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Chirp

How does an emulator work? I don't know!

So I wrote this, to see if i can find out.

Features:

  • 64 * 128 1bpp pixel display, scaled 8x
  • Full coverage of the original Chip-8 insn set
  • Partial coverage of the Super Chip-8 extension set
  • 64-bit floating point internal sound/delay timers
  • Pause/Resume
  • Set and unset breakpoints
  • A fairly nice command-line interface

Keybinds:

  • F1: Dump CPU registers
  • F2: Dump screen to terminal
  • F3: Dump screen to file
  • F4: Enable/Disable live disassembly
  • F5: Pause/Resume
  • F6: Single-step instruction
  • F7: Set breakpoint at current instruction
  • F8: Unset breakpoint at current instruction
  • F9: Soft-reset the CPU

Keypad mapping:

QWERTY:
1 2 3 4
Q W E R
A S D F
Z X C V

Chip-8:
1 2 3 C
4 5 6 D
7 8 9 E
A 0 B F

Command Line Interface:

Usage: chirp [OPTIONS]

Positional arguments:
  file                 Load a ROM to run on Chirp.

Optional arguments:
  -h, --help           Print this help message.
  -d, --debug          Enable debug mode at startup.
  -p, --pause          Enable pause mode at startup.
  -s, --speed SPEED    Set the instructions-per-frame rate.
  -S, --step STEP      Run the emulator as fast as possible for `step` instructions.
  -z, --vfreset        Disable setting vF to 0 after a bitwise operation.
  -x, --drawsync       Disable waiting for vblank after issuing a draw call.
  -c, --memory         Use CHIP-48 style DMA instructions, which don't touch I.
  -v, --shift          Use CHIP-48 style bit-shifts, which don't touch vY.
  -b, --jumping        Use SUPER-CHIP style indexed jump, which is indexed relative to v[adr].
  -B, --break BP       Set breakpoints for the emulator to stop at.
  -D, --data WORD      Load additional word at address 0x1fe
  -f, --frame-rate FR  Set the target framerate. (default: 60)

TODO:

  • Move the screen, stack, charset, and program memory into the CPU
  • Implement sound
  • Finish unit tests for "quirks"
  • Make pausing/unpausing the emulator less messy
  • Make resetting the emulator possible
  • Allow code to be passed in hex on the command line? Hmm
  • Assembler for my assembly syntax
  • Make a UI for realtime configuration
  • Cycle accuracy with original Chip-8 interpreter