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n65/examples/scales.asm

183 lines
3.5 KiB
NASM

.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
.inc <nes.sym>
.segment prog 0
;; SRAM Variables
.org $0000
.scope audio
.space timer 1
.space next_note 1
.space note_frequency 2
.
;; Interrupt vectors
.org $FFFA
.dw vblank
.dw main
.dw irq
.org $C000
.scope main
sei
cld
;; Setup the stack
ldx #$ff
txs
;; Disable rendering, reset APU
ldx #$00
stx nes.ppu.control
stx nes.ppu.mask
jsr zero_apu
.scope
wait_vblank:
bit nes.ppu.status
bpl wait_vblank
.
clear_ram:
lda #$00
sta $00, x
sta $100, x
sta $300, x
sta $400, x
sta $500, x
sta $600, x
sta $700, x
lda #$ff
sta $200, x
inx
bne clear_ram
.scope
wait_vblank:
bit nes.ppu.status
bpl wait_vblank
.
jsr initialize
forever:
jmp forever
rti
.
;; Zero the APU
.scope zero_apu
lda #$00
ldx #$00
loop:
sta $4000, x
inx
cpx $18
bne loop
rts
.
;; Initialize PPU and APU
.scope initialize
lda #%00000011
sta nes.apu.channel_enable
; Reenable interrupts, Turn Vblank back on
lda #%10000000
sta nes.ppu.control
; Initialize the audio structure
lda #$00
sta audio.timer zp
lda #$30
sta audio.next_note zp
cli
rts
.
;; Keep time via 60fps vblank
.scope vblank
; Update the audio timer so it resets every 64 frames
ldx audio.timer zp
inx
txa
and #%00000011
sta audio.timer zp
bne return
; Play the next note on reset
lda audio.next_note zp
cmp #$80
bmi continue
lda #$30
continue:
jsr play_note
sta audio.next_note zp
inc audio.next_note zp
return:
rti
.
;; Hi and lo byte tables for note frequencies
.scope midi_notes
.scope hi
.bytes $35, $32, $2f, $2c, $2a, $28, $25, $23, $21, $1f, $1d, $1c, $1a, $19, $17, $16
.bytes $15, $14, $12, $11, $10, $0f, $0e, $0e, $0d, $0c, $0b, $0b, $0a, $0a, $09, $08
.bytes $08, $07, $07, $07, $06, $06, $05, $05, $05, $05, $04, $04, $04, $03, $03, $03
.bytes $03, $03, $02, $02, $02, $02, $02, $02, $02, $01, $01, $01, $01, $01, $01, $01
.bytes $01, $01, $01, $01, $01, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00
.bytes $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00
.bytes $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00
.bytes $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00
.
.scope lo
.bytes $71, $71, $9c, $f0, $6a, $09, $ca, $ab, $aa, $c6, $fe, $4f, $b8, $38, $ce, $78
.bytes $35, $04, $e4, $d5, $d5, $e3, $fe, $27, $5b, $9c, $e6, $3b, $9a, $01, $72, $ea
.bytes $6a, $f1, $7f, $13, $ad, $4d, $f3, $9d, $4c, $00, $b8, $74, $34, $f8, $bf, $89
.bytes $56, $26, $f9, $ce, $a6, $80, $5c, $3a, $1a, $fb, $df, $c4, $ab, $93, $7c, $67
.bytes $52, $3f, $2d, $1c, $0c, $fd, $ef, $e1, $d5, $c9, $bd, $b3, $a9, $9f, $96, $8e
.bytes $86, $7e, $77, $70, $6a, $64, $5e, $59, $54, $4f, $4b, $46, $42, $3f, $3b, $38
.bytes $34, $31, $2f, $2c, $29, $27, $25, $23, $21, $1f, $1d, $1b, $1a, $18, $17, $15
.bytes $14, $13, $12, $11, $10, $0f, $0e, $0d, $0c, $0c, $0b, $0a, $0a, $09, $08, $08
.
.
;; Play midi note held in A
.scope play_note
pha
tax
lda #%10011111
sta nes.apu.pulse1.control
; Get the low byte of the timer
ldy midi_notes.lo, x
sty nes.apu.pulse1.ft
sty audio.note_frequency+1 zp
; Get the high 3 bits of the timer
ldy midi_notes.hi, x
tya
and #%00000111
ora #%11111000
sta nes.apu.pulse1.ct
sta audio.note_frequency zp
pla
rts
.
;; IRQ, we are not using
.scope irq
rti
.