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August 28, 2011 18:55
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Um "Hello, World!" feito para ilustrar a palestra sobre programação para Atari 2600 (slides em http://slideshare.net/chesterbr)
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; | |
; hello.asm | |
; | |
; Um "Hello, World!" feito para ilustrar a minha palestra sobre programação | |
; para Atari 2600 (slides em http://slideshare.net/chesterbr). | |
; | |
; O código é livre (vide final do arquivo). Para compilar use o DASM | |
; (http://dasm-dillon.sourceforge.net/), através do comando: | |
; | |
; dasm hello.asm -ohello.bin -f3 | |
; | |
PROCESSOR 6502 | |
INCLUDE "vcs.h" | |
ORG $F000 ; Início do cartucho (vide Mapa de Memória do Atari) | |
InicioFrame: | |
lda #%00000010 ; VSYNC inicia setando o bit 1 deste endereço | |
sta VSYNC | |
REPEAT 3 ; ...e dura 3 scanlines (WSYNC=fim da scanline) | |
sta WSYNC | |
REPEND | |
lda #0 | |
sta VSYNC ; VSYNC finaliza limpando o bit 1 | |
PreparaPlayfield: ; Vamos usar o início do VBLANK para ajustar cores | |
lda #$00 ; Cor de fundo (preto) | |
sta COLUBK | |
lda #$FF ; Cor do playfield (possivelmente amarelo) | |
sta COLUPF | |
lda #$00 ; Reset no bit 0 do CTRLPF (para duplicar e nao repetir) | |
sta CTRLPF | |
ldx #0 ; X é o nosso contador de scanlines (0-191) | |
REPEAT 37 ; Aguarda o final da primeira linha, e das outras 36 | |
sta WSYNC ; | |
REPEND | |
lda #0 ; Finaliza o VBLANK, "ligando o canhão" | |
sta VBLANK | |
Scanline: | |
cpx #174 ; "HELLO WORLD" = (11 chars x 8 linhas - 1) x 2 scanlines = | |
bcs FimScanline ; 174 (0 a 173). Passou disso, pula o desenho | |
txa ; Queremos 2 scanlines para cada linha da frase, então | |
lsr ; vamos fazer Y = X / 2. Para dividir por 2 usamos o | |
tay ; shift lógico (que só opera no A) | |
lda Frase,y ; "Frase,Y" = "Frase+Y" (Y-ésima linha da frase) | |
sta PF1 ; Coloca ela nos bits 5 a 11 do playfield | |
FimScanline: | |
sta WSYNC ; Aguarda o final do scanline | |
inx ; Incrementa o contador e repete até completar a tela | |
cpx #191 | |
bne Scanline | |
Overscan: | |
lda #%01000010 ; "Desliga o canhão:" | |
sta VBLANK ; | |
REPEAT 30 ; 30 scanlines de overscan... | |
sta WSYNC | |
REPEND | |
jmp InicioFrame ; ...e começamos tudo de novo! | |
Frase: | |
.BYTE %00000000 ; H | |
.BYTE %01000010 | |
.BYTE %01111110 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %00000000 | |
.BYTE %00000000 ; E | |
.BYTE %01111110 | |
.BYTE %01000000 | |
.BYTE %01111100 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01111110 | |
.BYTE %00000000 | |
.BYTE %00000000 ; L | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01111110 | |
.BYTE %00000000 | |
.BYTE %00000000 ; L | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01111110 | |
.BYTE %00000000 ; O | |
.BYTE %00000000 | |
.BYTE %00111100 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %00111100 | |
.BYTE %00000000 | |
.BYTE %00000000 ; espaço em branco | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 | |
.BYTE %00000000 ; W | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01011010 | |
.BYTE %00100100 | |
.BYTE %00000000 | |
.BYTE %00000000 ; O | |
.BYTE %00111100 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %00111100 | |
.BYTE %00000000 | |
.BYTE %00000000 ; R | |
.BYTE %01111100 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01111100 | |
.BYTE %01000100 | |
.BYTE %01000010 | |
.BYTE %00000000 | |
.BYTE %00000000 ; L | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01000000 | |
.BYTE %01111110 | |
.BYTE %00000000 | |
.BYTE %00000000 ; D | |
.BYTE %01111000 | |
.BYTE %01000100 | |
.BYTE %01000010 | |
.BYTE %01000010 | |
.BYTE %01000100 | |
.BYTE %01111000 | |
.BYTE %00000000 ; Último byte escrito no PF1 (importante, mantém o resto da tela "limpa") | |
ORG $FFFA ; Configurações que ficam no finalzinho do cartucho: | |
.WORD InicioFrame ; NMI | |
.WORD InicioFrame ; RESET | |
.WORD InicioFrame ; IRQ | |
END | |
; | |
; Copyright 2011 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. | |
; |
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