Last modified on 25 February 2013, at 17:57

Super NES Programming/Initialization Tutorial/Snes Init

 .MACRO Snes_Init
 	sei 	 	; Disabled interrupts
 	clc 	 	; clear carry to switch to native mode
 	xce 	 	; Xchange carry & emulation bit. native mode
 	rep 	#$18 	; Binary mode (decimal mode off), X/Y 16 bit
         ldx 	#$1FFF  ; set stack to $1FFF
         txs
 
         jsr Init
 .ENDM
 
 .bank 0
 .section "Snes_Init" SEMIFREE
 Init:
 	sep 	#$30    ; X,Y,A are 8 bit numbers
 	lda 	#$8F    ; screen off, full brightness
 	sta 	$2100   ; brightness + screen enable register 
 	stz 	$2101   ; Sprite register (size + address in VRAM) 
 	stz 	$2102   ; Sprite registers (address of sprite memory [OAM])
 	stz 	$2103   ;    ""                       ""
 	stz 	$2105   ; Mode 0, = Graphic mode register
 	stz 	$2106   ; noplanes, no mosaic, = Mosaic register
 	stz 	$2107   ; Plane 0 map VRAM location
 	stz 	$2108   ; Plane 1 map VRAM location
 	stz 	$2109   ; Plane 2 map VRAM location
 	stz 	$210A   ; Plane 3 map VRAM location
 	stz 	$210B   ; Plane 0+1 Tile data location
 	stz 	$210C   ; Plane 2+3 Tile data location
 	stz 	$210D   ; Plane 0 scroll x (first 8 bits)
 	stz 	$210D   ; Plane 0 scroll x (last 3 bits) #$0 - #$07ff
 	lda 	#$FF    ; The top pixel drawn on the screen isn't the top one in the tilemap, it's the one above that.
 	sta 	$210E   ; Plane 0 scroll y (first 8 bits)
 	sta 	$2110   ; Plane 1 scroll y (first 8 bits)
 	sta 	$2112   ; Plane 2 scroll y (first 8 bits)
 	sta 	$2114   ; Plane 3 scroll y (first 8 bits)
 	lda 	#$07    ; Since this could get quite annoying, it's better to edit the scrolling registers to fix this.
 	sta 	$210E   ; Plane 0 scroll y (last 3 bits) #$0 - #$07ff
 	sta 	$2110   ; Plane 1 scroll y (last 3 bits) #$0 - #$07ff
 	sta 	$2112   ; Plane 2 scroll y (last 3 bits) #$0 - #$07ff
 	sta 	$2114   ; Plane 3 scroll y (last 3 bits) #$0 - #$07ff
 	stz 	$210F   ; Plane 1 scroll x (first 8 bits)
 	stz 	$210F   ; Plane 1 scroll x (last 3 bits) #$0 - #$07ff
 	stz 	$2111   ; Plane 2 scroll x (first 8 bits)
 	stz 	$2111   ; Plane 2 scroll x (last 3 bits) #$0 - #$07ff
 	stz 	$2113   ; Plane 3 scroll x (first 8 bits)
 	stz 	$2113   ; Plane 3 scroll x (last 3 bits) #$0 - #$07ff
 	lda 	#$80    ; increase VRAM address after writing to $2119
 	sta 	$2115   ; VRAM address increment register
 	stz 	$2116   ; VRAM address low
 	stz 	$2117   ; VRAM address high
 	stz 	$211A   ; Initial Mode 7 setting register
 	stz 	$211B   ; Mode 7 matrix parameter A register (low)
 	lda 	#$01
 	sta 	$211B   ; Mode 7 matrix parameter A register (high)
 	stz 	$211C   ; Mode 7 matrix parameter B register (low)
 	stz 	$211C   ; Mode 7 matrix parameter B register (high)
 	stz 	$211D   ; Mode 7 matrix parameter C register (low)
 	stz 	$211D   ; Mode 7 matrix parameter C register (high)
 	stz 	$211E   ; Mode 7 matrix parameter D register (low)
 	sta 	$211E   ; Mode 7 matrix parameter D register (high)
 	stz 	$211F   ; Mode 7 center position X register (low)
 	stz 	$211F   ; Mode 7 center position X register (high)
 	stz 	$2120   ; Mode 7 center position Y register (low)
 	stz 	$2120   ; Mode 7 center position Y register (high)
 	stz 	$2121   ; Color number register ($0-ff)
 	stz 	$2123   ; BG1 & BG2 Window mask setting register
 	stz 	$2124   ; BG3 & BG4 Window mask setting register
 	stz 	$2125   ; OBJ & Color Window mask setting register
 	stz 	$2126   ; Window 1 left position register
 	stz 	$2127   ; Window 2 left position register
 	stz 	$2128   ; Window 3 left position register
 	stz 	$2129   ; Window 4 left position register
 	stz 	$212A   ; BG1, BG2, BG3, BG4 Window Logic register
 	stz 	$212B   ; OBJ, Color Window Logic Register (or,and,xor,xnor)
 	sta 	$212C   ; Main Screen designation (planes, sprites enable)
 	stz 	$212D   ; Sub Screen designation
 	stz 	$212E   ; Window mask for Main Screen
 	stz 	$212F   ; Window mask for Sub Screen
 	lda 	#$30
 	sta 	$2130   ; Color addition & screen addition init setting
 	stz 	$2131   ; Add/Sub sub designation for screen, sprite, color
 	lda 	#$E0
 	sta 	$2132   ; color data for addition/subtraction
 	stz 	$2133   ; Screen setting (interlace x,y/enable SFX data)
 	stz 	$4200   ; Enable V-blank, interrupt, Joypad register
 	lda 	#$FF
 	sta 	$4201   ; Programmable I/O port
 	stz 	$4202   ; Multiplicand A
 	stz 	$4203   ; Multiplier B
 	stz 	$4204   ; Multiplier C
 	stz 	$4205   ; Multiplicand C
 	stz 	$4206   ; Divisor B
 	stz 	$4207   ; Horizontal Count Timer
 	stz 	$4208   ; Horizontal Count Timer MSB (most significant bit)
 	stz 	$4209   ; Vertical Count Timer
 	stz 	$420A   ; Vertical Count Timer MSB
 	stz 	$420B   ; General DMA enable (bits 0-7)
 	stz 	$420C   ; Horizontal DMA (HDMA) enable (bits 0-7)
 	stz 	$420D	; Access cycle designation (slow/fast rom)
 	cli 	 	; Enable interrupts
 	rts
 .ends

ContributorsEdit

  • Written by the ancient Midfit, with the comment: ; Cool Init routine! use it in your own code!!
  • Bazz: This was a mess in conjunction with the tutorials. Fixed a ton of things.