Difference between revisions of "Display the Press Start Button text"
From Sonic Retro
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− | + | ''(Original guide by [[User:Quickman|Quickman]]. Updated for the latest GitHub disassembly by [[User:ArtmeierCompanies|Devon]].)'' | |
− | In | + | In Sonic 1, there is a invincible 'PRESS START BUTTON' message on the title screen. While seen in the [https://tcrf.net/images/8/81/Sonic1proto_titlescreen.png Sonic 1 Prototype], in the final version, it's there, but just not visible. |
− | <asm> | + | |
− | + | ==Hivebrain 2005 Disassembly== | |
− | + | This version of the guide is for the [[Disassemblies#Revision_00|Hivebrain 2005]] disassembly. | |
+ | |||
+ | To fix this, you simply need to go to '''sonic.asm''' and search for '''Title_ClrObjRam2:''' (Line 3235), where you will end up here: | ||
+ | <syntaxhighlight lang="asm"> lea ($FFFFD080).w,a1 | ||
+ | moveq #0,d0 | ||
+ | move.w #7,d1 | ||
Title_ClrObjRam2: | Title_ClrObjRam2: | ||
− | + | move.l d0,(a1)+ | |
− | + | dbf d1,Title_ClrObjRam2 | |
+ | </syntaxhighlight> | ||
+ | |||
+ | |||
+ | Change the '''7''' (derived from '''$20/4-1''') to '''$F''' (derived from '''$40/4-1'''): | ||
+ | <syntaxhighlight lang="asm"> lea ($FFFFD080).w,a1 | ||
+ | moveq #0,d0 | ||
+ | move.w #$F,d1 ; $40/4-1 | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
Title_ClrObjRam2: | Title_ClrObjRam2: | ||
− | + | move.l d0,(a1)+ | |
− | + | dbf d1,Title_ClrObjRam2 | |
− | + | </syntaxhighlight> | |
− | + | ||
+ | ==GitHub Disassembly== | ||
+ | This version of the guide is for the [https://github.com/sonicretro/s1disasm GitHub] disassembly. | ||
+ | |||
+ | To fix this, you simply need to go to '''sonic.asm''' and search for '''Tit_LoadText:'''. (Line 2173) and find this piece of code (scroll down until you see it): | ||
+ | <syntaxhighlight lang="asm"> ; Bug: this only clears half of the "SONIC TEAM PRESENTS" slot. | ||
+ | ; This is responsible for why the "PRESS START BUTTON" text doesn't | ||
+ | ; show up, as the routine ID isn't reset. | ||
+ | clearRAM v_sonicteam,v_sonicteam+object_size/2 | ||
+ | </syntaxhighlight> | ||
+ | |||
+ | |||
+ | Simply remove the '''/2''': | ||
+ | <syntaxhighlight lang="asm"> clearRAM v_sonicteam,v_sonicteam+object_size | ||
+ | </syntaxhighlight> | ||
− | + | ==Result== | |
+ | Now you should be able to see the '''PRESS START BUTTON''': | ||
[[File:S1-PressStart.png]] | [[File:S1-PressStart.png]] | ||
+ | '''Disclaimer:''' That screenshot depicts REV00 with the fix applied. REV01 slightly changed the background Y position. | ||
− | Original | + | ==Original Explanation== |
+ | Written by [[User:Quickman|Quickman]] on the {{linkRetro|topic=10240|title=Forums}}: | ||
{{quote|I've finally isolated precisely why the PRESS START BUTTON (PSB) text doesn't appear on the [[Sonic the Hedgehog (16-bit)|Sonic 1]] title screen, and given the nature I suspect it to be a bug in Sonic Team's original code. (You may now be shocked.) | {{quote|I've finally isolated precisely why the PRESS START BUTTON (PSB) text doesn't appear on the [[Sonic the Hedgehog (16-bit)|Sonic 1]] title screen, and given the nature I suspect it to be a bug in Sonic Team's original code. (You may now be shocked.) | ||
− | Now, the PSB object is initialised in object RAM slot $D080 on line 3237 of the disassembly I'm currently using (modified by [[ | + | Now, the PSB object is initialised in object RAM slot $D080 on line 3237 of the disassembly I'm currently using (modified by [[User:Puto|Puto]] to work on Linux; it's just under the label Title_ClrObjRam2, in case it's not the same line in an unmodified Sonic 1 disassembly). That same chunk of RAM is previously used for the SONIC TEAM PRESENTS (STP) object earlier in the TitleScreen routine (line 3162, adjust as necessary). |
− | The reason the PSB text doesn't appear is because the STP object scribbles in object RAM, but the TitleScreen routine only clears the top $1C bytes. Any data between $D09C and $D0A0 previously touched by the STB object is unmodified | + | The reason the PSB text doesn't appear is because the STP object scribbles in object RAM, but the TitleScreen routine only clears the top $1C bytes. Any data between $D09C and $D0A0 previously touched by the STB object is unmodified. |
− | The correction is simple enough; delete the object RAM for the object at $D080 more thoroughly. |2=[[Quickman]]}} | + | The correction is simple enough; delete the object RAM for the object at $D080 more thoroughly. |2=[[User:Quickman|Quickman]]}} |
− | + | {{S1Howtos}} | |
+ | |Display the Press Start Button text]] |
Latest revision as of 19:37, 3 June 2024
(Original guide by Quickman. Updated for the latest GitHub disassembly by Devon.)
In Sonic 1, there is a invincible 'PRESS START BUTTON' message on the title screen. While seen in the Sonic 1 Prototype, in the final version, it's there, but just not visible.
Hivebrain 2005 Disassembly
This version of the guide is for the Hivebrain 2005 disassembly.
To fix this, you simply need to go to sonic.asm and search for Title_ClrObjRam2: (Line 3235), where you will end up here:
lea ($FFFFD080).w,a1
moveq #0,d0
move.w #7,d1
Title_ClrObjRam2:
move.l d0,(a1)+
dbf d1,Title_ClrObjRam2
Change the 7 (derived from $20/4-1) to $F (derived from $40/4-1):
lea ($FFFFD080).w,a1
moveq #0,d0
move.w #$F,d1 ; $40/4-1
Title_ClrObjRam2:
move.l d0,(a1)+
dbf d1,Title_ClrObjRam2
GitHub Disassembly
This version of the guide is for the GitHub disassembly.
To fix this, you simply need to go to sonic.asm and search for Tit_LoadText:. (Line 2173) and find this piece of code (scroll down until you see it):
; Bug: this only clears half of the "SONIC TEAM PRESENTS" slot.
; This is responsible for why the "PRESS START BUTTON" text doesn't
; show up, as the routine ID isn't reset.
clearRAM v_sonicteam,v_sonicteam+object_size/2
Simply remove the /2:
clearRAM v_sonicteam,v_sonicteam+object_size
Result
Now you should be able to see the PRESS START BUTTON:
Disclaimer: That screenshot depicts REV00 with the fix applied. REV01 slightly changed the background Y position.
Original Explanation
Written by Quickman on the Forums:“ | I've finally isolated precisely why the PRESS START BUTTON (PSB) text doesn't appear on the Sonic 1 title screen, and given the nature I suspect it to be a bug in Sonic Team's original code. (You may now be shocked.)
Now, the PSB object is initialised in object RAM slot $D080 on line 3237 of the disassembly I'm currently using (modified by Puto to work on Linux; it's just under the label Title_ClrObjRam2, in case it's not the same line in an unmodified Sonic 1 disassembly). That same chunk of RAM is previously used for the SONIC TEAM PRESENTS (STP) object earlier in the TitleScreen routine (line 3162, adjust as necessary). The reason the PSB text doesn't appear is because the STP object scribbles in object RAM, but the TitleScreen routine only clears the top $1C bytes. Any data between $D09C and $D0A0 previously touched by the STB object is unmodified. The correction is simple enough; delete the object RAM for the object at $D080 more thoroughly. |
„ |
— Quickman |
|Display the Press Start Button text]]