credits music

credits.asm

@@ -59,10 +59,16 @@ ci_col:
     lda #$ff
     sta SPR_EN
 
+    jsr music_init       ; start the credits music
+    lda #0
+    sta sfx_timer        ; prevent SFX driver from touching voice 1
+
     +setupd credits_update
     rts
 
 credits_update:
+    jsr music_play       ; advance the music one tick
+
     ; ---- all the heavy drawing runs first, while the beam
     ; is still far above the scroller row ----
 
@@ -265,6 +271,8 @@ cu_input:
     beq cu_stay
     lda #$c8             ; leave with the scroll register clean
     sta XCTRL
+    jsr music_stop       ; silence all SID voices
+    jsr sfx_init         ; restore SFX driver volume
     jmp menu_init        ; back to the menu
 cu_stay:
 

defs.asm

@@ -26,7 +26,8 @@ SPR_XEX  = $d01d         ; horizontal expand
 SPR_COL  = $d027         ; sprite 0 color, +1 = sprite 1, ...
 
 
-; ---- SID registers (voice 1 used for SFX) ----
+; ---- SID registers ----
+SID_BASE = $d400
 SID_V1FL = $d400         ; voice 1 frequency low
 SID_V1FH = $d401         ; voice 1 frequency high
 SID_V1PL = $d402         ; voice 1 pulse width low
@@ -34,6 +35,20 @@ SID_V1PH = $d403         ; voice 1 pulse width high
 SID_V1CR = $d404         ; voice 1 control (waveform + gate)
 SID_V1AD = $d405         ; voice 1 attack/decay
 SID_V1SR = $d406         ; voice 1 sustain/release
+SID_V2FL = $d407         ; voice 2 frequency low
+SID_V2FH = $d408         ; voice 2 frequency high
+SID_V2PL = $d409         ; voice 2 pulse width low
+SID_V2PH = $d40a         ; voice 2 pulse width high
+SID_V2CR = $d40b         ; voice 2 control
+SID_V2AD = $d40c         ; voice 2 attack/decay
+SID_V2SR = $d40d         ; voice 2 sustain/release
+SID_V3FL = $d40e         ; voice 3 frequency low
+SID_V3FH = $d40f         ; voice 3 frequency high
+SID_V3PL = $d410         ; voice 3 pulse width low
+SID_V3PH = $d411         ; voice 3 pulse width high
+SID_V3CR = $d412         ; voice 3 control
+SID_V3AD = $d413         ; voice 3 attack/decay
+SID_V3SR = $d414         ; voice 3 sustain/release
 SID_VOL  = $d418         ; filter mode + master volume
 
 ; ---- SFX IDs ----

main.asm

@@ -124,4 +124,5 @@ wf_hit:
 !src "over.asm"
 !src "common.asm"
 !src "sound.asm"
+!src "music.asm"
 !src "tables.asm"

music.asm

@@ -0,0 +1,223 @@
+; -----------------------------------------------------------
+; music.asm - SID music driver (adapted from the c64-demo)
+;   voice 1: bass (pulse), voice 2: drums (noise),
+;   voice 3: echo lead (triangle)
+;   music_init:  clear SID, set instruments, restart song
+;   music_play:  call once per frame
+;   music_stop:  silence everything
+; -----------------------------------------------------------
+
+; ---- waveform control values ----
+BASS_ON   = $41                 ; pulse + gate
+BASS_OFF  = $40
+DRUM_ON   = $81                 ; noise + gate
+DRUM_OFF  = $80
+LEAD_ON   = $11                 ; triangle + gate
+LEAD_OFF  = $10
+
+SONG_LEN  = 128
+
+; ---- initialize SID and restart the song ----
+music_init:
+    ldx #24
+    lda #0
+mi_clr:
+    sta SID_BASE,x
+    dex
+    bpl mi_clr
+
+    lda #$00                    ; bass: instant attack, full sustain
+    sta SID_V1AD
+    lda #$f3
+    sta SID_V1SR
+    lda #$08                    ; bass pulse width 50%
+    sta SID_V1PH
+    lda #$00
+    sta SID_V1PL
+    lda #$04                    ; drums: instant attack, ~110 ms decay
+    sta SID_V2AD
+    lda #$00
+    sta SID_V2SR
+    lda #$06                    ; lead: pluck, ~200 ms decay
+    sta SID_V3AD
+    lda #$00
+    sta SID_V3SR
+
+    lda #$0f                    ; master volume = 15
+    sta SID_VOL
+
+    lda #0
+    sta mus_row
+    sta mus_spd_ix
+    sta mus_bcut
+    lda #1
+    sta mus_tick
+    rts
+
+; ---- play one tick: called once per frame ----
+music_play:
+    pha
+    txa
+    pha
+    tya
+    pha
+    jsr mp_core
+    pla
+    tay
+    pla
+    tax
+    pla
+    rts
+
+mp_core:
+    lda mus_bcut
+    beq mp_tick
+    dec mus_bcut
+    bne mp_tick
+    lda #BASS_OFF
+    sta SID_V1CR
+mp_tick:
+    dec mus_tick
+    beq mp_row
+    rts
+
+mp_row:
+    ldx mus_spd_ix
+    lda mus_spd_tbl,x
+    sta mus_tick
+    inx
+    cpx #6
+    bne mp_spd_ok
+    ldx #0
+mp_spd_ok:
+    stx mus_spd_ix
+
+    ldx mus_row
+
+    ; ---- voice 1: bass ----
+    lda bass_pat,x
+    beq mp_drums
+    cmp #1
+    bne mp_bass_note
+    lda #BASS_OFF
+    sta SID_V1CR
+    jmp mp_drums
+mp_bass_note:
+    and #$7f
+    tay
+    lda bass_flo,y
+    sta SID_V1FL
+    lda bass_fhi,y
+    sta SID_V1FH
+    lda #BASS_OFF
+    sta SID_V1CR
+    lda #BASS_ON
+    sta SID_V1CR
+
+    ; ---- voice 2: drums ----
+mp_drums:
+    lda drum_pat,x
+    beq mp_lead
+    cmp #1
+    bne mp_drum_note
+    lda #DRUM_OFF
+    sta SID_V2CR
+    jmp mp_lead
+mp_drum_note:
+    and #$7f
+    tay
+    lda drum_flo,y
+    sta SID_V2FL
+    lda drum_fhi,y
+    sta SID_V2FH
+    lda #DRUM_OFF
+    sta SID_V2CR
+    lda #DRUM_ON
+    sta SID_V2CR
+
+    ; ---- voice 3: lead echo ----
+mp_lead:
+    lda lead_pat,x
+    beq mp_next
+    and #$7f
+    tay
+    lda lead_flo,y
+    sta SID_V3FL
+    lda lead_fhi,y
+    sta SID_V3FH
+    lda #LEAD_OFF
+    sta SID_V3CR
+    lda #LEAD_ON
+    sta SID_V3CR
+
+mp_next:
+    inx
+    cpx #SONG_LEN
+    bne mp_store
+    ldx #0
+    stx mus_spd_ix
+mp_store:
+    stx mus_row
+    lda bass_pat,x
+    bpl mp_nocut
+    lda mus_tick
+    sec
+    sbc #2
+    sta mus_bcut
+mp_nocut:
+    rts
+
+; ---- stop: silence SID, restore for SFX use ----
+music_stop:
+    ldx #24
+    lda #0
+ms_clr:
+    sta SID_BASE,x
+    dex
+    bpl ms_clr
+    rts
+
+; ---- state ----
+mus_row:       !byte 0
+mus_tick:      !byte 1
+mus_spd_ix:    !byte 0
+mus_bcut:      !byte 0
+
+mus_spd_tbl:   !byte 4,4,4,4,4,4
+
+; ---- note tables (PAL SID) ----
+bass_flo: !byte $5a,$e0,$2d,$cf
+bass_fhi: !byte $04,$03,$05,$05
+drum_flo: !byte $9c,$ff
+drum_fhi: !byte $45,$ff
+lead_flo: !byte $ce,$02,$64,$76,$9c,$04,$c8,$eb
+lead_fhi: !byte $22,$1f,$29,$2e,$45,$3e,$52,$5c
+
+; ---- pattern data ----
+bass_pat:
+    !byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
+    !byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
+    !byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$01,$00,$80,$00,$01,$00,$00,$00,$81,$00,$80,$00
+    !byte $01,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $82,$00,$82,$00,$01,$00,$82,$00,$01,$00,$00,$00,$82,$00,$83,$00
+    !byte $01,$00,$83,$00,$01,$00,$83,$00,$83,$00,$01,$00,$83,$00,$01,$00
+drum_pat:
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$81,$00,$00,$00,$00,$00,$00,$00
+    !byte $80,$00,$00,$00,$00,$00,$80,$00,$81,$00,$00,$00,$00,$00,$00,$00
+lead_pat:
+    !byte $00,$00,$80,$00,$00,$00,$00,$00,$84,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$84,$00,$00,$00,$00,$00,$80,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$84,$00,$00,$00,$00,$00,$80,$00,$00,$00,$00,$00,$81,$00
+    !byte $80,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00,$00
+    !byte $00,$00,$82,$00,$86,$00,$00,$00,$82,$00,$00,$00,$00,$00,$86,$00
+    !byte $83,$00,$00,$00,$87,$00,$00,$00,$83,$00,$87,$00,$00,$00,$83,$00