initial commit

sound.asm

@@ -0,0 +1,71 @@
+; -----------------------------------------------------------
+; sound.asm - single-voice SFX driver: each effect is a
+; waveform + start pitch + per-frame pitch slide + duration,
+; played on SID voice 1 (sustain 0, the decay shapes it)
+; -----------------------------------------------------------
+
+sfx_init:
+    lda #$0f             ; full volume, no filter
+    sta SID_VOL
+    lda #0
+    sta SID_V1CR
+    sta sfx_timer
+    rts
+
+; ---- start effect A ----
+sfx_play:
+    tax
+    lda #0
+    sta SID_V1CR         ; retrigger the envelope cleanly
+    lda sfxad,x
+    sta SID_V1AD
+    lda #0
+    sta SID_V1SR
+    sta SID_V1FL
+    lda sfxfreq,x
+    sta SID_V1FH
+    sta sfx_fh
+    lda #$08             ; 50% pulse width, if a pulse wave is used
+    sta SID_V1PH
+    lda #0
+    sta SID_V1PL
+    lda sfxctrl,x
+    sta SID_V1CR
+    sta sfx_ctrl
+    lda sfxslide,x
+    sta sfx_slide
+    lda sfxdur,x
+    sta sfx_timer
+    rts
+
+; ---- called once per frame by the main loop ----
+sfx_update:
+    lda sfx_timer
+    beq su_idle
+    dec sfx_timer
+    bne su_slide
+    lda sfx_ctrl         ; time is up: gate off
+    and #$fe
+    sta SID_V1CR
+    rts
+su_slide:
+    lda sfx_fh           ; bend the pitch by the slide value
+    clc
+    adc sfx_slide
+    sta sfx_fh
+    sta SID_V1FH
+su_idle:
+    rts
+
+; ---- effect tables: cursor, select, rotate, deny, win, lose ----
+sfxfreq:  !byte $50, $20, $12, $06, $20, $38
+sfxslide: !byte $00, $04, $fe, $00, $02, $ff
+sfxctrl:  !byte $11, $21, $81, $21, $11, $21
+sfxad:    !byte $06, $08, $08, $08, $0a, $0a
+sfxdur:   !byte $04, $0a, $08, $0c, $28, $30
+
+; ---- driver variables ----
+sfx_timer: !byte 0       ; frames left of the current effect
+sfx_fh:    !byte 0       ; frequency high byte shadow
+sfx_slide: !byte 0       ; signed per-frame pitch step
+sfx_ctrl:  !byte 0       ; control register shadow