verilog-nes

< WORK IN PROGRESS >

Building a Nintendo Entertainment System in Verilog.

Aim: to play the original NES Super Mario Bros ROM.

Current Status

• Implemented
  • 6502 CPU working and passing tests (for official opcodes)
  • OAM DMA working
  • PPU background layer
• Emulation
  • Verilator emulation running in C++ with PixelGameEngine renderer from OneLoneCoder
  • Super Mario Bros - now able to reach splash screen
• FPGA
  • NES Running on ARTY A7 hardware
  • Arduino based interface for uploading ROMs and debugging the NES design
  • Super Mario Bros - now able to reach splash screen

Dependencies

• Bazel v5.0.0

  brew install bazel

• MacOS

C++ Debugging Bazel builds on MacOS

• Add '--spawn_strategy=local' and '--config debug' to bazel command line, to make sure symbols are correctly included in your build
  • When debugging in VSCode with a C++ config, you can see symbol values
  • Breakpoints can be set in source files via VSCode
  • When lldb stops execution at a breakpoint, VSCode is not currently able to load the correct source file - further investigation required

6502 cpu

Build Unit Tests

bazel build //nes:test-cpu6502 --incompatible_require_linker_input_cc_api=false

Run Unit Tests

./bazel-bin/nes/test-cpu6502

NES PPU (Picture Processing Unit)

Build Unit Tests

bazel build //nes:test-ppu --incompatible_require_linker_input_cc_api=false

Run Unit Tests

./bazel-bin/nes/test-ppu

NES CPU + PPU

Build Unit Tests

bazel build //nes:test-nes --incompatible_require_linker_input_cc_api=false

Run Unit Tests

./bazel-bin/nes/test-nes

VGA Output Emulator

Currently supported on MacOSX.

Implemented with the OneLoneCoder Pixel Game Engine.

Test the VGA output module.

Build

bazel build //nes:emulator-vga --incompatible_require_linker_input_cc_api=false --config release

Run

./bazel-bin/nes/emulator-vga

6502 Emulator

Currently supported on MacOSX.

Implemented with the OneLoneCoder Pixel Game Engine.

Build

bazel build //nes:emulator-cpu --incompatible_require_linker_input_cc_api=false --config release

Run

./bazel-bin/nes/emulator-cpu

Keyboard Controls

Key	Action
Z	Reset Simulation
R	Switch between single step and run mode
SPACE	Step through a single Opcode (in single step mode)

NES Emulator

Currently supported on MacOSX.

Implemented with the OneLoneCoder Pixel Game Engine.

Build

bazel build //nes:emulator-nes --incompatible_require_linker_input_cc_api=false --config release

Run

./bazel-bin/nes/emulator-nes

Debugger CPU

Debugger interface for interacting with CPU6502, intended for use with SPI comms.

Build

bazel build //nes:test-debugger-cpu --incompatible_require_linker_input_cc_api=false

Run

./bazel-bin/nes/test-debugger-cpu

Debugger NES

Debugger interface for interacting with NES, intended for use with SPI comms.

Build

bazel build //nes:test-debugger-nes --incompatible_require_linker_input_cc_api=false

Run

./bazel-bin/nes/test-debugger-nes

Games

Information from .nes rom headers dumped with scripts/parse_ines.py

• Super Mario World

PRG ROM 2 x 16 KB units
CHR ROM 1 x 8 KB units
mirroring:  horizontal
has batter backed prg rom:  False
has trainer:  False
ignore mirroring control:  False
mapper number:  0

• Super Mario World 2

PRG ROM 8 x 16 KB units
CHR ROM 16 x 8 KB units
mirroring:  vertical
has batter backed prg rom:  False
has trainer:  False
ignore mirroring control:  False
mapper number:  4

• Super Mario World 3

PRG ROM 16 x 16 KB units
CHR ROM 16 x 8 KB units
mirroring:  vertical
has batter backed prg rom:  False
has trainer:  False
ignore mirroring control:  False
mapper number:  4

• Kirby's Adventure ''' PRG ROM 32 x 16 KB units CHR ROM 32 x 8 KB units mirroring: vertical has batter backed prg rom: True has trainer: False ignore mirroring control: False mapper number: 4 '''

Mappers

• Mapper number: 0 = NROM
• Mapper number: 4 = MMC3

Disassembly

• Super Mario Disassembly - useful for stepping through code
  • NOTE: infinite loop at 0x8057 appears to be label "EndlessLoop"
  • perhaps we can step through code from 'start' to see what needs to be emulated so far