Adding an example of making noise

noise.asm

@@ -0,0 +1,99 @@
+;------------------------------------------------------------------------------
+;  This is a direct port of Michael Martin's tutorial project for NES101
+;  With some modifications to the tile map, and extra comments, and ported to
+;  suit my assembler. - Saf
+;  See:
+;  http://hackipedia.org/Platform/Nintendo/NES/tutorial,%20NES%20programming%20101/NES101.html
+;
+;;;;
+;  Create an iNES header
+.ines {"prog": 1, "char": 0, "mapper": 0, "mirror": 0}
+
+;;;;
+;  Here is a good spot to associate zero page memory addresses
+;  with quick access variables in the program.
+
+.org $0200
+sprite:
+
+
+;;;;
+;  Setup the interrupt vectors
+.org $FFFA
+.dw vblank
+.dw main
+.dw irq
+
+
+.org $C000
+;;;;
+;  Here is our code entry point, which we'll call main.
+main:
+  ;  Disable interrupts and decimal flag
+  sei
+	cld
+
+  ;  Wait for 2 vblanks
+  wait_vb1:
+    lda $2002
+    bpl wait_vb1
+  wait_vb2:
+    lda $2002
+    bpl wait_vb2
+
+  ;  Now we want to initialize the hardware to a known state
+  lda #$00
+  ldx #$00
+  clear_segments:
+    sta $00, X
+    sta $0100, X
+    sta $0200, X
+    sta $0300, X
+    sta $0400, X
+    sta $0500, X
+    sta $0600, X
+    sta $0700, X
+    inx
+    bne clear_segments
+
+  ;  Reset the stack pointer
+  ldx #$FF
+  txs
+
+	; Disable all graphics.
+  lda #$00
+  sta $2000
+  sta $2001
+
+  ;  Init APU
+  ldx #$0F
+  stx $4015
+
+  ;  Turn on noise tone
+  ldx #$85
+  stx $400E
+
+  ;  Set volume to max
+  ldx #$3F
+  stx $400C
+
+  ; Load Length counter
+  ldx #$01
+  stx $400F
+
+  ;  Resume interrupts and loop here forever
+	cli
+  forever:
+    jmp forever
+
+
+;;;;
+;  Update everything on every vblank
+vblank: 
+  rti
+
+
+;;;;
+;  Don't do anything on IRQ
+irq:    
+  rti