;============================================================================
; Faxanadu (U).nes
;
; PRG5 ($8000 - $bfff)
;============================================================================

.segment "PRG5"
.ORG $8000

;============================================================================
; Initialize sound effect playback.
;
; This is a thunking function that wraps
; SoundEffects_Init.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     SoundEffects_Init
;
; XREFS:
;     Game_InitScreenAndMusic
;============================================================================
[8000]thunk_SoundEffects_Init:; [$8000]
[8000]JMP SoundEffects_Init

;============================================================================
; Handle sound effects on hardware interrupt.
;
; This is a thunking function that wraps
; SoundEffects_HandleOnInterrupt.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     SoundEffects_HandleOnInterrupt
;
; XREFS:
;     OnInterrupt
;============================================================================
[8003]thunk_SoundEffects_HandleOnInterrupt:; [$8003]
[8003]JMP SoundEffects_HandleOnInterrupt

;============================================================================
; Initialize the playing state for music and sound effects.
;
; This is a thunking function that wraps
; Audio_InitPlayingState.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     Audio_InitPlayingState
;
; XREFS:
;     Game_InitScreenAndMusic
;============================================================================
[8006]thunk_Audio_InitPlayingState:; [$8006]
[8006]JMP Audio_InitPlayingState

;============================================================================
; Handle music on interrupt.
;
; This is a thunking function that wraps
; Music_HandleOnInterrupt.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     Music_HandleOnInterrupt
;
; XREFS:
;     OnInterrupt
;============================================================================
[8009]thunk_Music_HandleOnInterrupt:; [$8009]
[8009]JMP Music_HandleOnInterrupt
[800c].byte $ff; Unused padding byte.

;============================================================================
; Handle music on interrupt.
;
; If the game is paused, no music will play.
;
; If no music or sound effects are set, audio will be reset.
;
; If music is set but not playing, the music data will be
; loaded.
;
; If music is set and playing, the next actions or notes of
; the MScripts will be invoked, playing parts of the music.
;
; INPUTS:
;     Game_PausedState:
;         Whether the game is paused.
;
;     Music_Current:
;         The currently-set music.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     Audio_HandlePaused
;     Audio_ResetIfNothingSet
;     Music_Load
;     Music_PlayNext
;
; XREFS:
;     thunk_Music_HandleOnInterrupt
;============================================================================
[800d]Music_HandleOnInterrupt:; [$800d]
[800d]LDA a:Game_PausedState; Load the paused state.
[8010]BNE Audio_HandlePaused; If paused, then jump.


;
; The game is not paused. Music can be played.
;
[8012]LDA Music_Current; Load the current music to play.
[8014]BEQ Audio_ResetIfNothingSet; If unset, jump to reset audio if nothing else is playing.


;
; There is music to play.
;
; If bit 0x80 is set, then it's already playing. We'll just
; continue to play it.
;
; If it's not set, load the new music.
;
[8016]BPL Music_Load; Jump to load the music.


;
; Music is currently playing. Play the next piece of the
; music.
;
[8018]JMP Music_PlayNext; Jump to play the next part of the current music.

;============================================================================
; Initialize the music and sound effects state.
;
; This will clear out the music and sound effects
; in preparation for loading a new part of the game.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     Game_PausedState:
;     Music_Current:
;     SoundEffect_HandlerIndex:
;     SND_CHN:
;     SoundEffect_Current:
;     SoundEffect_Unused_PriorityID:
;         Cleared.
;
; XREFS:
;     thunk_Audio_InitPlayingState
;============================================================================
[801b]Audio_InitPlayingState:; [$801b]
[801b]LDA #$00
[801d]STA Music_Current; Clear the current music.
[801f]STA SoundEffect_Current; Clear the next sound effect.
[8021]STA a:SoundEffect_HandlerIndex
[8024]STA a:SND_CHN; Clear the sound channel.
[8027]STA a:Game_PausedState; Clear the paused flag.
[802a]STA a:SoundEffect_Unused_PriorityID; Clear the ID of the highest-priority sound effect.
[802d]RTS

;============================================================================
; Pause audio when the game is paused.
;
; This will mark the audio as paused in response to the game
; being paused.
;
; If there's no music set, and no sound effects set, then
; this will also trigger a full audio reset.
;
; INPUTS:
;     N:
;         The game/audio paused state.
;
;         See Game_PausedState for documentation.
;
;     Music_Current:
;         The current music to check.
;
;     SoundEffect_TicksRemaining:
;         The list of sound effect slots to check.
;
; OUTPUTS:
;     Game_PausedState:
;         The updated paused state.
;
; CALLS:
;     Audio_Reset
;     Audio_ResetIfNothingSet
;
; XREFS:
;     Music_HandleOnInterrupt
;============================================================================
[802e]Audio_HandlePaused:; [$802e]
;
; First, check if we've already handled an audio pause state.
;
[802e]BMI Audio_ResetIfNothingSet; If the audio paused state is already set, then jump.


;
; The game is paused, but audio is not. Set that bit and
; reset audio.
;
[8030]ORA #$80; Set bit 7 (audio paused).
[8032]STA a:Game_PausedState; Store it.
[8035]JSR Audio_Reset; Reset audio.

;
; v-- Fall through --v
;

;============================================================================
; Reset the audio state if no music or sounds are set.
;
; If there's no music set, and no sound effects set, then
; this will trigger a full audio reset.
;
; INPUTS:
;     Music_Current:
;         The current music to check.
;
;     SoundEffect_TicksRemaining:
;         The list of sound effect slots to check.
;
; OUTPUTS:
;     None.
;
; CALLS:
;     Audio_Reset
;
; XREFS:
;     Audio_HandlePaused
;     Music_HandleOnInterrupt
;============================================================================
[8038]Audio_ResetIfNothingSet:; [$8038]
[8038]LDA Music_Current; Load the current music.
[803a]BNE @_return; If it's set, return. Nothing to do.


;
; There's no music playing. Check if sound effects
; are playing.
;
[803c]LDX #$03; X = 3 (loop counter).

[803e]@_checkSoundEffectLoop:; [$803e]
[803e]LDA SoundEffect_TicksRemaining,X; Load the sound effect at the current index.
[8041]BNE @_return; If it's set, then return.
[8043]DEX; X-- (loop counter).
[8044]BPL @_checkSoundEffectLoop; If >= 0, loop.


;
; This has looped through all sound effects, and none
; were set. Audio can now be reset.
;
[8046]JMP Audio_Reset; Reset the audio.

[8049]@_return:; [$8049]
[8049]RTS

;============================================================================
; Reset all audio channels.
;
; Square Wave 1 Hi/Lo and Noise Volume will be set to 16.
; Everything else will be set to 0.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     SQ1_HI:
;     SQ1_LO:
;     NOISE_VOL:
;         Set to 16.
;
;     NOISE_HI:
;     NOISE_LO:
;     SQ1_SWEEP:
;     SQ1_VOL:
;     SQ2_HI:
;     SQ2_LO:
;     SQ2_SWEEP:
;     SQ2_VOL:
;     TRI_HI:
;     TRI_LINEAR:
;     TRI_LO:
;         Set to 0.
;
; XREFS:
;     Audio_HandlePaused
;     Audio_ResetIfNothingSet
;     Music_Load
;     SoundEffects_Init
;============================================================================
[804a]Audio_Reset:; [$804a]
[804a]LDA #$10
[804c]STA a:SQ1_VOL; Set to 16.
[804f]STA a:SQ2_VOL; Set to 16.
[8052]STA a:NOISE_VOL; Set to 16.
[8055]LDA #$00
[8057]STA a:SQ1_SWEEP; Set to 0.
[805a]STA a:SQ1_LO; Set to 0.
[805d]STA a:SQ1_HI; Set to 0.
[8060]STA a:SQ2_SWEEP; Set to 0.
[8063]STA a:SQ2_LO; Set to 0.
[8066]STA a:SQ2_HI; Set to 0.
[8069]STA a:TRI_LINEAR; Set to 0.
[806c]STA a:TRI_LO; Set to 0.
[806f]STA a:TRI_HI; Set to 0.
[8072]STA a:NOISE_LO; Set to 0.
[8075]STA a:NOISE_HI; Set to 0.
[8078]RTS

;============================================================================
; Load channel and MScript state for music.
;
; XREFS:
;     Music_HandleOnInterrupt
;============================================================================
[8079]Music_Load:; [$8079]
;
; Load the current music to play.
;
[8079]LDA Music_Current; Load the current music.
[807b]ORA #$80; Mark as currently playing.
[807d]STA Music_Current; Store that.


;
; Convert to a lookup index for the table.
;
; This will be multiplied by 8, giving us word boundaries
; across 4 channels.
;
[807f]ASL A; Convert to a word boundary.
[8080]ASL A; And multiply by 4 channels.
[8081]ASL A
[8082]TAY; Y = result (Music lookup index).


;
; Begin loading the starting MScripts.
;
; This will load all 4 channels of MScripts for the selected
; piece of music, indexed from last channel to first.
;
; Bear in mind, the loop counter is looping over addresses, so
; it loops 8 times, or 2 bytes * 4 channels. Indexes will be
; based off the music ID, though, not the loop counter.
;
[8083]LDX #$07; X = 7 (loop counter).

[8085]@_loadMusicLoop:; [$8085]
[8085]LDA MSCRIPTS_LOOKUP,Y; Load the MScript channel address at Y.
[8088]STA Music_CurrentScriptAddrs,X; Store it in the list of channel addresses.


;
; BUG: This tries to save the address for a return/repeat, but
;      it always saves in the first channel slot, which is
;      incorrect.
;
[808a]STA a:MScript_SavedAddr; Store it as the latest saved address as well, for push/pop purposes.


;
; Prepare for the next loop iteration and lookup.
;
[808d]DEY; Y-- (lookup index).
[808e]DEX; X-- (loop counter).
[808f]BPL @_loadMusicLoop; If X >= 0, loop.


;
; We're out of the loop. Clear a bunch of state.
;
[8091]INX; Set X back to 0 (-1 + 1 == 0).
[8092]STX a:Music_Global_Transpose
[8095]STX a:Music_Channel_Transpose
[8098]STX a:Music_Channel_Transpose_1_
[809b]STX a:Music_Channel_Transpose_2_
[809e]STX a:Music_SQ_Fades
[80a1]STX a:Music_SQ_Fades_1_
[80a4]STX a:Music_SQEnvelope_Mode
[80a7]STX a:Music_SQEnvelope_Mode_1_
[80aa]STX a:Music_SQEnvelope_Phase
[80ad]STX a:Music_SQEnvelope_Phase_1_
[80b0]STX a:Music_Current_SQ_Low
[80b3]STX a:Music_Current_SQ_Low_1_
[80b6]STX a:Music_Note_Period_Low
[80b9]STX a:Music_Note_Period_High
[80bc]STX a:MScript_Unused_RawValue
[80bf]STX a:Something_Music_Triangle_017e
[80c2]STX a:Music_Noise_Remaining
[80c5]STX a:Music_SQEffect_Delta
[80c8]STX a:MScript_CurValue
[80cb]STX a:Music_SQPitchDelta_Mask
[80ce]STX a:Music_SQPitchDelta_Mask_1_
[80d1]STX a:Music_SQ2_TimerLowBias


;
; Set the following to 1.
;
[80d4]INX; X = 1
[80d5]STX a:Music_NoteTicksRemaining
[80d8]STX a:Music_NoteTicksRemaining_1_
[80db]STX a:Music_NoteTicksRemaining_2_
[80de]STX a:Music_NoteTicksRemaining_3_


;
; Clear the repeat counts for each channel.
;
[80e1]STX a:MScript_NoteDurations
[80e4]STX a:MScript_NoteDurations_1_
[80e7]STX a:MScript_NoteDurations_2_
[80ea]STX a:MScript_NoteDurations_3_


;
; Set the following to 8.
;
[80ed]LDA #$08; A = 8
[80ef]STA a:Music_SQ_Note_Lengths
[80f2]STA a:Music_Note_Length_High
[80f5]STA a:Music_Unused_0166
[80f8]STA a:Music_Unused_0166_1_


;
; Set the following to 144.
;
[80fb]LDA #$90; A = 144
[80fd]STA a:Music_SQ_ControlBits
[8100]STA a:Music_SQ_ControlBits_1_


;
; Reset audio channels.
;
[8103]JMP Audio_Reset; Reset the audio channels.

;============================================================================
; Play the next op in each MScript channel.
;
; This will perform the next operation for each channel,
; unsetting the music if all are complete.
;
; If a channel has a repeat set, its repeat count will
; be reduced by 1 and the current note/value will be played.
; Otherwise, the next operation in the MScript will be
; invoked.
;
; Once all channels are marked completed, the music will be
; unset.
;
; INPUTS:
;     Music_NoteTicksRemaining:
;         The repeat counters for each channel.
;
; OUTPUTS:
;     Music_NoteTicksRemaining:
;         The updated repeat counters for each channel.
;
;     Music_NumChannelsCompleted:
;         The number of channels completed after this run.
;
;     Music_Current:
;         Unset, if all channels completed.
;
;     MScript_CurrentChannel:
;         Clobbered.
;
; CALLS:
;     MScripts_InvokeNext
;     Music_PlayForChannel
;
; XREFS:
;     Music_HandleOnInterrupt
;============================================================================
[8106]Music_PlayNext:; [$8106]
;
; Set the initial state for tracking per-channel playback
; for this invocation.
;
[8106]LDA #$00
[8108]STA a:Music_NumChannelsCompleted; Clear the number of completed channels.
[810b]STA a:MScript_CurrentChannel; Clear the current channel index.


;
; Loop through each of the channels.
;
; For each channel, the current value will be played and
; only advanced when the repeat count for the value hits 0.
;
[810e]@_loop:; [$810e]
[810e]LDX a:MScript_CurrentChannel; X = Current channel index
[8111]DEC Music_NoteTicksRemaining,X
[8114]BNE @_play
[8116]JSR MScripts_InvokeNext

[8119]@_play:; [$8119]
[8119]JSR Music_PlayForChannel; Play music on this channel.
[811c]INC a:MScript_CurrentChannel; Move to the next channel.
[811f]LDA a:MScript_CurrentChannel; Load that channel index.
[8122]CMP #$04; Is it < 4?
[8124]BCC @_loop; If so, loop.


;
; Check if all channels have finished.
;
[8126]LDA a:Music_NumChannelsCompleted; Load the number of completed channels.
[8129]CMP #$04; Is it 4?
[812b]BNE @_return; If not, return.


;
; All channels have finished, so clear the current music.
;
[812d]LDA #$00
[812f]STA Music_Current; Unset the current music.

[8131]@_return:; [$8131]
[8131]RTS

;============================================================================
; TODO: Document Music_PlayForChannel
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlayNext
;============================================================================
[8132]Music_PlayForChannel:; [$8132]
[8132]LDX a:MScript_CurrentChannel; Load the current channel index.
[8135]BEQ @_isSquareWave; If it's Square Wave 1, jump.
[8137]DEX
[8138]BEQ @_isSquareWave; If it's Square Wave 2, jump.
[813a]DEX
[813b]BEQ @_isTriangleWave; If it's Triangle Wave, jump.
[813d]RTS; Else, return.


;
; This is the Triangle Wave channel.
;
[813e]@_isTriangleWave:; [$813e]
[813e]LDX a:MScript_CurrentChannel; Load the current channel index.
[8141]LDA a:Something_Music_Triangle_017e
[8144]BEQ @_checkSoundEffectOnTri
[8146]DEC a:Something_Music_Triangle_017e
[8149]LDA #$c0

[814b]@_checkSoundEffectOnTri:; [$814b]
[814b]STA a:MScript_CurValue


;
; Check if there's currently a sound effect playing
; on the Triangle Wave channel.
;
[814e]LDA SoundEffect_TicksRemaining,X; Load the current sound effect on the Triangle Wave channel.
[8151]BNE @_clearTriangleWave; If one is set, jump to clear it.


;
; No sound effect is playing on the Triangle Wave channel.
;
[8153]LDA a:MScript_CurValue; Load the value to play.
[8156]STA a:TRI_LINEAR; Set it on the channel.
[8159]RTS; And return.

[815a]@_clearTriangleWave:; [$815a]
[815a]LDA #$00
[815c]STA a:TRI_LINEAR; Clear the Triangle Wave channel.
[815f]RTS; And return.


;
; This is a Square Wave channel.
;
[8160]@_isSquareWave:; [$8160]
[8160]LDX a:MScript_CurrentChannel
[8163]LDY Music_SQEnvelope_Mode,X
[8166]BEQ Music_PlaySQEnvelopeModeLinearTrailoff
[8168]DEY
[8169]BEQ Music_PlaySQEnvelopeModeCurveButHeld
[816b]DEY
[816c]BEQ Music_PlaySQEnvelopeModePluck
[816e]RTS

;============================================================================
; Play SQ envelope mode 0: Linear, trails off.
;
; This updates the Square Wave channel's volume level,
; optionally applying a square pitch effect.
;
; This is used to smoothly fade out the volume.
;
; INPUTS:
;     MScript_CurrentChannel:
;         The current MScript channel.
;
;     Music_SQEnvelope_Value:
;         The counter values for the mode, across
;         SQ channels.
;
;     SoundEffect_TicksRemaining:
;         The currently-playing sound effects.
;
; OUTPUTS:
;     Music_SQEnvelope_Value:
;         The updated counter values.
;
;     MScript_CurValue:
;         The updated volume.
;
; CALLS:
;     Music_ApplySQPitchEffectToLO:
;     Music_UpdateSQVolRegister
;
; XREFS:
;     Music_PlayForChannel
;============================================================================
[816f]Music_PlaySQEnvelopeModeLinearTrailoff:; [$816f]
[816f]LDX a:MScript_CurrentChannel; Load the current MScript channel.


;
; Check if the counter is 0. If so, it'll stay that way
; until playback finishes.
;
[8172]LDA Music_SQEnvelope_Value,X; Load the fade-out counter value for the mode.
[8175]BEQ @LAB_PRG5__817d; If it's 0, jump.


;
; The counter is a positive value. Subtract 3 and store it.
;
[8177]SEC
[8178]SBC #$03; Subtract 3 from the counter.
[817a]STA Music_SQEnvelope_Value,X; Store the new counter.


;
; Convert the value to a value between 0-15.
;
; This effectively shifts any value into the lower nibble.
;
[817d]@LAB_PRG5__817d:; [$817d]
[817d]LSR A; Shift into the lower nibble.
[817e]LSR A
[817f]LSR A
[8180]LSR A
[8181]AND #$0f; Mask out the upper nibble.
[8183]STA a:MScript_CurValue; Store as the new volume value for the Square Wave.


;
; Check if any special effects are playing on this channel.
;
[8186]LDA SoundEffect_TicksRemaining,X; Load any current special effects on this channel.
[8189]BNE @_return; If set, return.
[818b]JSR Music_UpdateSQVolRegister; Update the volume and flags the SQ*_VOL register.
[818e]JSR Music_ApplySQPitchEffectToLO; Apply the mode's pitch effect to the SQ*_LO register.

[8191]@_return:; [$8191]
[8191]RTS

;============================================================================
; TODO: Document Music_PlaySQEnvelopeModeCurveButHeld
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlayForChannel
;============================================================================
[8192]Music_PlaySQEnvelopeModeCurveButHeld:; [$8192]
;
; This is SQ Mode 1: Curve but held
;
[8192]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[8195]LDA Music_SQEnvelope_Value,X
[8198]AND #$0f
[819a]STA Music_SQEnvelope_Value,X
[819d]CMP #$0d
[819f]BCC @LAB_PRG5__81a7
[81a1]DEC Music_SQEnvelope_Value,X
[81a4]DEC Music_SQEnvelope_Value,X

[81a7]@LAB_PRG5__81a7:; [$81a7]
[81a7]INC Music_SQEnvelope_Phase,X
[81aa]LDA Music_SQEnvelope_Value,X
[81ad]STA a:MScript_CurValue
[81b0]LDA SoundEffect_TicksRemaining,X
[81b3]BNE @_return
[81b5]JSR Music_UpdateSQVolRegister
[81b8]JSR Music_ApplySQPitchEffectToLO

[81bb]@_return:; [$81bb]
[81bb]RTS

;============================================================================
; TODO: Document Music_PlaySQEnvelopeModePluck
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlayForChannel
;============================================================================
[81bc]Music_PlaySQEnvelopeModePluck:; [$81bc]
;
; This is SQ Mode 2: Table-based envelope (pluck effect)
;
[81bc]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[81bf]LDA Music_SQEnvelope_Phase,X
[81c2]LSR A
[81c3]LSR A
[81c4]TAY
[81c5]LDA SQ_MODE_2_PLUCK_VALUES,Y
[81c8]BEQ @LAB_PRG5__81cd
[81ca]INC Music_SQEnvelope_Phase,X

[81cd]@LAB_PRG5__81cd:; [$81cd]
[81cd]STA a:MScript_CurValue
[81d0]LDA SoundEffect_TicksRemaining,X
[81d3]BNE @_return
[81d5]JSR Music_UpdateSQVolRegister
[81d8]JSR Music_ApplySQPitchEffectToLO

[81db]@_return:; [$81db]
[81db]RTS

;
; XREFS:
;     Music_PlaySQEnvelopeModePluck
;
[81dc]SQ_MODE_2_PLUCK_VALUES:; [$81dc]
[81dc].byte $07; [0]:
[81dd].byte $0a; [1]:
[81de].byte $0d; [2]:
[81df].byte $0f; [3]:
[81e0].byte $0e; [4]:
[81e1].byte $0d; [5]:
[81e2].byte $0c; [6]:
[81e3].byte $0b; [7]:
[81e4].byte $0a; [8]:
[81e5].byte $09; [9]:
[81e6].byte $08; [10]:
[81e7].byte $07; [11]:
[81e8].byte $06; [12]:
[81e9].byte $05; [13]:
[81ea].byte $04; [14]:
[81eb].byte $03; [15]:
[81ec].byte $02; [16]:
[81ed].byte $02; [17]:
[81ee].byte $01; [18]:
[81ef].byte $01; [19]:
[81f0].byte $00; [20]:

;============================================================================
; Update the Square Wave volume and control bits.
;
; This will load in the pending value for square wave volume
; and reduce it by any fade set by an MScript op. This will
; be the volume for the SQ1_VOL or
; SQ2_VOL channel.
;
; The control bits (duty cycle, length counter halt,
; constant volume/envelope flag) will then be applied to
; the register.
;
; See https://www.nesdev.org/wiki/APU_Pulse
;
; INPUTS:
;     MScript_CurrentChannel:
;         The current channel being processed (0 or 1).
;
;     MScript_CurValue:
;         The current volume value to use as a base.
;
;     Music_SQ_Fades:
;         The fade values to subtract from the volume
;         (indexed by channel).
;
;     Music_SQ_ControlBits:
;         The control bits to set for the register.
;
; OUTPUTS:
;     SQ1_VOL:
;     SQ2_VOL:
;         The updated Square Wave register.
;
; XREFS:
;     Music_PlaySQEnvelopeModeCurveButHeld
;     Music_PlaySQEnvelopeModeLinearTrailoff
;     Music_PlaySQEnvelopeModePluck
;============================================================================
[81f1]Music_UpdateSQVolRegister:; [$81f1]
;
; Compute the address for the Square Wave volume register.
;
[81f1]LDX a:MScript_CurrentChannel; Load the MScript channel.
[81f4]TXA; A = result.
[81f5]ASL A; Convert to a word boundary.
[81f6]ASL A; And double, giving us the start of either SQ channel volume addresses.
[81f7]TAY; Y = resulting index.


;
; Apply any fade set.
;
[81f8]LDA a:MScript_CurValue; Load the volume to set.
[81fb]SEC
[81fc]SBC Music_SQ_Fades,X; Subtract any fade that was set.
[81ff]BCS @_setVolume; If positive, jump.


;
; The volume went negative. Cap to 0.
;
[8201]LDA #$00; Set the volume to 0.

[8203]@_setVolume:; [$8203]
[8203]LDX a:MScript_CurrentChannel; Load the current SQ channel as an index.
[8206]ORA Music_SQ_ControlBits,X; Apply control bits to the value to set for the register.
[8209]STA SQ1_VOL,Y; And set the register.
[820c]RTS

;============================================================================
; TODO: Document Music_ApplySQPitchEffectToLO
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlaySQEnvelopeModeCurveButHeld
;     Music_PlaySQEnvelopeModeLinearTrailoff
;     Music_PlaySQEnvelopeModePluck
;============================================================================
[820d]Music_ApplySQPitchEffectToLO:; [$820d]
[820d]LDX a:MScript_CurrentChannel; Load the current MScript channel.


;
; Make sure the phase counter reached 18 before we make any
; changes. This provides a delay.
;
[8210]LDA Music_SQEnvelope_Phase,X; Load the phase counter for the channel.
[8213]CMP #$12; Is it < 18?
[8215]BCC @_return; If so, end.


;
; The counter hit 18, so we can begin updating state.
;
; First we'll divide the counter by 4, giving a quarter speed.
; Then we'll AND with the depth mask, defining the range (e.g.,
; $04 == 0..4 repeating).
;
; The result is a delta used later.
;
[8217]LSR A; Divide by 4, giving quarter speed.
[8218]LSR A
[8219]AND Music_SQPitchDelta_Mask,X; AND with our depth mask, defining the range.
[821c]STA a:Music_SQEffect_Delta; Store as the delta.
[821f]LDA SoundEffect_TicksRemaining,X; Check for sound effects on this channel.
[8222]BNE @_return; If any are set, skip playing on this channel.


;
; No sound effects are playing, so we can continue.
;
[8224]LDA a:MScript_CurrentChannel; Load the current MScript channel.
[8227]ASL A; Convert to a word boundary.
[8228]ASL A; And multiply by 2 for the channel offset.
[8229]TAY; Y = resulting index.


;
; Don't apply the effect if the base is too small to subtract from.
;
[822a]LDA Music_Current_SQ_Low,X; Load the low value .
[822d]CMP Music_SQPitchDelta_Mask,X; Is it less than the depth mask?
[8230]BCC @_return; If so, return.


;
; Subtract the delta and store it in the SQ*_LO register.
;
[8232]SEC
[8233]SBC a:Music_SQEffect_Delta; Subtract the delta calculated above.
[8236]STA SQ1_LO,Y; And store it in the register.

[8239]@_return:; [$8239]
[8239]RTS

;============================================================================
; TODO: Document MScripts_InvokeNext
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScript_Op_BeginLoop
;     MScript_Op_EndLoop
;     MScript_Op_JumpSubroutine
;     MScript_Op_NextLoopIfNCompleted
;     MScript_Op_NoOp
;     MScript_Op_RestartChannel
;     MScript_Op_RestoreAddr
;     MScript_Op_Return
;     MScript_Op_SaveAddr
;     MScript_Op_SetChannelTranspose
;     MScript_Op_SetControlBits
;     MScript_Op_SetGlobalTranspose
;     MScript_Op_SetSQ2Detune
;     MScript_Op_SetSQEnvelopeMode
;     MScript_Op_SetSQPitchEffectDepth
;     MScript_Op_SetSQVol
;     MScripts_SetNoteLengthFromValue
;     Music_PlayNext
;============================================================================
[823a]MScripts_InvokeNext:; [$823a]
[823a]LDX a:MScript_CurrentChannel; X = Channel index being processed
[823d]CPX #$03; Is this the noise channel?
[823f]BNE @_loadNextValue; If not, jump.
[8241]LDA a:Music_Noise_Remaining; Is there noise to play?
[8244]BEQ @_loadNextValue; If not, process the next value in the script.
[8246]JMP Music_PlayNoise; Else, play the noise.

[8249]@_loadNextValue:; [$8249]
[8249]JSR MScripts_GetNextValue; Get the next value from the MScript.
[824c]STA a:MScript_CurValue; Store it.
[824f]TAY; Y = Value
[8250]BMI @_handleScriptValue; If the script value is >= 0x80, jump to handle it.
[8252]JMP MScripts_PlayIfHasValue; Play if there's a value, or finish if 0.


;
; Check if this is an MScript op (>= 0xEE).
;
[8255]@_handleScriptValue:; [$8255]
[8255]CMP #$ee; Is this < 0xEE?
[8257]BCC MScripts_SetNoteLengthFromNext; If so, jump.


;
; Determine the op handler to invoke.
;
[8259]SEC
[825a]LDA #$ff; A = 0xFF
[825c]SBC a:MScript_CurValue; Subtract the opcode, giving an index into the lookup table.
[825f]ASL A; Normalize to a word boundary for the lookup table.
[8260]TAY; Y = A
[8261]LDA MSCRIPT_OP_HANDLERS+1,Y; Load the address of the handler and push to the stack.
[8264]PHA
[8265]LDA MSCRIPT_OP_HANDLERS,Y
[8268]PHA
[8269]RTS


;============================================================================
; Lookup table of MScript operation handlers.
;
; XREFS:
;     MScripts_InvokeNext
;============================================================================

;
; XREFS:
;     MScripts_InvokeNext
;
[826a]MSCRIPT_OP_HANDLERS:; [$826a]
[826a].word MScript_Op_End-1; MScript_Op_End [$PRG5::826a]
[826c].word MScript_Op_RestoreAddr-1; MScript_Op_RestoreAddr [$PRG5::826c]
[826e].word MScript_Op_BeginLoop-1; MScript_Op_BeginLoop [$PRG5::826e]
[8270].word MScript_Op_EndLoop-1; MScript_Op_EndLoop [$PRG5::8270]
[8272].word MScript_Op_NextLoopIfNCompleted-1; MScript_Op_NextLoopIfNCompleted [$PRG5::8272]
[8274].word MScript_Op_NoOp-1; MScript_Op_NoOp [$PRG5::8274]
[8276].word MScript_Op_SaveAddr-1; MScript_Op_SaveAddr [$PRG5::8276]
[8278].word MScript_Op_JumpSubroutine-1; MScript_Op_JumpSubroutine [$PRG5::8278]
[827a].word MScript_Op_SetGlobalTranspose-1; MScript_Op_SetGlobalTranspose [$PRG5::827a]
[827c].word MScript_Op_SetChannelTranspose-1; MScript_Op_SetChannelTranspose [$PRG5::827c]
[827e].word MScript_Op_Return-1; MScript_Op_Return [$PRG5::827e]
[8280].word MScript_Op_RestartChannel-1; MScript_Op_RestartChannel [$PRG5::8280]
[8282].word MScript_Op_RepeatValue-1; MScript_Op_RepeatValue [$PRG5::8282]
[8284].word MScript_Op_SetControlBits-1; MScript_Op_SetControlBits [$PRG5::8284]
[8286].word MScript_Op_SetSQVol-1; MScript_Op_SetSQVol [$PRG5::8286]
[8288].word MScript_Op_SetSQEnvelopeMode-1; MScript_Op_SetSQEnvelopeMode [$PRG5::8288]
[828a].word MScript_Op_SetSQPitchEffectDepth-1; MScript_Op_SetSQPitchEffectDepth [$PRG5::828a]
[828c].word MScript_Op_SetSQ2Detune-1; MScript_Op_SetSQ2Detune [$PRG5::828c]

;============================================================================
; TODO: Document MScripts_SetNoteLengthFromNext
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScripts_InvokeNext
;============================================================================
[828e]MScripts_SetNoteLengthFromNext:; [$828e]
[828e]LDA a:MScript_CurValue; Load the current script value.
[8291]AND #$7f; Discard bit 7.
[8293]BPL MScripts_SetNoteLengthFromValue

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document MScript_Op_RepeatValue
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8295]MScript_Op_RepeatValue:; [$8295]
[8295]JSR MScripts_GetNextValue; Get the next value in the script.

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document MScripts_SetNoteLengthFromValue
;
; INPUTS:
;     A
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScripts_SetNoteLengthFromNext
;============================================================================
[8298]MScripts_SetNoteLengthFromValue:; [$8298]
[8298]LDX a:MScript_CurrentChannel
[829b]STA MScript_NoteDurations,X
[829e]STA a:MScript_CurValue
[82a1]LDX a:MScript_CurrentChannel
[82a4]CPX #$02
[82a6]BEQ MScripts_InvokeNext
[82a8]LDA a:MScript_CurValue
[82ab]PHA
[82ac]LSR A
[82ad]LSR A
[82ae]LSR A
[82af]STA a:MScript_CurValue
[82b2]PLA
[82b3]SEC
[82b4]SBC a:MScript_CurValue
[82b7]CMP #$10
[82b9]BCS @_beginCheckOffsets
[82bb]ASL A
[82bc]ASL A
[82bd]ASL A
[82be]ASL A
[82bf]ORA #$08
[82c1]STA Music_SQ_Note_Lengths,X
[82c4]CMP #$08
[82c6]BNE @_invokeNext
[82c8]LDA #$18
[82ca]BNE @_storeLength

[82cc]@_beginCheckOffsets:; [$82cc]
[82cc]LDY #$00

[82ce]@_checkOffsetLoop:; [$82ce]
[82ce]CMP MUSIC_CHANNEL_NOTE_OFFSETS_3_,Y
[82d1]BCS @_loadLength
[82d3]INY
[82d4]INY
[82d5]BNE @_checkOffsetLoop

[82d7]@_loadLength:; [$82d7]
[82d7]LDA BYTE_PRG5__8570,Y

[82da]@_storeLength:; [$82da]
[82da]STA Music_SQ_Note_Lengths,X

[82dd]@_invokeNext:; [$82dd]
[82dd]JMP MScripts_InvokeNext
[82e0]JMP MScripts_InvokeNext; Unreachable?

;============================================================================
; TODO: Document MScripts_PlayIfHasValue
;
; INPUTS:
;     A
;     Y
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScripts_InvokeNext
;============================================================================
[82e3]MScripts_PlayIfHasValue:; [$82e3]
[82e3]CMP #$00
[82e5]BNE Music_PlayWaveOrNoise
[82e7]JMP Music_StoreNoteDuration

;============================================================================
; TODO: Document Music_PlayWaveOrNoise
;
; INPUTS:
;     A
;     Y
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScripts_PlayIfHasValue
;============================================================================
[82ea]Music_PlayWaveOrNoise:; [$82ea]
[82ea]LDX a:MScript_CurrentChannel
[82ed]CPX #$03
[82ef]BNE Music_PlayWave


;
; This is the Noise channel.
;
[82f1]PHA
[82f2]AND #$0f
[82f4]STA a:Music_Noise_Remaining
[82f7]PLA
[82f8]LSR A
[82f9]LSR A
[82fa]LSR A
[82fb]LSR A
[82fc]STA a:Music_Noise_Index

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document Music_PlayNoise
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScripts_InvokeNext
;============================================================================
[82ff]Music_PlayNoise:; [$82ff]
[82ff]DEC a:Music_Noise_Remaining
[8302]LDA a:SoundEffect_TicksRemaining_3_
[8305]BEQ @LAB_PRG5__830a
[8307]JMP Music_StoreNoteDuration

[830a]@LAB_PRG5__830a:; [$830a]
[830a]LDA a:Music_Noise_Index
[830d]BNE @LAB_PRG5__8312
[830f]JMP Music_StoreNoteDuration

[8312]@LAB_PRG5__8312:; [$8312]
[8312]ASL A
[8313]ASL A
[8314]TAX
[8315]LDY #$00

[8317]@LAB_PRG5__8317:; [$8317]
[8317]LDA MUSIC_NOISE_VALUES,X
[831a]STA NOISE_VOL,Y
[831d]INX
[831e]INY
[831f]CPY #$04
[8321]BCC @LAB_PRG5__8317
[8323]JMP Music_StoreNoteDuration

;============================================================================
; TODO: Document Music_PlayWave
;
; INPUTS:
;     Y
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlayWaveOrNoise
;============================================================================
[8326]Music_PlayWave:; [$8326]
[8326]LDX a:MScript_CurrentChannel
[8329]LDA SoundEffect_TicksRemaining,X
[832c]BEQ @_setNote
[832e]JMP Music_StoreNoteDuration

[8331]@_setNote:; [$8331]
[8331]LDX a:MScript_CurrentChannel
[8334]BEQ @_setSquareWave1
[8336]DEX
[8337]BEQ @_setSquareWave2Sweep


;
; This is the Triangle Wave channel.
;
[8339]LDA #$c0
[833b]STA a:TRI_LINEAR
[833e]JSR Music_SetNote
[8341]LDA a:Music_Note_Period_Low
[8344]STA a:TRI_LO
[8347]LDX a:MScript_CurrentChannel
[834a]LDA a:Music_Note_Period_High; Load the note period to play.
[834d]ORA #$f8; Set the full play length.
[834f]STA a:TRI_HI; And set as the Triangle High.
[8352]JMP Music_PlayTriangleWave


;
; This is the Square Wave 1 channel.
;
[8355]@_setSquareWave1:; [$8355]
[8355]JSR Music_SetNote
[8358]LDA #$00
[835a]STA a:SQ1_SWEEP
[835d]LDA a:Music_Note_Period_Low
[8360]STA a:SQ1_LO
[8363]STA a:Music_Current_SQ_Low
[8366]LDA a:Music_Note_Period_High
[8369]ORA a:Music_SQ_Note_Lengths
[836c]STA a:SQ1_HI
[836f]LDA #$00
[8371]STA a:Music_SQEnvelope_Phase
[8374]BEQ @_finish


;
; This is the Square Wave 2 channel.
;
[8376]@_setSquareWave2Sweep:; [$8376]
[8376]JSR Music_SetNote
[8379]LDA #$00
[837b]STA a:SQ2_SWEEP
[837e]LDY a:MScript_CurValue
[8381]LDA a:Music_Note_Period_Low
[8384]CMP a:Music_SQ2_TimerLowBias
[8387]BCC @_setSQ2HiLo
[8389]SEC
[838a]SBC a:Music_SQ2_TimerLowBias

[838d]@_setSQ2HiLo:; [$838d]
[838d]STA a:SQ2_LO
[8390]STA a:Music_Current_SQ_Low_1_
[8393]LDA a:Music_Note_Period_High
[8396]ORA a:Music_Note_Length_High
[8399]STA a:SQ2_HI
[839c]LDA #$00
[839e]STA a:Music_SQEnvelope_Phase_1_

[83a1]@_finish:; [$83a1]
[83a1]LDX a:MScript_CurrentChannel
[83a4]LDA #$ff
[83a6]STA Music_SQEnvelope_Value,X
[83a9]JSR Music_StoreNoteDuration
[83ac]RTS

;============================================================================
; Set the current per-channel repeat duration.
;
; MScripts maintain a per-channel "repeat count", which
; controls how many update ticks the current
; note/rest/noise value should be held before the script
; advances to the next byte.
;
; This copies MScript_NoteDurations (set by a script) into
; Music_NoteTicksRemaining (used for play back) for the
; current channel, which is decremented by the main music
; update loop to delay script advancement.
;
; INPUTS:
;     MScript_CurrentChannel:
;         The current MScript channel.
;
;     MScript_NoteDurations:
;         The per-channel repeat counts set by the script.
;
; OUTPUTS:
;     Music_NoteTicksRemaining:
;         The remaining tick counts for playback.
;
; XREFS:
;     MScripts_PlayIfHasValue
;     Music_PlayNoise
;     Music_PlayTriangleWave
;     Music_PlayWave
;============================================================================
[83ad]Music_StoreNoteDuration:; [$83ad]
[83ad]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[83b0]LDA MScript_NoteDurations,X; Load the repeat counts for this channel.
[83b3]STA Music_NoteTicksRemaining,X; Copy them over.
[83b6]RTS

;============================================================================
; TODO: Document Music_PlayTriangleWave
;
; INPUTS:
;     A
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     Music_PlayWave
;============================================================================
[83b7]Music_PlayTriangleWave:; [$83b7]
[83b7]JSR Music_StoreNoteDuration
[83ba]STA a:MScript_CurValue
[83bd]LSR A
[83be]LSR A
[83bf]STA a:Music_SQEffect_Delta
[83c2]LDA a:MScript_CurValue
[83c5]SEC
[83c6]SBC a:Music_SQEffect_Delta
[83c9]STA a:Something_Music_Triangle_017e
[83cc]RTS

;============================================================================
; Set the note value to play.
;
; Note values are relative semitone indices, not absolute
; pitches. They are are converted into a playable frequency
; through several transformations.
;
; The final pitch depends on:
;
; 1. The channel base offset (MUSIC_CHANNEL_NOTE_OFFSETS)
; 2. The channel transposition (Music_Channel_Transpose)
; 3. The global transposition (Music_Global_Transpose)
; 4. An octave normalization loop (12 semitones per octave)
;
; A value of 0x00 represents a rest. Any other value is
; processed through the above steps.
;
; As a result, the same byte value in different MScripts
; (or on different channels) does not necessarily produce
; the same audible pitch.
;
; XREFS:
;     Music_PlayWave
;============================================================================
[83cd]Music_SetNote:; [$83cd]
[83cd]LDX a:MScript_CurrentChannel
[83d0]LDA a:MScript_CurValue
[83d3]CLC
[83d4]ADC MUSIC_CHANNEL_NOTE_OFFSETS,X
[83d7]CLC
[83d8]ADC Music_Channel_Transpose,X
[83db]CLC
[83dc]ADC a:Music_Global_Transpose
[83df]STY a:MScript_Unused_RawValue


;
; Loop, subtracting 12 (number of notes in our lookup
; table) each iteration, until < 0.
;
; The number of loop iterations will be used later to
; normalize the resulting note for the right octave.
;
[83e2]LDY #$01
[83e4]SEC

[83e5]@_loop1:; [$83e5]
[83e5]SBC #$0c
[83e7]INY
[83e8]BCS @_loop1


;
; TODO: Out of the loop.
;
[83ea]DEY
[83eb]ADC #$0d
[83ed]ASL A
[83ee]TAX
[83ef]LDA AUDIO_NOTES,X
[83f2]STA a:Music_Note_Period_Low
[83f5]LDA AUDIO_NOTES+1,X
[83f8]STA a:Music_Note_Period_High


;
; Convert to the note in the right octave based on
; the starting value.
;
[83fb]@_octaveLoop:; [$83fb]
[83fb]DEY
[83fc]BEQ @_return
[83fe]LSR a:Music_Note_Period_High
[8401]ROR a:Music_Note_Period_Low
[8404]JMP @_octaveLoop

[8407]@_return:; [$8407]
[8407]RTS

;============================================================================
; MScript Op 0xFF: End the channel's script.
;
; XREFS:
;     MSCRIPT_OP_HANDLERS [$PRG5::826a]
;============================================================================
[8408]MScript_Op_End:; [$8408]
[8408]LDX a:MScript_CurrentChannel; Load the current MScript channel.


;
; Repeat this every time it's called.
;
; This ensures that this channel stays on this
; instruction until every channel has completed.
;
[840b]LDA #$01
[840d]STA Music_NoteTicksRemaining,X; Set this to repeat 1 more time (infinitely).
[8410]TXA; A = MScript channel.
[8411]ASL A; Convert to a word boundary for an address index.
[8412]TAX; X = result.


;
; Decrement the offset into the script to keep it on this
; 0xFF operation until all channels complete.
;
[8413]LDA Music_CurrentScriptAddrs,X; Load the current script address for this channel.
[8415]BNE @_setAddr; If lower byte is not 0, jump.


;
; Lower byte of the address is 0. We'll need to decrement
; the upper byte.
;
[8417]DEC Music_CurrentScriptAddrs+1,X; Decrement the upper byte of the address.

[8419]@_setAddr:; [$8419]
[8419]DEC Music_CurrentScriptAddrs,X; Decrement the lower byte of the address.


;
; Mark this channel as completed.
;
[841b]INC a:Music_NumChannelsCompleted; Mark the channel as complete.
[841e]RTS

;============================================================================
; MScript Op $FD: Begin Loop.
;
; Marks the start of a loop. This address will be used
; when looping.
;
; The loop will end when after it completes the specified
; number of loops, or when another operation breaks out
; of the loop.
;
; The initial loop counter is set to 1 internally.
;
; Loops cannot be nested.
;
; ARGS:
;     1. Number of iterations (1 byte)
;============================================================================
[841f]MScript_Op_BeginLoop:; [$841f]
;
; Read the number of iterations to loop from the script.
;
[841f]JSR MScripts_GetNextValue; Load the next value from the script.
[8422]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[8425]STA MScript_LoopLength,X; Store the length of this loop to the next value.


;
; Set the starting value for the loop counter (1).
;
[8428]LDA #$01
[842a]STA MScript_LoopCounter,X; Set the starting loop counter to 1.


;
; Store the start address of the loop.
;
[842d]TXA; A = Loop length.
[842e]ASL A; Convert to a word boundary for an index.
[842f]TAX; X = resulting index.
[8430]LDA Music_CurrentScriptAddrs,X; Load the lower byte of the current script address for the channel.
[8432]STA MScript_LoopStartAddrs,X; Store as the lower byte of the starting address for the loop.
[8435]LDA Music_CurrentScriptAddrs+1,X; Load the upper byte.
[8437]STA MScript_LoopStartAddrs+1,X; Store that.


;
; We're done. Invoke the next op in the script.
;
[843a]JMP MScripts_InvokeNext; Invoke the next operation.

;============================================================================
; MSCript Op $FE: Restart Loop If >= N Iterations
;
; If >= N iterations have been completed, restart the
; loop, advancing the loop iteration count.
;
; If < N iterations have been completed, proceed with
; the next operation in the script.
;
; ARGS:
;     1. Number of iterations to check (1 byte)
;============================================================================
[843d]MScript_Op_NextLoopIfNCompleted:; [$843d]
[843d]JSR MScripts_GetNextValue; Load the current MScript channel.
[8440]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[8443]CMP MScript_LoopCounter,X; Has the specified number of loops been completed?
[8446]BCS @_invokeNext; If so, invoke the next operation within this loop.


;
; The specified number of loops have not been completed.
; Restart the loop.
;
[8448]TXA; A = Current channel.
[8449]ASL A; Convert to a word boundary for lookup tables.
[844a]TAX; X = result.
[844b]LDA MScript_LoopEndAddrs,X; Load the lower byte of the loop end address.
[844e]STA Music_CurrentScriptAddrs,X; Set as the lower byte of the next address.
[8450]LDA MScript_LoopEndAddrs+1,X; Load the upper byte of the loop end address.
[8453]STA Music_CurrentScriptAddrs+1,X; Set as the upper byte of the next address.

[8455]@_invokeNext:; [$8455]
[8455]JMP MScripts_InvokeNext

;============================================================================
; MScript Op $FC: End Loop.
;
; Marks the end of the loop.
;
; If the loop counter has hit the loop length (and
; remember, the loop counter is 1-based), the loop will
; end.
;
; If it's under the loop length, the loop will restart.
;============================================================================
[8458]MScript_Op_EndLoop:; [$8458]
[8458]LDX a:MScript_CurrentChannel; Load the current MScript channel.
[845b]LDA MScript_LoopCounter,X; Load the current loop counter.
[845e]CMP MScript_LoopLength,X; Is it >= the loop length?
[8461]BCS @_invokeNext; If so, invoke the next operation after the loop.


;
; The script can continue to loop.
;
[8463]INC MScript_LoopCounter,X; Increment the loop counter.
[8466]TXA; A = MScript channel.
[8467]ASL A; Convert to a word boundary for lookup tables.
[8468]TAX; X = resulting index.


;
; Set the current script address as the end of the loop.
;
[8469]LDA Music_CurrentScriptAddrs,X; Load the lower byte of the current script address.
[846b]STA MScript_LoopEndAddrs,X; Set as the lower byte of the end of the loop.
[846e]LDA Music_CurrentScriptAddrs+1,X; Load the upper byte of the current script address.
[8470]STA MScript_LoopEndAddrs+1,X; Set as the upper byte of the end of the loop.


;
; Set the start of the loop as the current script address.
;
[8473]LDA MScript_LoopStartAddrs,X; Load the lower byte of the address of the start of the loop.
[8476]STA Music_CurrentScriptAddrs,X; Set as the lower byte of the current script address.
[8478]LDA MScript_LoopStartAddrs+1,X; Load the upper byte of the address of the start of the loop.
[847b]STA Music_CurrentScriptAddrs+1,X; Set as the upper byte of the current script address.


;
; We're done. Proceed with the script, either looping or
; moving on from the loop.
;
[847d]@_invokeNext:; [$847d]
[847d]JMP MScripts_InvokeNext; Invoke the next operation in the script.

;============================================================================
; MScript Op $FA: No-Op
;
; Does nothing. Simply acts as padding to help keep
; scripts across channels in sync.
;============================================================================
[8480]MScript_Op_NoOp:; [$8480]
[8480]JMP MScripts_InvokeNext; Invoke the next operation in the script.

;============================================================================
; TODO: Document MScript_Op_SetControlBits
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8483]MScript_Op_SetControlBits:; [$8483]
[8483]JSR MScripts_GetNextValue
[8486]LDX a:MScript_CurrentChannel
[8489]STA Music_SQ_ControlBits,X
[848c]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_SaveAddr
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[848f]MScript_Op_SaveAddr:; [$848f]
[848f]JSR MScript_Op_SaveAddr_Store
[8492]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_SaveAddr_Store
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     MScript_Op_SaveAddr
;============================================================================
[8495]MScript_Op_SaveAddr_Store:; [$8495]
[8495]LDA a:MScript_CurrentChannel
[8498]ASL A
[8499]TAX
[849a]LDA Music_CurrentScriptAddrs,X
[849c]STA MScript_SavedAddr,X
[849f]LDA Music_CurrentScriptAddrs+1,X
[84a1]STA MScript_SavedAddr+1,X
[84a4]RTS

;============================================================================
; TODO: Document MScript_Op_RestoreAddr
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[84a5]MScript_Op_RestoreAddr:; [$84a5]
[84a5]LDA a:MScript_CurrentChannel
[84a8]ASL A
[84a9]TAX
[84aa]LDA MScript_SavedAddr,X
[84ad]STA Music_CurrentScriptAddrs,X
[84af]LDA MScript_SavedAddr+1,X
[84b2]STA Music_CurrentScriptAddrs+1,X
[84b4]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_RestartChannel
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[84b7]MScript_Op_RestartChannel:; [$84b7]
[84b7]LDA Music_Current
[84b9]ASL A
[84ba]ASL A
[84bb]SEC
[84bc]SBC #$04
[84be]ASL A
[84bf]TAY
[84c0]LDX #$00

[84c2]@_loop:; [$84c2]
[84c2]LDA MSCRIPTS_TITLESCREEN,Y
[84c5]STA Music_CurrentScriptAddrs,X
[84c7]INY
[84c8]INX
[84c9]CPX #$08
[84cb]BNE @_loop
[84cd]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_JumpSubroutine
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[84d0]MScript_Op_JumpSubroutine:; [$84d0]
[84d0]JSR MScripts_GetNextValue
[84d3]PHA
[84d4]JSR MScripts_GetNextValue
[84d7]PHA
[84d8]LDA a:MScript_CurrentChannel
[84db]ASL A
[84dc]TAX
[84dd]LDA Music_CurrentScriptAddrs,X
[84df]STA MScript_PushedAddrs,X
[84e2]LDA Music_CurrentScriptAddrs+1,X
[84e4]STA MScript_PushedAddrs+1,X
[84e7]PLA
[84e8]STA Music_CurrentScriptAddrs+1,X
[84ea]PLA
[84eb]STA Music_CurrentScriptAddrs,X
[84ed]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_Return
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[84f0]MScript_Op_Return:; [$84f0]
[84f0]LDA a:MScript_CurrentChannel; Load the current channel.
[84f3]ASL A; Shift to a word boundary.
[84f4]TAX; X = Result.
[84f5]LDA MScript_PushedAddrs,X; Load the lower byte of the pushed address.
[84f8]STA Music_CurrentScriptAddrs,X; Set for the script address.
[84fa]LDA MScript_PushedAddrs+1,X; Load the upper byte.
[84fd]STA Music_CurrentScriptAddrs+1,X; And set that.
[84ff]JMP MScripts_InvokeNext; Invoke the script there.

;============================================================================
; TODO: Document MScript_Op_SetChannelTranspose
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8502]MScript_Op_SetChannelTranspose:; [$8502]
[8502]JSR MScripts_GetNextValue
[8505]LDX a:MScript_CurrentChannel
[8508]STA Music_Channel_Transpose,X
[850b]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_SetGlobalTranspose
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[850e]MScript_Op_SetGlobalTranspose:; [$850e]
[850e]JSR MScripts_GetNextValue
[8511]STA a:Music_Global_Transpose
[8514]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_SetSQVol
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8517]MScript_Op_SetSQVol:; [$8517]
[8517]JSR MScripts_GetNextValue
[851a]LDX a:MScript_CurrentChannel
[851d]STA Music_SQ_Fades,X
[8520]JMP MScripts_InvokeNext

;============================================================================
; MScript Op $F0: Set the envelope mode for the Square Wave.
;
; This supports the following values:
;
; 0: Volume decay
;
;    Ramps down the volume smoothly.
;
; 1: Curve but held
;
;    Clamps the envelope into a range 0..15 and then slows
;    the decay.
;
; 2: Pre-built attack/decay curve
;
;    Pitches up and then down in a set pattern.
;============================================================================
[8523]MScript_Op_SetSQEnvelopeMode:; [$8523]
[8523]JSR MScripts_GetNextValue
[8526]LDX a:MScript_CurrentChannel
[8529]STA Music_SQEnvelope_Mode,X
[852c]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScript_Op_SetSQPitchEffectDepth
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[852f]MScript_Op_SetSQPitchEffectDepth:; [$852f]
[852f]JSR MScripts_GetNextValue
[8532]LDX a:MScript_CurrentChannel
[8535]STA Music_SQPitchDelta_Mask,X
[8538]JMP MScripts_InvokeNext

;============================================================================
; MScript Op $EE: Set the SQ2 pitch bias (detune).
;
; This operation applies a SQ2-only pitch adjustment by
; subtracting a small value from the low byte of the
; square wave timer period before writing to SQ2_LO.
;
; The value is compared against the computed timer low
; byte and clamped to avoid underflow. This produces a
; subtle upward pitch shift when non-zero.
;
; This is not related to note length or envelope timing.
; It is a pitch modification applied after note
; calculation, before writing to the APU.
;
; This may be used to provide a simple chorus/harmony
; effect.
;
; A value of 0 disables this effect.
;============================================================================
[853b]MScript_Op_SetSQ2Detune:; [$853b]
[853b]JSR MScripts_GetNextValue
[853e]STA a:Music_SQ2_TimerLowBias
[8541]JMP MScripts_InvokeNext

;============================================================================
; TODO: Document MScripts_GetNextValue
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;
; XREFS:
;     MScript_Op_BeginLoop
;     MScript_Op_JumpSubroutine
;     MScript_Op_NextLoopIfNCompleted
;     MScript_Op_RepeatValue
;     MScript_Op_SetChannelTranspose
;     MScript_Op_SetControlBits
;     MScript_Op_SetGlobalTranspose
;     MScript_Op_SetSQ2Detune
;     MScript_Op_SetSQEnvelopeMode
;     MScript_Op_SetSQPitchEffectDepth
;     MScript_Op_SetSQVol
;     MScripts_InvokeNext
;============================================================================
[8544]MScripts_GetNextValue:; [$8544]
[8544]LDA a:MScript_CurrentChannel
[8547]ASL A
[8548]TAX
[8549]LDA (Music_CurrentScriptAddrs,X)
[854b]INC Music_CurrentScriptAddrs,X
[854d]BNE @_return
[854f]INC Music_CurrentScriptAddrs+1,X

[8551]@_return:; [$8551]
[8551]RTS


;============================================================================
; Base note lookup table for 12 semitones (C..B), used
; with octave normalization.
;
; XREFS:
;     Music_SetNote
;     SoundEffect_SetNote
;============================================================================

;
; XREFS:
;     Music_SetNote
;     SoundEffect_SetNote
;
[8552]AUDIO_NOTES:; [$8552]
[8552].word $0000; [0]: Unused/padding
[8554].word $06ae; [1]: C2
[8556].word $064e; [2]: C2#2
[8558].word $05f3; [3]: D2
[855a].word $059f; [4]: D2#2
[855c].word $054d; [5]: E2
[855e].word $0501; [6]: F2
[8560].word $04b9; [7]: F2#2
[8562].word $0475; [8]: G2
[8564].word $0435; [9]: G2#2
[8566].word $03f8; [10]: A2
[8568].word $03bf; [11]: A2#2
[856a].word $0389; [12]: B2


;============================================================================
; Signed semitone offsets for pitched channels.
;
; Noise appears to be a sentinel.
;
; XREFS:
;     Music_SetNote
;============================================================================

;
; XREFS:
;     Music_SetNote
;
[856c]MUSIC_CHANNEL_NOTE_OFFSETS:; [$856c]
[856c].byte $f4; [0]: SQ1 (one octave down)
[856d].byte $f4; [1]: SQ2 (one octave down)
[856e].byte $0c; [2]: Triangle (1 octave up)

;
; XREFS:
;     MScripts_SetNoteLengthFromValue
;
[856f]MUSIC_CHANNEL_NOTE_OFFSETS_3_:; [$856f]
[856f].byte $7f; [3]: Noise (sentinel?)

;
; XREFS:
;     MScripts_SetNoteLengthFromValue
;
[8570]BYTE_PRG5__8570:; [$8570]
[8570].byte $08; [$8570] byte

;
; XREFS:
;     MScripts_SetNoteLengthFromValue
;
[8571]BYTE_PRG5__8571:; [$8571]
[8571].byte $60; [$8571] byte

;
; XREFS:
;     MScripts_SetNoteLengthFromValue
;
[8572]BYTE_PRG5__8572:; [$8572]
[8572].byte $c0,$50,$40,$30,$b0,$28,$30,$24; [$8572] byte
[857a].byte $d0,$1e,$50,$18,$a0; [$857a] byte

;
; XREFS:
;     Music_PlayNoise
;
[857f]MUSIC_NOISE_VALUES:; [$857f]
[857f].byte $14; [0]:
[8580].byte $20; [1]:
[8581].byte $00; [2]:
[8582].byte $f0; [3]:
[8583].byte $00; [0]:
[8584].byte $00; [1]:
[8585].byte $0f; [2]:
[8586].byte $20; [3]:
[8587].byte $00; [0]:
[8588].byte $00; [1]:
[8589].byte $0a; [2]:
[858a].byte $10; [3]:
[858b].byte $00; [0]:
[858c].byte $00; [1]:
[858d].byte $05; [2]:
[858e].byte $00; [3]:
[858f].byte $ff; [$858f] byte


;============================================================================
; Table of sound effects to handler table indexes.
;
; XREFS:
;     SoundEffects_HandleOnInterrupt
;============================================================================

;
; XREFS:
;     SoundEffects_HandleOnInterrupt
;
[8590]SOUND_EFFECT_HANDLER_INDEXES:; [$8590]
[8590].byte $00; [0]: Set up sound effects
[8591].byte $2c; [1]: Message
[8592].byte $60; [2]: Hit Enemy
[8593].byte $5c; [3]: Enemy died
[8594].byte $64; [4]: Player hit
[8595].byte $70; [5]: Magic
[8596].byte $38; [6]: Open door
[8597].byte $40; [7]: Typing
[8598].byte $4c; [8]: Item picked up
[8599].byte $50; [9]: Coin touched
[859a].byte $68; [10]: Magic hit by obstacle
[859b].byte $30; [11]: Cursor moved
[859c].byte $58; [12]: Shield hit by magic
[859d].byte $34; [13]: Character inputted
[859e].byte $28; [14]: Password character entered
[859f].byte $3c; [15]: Pushing block
[85a0].byte $54; [16]: Coin dropped
[85a1].byte $48; [17]: ?? Unused
[85a2].byte $44; [18]: Pakukame
[85a3].byte $24; [19]: Fill HP or MP
[85a4].byte $6c; [20]: Tilte magic spell
[85a5].byte $1c; [21]: Step sound
[85a6].byte $10; [22]: Player died
[85a7].byte $14; [23]: Ladder dropped
[85a8].byte $18; [24]: Show player menu
[85a9].byte $20; [25]: Changed gold amount
[85aa].byte $0c; [26]: Use special item 2
[85ab].byte $08; [27]: Bread touched
[85ac].byte $04; [28]: Coin touched


;============================================================================
; A jump table of sound effect handler functions.
;
; This table is in pairs of sound effect setup and on-tick
; handlers. The setup handler runs when loading a new sound
; effect, and the on-tick handler runs for any existing
; loaded sound effect.
;
; These may be separate functions, or two parts of
; essentially the same function.
;
; XREFS:
;     SoundEffects_HandleOnInterrupt
;============================================================================

;
; XREFS:
;     SoundEffects_HandleOnInterrupt
;
[85ad]SOUND_EFFECT_HANDLERS:; [$85ad]
[85ad].word SoundEffects_Init-1; SoundEffects_Init [$PRG5::85ad]
[85af].word SoundEffect_NoOp-1; SoundEffect_NoOp [$PRG5::85af]
[85b1].word SoundEffect_CoinTouched_Setup-1; 0x04
[85b3].word SoundEffect_CoinTouched_OnTick-1; SoundEffect_CoinTouched_OnTick [$PRG5::85b3]
[85b5].word SoundEffect_BreadTouched_Setup-1; 0x08
[85b7].word SoundEffect_BreadTouched_OnTick-1; SoundEffect_BreadTouched_OnTick [$PRG5::85b7]
[85b9].word SoundEffect_Maybe_UseSpecialItem2_Setup-1; 0x0C
[85bb].word SoundEffect_Maybe_UseSpecialItem2_OnTick-1; SoundEffect_Maybe_UseSpecialItem2_OnTick [$PRG5::85bb]
[85bd].word SoundEffect_PlayerDied_Setup-1; 0x10
[85bf].word SoundEffect_PlayerDied_OnTick-1; SoundEffect_PlayerDied_OnTick [$PRG5::85bf]
[85c1].word SoundEffect_LadderDropped_Setup-1; 0x14
[85c3].word SoundEffect_LadderDropped_OnTick-1; SoundEffect_LadderDropped_OnTick [$PRG5::85c3]
[85c5].word SoundEffect_ShowPlayerMenu_Setup-1; 0x18
[85c7].word SoundEffect_ShowPlayerMenu_OnTick-1; SoundEffect_ShowPlayerMenu_OnTick [$PRG5::85c7]
[85c9].word SoundEffect_Maybe_Step_Setup-1; 0x1C
[85cb].word SoundEffect_Maybe_Step_OnTick-1; SoundEffect_Maybe_Step_OnTick [$PRG5::85cb]
[85cd].word SoundEffect_GoldAmountChanged_Setup-1; 0x20
[85cf].word SoundEffects_DecrementCounter-1; SoundEffects_DecrementCounter [$PRG5::85cf]
[85d1].word SoundEffect_FillHPOrMP_Setup-1; 0x24
[85d3].word SoundEffect_FillHPOrMP_OnTick-1; SoundEffect_FillHPOrMP_OnTick [$PRG5::85d3]
[85d5].word SoundEffect_PasswordCharInput_Setup-1; 0x28
[85d7].word SoundEffects_DecrementCounter-1; SoundEffects_DecrementCounter [$PRG5::85d7]
[85d9].word SoundEffect_Message_Setup-1; 0x2C
[85db].word SoundEffect_Message_OnTick-1; SoundEffect_Message_OnTick [$PRG5::85db]
[85dd].word SoundEffect_CursorMoved_Setup-1; 0x30
[85df].word SoundEffect_CursorMoved_OnTick-1; SoundEffect_CursorMoved_OnTick [$PRG5::85df]
[85e1].word SoundEffect_CharacterInput_Setup-1; 0x34
[85e3].word SoundEffect_CharacterInput_OnTick-1; SoundEffect_CharacterInput_OnTick [$PRG5::85e3]
[85e5].word SoundEffect_OpenDoor_Setup-1; 0x38
[85e7].word SoundEffect_OpenDoor_OnTick-1; SoundEffect_OpenDoor_OnTick [$PRG5::85e7]
[85e9].word SoundEffect_PushBlock_Setup-1; 0x3C
[85eb].word SoundEffect_PushBlock_OnTick-1; SoundEffect_PushBlock_OnTick [$PRG5::85eb]
[85ed].word SoundEffect_Maybe_Typing_Setup-1; 0x40
[85ef].word SoundEffect_Maybe_Typing_OnTick-1; SoundEffect_Maybe_Typing_OnTick [$PRG5::85ef]
[85f1].word SoundEffect_Pakukame_Setup-1; 0x44
[85f3].word SoundEffect_Pakukame_OnTick-1; SoundEffect_Pakukame_OnTick [$PRG5::85f3]
[85f5].word SoundEffect_0x48_Setup-1; 0x48
[85f7].word SoundEffect_0x48_OnTick-1; SoundEffect_0x48_OnTick [$PRG5::85f7]
[85f9].word SoundEffect_ItemPickedUp_Setup-1; 0x4C
[85fb].word SoundEffect_ItemPickedUp_OnTick-1; SoundEffect_ItemPickedUp_OnTick [$PRG5::85fb]
[85fd].word SoundEffect_CoinTouchedCommon_Setup-1; 0x50
[85ff].word SoundEffect_CoinTouchedCommon_OnTick-1; SoundEffect_CoinTouchedCommon_OnTick [$PRG5::85ff]
[8601].word SoundEffect_CoinDropped_Setup-1; 0x54
[8603].word SoundEffect_CoinDropped_OnTick-1; SoundEffect_CoinDropped_OnTick [$PRG5::8603]
[8605].word SoundEffect_ShieldHitByMagic_Setup-1; 0x58
[8607].word SoundEffect_ShieldHitByMagic_OnTick-1; SoundEffect_ShieldHitByMagic_OnTick [$PRG5::8607]
[8609].word SoundEffect_EnemyDied_Setup-1; 0x5C
[860b].word SoundEffect_EnemyDied_OnTick-1; SoundEffect_EnemyDied_OnTick [$PRG5::860b]
[860d].word SoundEffect_HitEnemy_Setup-1; 0x60
[860f].word SoundEffect_HitEnemy_OnTick-1; SoundEffect_HitEnemy_OnTick [$PRG5::860f]
[8611].word SoundEffect_HitPlayer_Setup-1; 0x64
[8613].word SoundEffect_HitPlayer_OnTick-1; SoundEffect_HitPlayer_OnTick [$PRG5::8613]
[8615].word SoundEffect_MagicHitObstacle_Setup-1; 0x68
[8617].word SoundEffect_MagicHitObstacle_OnTick-1; SoundEffect_MagicHitObstacle_OnTick [$PRG5::8617]
[8619].word SoundEffect_Tilte_Setup-1; 0x6C
[861b].word SoundEffect_Tilte_OnTick-1; SoundEffect_Tilte_OnTick [$PRG5::861b]
[861d].word SoundEffect_Magic_Setup-1; 0x70
[861f].word SoundEffect_Magic_OnTick-1; SoundEffect_Magic_OnTick [$PRG5::861f]

;============================================================================
; TODO: Document SoundEffects_DecrementCounter
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8621]SoundEffects_DecrementCounter:; [$8621]
[8621]DEC a:SoundEffect_State_Counter
[8624]BNE Sound_ResetCurrentSound_Return

;============================================================================
; TODO: Document Sound_ResetCurrentSound
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     SoundEffect_0x48_OnTick
;     SoundEffect_BreadTouched_OnTick
;     SoundEffect_CharacterInput_OnTick
;     SoundEffect_CoinDropped_OnTick
;     SoundEffect_CoinTouchedCommon_OnTick
;     SoundEffect_CursorMoved_OnTick
;     SoundEffect_EnemyDied_OnTick
;     SoundEffect_FillHPOrMP_OnTick
;     SoundEffect_HitEnemy_OnTick
;     SoundEffect_HitPlayer_OnTick
;     SoundEffect_ItemPickedUp_OnTick
;     SoundEffect_LadderDropped_OnTick
;     SoundEffect_MagicHitObstacle_OnTick
;     SoundEffect_Magic_OnTick
;     SoundEffect_Maybe_Step_OnTick
;     SoundEffect_Maybe_Typing_OnTick
;     SoundEffect_Maybe_UseSpecialItem2_OnTick
;     SoundEffect_Message_OnTick
;     SoundEffect_OpenDoor_OnTick
;     SoundEffect_Pakukame_OnTick
;     SoundEffect_PlayerDied_OnTick
;     SoundEffect_PushBlock_OnTick
;     SoundEffect_ShieldHitByMagic_OnTick
;     SoundEffect_ShowPlayerMenu_OnTick
;     SoundEffect_Tilte_OnTick
;     SoundEffects_HandleOnInterrupt
;============================================================================
[8626]Sound_ResetCurrentSound:; [$8626]
[8626]LDA #$00
[8628]STA a:SoundEffect_HandlerIndex
[862b]STA a:SoundEffect_Unused_PriorityID

;
; XREFS:
;     SoundEffects_DecrementCounter
;
[862e]Sound_ResetCurrentSound_Return:; [$862e]
[862e]RTS

;============================================================================
; TODO: Document SoundEffects_HandleOnInterrupt
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     thunk_SoundEffects_HandleOnInterrupt
;============================================================================
[862f]SoundEffects_HandleOnInterrupt:; [$862f]
;
; Loop through all channels, decrementing the sound effect
; tick count for each.
;
[862f]LDX #$03; X = 3 (channel loop counter).

[8631]@_checkActiveEffectsLoop:; [$8631]
[8631]LDA SoundEffect_TicksRemaining,X; Load the sound effect ticks remaining for this channel.
[8634]BEQ @_prepareNextActiveEffectsLoopIter; If this channel is done, prepare for the next iteration.
[8636]DEC SoundEffect_TicksRemaining,X; Reduce the ticks remaining by 1.

[8639]@_prepareNextActiveEffectsLoopIter:; [$8639]
[8639]DEX; X-- (loop counter).
[863a]BPL @_checkActiveEffectsLoop; If >= 0, loop.


;
; Check if the current sound effect is playing or just set.
;
; Playing is indicated by bit 7 == 1.
;
[863c]LDA SoundEffect_Current; Load the ID of the sound effect that's set.
[863e]BMI @_runOnTickHandler; If the sound effect is playing (bit 7 is set), jump to load the current handler.


;
; The sound effect is set but not currently playing.
; Mark it as playing.
;
[8640]TAX; X = A (sound effect ID).
[8641]ORA #$80; Set the Playing state (bit 7).
[8643]STA SoundEffect_Current; Update the sound effect.
[8645]CPX #$1d; Is this sound ID in range?
[8647]BCS @_runOnTickHandler; If so, load and run the on-tick handler.


;
; The sound effect ID is in range. Check if we have a
; computed sound effect handler for it.
;
[8649]LDA a:SoundEffect_HandlerIndex; Load the current sound effect handler index.
[864c]BEQ @_newHandler; If 0 (init sound), we're ready to jump to load a new handler.


;
; There's an existing sound effect handler being used.
; Check if it matches the sound effect to play, and then
; either use it or load a new handler.
;
[864e]LDA SOUND_EFFECT_HANDLER_INDEXES,X; Load the sound effect handler index for this sound effect.
[8651]CMP a:SoundEffect_HandlerIndex; Does it match the existing handler?
[8654]BCC @_newHandler; If not, look for a new handler and reset for the sound.
[8656]BNE @_runOnTickHandler; Else, it's a match, so just load the handler to run it.


;
; Reset the sound effect handler and state for a new sound
; effect.
;
[8658]@_newHandler:; [$8658]
[8658]LDA SOUND_EFFECT_HANDLER_INDEXES,X; Load the sound effect handler index for this ID.
[865b]STA a:SoundEffect_HandlerIndex; Store as the new index.
[865e]TAX; X = A (index).


;
; Clear out the number of ticks remaining for the old sound
; effect.
;
[865f]LDA #$00
[8661]STA a:SoundEffect_TicksRemaining; SQ1 ticks remaining = 0
[8664]STA a:SoundEffect_TicksRemaining_1_; SQ2 ticks remaining = 0
[8667]STA a:SoundEffect_TicksRemaining_2_; TRI ticks remaining = 0
[866a]STA a:SoundEffect_TicksRemaining_3_; Noise ticks remaining = 0
[866d]BEQ @_checkAndRunHandler; Immediately jump to check and run the setup handler for the sound effect.


;
; Load the secondary, on-tick stage for the sound effect
; handler.
;
; Every sound effect handler has a setup stage and an
; on-tick stage. Pairs of each are in the sound effect
; handlers table.
;
[866f]@_runOnTickHandler:; [$866f]
[866f]LDX a:SoundEffect_HandlerIndex; Load the index of the sound effect handler.
[8672]INX; Advance to the next address for the on-tick handler.
[8673]INX


;
; Check if the sound effect index is within bounds of the
; handlers table.
;
; Note that the last sound effect handler index is 0x70, but
; 0x72 would be the last on-tick handler. This is checking
; that this is < 0x74, with the idea being that 0x73 would
; never be set (unless there was a major programming flaw).
;
[8674]@_checkAndRunHandler:; [$8674]
[8674]CPX #$74; Is this a valid sound effect within the handlers lookup table?
[8676]BCS Sound_ResetCurrentSound; If not, reset the current sound effect.
[8678]LDA SOUND_EFFECT_HANDLERS+1,X; Load the upper byte of the handler address.
[867b]PHA; Push it to the stack.
[867c]LDA SOUND_EFFECT_HANDLERS,X; Load the lower byte.
[867f]PHA; Push it to the stack.

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_NoOp
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[8680]SoundEffect_NoOp:; [$8680]
[8680]RTS

;============================================================================
; Initialize support for sound effects.
;
; This will clear out state, perform an audio reset, and
; then enable the SQ1, SQ2, TRI, and Noise channels.
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     DMC_RAW:
;         Set to 0.
;
;     SND_CHN:
;         Set to 0xF (SQ1/SQ2/TRI/Noise).
;
;     SoundEffect_Unused_PriorityID:
;     SoundEffect_TicksRemaining:
;     SoundEffect_TicksRemaining+1:
;     $0125:
;     $0126:
;         Set to 0.
;
; CALLS:
;     Audio_Reset
;
; XREFS:
;     SOUND_EFFECT_HANDLERS [$PRG5::85ad]
;     thunk_SoundEffects_Init
;============================================================================
[8681]SoundEffects_Init:; [$8681]
[8681]LDA #$00
[8683]STA a:DMC_RAW; Disable raw DMC.


;
; Clear the ticks remaining for all sound effect channels.
;
[8686]STA a:SoundEffect_TicksRemaining; Set SQ1 ticks remaining = 0.
[8689]STA a:SoundEffect_TicksRemaining_1_; Set SQ2 ticks remaining = 0.
[868c]STA a:SoundEffect_TicksRemaining_2_; Set TRI ticks remaining = 0.
[868f]STA a:SoundEffect_TicksRemaining_3_; Set Noise ticks remaining = 0.
[8692]STA a:SoundEffect_Unused_PriorityID; Set priority ID (unused) to 0.


;
; Perform an audio reset and then enable the SQ1/SQ2/TRI/Noise
; channels.
;
[8695]JSR Audio_Reset; Reset the audio.
[8698]LDA #$0f
[869a]STA a:SND_CHN; Enable channels.
[869d]RTS

;============================================================================
; TODO: Document SoundEffect_Message_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[869e]SoundEffect_Message_Setup:; [$869e]
[869e]LDA #$06
[86a0]STA a:SoundEffect_TicksRemaining_3_; Set TRI ticks remaining to 6.
[86a3]LDA #$00
[86a5]STA a:SoundEffect_State_Counter; Set state counter to 0.

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_Message_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;============================================================================
[86a8]SoundEffect_Message_OnTick:; [$86a8]
[86a8]LDA #$1f
[86aa]STA a:NOISE_VOL; Set Noise volume to 31.


;
; Load a value from the lookup table for NOISE_LO.
;
; This switches sounds every 2 ticks, producing a typing
; sound.
;
; BUG:
;     And this is fascinating. The loud clack-clack typing
;     sound, reminiscent of an old typewriter, appears to
;     be a bug.
;
;     SOUNDEFFECT_MESSAGE_NOISE_LO defines the
;     typing sounds, and produces a much softer sound, one
;     that feels more appropriate considering other NES
;     games.
;
;     That's not what's used, though. The AND #$02 instruction
;     produces an offset of 0 or 2, with 2 causing an
;     out-of-bounds read, pulling #$A9 out of the following
;     function (an LDA instruction). This is much sharper than
;     #$01, producing that sound.
;
;     My guess is they originally had an AND #$01, and wanted
;     to reduce the sound change from every tick to every
;     other tick, but didn't update the table with a padding
;     byte, so it overflowed.
;
;     Maybe they were aiming for this as a hack at this
;     point, or maybe they messed up but nobody really noticed
;     because the sound ended up sounding so good and thus
;     passed QA. In any case, the shipped behavior does not
;     match the original intent of this code.
;
[86ad]LDA a:SoundEffect_State_Counter; Load the sound effect counter.
[86b0]AND #$02; Keep bit 1 (on 2 ticks, off 2 ticks).
[86b2]TAX; X = result.
[86b3]LDA SOUNDEFFECT_MESSAGE_NOISE_LO,X; Load the NOISE_LO value for this state.
[86b6]STA a:NOISE_LO
[86b9]LDA #$00
[86bb]STA a:NOISE_HI
[86be]INC a:SoundEffect_State_Counter
[86c1]LDA a:SoundEffect_State_Counter
[86c4]CMP #$04
[86c6]BCC @_return
[86c8]LDA #$10
[86ca]STA a:NOISE_VOL
[86cd]JMP Sound_ResetCurrentSound

[86d0]@_return:; [$86d0]
[86d0]RTS

;
; XREFS:
;     SoundEffect_Message_OnTick
;
[86d1]SOUNDEFFECT_MESSAGE_NOISE_LO:; [$86d1]
[86d1].byte $10; [0]:
[86d2].byte $01; [1]:

;============================================================================
; TODO: Document SoundEffect_HitEnemy_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[86d3]SoundEffect_HitEnemy_Setup:; [$86d3]
[86d3]LDA #$14
[86d5]STA a:SoundEffect_TicksRemaining_1_
[86d8]STA a:SoundEffect_TicksRemaining_3_
[86db]LDA #$00
[86dd]STA a:SoundEffect_State_Counter

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_HitEnemy_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[86e0]SoundEffect_HitEnemy_OnTick:; [$86e0]
[86e0]LDX a:SoundEffect_State_Counter
[86e3]LDA SOUNDEFFECT_HIT_ENEMY_NOTES,X
[86e6]CMP #$ff
[86e8]BNE @_play
[86ea]LDA #$10
[86ec]STA a:SQ2_VOL
[86ef]STA a:NOISE_VOL
[86f2]JMP Sound_ResetCurrentSound

[86f5]@_play:; [$86f5]
[86f5]JSR SoundEffect_SetNote
[86f8]LDA #$5f
[86fa]STA a:SQ2_VOL
[86fd]STA a:NOISE_VOL
[8700]LDA a:SoundEffect_State_Counter
[8703]EOR #$0f
[8705]ORA #$98
[8707]STA a:SQ2_SWEEP
[870a]LDA a:SoundEffect_Note_Low
[870d]STA a:SQ2_LO
[8710]AND #$07
[8712]STA a:NOISE_LO
[8715]LDA #$00
[8717]STA a:NOISE_HI
[871a]LDA a:SoundEffect_Note_High
[871d]STA a:SQ2_HI
[8720]INC a:SoundEffect_State_Counter
[8723]RTS

;
; XREFS:
;     SoundEffect_HitEnemy_OnTick
;
[8724]SOUNDEFFECT_HIT_ENEMY_NOTES:; [$8724]
[8724].byte $62; [0]:
[8725].byte $4e; [1]:
[8726].byte $3c; [2]:
[8727].byte $50; [3]:
[8728].byte $48; [4]:
[8729].byte $65; [5]:
[872a].byte $51; [6]:
[872b].byte $48; [7]:
[872c].byte $56; [8]:
[872d].byte $52; [9]:
[872e].byte $5f; [10]:
[872f].byte $58; [11]:
[8730].byte $65; [12]:
[8731].byte $4d; [13]:
[8732].byte $55; [14]:
[8733].byte $ff; [15]:

;============================================================================
; TODO: Document SoundEffect_EnemyDied_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[8734]SoundEffect_EnemyDied_Setup:; [$8734]
[8734]LDA #$16
[8736]STA a:SoundEffect_TicksRemaining_3_
[8739]LDA #$14
[873b]STA a:SoundEffect_State_Counter
[873e]LDA #$00
[8740]STA a:SoundEffect_State_0128

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_EnemyDied_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[8743]SoundEffect_EnemyDied_OnTick:; [$8743]
[8743]DEC a:SoundEffect_State_Counter
[8746]BNE @_play
[8748]LDA #$10
[874a]STA a:NOISE_VOL
[874d]JMP Sound_ResetCurrentSound

[8750]@_play:; [$8750]
[8750]LDX a:SoundEffect_State_0128
[8753]LDA #$1f
[8755]STA a:NOISE_VOL
[8758]LDA SOUNDEFFECT_ENEMY_DIED_NOISE_LO,X
[875b]STA a:NOISE_LO
[875e]LDA #$00
[8760]STA a:NOISE_HI
[8763]INC a:SoundEffect_State_0128
[8766]RTS

;
; XREFS:
;     SoundEffect_EnemyDied_OnTick
;
[8767]SOUNDEFFECT_ENEMY_DIED_NOISE_LO:; [$8767]
[8767].byte $0f; [0]:
[8768].byte $0c; [1]:
[8769].byte $0e; [2]:
[876a].byte $0b; [3]:
[876b].byte $0d; [4]:
[876c].byte $09; [5]:
[876d].byte $03; [6]:
[876e].byte $02; [7]:
[876f].byte $01; [8]:
[8770].byte $00; [9]:

;============================================================================
; TODO: Document SoundEffect_HitPlayer_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[8771]SoundEffect_HitPlayer_Setup:; [$8771]
[8771]LDA #$0f
[8773]STA a:SoundEffect_TicksRemaining_1_
[8776]LDA #$00
[8778]STA a:SoundEffect_State_Counter

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_HitPlayer_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[877b]SoundEffect_HitPlayer_OnTick:; [$877b]
[877b]LDX a:SoundEffect_State_Counter
[877e]LDA SOUNDEFFECT_HITPLAYER_NOTES,X
[8781]CMP #$ff
[8783]BNE @_play
[8785]LDA #$10
[8787]STA a:SQ2_VOL
[878a]JMP Sound_ResetCurrentSound

[878d]@_play:; [$878d]
[878d]JSR SoundEffect_SetNote
[8790]LDA #$df
[8792]STA a:SQ2_VOL
[8795]LDA #$00
[8797]STA a:SQ2_SWEEP
[879a]LDA a:SoundEffect_Note_Low
[879d]STA a:SQ2_LO
[87a0]LDA a:SoundEffect_Note_High
[87a3]STA a:SQ2_HI
[87a6]INC a:SoundEffect_State_Counter
[87a9]RTS

;
; XREFS:
;     SoundEffect_HitPlayer_OnTick
;
[87aa]SOUNDEFFECT_HITPLAYER_NOTES:; [$87aa]
[87aa].byte $29; [0]:
[87ab].byte $24; [1]:
[87ac].byte $28; [2]:
[87ad].byte $22; [3]:
[87ae].byte $1f; [4]:
[87af].byte $29; [5]:
[87b0].byte $2b; [6]:
[87b1].byte $2c; [7]:
[87b2].byte $2d; [8]:
[87b3].byte $2a; [9]:
[87b4].byte $ff; [10]:

;============================================================================
; TODO: Document SoundEffect_Magic_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[87b5]SoundEffect_Magic_Setup:; [$87b5]
[87b5]LDA #$32
[87b7]STA a:SoundEffect_TicksRemaining_1_
[87ba]LDA #$00
[87bc]STA a:SoundEffect_State_Counter
[87bf]STA a:SoundEffect_State_0128

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_Magic_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[87c2]SoundEffect_Magic_OnTick:; [$87c2]
[87c2]LDX a:SoundEffect_State_0128
[87c5]LDA SOUNDEFFECT_MAGIC_SQ2_VOL,X
[87c8]BNE @_play
[87ca]LDA #$10
[87cc]STA a:SQ2_VOL
[87cf]JMP Sound_ResetCurrentSound

[87d2]@_play:; [$87d2]
[87d2]ORA #$50
[87d4]STA a:SQ2_VOL
[87d7]LDA #$00
[87d9]STA a:SQ2_SWEEP
[87dc]LDA a:SoundEffect_State_Counter
[87df]AND #$03
[87e1]TAX
[87e2]LDA SOUNDEFFECT_MAGIC_SQ2_LO,X
[87e5]STA a:SQ2_LO
[87e8]LDA #$00
[87ea]STA a:SQ2_HI
[87ed]INC a:SoundEffect_State_Counter
[87f0]LDA a:SoundEffect_State_Counter
[87f3]CMP #$08
[87f5]BNE @_return
[87f7]LDA #$00
[87f9]STA a:SoundEffect_State_Counter
[87fc]INC a:SoundEffect_State_0128

[87ff]@_return:; [$87ff]
[87ff]RTS

;
; XREFS:
;     SoundEffect_Magic_OnTick
;
[8800]SOUNDEFFECT_MAGIC_SQ2_VOL:; [$8800]
[8800].byte $0f,$0b,$07,$04,$01,$00; [$8800] byte

;
; XREFS:
;     SoundEffect_Magic_OnTick
;
[8806]SOUNDEFFECT_MAGIC_SQ2_LO:; [$8806]
[8806].byte $b0,$a0,$a8,$98; [$8806] byte

;============================================================================
; TODO: Document SoundEffect_OpenDoor_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[880a]SoundEffect_OpenDoor_Setup:; [$880a]
[880a]LDA #$3c
[880c]STA a:SoundEffect_TicksRemaining_1_
[880f]STA a:SoundEffect_TicksRemaining_3_
[8812]LDA #$37
[8814]STA a:SoundEffect_State_0129
[8817]LDA #$00
[8819]STA a:SoundEffect_State_Counter
[881c]STA a:SoundEffect_State_0128

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_OpenDoor_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[881f]SoundEffect_OpenDoor_OnTick:; [$881f]
[881f]DEC a:SoundEffect_State_0129
[8822]BNE @_play
[8824]LDA #$10
[8826]STA a:SQ2_VOL
[8829]STA a:NOISE_VOL
[882c]JMP Sound_ResetCurrentSound

[882f]@_play:; [$882f]
[882f]LDA a:SoundEffect_State_Counter
[8832]LSR A
[8833]LSR A
[8834]EOR #$ff
[8836]AND #$0f
[8838]ORA #$50
[883a]STA a:NOISE_VOL
[883d]STA a:SQ2_VOL
[8840]LDA #$00
[8842]STA a:SQ2_SWEEP
[8845]LDA a:SoundEffect_State_Counter
[8848]AND #$07
[884a]TAY
[884b]LDA #$60
[884d]SEC
[884e]SBC SOUNDEFFECT_OPEN_DOOR_SQ2_NOISE_LO,Y
[8851]STA a:SQ2_LO
[8854]AND #$0f
[8856]STA a:NOISE_LO
[8859]LDA #$00
[885b]STA a:SQ2_HI
[885e]STA a:NOISE_HI
[8861]INC a:SoundEffect_State_Counter
[8864]RTS

;
; XREFS:
;     SoundEffect_OpenDoor_OnTick
;
[8865]SOUNDEFFECT_OPEN_DOOR_SQ2_NOISE_LO:; [$8865]
[8865].byte $00,$03,$0a,$15,$25,$15,$0a,$03; [$8865] byte

;============================================================================
; TODO: Document SoundEffect_Maybe_Typing_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[886d]SoundEffect_Maybe_Typing_Setup:; [$886d]
[886d]LDA #$28
[886f]STA a:SoundEffect_TicksRemaining_1_
[8872]LDA #$00
[8874]STA a:SoundEffect_State_Counter

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_Maybe_Typing_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[8877]SoundEffect_Maybe_Typing_OnTick:; [$8877]
[8877]LDA a:SoundEffect_TicksRemaining_1_
[887a]AND #$01
[887c]BNE @_return
[887e]LDX a:SoundEffect_State_Counter
[8881]LDA SOUNDEFFECT_MAYBE_TYPING_NOTES,X
[8884]CMP #$ff
[8886]BNE @_play
[8888]LDA #$10
[888a]STA a:SQ2_VOL
[888d]JMP Sound_ResetCurrentSound

[8890]@_play:; [$8890]
[8890]JSR SoundEffect_SetNote
[8893]INC a:SoundEffect_State_Counter
[8896]LDA a:SoundEffect_State_Counter
[8899]EOR #$ff
[889b]AND #$0f
[889d]ORA #$d4
[889f]STA a:SQ2_VOL
[88a2]LDA #$91
[88a4]STA a:SQ2_SWEEP
[88a7]LDA a:SoundEffect_Note_Low
[88aa]STA a:SQ2_LO
[88ad]LDA a:SoundEffect_Note_High
[88b0]STA a:SQ2_HI

[88b3]@_return:; [$88b3]
[88b3]RTS

;
; XREFS:
;     SoundEffect_Maybe_Typing_OnTick
;
[88b4]SOUNDEFFECT_MAYBE_TYPING_NOTES:; [$88b4]
[88b4].byte $2b,$2d,$2f,$24,$38,$2a,$37,$39; [$88b4] byte
[88bc].byte $3b,$24,$38,$42,$2b,$2d,$2f,$18; [$88bc] byte
[88c4].byte $ff; [$88c4] byte

;============================================================================
; TODO: Document SoundEffect_ItemPickedUp_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[88c5]SoundEffect_ItemPickedUp_Setup:; [$88c5]
[88c5]LDA #$3c
[88c7]STA a:SoundEffect_TicksRemaining_1_
[88ca]LDA #$00
[88cc]STA a:SoundEffect_State_Counter
[88cf]STA a:SoundEffect_State_0128

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_ItemPickedUp_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;============================================================================
[88d2]SoundEffect_ItemPickedUp_OnTick:; [$88d2]
[88d2]LDX a:SoundEffect_State_Counter
[88d5]LDA SOUNDEFFECT_ITEM_PICKED_UP_NOTES,X
[88d8]CMP #$ff
[88da]BNE @_playNote
[88dc]INC a:SoundEffect_State_0128
[88df]LDA #$00
[88e1]STA a:SoundEffect_State_Counter
[88e4]RTS

[88e5]@_playNote:; [$88e5]
[88e5]JSR SoundEffect_SetNote
[88e8]LDX a:SoundEffect_State_0128
[88eb]LDA SOUNDEFFECT_ITEM_PICKED_UP_SQ2_VOLS,X
[88ee]BNE @_playSQ2
[88f0]LDA #$10
[88f2]STA a:SQ2_VOL
[88f5]JMP Sound_ResetCurrentSound

[88f8]@_playSQ2:; [$88f8]
[88f8]ORA #$90
[88fa]STA a:SQ2_VOL
[88fd]LDA #$00
[88ff]STA a:SQ2_SWEEP
[8902]LDA a:SoundEffect_Note_Low
[8905]STA a:SQ2_LO
[8908]LDA a:SoundEffect_Note_High
[890b]STA a:SQ2_HI
[890e]INC a:SoundEffect_State_Counter
[8911]RTS

;
; XREFS:
;     SoundEffect_ItemPickedUp_OnTick
;
[8912]SOUNDEFFECT_ITEM_PICKED_UP_SQ2_VOLS:; [$8912]
[8912].byte $0f,$0c,$09,$05,$02,$00; [$8912] byte

;
; XREFS:
;     SoundEffect_ItemPickedUp_OnTick
;
[8918]SOUNDEFFECT_ITEM_PICKED_UP_NOTES:; [$8918]
[8918].byte $3f,$43,$4a,$55,$5b,$60,$ff; [$8918] byte

;============================================================================
; TODO: Document SoundEffect_CoinTouchedCommon_Setup
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     TODO
;
; XREFS:
;     SoundEffect_CoinTouched_Setup
;============================================================================
[891f]SoundEffect_CoinTouchedCommon_Setup:; [$891f]
[891f]LDA #$1e
[8921]STA a:SoundEffect_TicksRemaining_1_
[8924]LDA #$50
[8926]STA a:SoundEffect_State_Counter
[8929]LDA #$00
[892b]STA a:SoundEffect_State_0128

;
; v-- Fall through --v
;

;============================================================================
; TODO: Document SoundEffect_CoinTouchedCommon_OnTick
;
; INPUTS:
;     None.
;
; OUTPUTS:
;     A
;
; XREFS:
;     SoundEffect_CoinTouched_OnTick
;============================================================================
[892e]SoundEffect_CoinTouchedCommon_OnTick:; [$892e]
[892e]LDX a:SoundEffect_State_0128
[8931]LDA SOUNDEFFECT_COIN_TOUCHED_SQ2_VOL,X
[8934]BNE @_play
[8936]LDA #$10
[8938]STA a:SQ2_VOL
[893b]JMP Sound_ResetCurrentSound

[893e]@_play:; [$893e]
[893e]ORA #$d0
[8940]STA a:SQ2_VOL
[8943]LDA #$00
[8945]STA a:SQ2_SWEEP
[8948]LDA a:SoundEffect_State_Counter
[894b]STA a:SQ2_LO
[894e]CLC
[894f]ADC #$04
[8951]STA a:SQ2_LO
[8954]LDA #$00
[8956]STA a:SQ2_HI
[8959]LDA a:SoundEffect_State_Counter
[895c]SEC
[895d]SBC #$10
[895f]STA a:SoundEffect_State_Counter
[8962]BNE @_return
[8964]INC a:SoundEffect_State_0128
[8967]LDA #$50
[8969]STA a:SoundEffect_State_Counter

[896c]@_return:; [$896c]
[896c]RTS

;
; XREFS:
;     SoundEffect_CoinTouchedCommon_OnTick
;
[896d]SOUNDEFFECT_COIN_TOUCHED_SQ2_VOL:; [$896d]
[896d].byte $0f,$0c,$09,$06,$03,$00; [$896d] byte