🕹️

ATARI 2600 ASSEMBLER

"Because 128 bytes of RAM should be enough for anybody."

6507 CPU
ROM:THEME:
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; Solid Color Background ; Classic "Hello World" for Atari 2600 ; Sets the background color and draws a stable frame processor 6502 org $F000 Start: SEI ; Disable interrupts CLD ; Clear decimal mode LDX #$FF TXS ; Set stack pointer ; Clear zero page RAM LDA #0 LDX #$FF ClearMem: STA $00,X DEX BNE ClearMem MainLoop: ; ── VSYNC (3 scanlines) ── LDA #2 STA VSYNC ; Turn on VSYNC STA WSYNC ; Wait for scanline 1 STA WSYNC ; Wait for scanline 2 STA WSYNC ; Wait for scanline 3 LDA #0 STA VSYNC ; Turn off VSYNC ; ── VBLANK (37 scanlines) ── LDA #2 STA VBLANK ; Turn on VBLANK LDX #37 VBlankLoop: STA WSYNC DEX BNE VBlankLoop LDA #0 STA VBLANK ; Turn off VBLANK ; ── VISIBLE AREA (192 scanlines) ── LDA #$84 ; Color: blue STA COLUBK ; Set background color LDX #192 ScanLoop: STA WSYNC ; Wait for scanline DEX BNE ScanLoop ; ── OVERSCAN (30 scanlines) ── LDA #2 STA VBLANK ; Turn on VBLANK LDX #30 OverscanLoop: STA WSYNC DEX BNE OverscanLoop JMP MainLoop ; Back to top ; ── Reset/Interrupt Vectors ── org $FFFC .word Start ; Reset vector .word Start ; IRQ vector
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