite air glitch ==
+
=== Fixing the infinite air glitch ===
 
(Section by Inferno Gear, code by theocas.)
 
(Section by Inferno Gear, code by theocas.)
 
Place the following code at the end of Obj0D_Touch, but before locret_EBBA.
 
Place the following code at the end of Obj0D_Touch, but before locret_EBBA.
Line 152: Line 152:
 
...</syntaxhighlight>
 
...</syntaxhighlight>
 
That's the bug fixed! It's that simple. So, now the goggle check turns off at the end of a level.
 
That's the bug fixed! It's that simple. So, now the goggle check turns off at the end of a level.
 +
 +
==GitHub disassembly ==
 +
=== Quick guide ===
 +
I know there are many people who just want to rip off the code without learning because they think they have better things to do. For those people I took the time to make a simple copy/paste guide:
 +
 +
In _incObj\2E Monitor Content Power-Up.asm, search for ''Pow_ChkS:'' and replace everything from there with this:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
cmpi.b #8,d0 ; does monitor contain Goggles?
 +
bne.s Pow_ChkEnd ; if not, branch to Pow_ChkEnd
 +
nop</syntaxhighlight>
 +
That was everything. If you are too dumb to add/understand this, then you weren't reading the real guide.
 +
 +
=== Full guide ===
 +
This version tells you how to do this in detail, and very well explained. It's not more than what you can see in the quick version, but with comments and explanations you can learn something, so this one is recommended.
 +
 +
First off, open ''_incObj\2E Monitor Content Power-Up.asm' and go to the Routine for the S monitor contents (Pow_ChkS). You should see this.
 +
<syntaxhighlight lang="asm"> ...
 +
Pow_RingSound:
 +
music sfx_Ring,1,0,0 ; play ring sound
 +
; ===========================================================================
 +
 +
Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkEnd
 +
nop
 +
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing
 +
; ===========================================================================
 +
 +
Pow_Delete: ; XREF: Obj2E_Index
 +
subq.w #1,obTimeFrame(a0)
 +
bmi.w DeleteObject ; delete after half a second
 +
rts</syntaxhighlight>
 +
 +
As you can see, there is no Goggle Code. But there is code that checks if the monitor contains 'S'. However, you can open [[SonED2]] and add a new monitor using the object editor. Scroll through the different monitors, and you will see, in ''_incObj\2E Monitor Content Power-Up.asm' are the monitors in the same order as in SonED2. The Goggle monitor is the last monitor in this list. This means that you will have to add your new code under the code for the S.
 +
 +
Before Pow_ChkEnd add a new label. The most fitting one is ''Pow_ChkGoggles:'' in my opinion:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkEnd
 +
nop
 +
 +
Pow_ChkGoggles:
 +
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 +
 +
In ChkS is a code to branch to ChkEnd. Scroll up and you will see, there is in every monitor a code like this, but instead of branching to ChkEnd, they are branching to the next monitor code. So do the same with the S code. Change ''bne.s Pow_ChkEnd'' to ''bne.s Pow_ChkGoggles'':
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 +
 +
Okay, we've set a few things up, but we are not done yet. Maybe you've noticed with the last step, those 2 lines in each monitor at the beginning (a 'cmpi.b' code and a 'bne.s' code). They are there to check if that monitor was destroyed and if so, do the code under it, otherwise check for the next monitor. We need that for the goggle monitor as well, so copy any of these 2 lines to your ''Pow_ChkGoggles:'' label. I'm using the lines of ChkS:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 +
 +
As you can see, this can't work, because they are checking for the same things! Look up again. Every monitor has a higher number in the cmpi.b command. The number in S was 7. So what is the next number? 8 of course! So change the 7 to 8 in your Goggle code:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
cmpi.b #8,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 +
 +
7: We are nearly done. The last thing we have to do is to change the bne command in your Goggle code to ChkEnd. Like this:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
cmpi.b #8,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkEnd ; if not, branch to Goggle code
 +
 +
Pow_ChkEnd:
 +
rts ; 'S' and Goggles monitors do nothing</syntaxhighlight>
 +
 +
Now we're done, and you can insert code to run when you destroy a Goggle monitor. But if you don't wanna add code for now, you have to add a ''nop'' under the bne command, otherwise you will get an '''Illegal zero length branch''' error when building. Also, you should change the comments, because they are really misleading. Here is my finished code:
 +
<syntaxhighlight lang="asm">Pow_ChkS:
 +
cmpi.b #7,d0 ; does monitor contain 'S'
 +
bne.s Pow_ChkGoggles ; if not, branch to Goggle code
 +
nop
 +
 +
Pow_ChkGoggles:
 +
cmpi.b #8,d0 ; does monitor contain Goggles?
 +
bne.s Pow_ChkEnd ; if not, branch to ChkEnd
 +
nop
 +
 +
Pow_ChkEnd:
 +
rts</syntaxhighlight>
 +
 +
=== Example Code ===
 +
Although that code is perfect now, it still does nothing. Unless you already have plans to do something with it, you can use this very simple code, that gives infinite air in LZ.
 +
 +
==== Preparation ====
 +
In Variables.asm, at the end of the file in a good spot, put the following piece of code.
 +
<syntaxhighlight lang="asm">f_gogglecheck = ramaddr ( $FFFFFFA0 ) ; goggle flag</syntaxhighlight>
 +
 +
==== Adding the code ====
 +
 +
Go to the Goggle code and add a line, which is moving $1 to an unused RAM adress:
 +
<syntaxhighlight lang="asm"> move.b #1,(f_gogglecheck).w ; move 1 to the goggle check</syntaxhighlight>
 +
 +
It should look like this:
 +
<syntaxhighlight lang="asm"> ...
 +
nop
 +
 +
Pow_ChkGoggles:
 +
cmpi.b #8,d0 ; does monitor contain Goggles?
 +
bne Pow_ChkEnd ; if not, branch to ChkEnd
 +
move.b #1,(f_gogglecheck).w ; move 1 to the goggle check
 +
 +
Pow_ChkEnd:
 +
...</syntaxhighlight>
 +
 +
Next find _incObj\0A Drowning Countdown and find ''.reduceair / @reduceair'' and add these 2 lines right after the label:
 +
<syntaxhighlight lang="asm"> tst.b (f_gogglecheck).w ; was a goggle monitor broken?
 +
bne Obj0A_GoMakeItem ; if yes, branch</syntaxhighlight>
 +
 +
It should look like this:
 +
<syntaxhighlight lang="asm">@reduceair
 +
tst.b (f_gogglecheck).w ; was a goggle monitor broken?
 +
bne @gotomakenum ; if yes, branch
 +
...</syntaxhighlight>
 +
 +
=== Fixing the infinite air glitch ===
 +
(Section by Inferno Gear, code by theocas.)
 +
Place the following code in _incObj\0D Signpost.asm and place it at the end of Sign_Touch, but before @notouch.
 +
<syntaxhighlight lang="asm"> ...
 +
move.b #0,(f_gogglecheck).w ; move 0 to the goggle check
 +
...</syntaxhighlight>
 +
That's the bug fixed! It's that simple. So, now the goggle check turns off at the end of a level.
 +
  
  
 
{{S1Howtos}}
 
{{S1Howtos}}
 
[[Category:SCHG How-tos|Set up the Goggle Monitor to work with it]]
 
[[Category:SCHG How-tos|Set up the Goggle Monitor to work with it]]

Revision as of 16:32, 21 October 2017

Did you know that there are 2 unused monitors in Sonic 1? The 'S' and 'Goggle' monitors. You can place and also destroy them, but nothing will happen. In the split is under "Obj2E_ChkS:" the code for the S monitor, but there is no code for the Goggle monitor! If you want to have that monitor to do something, you need to set it up first. It's not too hard, so I will explain it you step-by-step. (Bug fix and GitHub adaption added by Inferno Gear.)

Hivebrain disassembly

Quick guide

I know there are many people who just want to rip off the code without learning because they think they have better things to do. For those people I took the time to make a simple copy/paste guide:

Search for Obj2E_ChkS: and replace everything from there with this: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne	Obj2E_ChkEnd		; if not, branch to ChkEnd
		nop

That was everything. If you are too dumb to add/understand this, then you weren't reading the real guide.

Full guide

This version tells you how to do this in detail, and very well explained. It's not more than what you can see in the quick version, but with comments and explanations you can learn something, so this one is recommended.

First off, open sonic1.asm and go to the Routine for the monitor contents (Obj2E). Scroll down until you see this: 

	...
Obj2E_RingSound:
		move.w	#$B5,d0
		jmp	(PlaySound).l	; play ring sound
; ===========================================================================

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkEnd
		nop	

Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing
; ===========================================================================

Obj2E_Delete:				; XREF: Obj2E_Index
		subq.w	#1,$1E(a0)
		bmi.w	DeleteObject
		rts

As you can see, there is no Goggle Code. But there is code that checks if the monitor contains 'S'. However, you can open SonED2 and add a new monitor using the object editor. Scroll through the different monitors, and you will see, in Obj2E are the monitors in the same order as in SonED2. The Goggle monitor is the last monitor in this list. This means that you will have to add your new code under the code for the S.

Before Obj2E_ChkEnd add a new label. The most fitting one is Obj2E_ChkGoggles: in my opinion: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkEnd
		nop

Obj2E_ChkGoggles:	

Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

In ChkS is a code to branch to ChkEnd. Scroll up and you will see, there is in every monitor a code like this, but instead of branching to ChkEnd, they are branching to the next monitor code. So do the same with the S code. Change bne Obj2E_ChkEnd to bne Obj2E_ChkGoggles: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	

Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

Okay, we've set a few things up, but we are not done yet. Maybe you've noticed with the last step, those 2 lines in each monitor at the beginning (a 'cmpi.b' code and a 'bne' code). They are there to check if that monitor was destroyed and if so, do the code under it, otherwise check for the next monitor. We need that for the goggle monitor as well, so copy any of these 2 lines to your Obj2E_ChkGoggles: label. I'm using the lines of ChkS: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code

		cmpi.b	#7,d0		; does monitor contain 'S'
Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

As you can see, this can't work, because they are checking for the same things! Look up again. Every monitor has a higher number in the cmpi.b command. The number in S was 7. So what is the next number? 8 of course! So change the 7 to 8 in your Goggle code: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code

Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

7: We are nearly done. The last thing we have to do is to change the bne command in your Goggle code to ChkEnd. Like this: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain 'S'
		bne	Obj2E_ChkEnd		; if not, branch to Goggle code

Obj2E_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

Now we're done, and you can insert code to run when you destroy a Goggle monitor. But if you don't wanna add code for now, you have to add a nop under the bne command, otherwise you will get an Illegal zero length branch error when building. Also, you should change the comments, because they are really misleading. Here is my finished code: 

Obj2E_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne	Obj2E_ChkGoggles		; if not, branch to Goggle code
		nop

Obj2E_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne	Obj2E_ChkEnd		; if not, branch to ChkEnd
		nop

Obj2E_ChkEnd:
		rts

Example Code

Although that code is perfect now, it still does nothing. Unless you already have plans to do something with it, you can use this very simple code, that gives infinite air in LZ.

Go to the Goggle code and add a line, which is moving $1 to an unused RAM adress: 

		move.b	#1,($FFFFFFA0).w ; move 1 to the goggle check

It should look like this: 

		...
		nop

Obj2E_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne	Obj2E_ChkEnd		; if not, branch to ChkEnd
		move.b	#1,($FFFFFFA0).w ; move 1 to the goggle check

Obj2E_ChkEnd:
		...

Next go to to Obj0A_ReduceAir: and add these 2 lines right after the label: 

		tst.b	($FFFFFFA0).w	; was a goggle monitor broken?
		bne	Obj0A_GoMakeItem	; if yes, branch

It should look like this: 

Obj0A_ReduceAir:
		tst.b	($FFFFFFA0).w	; was a goggle monitor broken?
		bne	Obj0A_GoMakeItem	; if yes, branch
		...

Fixing the infinite air glitch

(Section by Inferno Gear, code by theocas.) Place the following code at the end of Obj0D_Touch, but before locret_EBBA. 

		...
		move.b	#0,($FFFFFFA0).w ; move 0 to the goggle check
		...

That's the bug fixed! It's that simple. So, now the goggle check turns off at the end of a level.

GitHub disassembly

Quick guide

I know there are many people who just want to rip off the code without learning because they think they have better things to do. For those people I took the time to make a simple copy/paste guide:

In _incObj\2E Monitor Content Power-Up.asm, search for Pow_ChkS: and replace everything from there with this: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne.s	Pow_ChkEnd		; if not, branch to Pow_ChkEnd
		nop

That was everything. If you are too dumb to add/understand this, then you weren't reading the real guide.

Full guide

This version tells you how to do this in detail, and very well explained. It's not more than what you can see in the quick version, but with comments and explanations you can learn something, so this one is recommended.

First off, open _incObj\2E Monitor Content Power-Up.asm' and go to the Routine for the S monitor contents (Pow_ChkS). You should see this. 

	...
Pow_RingSound:
		music	sfx_Ring,1,0,0	; play ring sound
; ===========================================================================

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkEnd
		nop	

Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing
; ===========================================================================

Pow_Delete:				; XREF: Obj2E_Index
		subq.w	#1,obTimeFrame(a0)
		bmi.w	DeleteObject	; delete after half a second
		rts

As you can see, there is no Goggle Code. But there is code that checks if the monitor contains 'S'. However, you can open SonED2 and add a new monitor using the object editor. Scroll through the different monitors, and you will see, in _incObj\2E Monitor Content Power-Up.asm' are the monitors in the same order as in SonED2. The Goggle monitor is the last monitor in this list. This means that you will have to add your new code under the code for the S.

Before Pow_ChkEnd add a new label. The most fitting one is Pow_ChkGoggles: in my opinion: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkEnd
		nop

Pow_ChkGoggles:	

Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

In ChkS is a code to branch to ChkEnd. Scroll up and you will see, there is in every monitor a code like this, but instead of branching to ChkEnd, they are branching to the next monitor code. So do the same with the S code. Change bne.s Pow_ChkEnd to bne.s Pow_ChkGoggles: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	

Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

Okay, we've set a few things up, but we are not done yet. Maybe you've noticed with the last step, those 2 lines in each monitor at the beginning (a 'cmpi.b' code and a 'bne.s' code). They are there to check if that monitor was destroyed and if so, do the code under it, otherwise check for the next monitor. We need that for the goggle monitor as well, so copy any of these 2 lines to your Pow_ChkGoggles: label. I'm using the lines of ChkS: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code

		cmpi.b	#7,d0		; does monitor contain 'S'
Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

As you can see, this can't work, because they are checking for the same things! Look up again. Every monitor has a higher number in the cmpi.b command. The number in S was 7. So what is the next number? 8 of course! So change the 7 to 8 in your Goggle code: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code

Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

7: We are nearly done. The last thing we have to do is to change the bne command in your Goggle code to ChkEnd. Like this: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain 'S'
		bne.s	Pow_ChkEnd		; if not, branch to Goggle code

Pow_ChkEnd:
		rts			; 'S' and Goggles monitors do nothing

Now we're done, and you can insert code to run when you destroy a Goggle monitor. But if you don't wanna add code for now, you have to add a nop under the bne command, otherwise you will get an Illegal zero length branch error when building. Also, you should change the comments, because they are really misleading. Here is my finished code: 

Pow_ChkS:
		cmpi.b	#7,d0		; does monitor contain 'S'
		bne.s	Pow_ChkGoggles		; if not, branch to Goggle code
		nop

Pow_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne.s	Pow_ChkEnd		; if not, branch to ChkEnd
		nop

Pow_ChkEnd:
		rts

Example Code

Although that code is perfect now, it still does nothing. Unless you already have plans to do something with it, you can use this very simple code, that gives infinite air in LZ.

Preparation

In Variables.asm, at the end of the file in a good spot, put the following piece of code. 

f_gogglecheck	= ramaddr ( $FFFFFFA0 )	; goggle flag

Adding the code

Go to the Goggle code and add a line, which is moving $1 to an unused RAM adress: 

		move.b	#1,(f_gogglecheck).w ; move 1 to the goggle check

It should look like this: 

		...
		nop

Pow_ChkGoggles:	
		cmpi.b	#8,d0		; does monitor contain Goggles?
		bne	Pow_ChkEnd		; if not, branch to ChkEnd
		move.b	#1,(f_gogglecheck).w ; move 1 to the goggle check

Pow_ChkEnd:
		...

Next find _incObj\0A Drowning Countdown and find .reduceair / @reduceair and add these 2 lines right after the label: 

		tst.b	(f_gogglecheck).w	; was a goggle monitor broken?
		bne	Obj0A_GoMakeItem	; if yes, branch

It should look like this: 

@reduceair
		tst.b	(f_gogglecheck).w	; was a goggle monitor broken?
		bne	@gotomakenum	; if yes, branch
		...

Fixing the infinite air glitch

(Section by Inferno Gear, code by theocas.) Place the following code in _incObj\0D Signpost.asm and place it at the end of Sign_Touch, but before @notouch. 

		...
		move.b	#0,(f_gogglecheck).w ; move 0 to the goggle check
		...

That's the bug fixed! It's that simple. So, now the goggle check turns off at the end of a level.


SCHG How-To Guide: Sonic the Hedgehog (16-bit)
Fixing Bugs
Fix Demo Playback | Fix a Race Condition with Pattern Load Cues | Fix the SEGA Sound | Display the Press Start Button Text | Fix the Level Select Menu | Fix the Hidden Points Bug | Fix Accidental Deletion of Scattered Rings | Fix Ring Timers | Fix the Walk-Jump Bug | Correct Drowning Bugs | Fix the Death Boundary Bug | Fix the Camera Follow Bug | Fix Song Restoration Bugs | Fix the HUD Blinking | Fix the Level Select Graphics Bug | Fix a remember sprite related bug
Changing Design Choices
Change Spike Behavior | Collide with Water After Being Hurt | Fix Special Stage Jumping Physics | Improve the Fade In\Fade Out Progression Routines | Fix Scattered Rings' Underwater Physics | Remove the Speed Cap | Port the REV01 Background Effects | Port Sonic 2's Level Art Loader | Retain Rings Between Acts | Add Sonic 2 (Simon Wai Prototype) Level Select | Improve ObjectMove Subroutines | Port Sonic 2 Level Select
Adding Features
Add Spin Dash ( Part 1 / Part 2 / Part 3 / Part 4 ) | Add Eggman Monitor | Add Super Sonic | Add the Air Roll
Sound Features
Expand the Sound Index | Play Different Songs Per Act | Port Sonic 2 Final Sound Driver | Port Sonic 3's Sound Driver | Port Flamewing's Sonic 3 & Knuckles Sound Driver | Change The SEGA Sound
Extending the Game
Load Chunks From ROM | Add Extra Characters | Make an Alternative Title Screen | Use Dynamic Tilesets | Make GHZ Load Alternate Art | Make Ending Load Alternate Art | Add a New Zone | Set Up the Goggle Monitor | Add New Moves | Add a Dynamic Collision System | Dynamic Special Stage Walls System | Extend Sprite Mappings and Art Limit | Enigma Credits | Use Dynamic Palettes
Miscellaneous
Convert the Hivebrain 2005 Disassembly to ASM68K
Split Disassembly Guides
Set Up a Split Disassembly | Basic Level Editing | Basic Art Editing | Basic ASM Editing (Spin Dash)
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