Assembler Atari 2600.asm

; A "Hello, World!" which illustrates an Atari 2600 programming
; introduction talk (slides at http://slideshare.net/chesterbr).
;
; This is free software (see license below). Build it with DASM
; (http://dasm-dillon.sourceforge.net/), by running:
;
;   dasm hello.asm -ohello.bin -f3
;

    PROCESSOR 6502
    INCLUDE "vcs.h"

    ORG $F000
StartFrame:
    lda #%00000010  
    sta VSYNC
    REPEAT 3      
        sta WSYNC   
    REPEND
    lda #0
    sta VSYNC       

PreparePlayfield:  
    lda #$00       
    sta ENABL      
    sta ENAM0
    sta ENAM1
    sta GRP0
    sta GRP1
    sta COLUBK      
    sta PF0         
    sta PF2
    lda #$FF       
    sta COLUPF
    lda #$00        
    sta CTRLPF
    ldx #0          
    REPEAT 37       
        sta WSYNC   
    REPEND
    lda #0          
    sta VBLANK

Scanline:
    cpx #174        
    bcs ScanlineEnd 
    txa             
    lsr             
    tay             
    lda Phrase,y   
    sta PF1       
ScanlineEnd:
    sta WSYNC    
    inx             
    cpx #191
    bne Scanline

Overscan:
    lda #%01000010  
    sta VBLANK      
    REPEAT 30       
        sta WSYNC
    REPEND
    jmp StartFrame 

Phrase:
    .BYTE %00000000 
    .BYTE %01000010
    .BYTE %01111110
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01111110
    .BYTE %01000000
    .BYTE %01111100
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01111110
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01111110
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01111110
    .BYTE %00000000 
    .BYTE %00000000
    .BYTE %00111100
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %00111100
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01011010
    .BYTE %00100100
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %00111100
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %00111100
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01111100
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01111100
    .BYTE %01000100
    .BYTE %01000010
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01000000
    .BYTE %01111110
    .BYTE %00000000
    .BYTE %00000000 
    .BYTE %01111000
    .BYTE %01000100
    .BYTE %01000010
    .BYTE %01000010
    .BYTE %01000100
    .BYTE %01111000
    .BYTE %00000000)

    ORG $FFFA
    .WORD StartFrame     
    .WORD StartFrame     
    .WORD StartFrame   

    END

;
; Copyright 2011-2013 Carlos Duarte do Nascimento (Chester). All rights reserved.
;
; Redistribution and use in source and binary forms, with or without modification, are
; permitted provided that the following conditions are met:
;
;    1. Redistributions of source code must retain the above copyright notice, this list of
;       conditions and the following disclaimer.
;
;    2. Redistributions in binary form must reproduce the above copyright notice, this list
;       of conditions and the following disclaimer in the documentation and/or other materials
;       provided with the distribution.
;
; THIS SOFTWARE IS PROVIDED BY CHESTER ''AS IS'' AND ANY EXPRESS OR IMPLIED
; WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
; FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL <COPYRIGHT HOLDER> OR
; CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
; CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
; SERVICES;  LOSS OF USE, DATA, OR PROFITS;  OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
; ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
; NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
; ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;
; The views and conclusions contained in the software and documentation are those of the
; authors and should not be interpreted as representing official policies, either expressed
; or implied, of Chester.
;