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List of modes

This is a list of supported interpeter modes/CHIP-8 extensions. The instruction sets are listed to describe the features of this interpreter, please refer to the original sources for an accurate description. The name in parantheses is understood by the mode option.

CHIP-8 (chip8)

https://chip-8.github.io/extensions/#chip-8 https://github.com/mattmikolay/chip-8/wiki/CHIP%E2%80%908-Instruction-Set

The original CHIP-8:

  • resolution: 64 x 32, 2 colors
  • program starts at 0x200
opcode description note
0000 unknown opcode / end of program
00e0 clear screen
00ee return
0nnn call machine language subroutine at nnn not implemented
1nnn jump to nnn
2nnn call subroutine at nnn
3xnn skip if Vx == nn
4xnn skip if Vx != nn
5xy0 skip if Vx == Vy
6xnn Vx = nn
7xnn Vx += nn
8xy0 Vx = Vy
8xy1 Vx = Vy
8xy2 Vx &= Vy
8xy3 Vx ^= Vy
8xy4 Vx += Vy; Vf = carry ? 1 : 0
8xy5 Vx -= Vy; Vf = borrow ? 0 : 1
8xy6 Vx = Vy >> 1; Vf = Vy & 0x01
8xy7 Vx = Vy - Vx; Vf = borrow ? 0 : 1
8xye Vx = Vy << 1; Vf = Vy & 0x80
9xy0 skip if Vx != Vy
annn I = nnn
bnnn jump to nnn + V0
cxnn Vx = random & nn
dxyn draw n bytes at (Vx, Vy)
ex9e skip if pressed key == Vx
exa1 skip if pressed key != Vx
fx07 Vx = delay timer
fx0a wait for keypress; Vx = key
fx15 delay timer = Vx
fx18 sound timer = Vx
fx1e I += Vx
fx29 I = address of sprite of hex digit in Vx
fx33 memory[I, I+1, I+2] = BCD of Vx
fx55 store V0 to Vx in memory starting at I; I = I + x + 1
fx65 load V0 to Vx from memory starting at I; I = I + x + 1

CHIP-10 (chip10)

https://chip-8.github.io/extensions/#chip-10 https://github.com/mattmikolay/viper/blob/master/volume1/issue7.pdf

Increased resolution: 128x64, otherwise identical to CHIP-8. In the original interpreter the memory from 0x055f to 0x0fff is reserved, this limitation doesn't exist in this interpreter.

CHIP-8E (chip8e)

https://chip-8.github.io/extensions/#chip-8e https://raw.githubusercontent.com/mattmikolay/viper/master/volume2/issue8_9.pdf

This extension was described by Gilles Detillieux in VIPER volume 2, issue 8/9. In some places the extension by Paul C. Moews from Programs for the COSMAC ELF – Interpreters is called CHIP-8E, however these extensions are different and not compatible.

Identical to CHIP-8, with the following opcodes added:

opcode description note
00ed stop execution
00f2 no operation
0151 wait until the delay timer reaches 0
0188 skip the next instruction
5xy1 skip if Vx > Vy
5xy2 store Vx to Vy in memory starting at I; I = I + (x-y) + 1
5xy3 load Vx to Vy from memory starting at I; I = I + (x-y) + 1
bbnn jump to current instruction - nn bytes
bfnn jump to current instruction + nn bytes
fx03 send Vx to output port 3 implemented as Lua callback (output_port_3)
fx1b skip Vx bytes
fx4f delay timer = Vx; wait until the delay timer reaches 0
fxe3 wait for strobe at EF4; read Vx from input port 3 implemented as Lua callback (input_port_3_wait)
fxe7 read Vx from input port 3 implemented as Lua callback (input_port_3)

CHIP-8 modification for saving and restoring variables (chip8_fxf2_fx55_fx65)

https://chip-8.github.io/extensions/#chip-8-modification-for-saving-and-restoring-variables https://github.com/mattmikolay/viper/blob/master/volume1/issue10.pdf

Extension to CHIP-8 by John Bennett, adds the fxf2 instruction to allow the following combinations:

  • fxf2 + fy55: store Vx to Vy in memory starting at I; I = I + x + 1
  • fxf2 + fy65: load Vx to Vy from memory starting at I; I = I + x + 1

CHIP-8 with improved BNNN (chip8_fxf2_bnnn)

https://chip-8.github.io/extensions/#chip-8-with-improved-bnnn https://github.com/mattmikolay/viper/blob/master/volume2/issue8_9.pdf

Extension to CHIP-8 by George Ziniewicz, adds the fxf2 instruction to allow the following combination:

  • fxf2 + bnnn: jump to nnn + Vx

CHIP-8 with FXF2 (chip8_fxf2)

A combination of chip8_fxf2_fx55_fx65 and chip8_fxf2_bnnn:

  • fxf2 + fy55: store Vx to Vy in memory starting at I; I = I + x + 1
  • fxf2 + fy65: load Vx to Vy from memory starting at I; I = I + x + 1
  • fxf2 + bnnn: jump to nnn + Vx

CHIP-48 (chip48)

Same opcodes as CHIP-8, but with quirks.

CHIP-8 for ETI-660 (eti660)

https://chip-8.github.io/extensions/#chip-8-for-eti-660 https://archive.org/details/ETIA1981/ETI%201981-11%20November/page/n114/mode/2up

  • Increased resolution: 64x48
  • Programs start at 0x0600

Added opcodes:

opcode description note
0000 stop execution
00f8 display on
00fc display off
00ff no operation
fx00 set sound frequency the correct mapping of Vx to a frequency is unknown

CHIP-8 with color support for ETI-660 (eti660color)

https://chip-8.github.io/extensions/#chip-8-with-color-support-for-eti-660 https://archive.org/stream/ETIA1982/ETI%201982-04%20April#page/n87/mode/2up

Based on the ETI-660 version, with color.

Added opcodes:

opcode description note
07a2 step background color
07c1 enable color instructions
27ab set foreground color in area given by VE (x) and VF (y) to VD

CHIP-8 with high resolution and color support for ETI-660 (eti660color_highres)

https://chip-8.github.io/extensions/#chip-8-for-eti-660-with-high-resolution https://archive.org/stream/ETIA1984/ETI%201984-02%20February#page/n87/mode/1up

Similar to the ETI-660 color extension:

  • Increased resolution: 64x64
  • Different color opcodes
  • Programs start at 0x0700

Added opcodes:

opcode description note
049f step background color
04a2 enable color instructions
04b2 set foreground color in area given by V1 (x) and V2 (y) to V0

SUPER-CHIP 1.0 (schip10)

https://chip-8.github.io/extensions/#super-chip-10

  • Increased resolution: 128x64
  • Same quirks as CHIP-48
  • opcode fx29 has support for large digit sprites
  • dxy0 draws a 16x16 sprite in high resolution mode

Added opcodes:

opcode description note
00fd stop execution
00fe disable high resolution mode
00ff enable high resolution mode
fx75 store V0 - Vx in RPL user flags (0 <= x <= 7)
fx85 load V0 - Vx from RPL user flags (0 <= x <= 7)

CHIP-8 for COSMAC ELF (chip8elf)

https://chip-8.github.io/extensions/#chip-8-for-cosmac-elf https://raw.githubusercontent.com/trapexit/chip-8_documentation/master/Programs%20for%20the%20COSMAC%20ELF%20-%20Paul%20C.%20Moews/Interpreters%20-%20Paul%20C.%20Moews.pdf

From Programs for the COSMAC ELF – Interpreters, adds a few instructions:

opcode description note
5xy1 skip if Vx > Vy
5xy2 skip if Vx < Vy
5xy3 skip if Vx != Vy
9xy1 Vf,Vx = Vx * Vy
9xy2 Vx = Vx / Vy, Vf = remainder
9xy3 convert Vx,Vy to BCD stored at I,I+1,I+2,I+3,I+4
fx75 output Vx to hex display implemented as Lua callback
fx94 set I to location of ASCII character in Vx

SUPER-CHIP 1.1 (schip11)

http://devernay.free.fr/hacks/chip8/schip.txt https://chip-8.github.io/extensions/#super-chip-11

  • Mostly identical (added opcodes, quirks) to SUPER-CHIP 1.0
  • fx29 doesn't support large digit sprites

Added opcodes:

opcode description note
00cn scroll display n pixels down
00fb scroll display 4 pixels right
00fc scroll display n pixels left
fx30 I = address of large sprite of digit in Vx

SUPER-CHIP Compatibility (schpc)

https://chip-8.github.io/extensions/#schip-compatibility-schpc-and-gchip-compatibility-gchpc

Same as SUPER-CHIP 1.1, but all instructions behave as in CHIP-8

SUPER-CHIP 1.1 with FX1E quirks (schip11_fx1e)

https://github.com/jameskozlowski/Chip8-C/blob/master/sctest.c8

SUPER-CHIP 1.1 with the following quirks to be compatible with the sctest test program:

  • fx1e sets vF to 1 if I overflows, otherwise to 0
  • fx1e causes I to overflow if it becomes greater than the memory size

SUPER-CHIP Compatibility with FX1E quirks (schpc_fx1e)

SUPER-CHIP Compatibility with the same quirks as SUPER-CHIP 1.1 with FX1E quirks.

SUPER-CHIP with scroll up (schip11scu)

https://chip-8.github.io/extensions/#super-chip-with-scroll-up https://massung.github.io/CHIP-8/

Identical to SUPER-CHIP 1.1 with one added instruction:

  • 00bn: scroll display n pixels up

chip8run (chip8run)

http://chip8.sourceforge.net/ http://chip8.sourceforge.net/chip8-1.1.pdf https://chip-8.github.io/extensions/#chip8run

Based on SUPER-CHIP 1.1 with different quirks and additional opcodes.

opcode description note
001n stop execution with exit status n n is ignored
00fa enable the fx55_fx65_no_increment quirk

CHIP-8X (chip8x)

https://chip-8.github.io/extensions/#chip-8x https://github.com/trapexit/chip-8_documentation/blob/master/Misc/VP580%2C%20VP585%2C%20VP590%2C%20VP595%20Instruction%20Manual%20Including%20CHIP-8X.pdf

This extension adds instructions to control the Color Card, Simple Sound and expansion hex keyboard.

  • Programs start at 0x0300
  • bnnn is unavailable (replaced with the bxyn instruction)

Added opcodes:

opcode description note
02a0 step background color
5xy1 for each nibble in Vx, Vy: Vx = (Vx + Vy) % 8
bxy0 set foreground color in area given by Vx and Vx+1 to Vy
bxyn set foreground color at Vx,Vx+1 for n rows to Vy
exf2 skip if key Vx is pressed on keyboard 2 == Vx TODO
exf5 skip if key Vx is not pressed on keyboard 2 == Vx TODO
fxf8 output Vx to port (set sound frequency)
fxfb wait for input from port and store it in Vx not implemented

background colors: blue (default), black, green, red

foreground colors:

value color
0 black
1 red
2 blue
3 violet
4 green
5 yellow
6 aqua
7 white (default)

XO-CHIP (xochip)

https://github.com/JohnEarnest/Octo/blob/gh-pages/docs/XO-ChipSpecification.md https://chip-8.github.io/extensions/#xo-chip

Based on SUPER-CHIP 1.1:

  • 64 kiB of memory
  • supports 4 colors
opcode description note
00dn scroll display n pixels up
5xy2 save Vx to Vy (ascending or descending) in memory starting at I
5xy3 load Vx to Vy (ascending or descending) from memory starting at I
f000 nnnn I = nnnn
fn01 set active drawing planes to n
f002 store 16 bytes starting at I in the audio pattern buffer
fx3a pitch register = Vx

Octo (octo)

https://github.com/JohnEarnest/Octo https://github.com/JohnEarnest/c-octo

XO-CHIP with different quirks and one added intruction:

  • 0000: stop execution