SCHG How-to:Port Sonic 3's Sound Driver to Sonic 1

You probably saw a quick and dirty way to do this on SSRG, but lets do it the proper way, the way that sonic team would do it.

Overview

First off, Sonic 3's sound driver has the V_Int reloader built into it so it is not needed, some routines need replacement, sounds need fixing, and we need to replace the sounds and music. We will be using the hivebrain version, if you wish to do it via svn version, I am sure you can come up with a way that works by seeing what changes I made in the hivebrain version.

Preparing to use Sonic 3/K/3K sound system

The Vertical Interrupt and Horizontal Interrupt need to be fixed, since the sonic 1/2 system uses them but the Sonic 3/K/3K system doesn't.

first we will fix the vertical interrupt, by changing: <asm> loc_B5E: ; XREF: loc_B88 jsr (sub_71B4C).l </asm>

to: <asm> loc_B5E: ; XREF: loc_B88 nop </asm>

Now we locate: <asm> loc_119E: ; XREF: PalToCRAM clr.b ($FFFFF64F).w movem.l d0-a6,-(sp) bsr.w Demo_Time jsr (sub_71B4C).l movem.l (sp)+,d0-a6 rte

End of function PalToCRAM

</asm> See another familiar line? Yes, you've got it, do the same thing to it: <asm> loc_119E: ; XREF: PalToCRAM clr.b ($FFFFF64F).w movem.l d0-a6,-(sp) bsr.w Demo_Time nop movem.l (sp)+,d0-a6 rte

End of function PalToCRAM

</asm> That effectively disables the sonic1 style v_int and h_int driver reloading that we will not need and prevents a nasty error down the road.

Upgrading the Load Driver Routine

Okay, we disabled the sonic1 driver junk, wouldn't we want now to use the sonic3 driver instead? Here is where we start installing it. Locate: <asm>

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Subroutine to load the sound driver

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SoundDriverLoad: ; XREF: GameClrRAM; TitleScreen nop move.w #$100,($A11100).l ; stop the Z80 move.w #$100,($A11200).l ; reset the Z80 lea (Kos_Z80).l,a0 ; load sound driver lea ($A00000).l,a1 bsr.w KosDec ; decompress move.w #0,($A11200).l nop nop nop nop move.w #$100,($A11200).l ; reset the Z80 move.w #0,($A11100).l ; start the Z80 rts

End of function SoundDriverLoad

</asm>

and replace it all with: <asm>

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Subroutine to load the sound driver

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SoundDriverLoad: ; XREF: GameClrRAM; TitleScreen nop move.w #$100,($A11100).l ; Z80 bus request - Start move.w #$100,($A11200).l ; Z80 stop reset lea (DriverData).l,a0 lea ($A00000).l,a1 move.w #DriverDataEnd-DriverData,d0

DriverLoadLoop: move.b (a0)+,(a1)+ dbf d0,DriverLoadLoop lea (DriverPointers).l,a0 lea ($A01300).l,a1 move.w #DriverPointersEnd-DriverPointers,d0

DriverPointersLoadLoop: move.b (a0)+,(a1)+ dbf d0, DriverPointersLoadLoop lea (UniversalVoiceBank).l,a0 lea ($A017D8).l,a1 move.w #UniversalVoiceBankEnd-UniversalVoiceBank,d0

UniversalVoiceBankLoadLoop: move.b (a0)+,(a1)+ dbf d0,UniversalVoiceBankLoadLoop lea (DriverResetData).l,a0 lea ($A01C00).l,a1 move.w #DriverResetDataEnd-DriverResetData,d0

DriverResetDataLoadLoop: move.b (a0)+,(a1)+ dbf d0,DriverResetDataLoadLoop btst #6,($FFFFFFF8).w beq.s DriverAlreadyInitialized move.b #1,($A01C02).l

DriverAlreadyInitialized: move.w #0,($A11200).l nop nop nop nop move.w #$100,($A11200).l ; Z80 start reset move.w #0,($A11100).l ; Z80 bus request - Stop rts

End of function SoundDriverLoad

DriverResetData: dc.b 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 DriverResetDataEnd: </asm>

Upgrading the Playback Routines

Now we have the code to load the new driver, time to add the new playback routines.

First the PlaySound routine, locate: <asm>

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Subroutine to play a sound or music track

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PlaySound: move.b d0,($FFFFF00A).w rts

End of function PlaySound

</asm>

and replace it completely with: <asm>

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Subroutine to play a sound or music track

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PlaySound: cmpi.w #$FB,d0 blt.s PlayNotSpecialFlag bhi.s TestForNormalSpeed move #8,d0 jmp SetTempo

TestForNormalSpeed: cmpi.w #$FC,d0 bne.s PlayNotSpecialFlag clr.w d0 jmp SetTempo

PlayNotSpecialFlag: move.w #$100,($A11100).l

PlaySoundZ80NotStopped: btst #0,($A11100).l bne.s PlaySoundZ80NotStopped ; loop until it says it's stopped move.b d0,($A01C0A).l move.w #0,($A11100).l rts

End of function PlaySound

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Exclusive sound/music subroutine

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PlaySound_Ex: tst.b 4(A0) bpl.s SkipPlaySound_Special </asm>

Now we will replace that unused routine with something more appropriate as well as upgrade the PlaySound_Special routine, find: <asm>

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Subroutine to play a special sound/music (E0-E4)

E0 - Fade out

E1 - Sega

E2 - Speed up

E3 - Normal speed

E4 - Stop

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PlaySound_Special: move.b d0,($FFFFF00B).w rts

End of function PlaySound_Special

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Unused sound/music subroutine

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PlaySound_Unk: move.b d0,($FFFFF00C).w rts </asm>

and replace it entirely with: <asm>

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Unused sound/music subroutine

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PlaySound_Unk: nop

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Subroutine to play a special sound/music (FB-FF)

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PlaySound_Special: move.w #$100,($A11100).l

PlaySound_SpecialZ80NotStopped: btst #0,($A11100).l bne.s PlaySound_SpecialZ80NotStopped cmp.b ($A01C0B).l,d0 beq.s PlaySound_Special1 tst.b ($A01C0B).l bne.s PlaySound_Special0 move.b d0,($A01C0B).l move.w #0,($A11100).l rts

PlaySound_Special0: move.b d0,($A01C0C).l

PlaySound_Special1: move.w #0,($A11100).l

SkipPlaySound_Special: rts

End of function PlaySound_Special

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Subroutine to change the music tempo

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SetTempo: move.w #$100,($A11100).l

SetTempoZ80NotStopped: btst #0,($A11100).l bne.s SetTempoZ80NotStopped move.b D0,($A01C08).l move.w #0,($A11100).l rts </asm>