Skip to content

Latest commit

 

History

History
92 lines (68 loc) · 3.88 KB

README.md

File metadata and controls

92 lines (68 loc) · 3.88 KB

6502 Emulator

Emulates a MOS 6502 chip with an interactive debugger.
LIVE DEMO

Snake.mp4

Source Code for snake

Build and Execution

  1. Clone the repository:
    git clone https://github.com/ArchUsr64/6502_emulator
  2. Change to newly created directory:
    cd 6502_emulator
  3. Run the emulator:
    cargo run --release

Usage

Assemble one of the provided examples under examples/ using the provided python build script:
python build_asm.py examples/snake.asm
This should build an a.out binary which the emulator can understand along with symbols.dbg for debugging.

Run the emulator with the newly generated files:

cargo run -- -a examples/snake.asm -d symbols.dbg a.out

Debugging

Click the 'Pause Execution' button in the Debug Controls window to pause the execution at any time or start in paused state via the -s flag. Once paused, use the Step button to execute the next instruction. Add breakpoints from the 'Breakpoints' window and press the 'X' button to remove previously added entires. Watchpoints can be used to observe and change memory addresses at runtime.

The symbols required for debugging are included in a newline delimited entries of line numbers and program counter addresses, with the addresses in hexadecimal. For an example take a look at the provided symbols.dbg.

CLI Arguments

Usage: nemu [OPTIONS] [EXECUTABLE]

Option Description Default
-v Verbosity: Verbosity level for console logs 0 (Errors only)
-s Start debug: Stard the emulator in debug mode false
-i Instructions per frame: The number of CPU instructions to execute per rendered frame 100
-d Debug symbols: Path for the file containing debug symbols symbols.dbg
-a Assembly source: Path for the assembly source file examples/snake.asm

Inputs

Use WASD or the arrow keys to provide input events.

Memory Layout

Address Description
0xfb - 0xfe Keyboard Inputs stored here in: left, down, up, right order where 1 indicates KeyDown
0xff Random Number Generator (Value is updated to a random byte on every instruction execution
0x100 - 0x1ff Stack to store subroutine return addresses
0xfb00 - 0xffff 0x400 (1024) byte space to store the RGB values for pixels on a 32x32 grid in standard raster scan order

RGB color format:

Each color byte is divided into bit fields of size 3, 3 and 2. The bit field if size 2 is least significant and represents the blue color, with the most significant bit field representing red as shown below:

MSB      LSB
 ^        ^
 765 432 10
 |   |   |
 RRR GGG BB

color_palette

Screenshots

Debugger UI

image

Console Logs

image

Thanks

Similar Projects