; Digitized Sound
; by Clay Cowgill
; Date: 1/13/97
; System Executive Entry Points
dptoD0                  EQU     $f1aa
        ORG     $0000
; Magic Init Block
        FCB     $67,$20
        FCC     "GCE XXXX"
        FCB     $80
        FDB     music
        FDB     $f850
        FDB     $30b8
        FCC     "AUDIO"
        FCB     $80,$0
start:
        bra    snd_start                     ; branch always to init code
; *****************************
; This is the entry point for
; the main loop
; *****************************
snd_start:
        ldd     #$0000
        jsr     dptoD0
        direct d0
        lda     $00             ; data reg B from 6522
        anda    #$f8            ; save top 5 bits, mask off bottom 3
        ora     #$06            ; set S/H, SEL 0, SEL 1
        sta     $00             ; write back to reg B in 6522
        ldx     #snd_four
        ldy     #$0BD0          ; length of four
        jsr     >play_sound
        ldx     #snd_three
        ldy     #$1100          ; length of three
        jsr     >play_sound
        ldx     #snd_two
        ldy     #$0E10          ; length of two
        jsr     >play_sound
        ldx     #snd_one
        ldy     #$0ac0          ; length of one
        jsr     >play_sound
        ldx     #snd_ignite         ; address of sound
        ldy     #$16e0          ; length of ignition
        jsr     >play_sound
        jmp     >snd_start
; *****************************
;       Play a Sound
;       Length in Y
;       Start Address in X
; *****************************
play_sound:
next_byte:
        lda     ,-y
        lda     ,x+             ; get sound byte
        sta     $01             ; store in reg A in 6522
        cmpy    #$0000
        beq     >done_snd
        ldb     #$19            ; delay
delay:
        decb
        cmpb    #$00
        bne     delay
        jmp     >next_byte
done_snd:
        rts
music:
        FDB     $ed8f
        FDB     $feb6
        FCB     4,10
        FCB     0,$80
        ZMB     $1000-*         ; pad out to even boundard (just looks nicer)
; Sound samples here...
        ORG     $1000
snd_ignite:
        ORG     $26e0
snd_four:
        ORG     $32b0
snd_three:
        ORG     $43b0
snd_two:
        ORG     $51c0
snd_one: