This is a fully functional CHIP-8 and SCHIP interpreter with an integrated debug mode, utilizing libc8 with SDL2.

Usage

c8 [-dvV] [-c clockspeed] [-f small,big] [-p file] [-P colors] [-q quirks] file

-c sets the number of instructions to be executed per second (default: 1000).
-d enables debug mode. This can be used to add breakpoints, display the current memory, and step through instructions individually.
-f loads the specified comma-separated fonts. Big font is optional.
-p loads a color palette from a file containing two newline-separated 24-bit hex codes.
-P sets the color palette from a string containing two comma-separated 24-bit hex codes.
-q sets the quirks to enable from string with non-separated quirk identifiers
-v enables verbose mode. This will print each instruction that is executed.
-V prints the version number.

Keyboard layout is the following:

  Key       CHIP-8 keycode
1 2 3 4        1 2 3 C
q w e r  ==>   4 5 6 D
a s d f        7 8 9 E
z x c v        A 0 B F

Fonts

Same as Octo.

Small fonts:

octo
vip
dream6800
eti660
fish

Big fonts:

octo
schip
fish

Quirks

The following quirks are available:

b: After AND, OR, and XOR: Clear VF.
d: For DRW: Clip sprites at edge of display.
j: For JP V0, nnn: Jump to nnn + V[(nnn>>8)&0xF] instead.
l: After LD [I], Vx and LD Vx, [I]: Set I to address I + x + 1.
s: Before SHL Vx, Vy and SHR Vx, Vy: Shift Vx in place, ignore Vy.

Debug mode

Debug mode can be enabled via the -d command-line argument or by pressing P at any time during execution. It can also be disabled at any time by pressing M.

The following commands are supported in debug mode:

break [ADDRESS]: Add breakpoint to PC or ADDRESS, if given.
rmbreak [ADDRESS]: Remove breakpoint at PC or ADDRESS, if given and exists.
continue: Exit debug mode until next breakpoint or until execution is complete.
help: Print a help string.
load PATH: Load program state from PATH.
loadflags PATH: Load flag registers from PATH.
next: Step to the next instruction.
print [ATTRIBUTE]: Print current value of the given attribute.
quit: Terminate the program.
save PATH: Save program state to PATH.
saveflags PATH: Save flag registers to PATH.
set ATTRIBUTE VALUE: Set the given attribute to the given value.

Attributes:

PC: Program counter
SP: Stack pointer
DT: Delay timer
ST: Sound timer
I: I value
K: Register to store next keypress
V[x]: All V register values or value of Vx, if given
R[x]: All R (flag) register values or value of Rx, if given
bfont: Big font name
sfont: Small font name
stack: All stack values
bg: Background color
fg: Foreground color
$[address]: Value at given address

If no argument is given to print, it will print all of the above attributes except for address values.