SMB NSF

	.inesprg 2
	.ineschr 0
	.inesmir 0
	.inesmap 0
	.code

	.bank 0
	.org $8000
Reset_Routine:
   cld         ; clear decimal flag
   sei         ; disable interrupts
   lda #%00000000      ; disable vblank interrupts by clearing
   sta $2000      ; the most significant bit of $2000

; *** WAIT 2 VBLANKS ***
WaitV1:
   lda $2002      ; give the PPU a little time to initialize
   bpl WaitV1      ; by waiting for a vblank
WaitV2:
   lda $2002      ; wait for a second vblank to be safe
   bpl WaitV2      ; and now the PPU should be initialized

; *** CLEAR SOUND REGISTERS ***
   lda #$00      ; clear all the sound registers by setting
   ldx #$00      ; everything to 0 in the Clear_Sound loop
Clear_Sound:
   sta $4000,x      ; store accumulator at $4000 offset by x
   inx         ; increment x
   cpx #$0F      ; compare x to $0F
   bne Clear_Sound      ; branch back to Clear_Sound if x != $0F

   lda #$10      ; load accumulator with $10
   sta $4010      ; store accumulator in $4010
   lda #$00      ; load accumulator with 0
   sta $4011      ; clear these 3 registers that are
   sta $4012      ; associated with the delta modulation
   sta $4013      ; channel of the NES

; *** ENABLE SOUND CHANNELS ***
   lda #%00001111      ; enable all sound channels except
   sta $4015      ; the delta modulation channel

; *** RESET FRAME COUNTER AND CLOCK DIVIDER ***
   lda #$C0      ; synchronize the sound playback routine
   sta $4017      ; to the internal timing of the NES

; *** SET SONG # & PAL/NTSC SETTING ***
   lda #$00      ; replace dashes with song number
   ldx #$00      ; replace with $00 for NTSC or $01 for PAL
   jsr $BE34      ; replace dashes with init address

; *** ENABLE VBLANK NMI ***
   lda #%10000000      ; enable vblank interrupts by setting the
   sta $2000      ; most significant bit of $2000

loop:
   jmp loop

NMI_Routine:
   lda $2002      ; read $2002 to reset the vblank flag
   lda #%00000000      ; clear the first PPU control register
   sta $2000      ; writing 0 to it
   lda #%10000000      ; reenable vblank interrupts by setting
   sta $2000      ; the most significant bit of $2000
   jsr $F2D0      ; replace dashes with play address
   rti         ; return from interrupt routine

IRQ_Routine:
   rti         ; return from interrupt routine


	.bank 1
	.org $BDC4      ; replace dashes with load address MINUS $80
	.incbin "SMB.nsf"   ; include NSF tune

	.bank 3
	.org $FFFA			;ditto
   .dw   NMI_Routine   ; setup the NMI vector at $FFFA
   .dw   Reset_Routine   ; setup the Reset vector at $FFFC
   .dw   IRQ_Routine   ; setup the IRQ vector at $FFFE