; music and SFX from GoatTracker 2 sample files
; http://sourceforge.net/projects/goattracker2

.segment "SIDFILE"

.incbin "sidmusic1.bin"

.segment "LOWCODE"

.global _sid_init, _sid_update, _sid_sfx
.global _sid_start

_sid_init:
        jmp $1000

_sid_update:
	jmp $1003

_sid_sfx:
	tax
        lda sfxtbllo,x     ;Address in A,Y
        ldy sfxtblhi,x
        ldx #$0e           ;Channel index in X
        jmp $1006          ;(0, 7 or 14)

SID_IRQ:
	jsr $1003
	ASL $D019            ; acknowledge the interrupt by clearing the VIC's interrupt flag
	JMP $EA31            ; jump into KERNAL's standard interrupt service routine to handle keyboard scan, cursor display etc.

_sid_start:
        SEI                  ; set interrupt bit, make the CPU ignore interrupt requests
        LDA #%01111111       ; switch off interrupt signals from CIA-1
        STA $DC0D

        AND $D011            ; clear most significant bit of VIC's raster register
        STA $D011

        LDA $DC0D            ; acknowledge pending interrupts from CIA-1
        LDA $DD0D            ; acknowledge pending interrupts from CIA-2

        LDA #210             ; set rasterline where interrupt shall occur
        STA $D012

        LDA #<SID_IRQ            ; set interrupt vectors, pointing to interrupt service routine below
        STA $0314
        LDA #>SID_IRQ
        STA $0315

        LDA #%00000001       ; enable raster interrupt signals from VIC
        STA $D01A

        CLI                  ; clear interrupt flag, allowing the CPU to respond to interrupt requests
        RTS


sfxtbllo:       .byte <arpeggio2
                .byte <arpeggio1
                .byte <gunshot
                .byte <explosion

sfxtblhi:       .byte >arpeggio2
                .byte >arpeggio1
                .byte >gunshot
                .byte >explosion

arpeggio2:
        .byte $00,$89,$04,$A2,$41,$A2,$A2,$A6,$A6,$A6,$40,$A9,$A9,$A9,$A2,$A2
        .byte $A2,$A6,$A6,$A6,$A9,$A9,$A9,$A2,$A2,$A2,$A6,$A6,$A6,$A9,$A9,$A9
        .byte $A2,$A2,$A2,$A6,$A6,$A6,$A9,$A9,$A9,$00
        
arpeggio1:
        .byte $0A,$00,$02,$A0,$41,$A0,$A0,$A4,$A4,$A4,$A7,$A7,$A7,$A0,$A0,$A0
        .byte $A4,$A4,$A4,$A7,$A7,$A7,$A0,$A0,$A0,$A4,$A4,$A4,$A7,$A7,$A7,$A0
        .byte $A0,$A0,$A4,$A4,$A4,$A7,$A7,$A7,$00
        
gunshot:
        .byte $00,$F9,$08,$C4,$81,$A8,$41,$C0,$81,$BE,$BC,$80,$BA,$B8,$B6,$B4
        .byte $B2,$B0,$AE,$AC,$AA,$A8,$A6,$A4,$A2,$A0,$9E,$9C,$9A,$98,$96,$94
        .byte $92,$90,$00

explosion:
        .byte $00,$FA,$08,$B8,$81,$A4,$41,$A0,$B4,$81,$98,$92,$9C,$90,$95,$9E
        .byte $92,$80,$94,$8F,$8E,$8D,$8C,$8B,$8A,$89,$88,$87,$86,$84,$00