Added NES 6502 Hello World

Nintendo Entertainment System/README.txt

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+**************************************************************
+* NES Hello World
+* Made by Pedro A. Fabri - https://github.com/pedroafabri
+* Based on Nerdy Nights Tutorials:
+*	http://nintendoage.com/forum/messageview.cfm?catid=22&threadid=7155
+**************************************************************
+
+How to see the Hello World:
+	It's basically a game, so you just need to open "helloworld.nes" with your NES emulator of choice!
+
+Source Files:
+	scr/helloworld.asm - 6502 Assembly file. All the logic is there.
+	src/mario.chr - CHR file extracted from Super Mario Bros 1. It contains all the sprites of the game!
+
+How to compile:
+	> Download NESASM3.exe. It's the 6502 compiler. Sadly I only have the windows version of it. I don't know anything about linux versions...
+	  Link: http://nespowerpak.com/nesasm/
+	> Put NESASM3.exe at /src folder
+	> cd /src
+	> NESASM3 helloworld.asm
+	> TaaDaa!

Nintendo Entertainment System/src/helloworld.asm

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+;*********************************************
+; NES Hello World
+; Made by: Pedro A. Fabri
+; Based on Nerdy Nights Tutorials
+;*********************************************
+
+;*********************************************
+; Variables
+;*********************************************
+  .rsset $0000
+
+;*********************************************
+; NES Header
+;*********************************************
+  .inesprg 1   ; 1x 16KB PRG code
+  .ineschr 1   ; 1x  8KB CHR data
+  .inesmap 0   ; mapper 0 = NROM, no bank swapping
+  .inesmir 1   ; background mirroring
+
+  
+;*********************************************
+; Bank 0
+;*********************************************
+  .bank 0
+
+  .org $C000 
+
+RESET:
+  SEI          ; disable IRQs
+  CLD          ; disable decimal mode
+  LDX #$40
+  STX $4017    ; disable APU frame IRQ
+  LDX #$FF
+  TXS          ; Set up stack
+  INX          ; now X = 0
+  STX $2000    ; disable NMI
+  STX $2001    ; disable rendering
+  STX $4010    ; disable DMC IRQs
+
+  JSR vblankwait
+
+clrmem:
+  LDA #$00
+  STA $0000, x
+  STA $0100, x
+  STA $0200, x
+  STA $0400, x
+  STA $0500, x
+  STA $0600, x
+  STA $0700, x
+  LDA #$FE
+  STA $0300, x
+  INX
+  BNE clrmem
+
+  JSR vblankwait
+
+;*********************************************
+; Load Palettes
+;*********************************************
+LoadPalettes:
+  LDA $2002             ; read PPU status to reset the high/low latch
+  LDA #$3F
+  STA $2006             ; write the high byte of $3F00 address
+  LDA #$00
+  STA $2006             ; write the low byte of $3F00 address
+  LDX #$00              ; start out at 0
+LoadPalettesLoop:
+  LDA palette, x        ; load data from address (palette + the value in x)
+  STA $2007             ; write to PPU
+  INX                   ; X = X + 1
+  CPX #$20              ; Compare X to hex $10, decimal 16 - copying 16 bytes = 4 sprites
+  BNE LoadPalettesLoop  ; Branch to LoadPalettesLoop if compare was Not Equal to zero
+
+;*********************************************
+; Load Sprites
+;*********************************************
+LoadSprites:
+  LDX #$00              ; start at 0
+LoadSpritesLoop:
+  LDA sprites, x        ; load data from address (sprites +  x)
+  STA $0200, x          ; store into RAM address ($0200 + x)
+  INX                   ; X = X + 1
+  CPX #$28              ; Compare X to hex $14, decimal 20
+  BNE LoadSpritesLoop   ; Branch to LoadSpritesLoop if compare was Not Equal to zero
+            
+  LDA #%10001000        ; enable NMI, sprites from Pattern Table 1
+  STA $2000
+
+  LDA #%00010000        ; enable sprites
+  STA $2001
+
+;*********************************************
+; Main Logic
+;*********************************************
+
+Forever:
+  JMP Forever     ;jump back to Forever, infinite loop
+
+;*********************************************
+; NMI Interrupt
+;*********************************************
+NMI:
+
+  LDA #$00
+  STA $2003       ; set the low byte (00) of the RAM address
+  LDA #$02
+  STA $4014       ; set the high byte (02) of the RAM address, start the transfer
+
+
+
+  RTI             ; return from interrupt
+
+;*********************************************
+; General Functions
+;*********************************************
+;*********************************************
+; VBlank Wait
+;*********************************************
+vblankwait:
+  BIT $2002
+  BPL vblankwait
+  RTS
+
+;*********************************************
+; Read Buttons
+;*********************************************
+
+  RTS
+
+;*********************************************
+; Bank 1 - DBs
+;*********************************************
+  .bank 1
+  .org $E000
+
+palette:
+
+  .db $0F,$31,$32,$33,$34,$35,$36,$37,$38,$39,$3A,$3B,$3C,$3D,$3E,$0F
+  .db $0F,$1C,$15,$14,$31,$02,$38,$3C,$0F,$1C,$15,$14,$31,$02,$38,$3C
+
+sprites:
+     ; X  tile  attr  Y
+  .db $60, $11, $00, $68   ; H
+  .db $60, $0E, $00, $70   ; E
+  .db $60, $15, $00, $78   ; L
+  .db $60, $15, $00, $80   ; L
+  .db $60, $18, $00, $88   ; O
+  .db $70, $20, $00, $68   ; W
+  .db $70, $18, $00, $70   ; O
+  .db $70, $1B, $00, $78   ; R
+  .db $70, $15, $00, $80   ; L
+  .db $70, $0D, $00, $88   ; D
+
+
+  .org $FFFA     ;first of the three vectors starts here
+  .dw NMI        ;when an NMI happens (once per frame if enabled) the 
+  .dw RESET      ;when the processor first turns on or is reset, it will jump
+  .dw 0          ;external interrupt IRQ is not used in this tutorial
+
+;*********************************************
+; Bank 2 - Graphic Binary
+;*********************************************
+  .bank 2
+
+  .org $0000
+
+  .incbin "mario.chr"   ;includes 8KB graphics file from SMB1