Skip to content

chip8.md

Latest commit

 

History

History
112 lines (91 loc) · 6.16 KB

chip8.md

File metadata and controls

112 lines (91 loc) · 6.16 KB
Raw

chip8 (CHIP-8 Interpreter)

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

Table of Contents

Usage

chip8 [-dsvV] [-c tickspeed] [-f small,big] [-p file] [-P colors] [-q quirks] file

Options

Option Description
-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 (prefixed by 0x or x).
-P Sets the color palette from a string containing two comma-separated 24-bit hex codes (prefixed by 0x or x).
-q Sets the quirks to enable from string with non-separated quirk identifiers
-s Enables SCHIP mode.
-v Enables verbose mode. This will print each instruction that is executed.
-V Prints the version number.

Keyboard Layout

  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.

Font Small Big
octo ☑ ☑
schip ☑ ☑
fish ☑ ☑
vip ☑ ❌
dream6800 ☑ ❌
eti660 ☑ ❌

Quirks

The following quirks are available:

Quirk Definition CHIP-8 Default SCHIP Default
c Clip sprites at bottom edge of screen instead of wrapping. ☑ ☑
j For JP V0, nnn: Jump to nnn + V[(nnn>>8)&0xF] instead. ❌ ☑
m After LD [I], Vx and LD Vx, [I]: Set I to address I + x + 1. ☑ ❌
r DRW halts execution until the next frame. ☑ ☑
s Before SHL Vx, Vy and SHR Vx, Vy: Shift Vx in place, ignore Vy. ❌ ☑
v After AND, OR, and XOR: Clear VF. ☑ ❌

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 and attributes are supported in debug mode:

Command Description
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.
Attribute Description
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

Note

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