;******************************************************************************* ; Init ; Initializes the sound driver and the hardware. ;------------------------------------------------------------------------------- ; continues in IdleLoop ;******************************************************************************* Init: ld sp, 800h ; Set up stack ld a, YMREG_TIMERB ; Set up timer B frequency ld (YmAddr1), a ; It defaults to around the NTSC ld a, $C8 ; refresh rate and is the speed at ld (YmData1), a ; which the tracks tick ld b, 9 ; 32X PSG fix (see 32X tech bulletin ld hl, BankPort ; #22), the 68000 bank must not point SetLastBankLoop: ; to any cartridge slot or 32X area ld (hl), l ; when accessing PSG. Since this djnz SetLastBankLoop ; driver never accesses the cartridge ; we'll just point it to work RAM ; permanently. ld a, YMREG_MODE ; Start up timer B ld (YmAddr1), a ld a, YMACK_TIMERB ld (YmData1), a ; fallthrough to IdleLoop... ;******************************************************************************* ; IdleLoop ; Main loop for the sound driver. It stays here until something needs attention. ;******************************************************************************* IdleLoop: ld a, (Command) ; Did the 68000 send us a command? or a call nz, ProcessCommand ld a, (YmAddr1) ; Did timer B tick yet? rra ; If not, keep waiting until it does rra ; Otherwise, it's time to update the jr nc, IdleLoop ; tracks ld a, YMREG_MODE ; Acknowledge timer B ld (YmAddr1), a ld a, YMACK_TIMERB ld (YmData1), a call RemapToBgmOrSfx ; Assign channels that may be shared by ; BGM and SFX to the correct tracks ; before proceeding ld ix, SfxTrackData_Psg4 ; Pointer to last track ld b, NUM_TRACKS ; Loop through all tracks (in reverse) UpdateTrackCount: equ $-1 ; <-- How many tracks to process? UpdateTrackLoop: call UpdateTrack ; Update this track ld de, -SIZEOF_TRACK ; Pointer to previous track add ix, de djnz UpdateTrackLoop ; Keep looping ld iy, FmChanData ; Pointer to 1st FM channel ld b, NUM_FMCHAN ; Loop through all FM channels UpdateFmChanLoop: push bc ; Save loop pointer call UpdateFmChan ; Update FM channel ld de, SIZEOF_FMCHAN ; Pointer to next channel add iy, de pop bc ; Restore loop pointer djnz UpdateFmChanLoop ; Keep looping ld iy, PsgChanData ; Pointer to 1st PSG channel ld b, NUM_PSGCHAN-1 ; Loop through all PSG channels except UpdatePsgChanLoop: ; the noise one push bc ; Save loop pointer call UpdatePsgChan ; Update PSG channel call UpdatePsgFreq ld de, SIZEOF_PSGCHAN ; Pointer to next channel add iy, de pop bc ; Restore loop pointer djnz UpdatePsgChanLoop ; Keep looping call UpdatePsgChan ; Update PSG noise channel (which call UpdatePsgNoise ; doesn't use frequency but treats ; the pitch as a noise value as-is) ld bc, (NUM_BGMTRACKS<<8)|$01 ; Check if BGM is playing by ld hl, BgmTrackData+TRACK_ADDR_HI ; comparing the address of every ld de, SIZEOF_TRACK ; track with the driver's address BgmCheckLoop: ; range (if it's inside the driver ld a, (hl) ; then it's within the stop code) cp $800>>8 ; jr nc, BgmIsPlaying ; TO-DO: find a way to do this add hl, de ; that takes up less space. djnz BgmCheckLoop dec c BgmIsPlaying: ld a, c ; Store result in the status flags ld (Status), a ; $00 = BGM not playing ; $01 = BGM playing jr IdleLoop ; Back to idling ;******************************************************************************* ; ProcessCommand ; Executes a command sent by the 68000. ;------------------------------------------------------------------------------- ; input a ..... command sent ;------------------------------------------------------------------------------- ; modifies .... all ;******************************************************************************* ProcessCommand: cp FIRST_CMD ; Special command? jr nc, ProcessCommandEx dec a ; Play BGM? ld hl, NumBgm cp (hl) jp c, PlayBgm sub (hl) ; Play SFX? inc hl cp (hl) jp c, PlaySfx EndOfCommand: ld hl, (Command2) ; Pop off the 1st command from the ld (Command), hl ; queue, and make room for a new xor a ; 3rd command ld (Command3), a ret ; Back to the idle loop (if there was ; another command pending, it'll be ; processed immediately) ProcessCommandEx: sub $FD ; Use the jump table below to process add a, a ; the command ld ($+4), a jr $ jr Unpause ; $FD - Unpause music jr Pause ; $FE - Pause music jr StopAllSoundCmd ; $FF - Stop music ;******************************************************************************* ; StopAllSoundCmd ; Processes a 68000 command to stop all sound. ;------------------------------------------------------------------------------- ; continues in EndOfCommand, then returns to idle loop ;******************************************************************************* StopAllSoundCmd: call StopAllSound ; This is a wrapper for that subroutine jr EndOfCommand ; End of command, do clean-up ;------------------------------------------------------------------------------- StopAllSound: ld hl, TrackData ; Pointer to 1st track state ld b, NUM_TRACKS ; Loop through all tracks StopAllTracksLoop: push bc ; Save loop counter ld de, DefaultEndSfx ; Track that stops all sound call InitTrack ; Initialize track with that pop bc ; Restore loop counter djnz StopAllTracksLoop ; Go for next track ret ; End of subroutine ;******************************************************************************* ; Pause ; Processes a 68000 command to pause playback. ;------------------------------------------------------------------------------- ; continues in EndOfCommand, then returns to idle loop ;******************************************************************************* Pause: ld hl, SfxTrackData ; Pointer to 1st SFX track ld b, NUM_SFXTRACKS ; Number of SFX tracks call StopAllTracksLoop ; Stop all the SFX tracks ld a, NUM_SFXTRACKS ; Change the update loop to only process ld (UpdateTrackCount), a ; the SFX tracks (we need to keep this ; in case a SFX is played *after* we ; pause music) call MuteFm ; Mute all the channels call MutePsg jr EndOfCommand ; End of command, do clean-up ;******************************************************************************* ; Unpause ; Processes a 68000 command to unpause playback. ;------------------------------------------------------------------------------- ; continues in EndOfCommand, then returns to idle loop ;******************************************************************************* Unpause: ld hl, TrackData+TRACK_FLAGS ; Mark all tracks as needing a full ld de, SIZEOF_TRACK ; refresh ld b, NUM_TRACKS UnpauseTrackLoop: ld (hl), FLAGMASK_REFRESH add hl, de djnz UnpauseTrackLoop ld a, NUM_TRACKS ; Change the update loop to process all ld (UpdateTrackCount), a ; the tracks again jr EndOfCommand ; End of command, do clean-up ;******************************************************************************* ; PlayBgm ; Processes a 68000 command to play a BGM. ;------------------------------------------------------------------------------- ; input a .... BGM ID, counting from 0 ;------------------------------------------------------------------------------- ; continues in Unpause, then EndOfCommand, then returns to idle loop ;******************************************************************************* PlayBgm: push af ; First stop anything that was playing call StopAllSound pop af ld hl, (BgmList) ; Get pointer to the BGM data call GetWordFromList DoPlayBgm: exx ; Set up FM tracks, if any ld hl, BgmTrackData_Fm1 call InitBgmDoLoop exx ; Set up PSG tracks, if any ld hl, BgmTrackData_Psg1 call InitBgmDoLoop jr Unpause ; Just in case, unpause the driver ;------------------------------------------------------------------------------- InitBgmDoLoop: exx ; b = loop counter ; de = scratch ; hl = pointer to BGM header data ; a' = scratch (modified by InitTrack) ; bc' = scratch (modified by InitTrack) ; de' = scratch (argument to InitTrack) ; hl' = pointer to track state ld b, (hl) ; Get how many channels inc hl inc b ; Skip to the end of the loop (this jr InitBgmLoopEnd ; will handle the 0 channel case) InitBgmLoop: ld e, (hl) ; Get pointer to track data inc hl ld d, (hl) inc hl push de ; We need it in DE' since we don't want exx ; to stomp on the data pointer or the pop de ; loop counter call InitTrack ; Initialize track exx ; Back to main registers InitBgmLoopEnd: djnz InitBgmLoop ; Set up next track ret ; Back to subroutine ;******************************************************************************* ; PlaySfx ; Processes a 68000 command to play a SFX. ;------------------------------------------------------------------------------- ; input a .... SFX ID, counting from 0 ;------------------------------------------------------------------------------- ; continues in EndOfCommand, then returns to idle loop ;******************************************************************************* PlaySfx: ; a = SFX priority ; b = loop counter ; c = SFX channel flags ; hl = pointer to SFX header ; hl' = pointer to SFX track ; iy = pointer to SFX priorities ; de, a', bc', de', ix = scratch ld iy, SfxPriority-1 ; List of SFX channel priorities ; The -1 is needed because we always ; increment before using the pointer ld hl, SfxTrackData ; Pointer to SFX tracks exx ; Keep it in the alternate register set ; (since InitTrack stomps over most ; registers) ld hl, (SfxList) ; Get pointer to the SFX data call GetWordFromList ld c, (hl) ; Get channel flags inc hl ; bit 0 = use FM channel 5 ; bit 1 = use FM channel 6 ; bit 2 = use PSG channel 3 ; bit 3 = use PSG channel 4 ld a, c ; Get SFX priority or $0F ; Priority is OR'd with $0F so we ; can distinguish priority 0 ($0F) ; from unused channel ($00) while ; still filtering out the flags ld b, 4 ; Loop through all possible channels InitSfxLoop: inc iy ; Point to this channel's priority rr c ; Check if next channel is used jr nc, SkipSfxChan ; No? Skip all this then ld e, (hl) ; Read pointer to track data for this inc hl ; channel ld d, (hl) inc hl cp (iy+0) ; Is this channel already taken by a jr c, SkipSfxChan ; higher priority SFX? If so, also ; skip over it ld (iy+0), a ; Claim the channel by writing the new ; priority push de ; Move pointer to the alternate register exx ; set where we can call InitTrack pop de ex af, af' ; Save priority call InitTrack ; Initialize the track ex af, af' ; Restore priority push hl ; Replace default loop with one that pop ix ; will restore the channel to BGM ld (ix+TRACK_LOOP_LO-SIZEOF_TRACK), DefaultEndSfx&$FF ld (ix+TRACK_LOOP_HI-SIZEOF_TRACK), DefaultEndSfx>>8 jr InitSfxLoopEnd ; Skip to end of loop SkipSfxChan: exx ; Advance track pointer since we didn't ld de, SIZEOF_TRACK ; call InitTrack to do it for us add hl, de InitSfxLoopEnd: exx ; Back to main register set djnz InitSfxLoop ; Go check next channel jp EndOfCommand ; End of command, do clean-up ;******************************************************************************* ; RemapToBgmOrSfx ; Checks which channels are under SFX control or not, and assigns their tracks ; accordingly. ;------------------------------------------------------------------------------- ; modifies .... all ;******************************************************************************* RemapToBgmOrSfx: ld iy, RemapTable+1 ; Table with all the assignment info. ; The +1 is because when we index ; whether it's a BGM or SFX track ; we use offsets 0 and -1, so we need ; to compensate for it. ld hl, SfxPriority ; List of SFX channel priorities ld b, 4 ; Loop through all SFX channels RemapLoop: xor a ; Check if this channel's priority is 0 sub (hl) ; (priority is 0 when a channel is not sbc a, a ; under SFX control) ; A = 0 when under BGM control ; A = -1 when under SFX control ld (RemapWhich), a ; Get which track to assign to this ld a, (iy+0) ; channel based on the above check RemapWhich: equ $-1 ld e, (iy+1) ; Get pointer to variable keeping the ld d, (iy+2) ; offset to the track ex de, hl ; Check if the channel is already cp (hl) ; assigned to this track or not (if ex de, hl ; already assigned then do nothing) jr z, NoRemapNeeded ld (de), a ; Store new assignment ld e, a ; Set the track's flags to refresh the call GetTrackStateAddr ; whole channel ld (ix+TRACK_FLAGS), FLAGMASK_REFRESH NoRemapNeeded: ld de, 4 ; Advance table pointer add iy, de inc hl ; Advance priority pointer djnz RemapLoop ; Go check next channel ret ; End of subroutine ;------------------------------------------------------------------------------- RemapTable: db SfxTrackData_Fm5-TrackData db BgmTrackData_Fm5-TrackData dw FmChanData_Fm5+FMCHAN_TRACK db SfxTrackData_Fm6-TrackData db BgmTrackData_Fm6-TrackData dw FmChanData_Fm6+FMCHAN_TRACK db SfxTrackData_Psg3-TrackData db BgmTrackData_Psg3-TrackData dw PsgChanData_Psg3+PSGCHAN_TRACK db SfxTrackData_Psg4-TrackData db BgmTrackData_Psg4-TrackData dw PsgChanData_Psg4+PSGCHAN_TRACK