6502 Assembly Simulator

This page contains an interactive 6502 assembly language simulator. You can write, assemble, and run 6502 assembly code in your browser.

6502 Assembly Simulator

Below is an interactive 6502 assembler and simulator. You can write 6502 assembly code, assemble it, and run it in the virtual machine.

Debugger

Monitor Start: $ Length: $

Notes: Memory location $fe contains a new random byte on every instruction. Memory location $ff contains the ascii code of the last key pressed. Memory locations $200 to $5ff map to the screen pixels. Different values will draw different colour pixels. The colours are: $0: Black $1: White $2: Red $3: Cyan $4: Purple $5: Green $6: Blue $7: Yellow $8: Orange $9: Brown $a: Light red $b: Dark grey $c: Grey $d: Light green $e: Light blue $f: Light grey

How to Use

1. Write Assembly Code: Type your 6502 assembly code in the text area
2. Assemble: Click “Assemble” to convert your code to machine code
3. Run: Click “Run” to execute the program
4. Debug: Enable the debugger to step through code instruction by instruction
5. Monitor: View memory contents in real-time

Example Code

Try this simple program that draws a colored pixel:

LDA #$05    ; Load green color
STA $200    ; Store to screen memory
BRK         ; Break execution

Memory Map

• $0000-$00FF: Zero page (fast access)
• $0100-$01FF: Stack
• $0200-$05FF: Screen memory (160x160 pixels)
• $FE: Random byte generator
• $FF: Last key pressed

The simulator provides a complete 6502 environment for learning assembly programming and retro game development.