Simple SNES SPC700 Code

arch spc700-raw
ORG $000500

Main:
	mov a, #$0C
	mov $F2, a
	mov a, #$7F
	mov $F3, a	;Set Left Main Volume

	mov a, #$1C
	mov $F2, a
	mov a, #$7F
	mov $F3, a	;Set Right Main Volume

	mov a, #$6C
	mov $F2, a
	mov a, #$3E
	mov $F3, a ;Unmute, enable 16KHz noise

	mov a, #$3D
	mov $F2, a
	mov a, #$01
	mov $F3, a ;Enable noise on channel 0

	mov a, #$00
	mov $F2, a
	mov a, #$7F
	mov $F3, a ;Set the left volume of channel 0

	mov a, #$01
	mov $F2, a
	mov a, #$7F
	mov $F3, a ;Set the right volume of channel 0

	mov a, #$07
	mov $F2, a
	mov a, #$1F
	mov $F3, a	;Ignore envelope settings

	mov a, #$4C
	mov $F2, a
	mov a, #$01
	mov $F3, a ;Start voice 0

	mov a, #$00
	mov $0000, a

Loop:
	mov a, $00
	cmp a, $F4		;Check if the SNES sent a new byte to PORT0
	beq NoNewData

	nop
	nop
	mov $00, $F4

	mov a, $F5
	cmp a, #$00
	beq TurnNoiseOff

TurnNoiseOn:
	mov a, #$00
	mov $F2, a
	mov a, #$7F
	mov $F3, a ;Set the left volume of channel 0

	mov a, #$01
	mov $F2, a
	mov a, #$7F
	mov $F3, a ;Set the right volume of channel 0
	jmp Done
TurnNoiseOff:
	mov a, #$00
	mov $F2, a
	mov a, #$00
	mov $F3, a ;Set the left volume of channel 0

	mov a, #$01
	mov $F2, a
	mov a, #$00
	mov $F3, a ;Set the right volume of channel 0
Done:

	mov $F4, $00	;Echo the value back

NoNewData:

	jmp Loop   ;An infinite loop, so the SPC700 doesn't crash