CHIP-8 interpreter

CHIP-8 interpreter written using Python language & pygame library.

Some details

CHIP-8 is an interpreted programming language which was initially used in the late 1970s. It was made to allow more easily programed game for those computers. All programs written in CHIP-8 are run on a virtual machine which interprets each instruction.

Memory map

The most common implementation of CHIP-8 has 4096 (0x1000) bytes of RAM, starting at location 0x000 (0) to 0xFFF (4095). The first 512 (0x200) bytes are reserved for the CHIP-8 interpreter, in my case this space is used to store fonts data and stack.

+----------------+= 0xFFF (4095) End of CHIP-8 RAM
|                |
|                |
|                |
|                |
|                |
| 0x200 to 0xFFF |
| CHIP-8 Program |
|                |
|                |
|                |
|                |
|                |
+----------------+= 0x200 (512) Start of program
|                |
| 0x050 to 0x1FF |
|     Stack      |
|                | 
+----------------+= 0x050 (80) Start of stack 
| 0x000 to 0x049 | 
|     Fonts      |
+----------------+= 0x000 (0) Start of CHIP-8 RAM

Instruction Set Table

Mnemonic	Opcode	Description
CLS	00EE	Clear the display.
RET	00EE	Return from a subroutine.
JMP	1nnn	Jump to location nnn.
CALL	2nnn	Execute subroutine starting at address nnn.
SE	3xkk	Skip the following instruction if the value of Vx equals kk.
SNE	4xkk	Skip the following instruction if the value of Vx not equals kk.
SER	5xy0	Skip the following instruction if the value of Vx equals Vy.
LD	6xkk	Store the value kk in register Vx.
ADD	7xkk	Add the value kk to the value of register Vx.
LDR	8xy0	Store the value of register Vy in register Vx.
OR	8xy1	Store the value of (Vx OR Vy) in register Vx.
AND	8xy2	Store the value of (Vx AND Vy) in register Vx.
XOR	8xy3	Store the value of (Vx XOR Vy) in register Vx.
ADDR	8xy4	Add the value of register Vx to register Vy. Set register VF to 1 if a carry occurs otherwise set to 0.
SUB	8xy5	Subtract the value of register Vy from register Vx. Set register VF to 1 if a borrow occurs otherwise set to 0.
SHR	8xy6	Set register VF to 1 if the least-significant bit of Vx is 1 otherwise set to 0. Store the value of register Vx shifted right by one in register Vx.
SUBN	8xy7	Subtract the value of register Vx from register Vy. Store result in register Vx. Set register VF to 0 if Vy borrow occurs otherwise set to 1.
SHL	8xyE	Set register VF to 1 if the most-significant bit of Vx is 1 otherwise set to 0 Store the value of register Vx shifted left by one in register Vx.
SNER	9xy0	Skip the following instruction if value of the register Vx is not equal the value of register Vy.
LDI	Annn	Store address nnn in register I.
JMPR	Bnnn	Jump to address nnn + V0.
RND	Cxkk	Set register Vx to random number ANDed with the value kk.
DRW	Dxyn	Draw n-byte sprite starting at memory location I at (Vx, Vy). Set register VF to 1 if any pixels are erased otherwise set to 0.
SKP	Ex9E	Skip the following instruction if key with the value of Vx is pressed.
SNKP	ExA1	Skip the following instruction if key with the value of Vx is not pressed.
LDT	Fx07	Store the value of the delay timer in register Vx.
LDK	Fx0A	Wait for a keypress and store the value of the key in register Vx.
LDDT	Fx15	Set delay timer to the value of register Vx.
LDST	Fx18	Set sound timer to the value of register Vx.
ADDI	Fx1E	Set register I to the value of (I + Vx).
LDF	Fx29	Set register I to the location for sprite corresponding to the value of Vx.
LDB	Fx33	Store BCD representation of Vx in memory at address I, I+1 and I+2.
LDIR	Fx55	Store the values of registers V0 through Vx in memory starting at address I.
LDRI	Fx65	Read registers V0 through Vx from memory starting at address I.

Installation / Requirements

• Python 2.7
• Pygame

You can also easly install the require packages using the following command:

pip install -r requirements.txt

Usage

Just run chip8.py and specify the positional argument which is the CHIP-8 ROM.

usage: ./chip8.py [-h] [-d DELAY] [-s SCALE] [-v] program

CHIP-8 interpreter

positional arguments:
  program                  CHIP-8 ROM

optional arguments:
  -h, --help               show this help message and exit
  -d DELAY, --delay DELAY  Specify delay for every instruction (default=1ms)
  -s SCALE, --scale SCALE  Specify scale for width & height (default=10)
  -v, --verbose            Enable verbose output

Have fun! 🎉

License

MIT © Mateusz Furga