CHIP-8

Versions

CHIP-8: Interpreter / VM created for RCA 1802 based machines designed for writing simple video games. Later picked up by HP-48 enthusiasts.
CHIP-8C: An (unreleased?) version of the CHIP-8 language mentioned in VIPER Volume 1 Issue 2.
- New from RCA. The VIP will be sporting vivid color this fall with the introduction of the VIP COLOR BOARD from RCA. You'll have program control of three background colors & eight foreground colors with CHIP-8C, the color-langauge addition to CHIP-8. Available late October. Priced under $80.00.
CHIP-8E: Extended instructions found in Paul C. Moews' 1979 Programs for the COSMAC ELF Interpreters.
CHIP-8X: an expanded version of the original CHIP-8 interpreter which allows easy control over RCA's new options for the VIP: color card, simple sound, and expansion hex keyboard.
CHIP-8I: From VIPER Volume 1 Issue 03: A Modification of CHIP-8 to Provide I/O Instructions by Rick Simpson
CHIP-10: A high resolution mode (128x64) on top of the CDP-1861 as described in VIPER Volume 1 Issue 7.
HiRes CHIP-8: A version with a high resolution (64x64) mode.
SCHIP-8: An extended version of CHIP-8 created originally for the HP-48 calculator. Provided twice the resolution of the original CHIP-8 platform plus several additional instructions.

NOTE: Some of the above conflict with one another which is why you may see opcodes that overlap.

Opcodes

Each opcode is 16bits. References to registers are usually refered to by X and Y. Immediate values as N, NN, and NNN. NNN used for 12bit addresses. Registers include 8bit V0 through VF, 12bit memory location I, 12bit program counter PC, 8bit delay timer DT, 8bit sound timer ST. There is also a 12bit stack pointer SP.

Opcode	Mnemonic	Origin/Version	Description
001N	EXIT N	CHIP-8	From Peter Miller's chip8run. Exit emulator with a return value of `N`.
00CN	SCD N	SCHIP-8	Scroll display `N` lines down.
00E0	CLS	CHIP-8	Clears the display. Sets all pixels to `off`.
00EE	RET	CHIP-8	Return from subroutine. Set the `PC` to the address at the top of the stack and subtract `1` from the `SP`.
00FA	COMPAT	CHIP-8	Non-standard. Toggles changing of the `I` register by `save (FX55)` and `restore (FX65)` opcodes.
00FB	SCR	SCHIP-8	Scroll display `4` pixels to the right.
00FC	SCL	SCHIP-8	Scroll display `4` pixels to the left.
00FD	EXIT	SCHIP-8	Exit the interpreter.
00FE	LOW	SCHIP-8	Enable low res (64x32) mode.
00FF	HIGH	SCHIP-8	Enable high res (128x64) mode.
0NNN	CALL NNN	CHIP-8	Call machine language subroutine at address `NNN`.
02A0	STEPCOL	CHIP-8X	Steps background 1 color (-> blue -> black -> green -> red ->)
1NNN	JMP NNN	CHIP-8	Set `PC` to `NNN`.
2NNN	CALL NNN	CHIP-8	Call subroutine a `NNN`. Increment the `SP` and put the current `PC` value on the top of the stack. Then set the `PC` to `NNN`. Generally there is a limit of 16 successive calls.
3XNN	SE VX, NN	CHIP-8	Skip the next instruction if register `VX` is equal to `NN`.
4XNN	SNE VX, NN	CHIP-8	Skip the next instruction if register `VX` is not equal to `NN`.
5XY0	SE VX, VY	CHIP-8	Skip the next instruction if register `VX` equals `VY`.
5XY1	SGT VX, VY	CHIP-8E	Skip the next instruction if register `VX` is greater than `VY`.
5XY1	ADD VX, VY	CHIP-8X	Let `VX = VX + VY` (hex digits 00 to 77) (useful for manipulating the `NH, NV` parameters for low resolution color.)
5XY2	SLT VX, VY	CHIP-8E	Skip the next instruction if register `VX` is less than `VY`.
5XY3	SNE VX, VY	CHIP-8E	Skip the next instruction if register `VX` does not equal `VY`.
6XNN	LD VX, NN	CHIP-8	Load immediate value `NN` into register `VX`.
7XNN	ADD VX, NN	CHIP-8	Add immediate value `NN` to register VX. Does not effect `VF`.
8XY0	LD VX, VY	CHIP-8	Copy the value in register `VY` into `VX`
8XY1	OR VX, VY	CHIP-8	Set `VX` equal to the bitwise `or` of the values in `VX` and `VY`.
8XY2	AND VX, VY	CHIP-8	Set `VX` equal to the bitwise `and` of the values in `VX` and `VY`.
8XY3	XOR VX, VY	CHIP-8	Set `VX` equal to the bitwise `xor` of the values in `VX` and `VY`. Note: This instruction was originally undocumented but functional due to how the 8XXX instructions were implemented on teh COSMAC VIP.
8XY4	ADD VX, VY	CHIP-8	Set `VX` equal to `VX` plus `VY`. In the case of an overflow `VF` is set to `1`. Otherwise `0`.
8XY5	SUB VX, VY	CHIP-8	Set `VX` equal to `VX` minus `VY`. In the case of an underflow `VF` is set `0`. Otherwise `1`. (`VF = VX > VY`)
8XY6	SHR VX, VY	CHIP-8	Set `VX` equal to `VX` bitshifted right `1`. `VF` is set to the least significant bit of `VX` prior to the shift. Originally this opcode meant set `VX` equal to `VY` bitshifted right `1` but emulators and software seem to ignore `VY` now. Note: This instruction was originally undocumented but functional due to how the 8XXX instructions were implemented on teh COSMAC VIP.
8XY7	SUBN VX, VY	CHIP-8	Set `VX` equal to `VY` minus `VX`. `VF` is set to `1` if `VY` > `VX`. Otherwise `0`. Note: This instruction was originally undocumented but functional due to how the 8XXX instructions were implemented on teh COSMAC VIP.
8XYE	SHL VX, VY	CHIP-8	Set `VX` equal to `VX` bitshifted left `1`. `VF` is set to the most significant bit of `VX` prior to the shift. Originally this opcode meant set `VX` equal to `VY` bitshifted left `1` but emulators and software seem to ignore `VY` now. Note: This instruction was originally undocumented but functional due to how the 8XXX instructions were implemented on teh COSMAC VIP.
9XY0	SNE VX, VY	CHIP-8	Skip the next instruction if `VX` does not equal `VY`.
9XY1	MUL VX, VY	CHIP-8E	Set `VF`, `VX` equal to `VX` multipled by `VY` where `VF` is the most significant byte of a 16bit word.
9XY2	DIV VX, VY	CHIP-8E	Set `VX` equal to `VX` divided by `VY`. `VF` is set to the remainder.
9XY3	BCD VX, VY	CHIP-8E	Let `VX`, `VY` be treated as a 16bit word with `VX` the most significant part. Convert that word to BCD and store the 5 digits at memory location `I` through `I+4`. `I` does not change.
ANNN	LD I, NNN	CHIP-8	Set `I` equal to `NNN`.
BNNN	JMP V0, NNN	CHIP-8	Set the `PC` to `NNN` plus the value in `V0`.
B0NN	OUT NN	CHIP-8I	Output `NN` to port.
B1X0	OUT VX	CHIP-8I	Output contents of `VX` to port.
B1X1	IN VX	CHIP-8I	Read input from port and palce in `VX`.
BXY0	COL VX, VY	CHIP-8X	Set `VY` color @ `VX(NH)`, `VX+1(NV)` (provides low resolution color 8x8.)
BXYN	COL VX, VY, N	CHIP-8X	`N != 0`, set `VY` color @ `VX`, `VX+1` byte `N` bytes vertically (provides high resolution 8x32.)
CXNN	RND VX, NN	CHIP-8	Set `VX` equal to a random number ranging from `0` to `255` which is logically `and`ed with `NN`.
DXY0	DRW VX, VX, 0	SCHIP-8	When in high res mode show a `16x16` sprite at `(VX, VY)`.
DXYN	DRW VX, VY, N	CHIP-8	Display `N`-byte sprite starting at memory location `I` at `(VX, VY)`. Each set bit of `xor`ed with what's already drawn. `VF` is set to `1` if a collision occurs. `0` otherwise.
EX9E	SKP VX	CHIP-8	Skip the following instruction if the key represented by the value in `VX` is pressed.
EXA1	SKNP VX	CHIP-8	Skip the following instruction if the key represented by the value in `VX` is not pressed.
EXF2	SKP2 VX	CHIP-8X	Skip the following instruction if the key represented by the value in `VX` is pressed on hex keyboard 2.
EXF5	SKNP2 VX	CHIP-8X	Skip the following instruction the the key represented by the value in `VX` is not pressed on hex keyboard 2.
FX07	LD VX, DT	CHIP-8	Set `VX` equal to the `delay timer`.
FX0A	LD VX, KEY	CHIP-8	Wait for a key press and store the value of the key into `VX`.
FX15	LD DT, VX	CHIP-8	Set the delay timer `DT` to `VX`.
FX18	LD ST, VX	CHIP-8	Set the sound timer `ST` to `VX`.
FX1E	ADD I, VX	CHIP-8	Add `VX` to `I`. `VF` is set to `1` if `I > 0x0FFF`. Otherwise set to `0`.
FX29	LD I, FONT(VX)	CHIP-8	Set `I` to the address of the CHIP-8 8x5 font sprite representing the value in `VX`.
FX30	LD I, FONT(VX)	SCHIP-8	Set `I` to the address of the SCHIP-8 16x10 font sprite representing the value in `VX`.
FX33	BCD VX	CHIP-8	Convert that word to BCD and store the 3 digits at memory location `I` through `I+2`. `I` does not change.
FX55	LD [I], VX	CHIP-8	Store registers `V0` through `VX` in memory starting at location `I`. `I` does not change. '
FX65	LD VX, [I]	CHIP-8	Copy values from memory location `I` through `I + X` into registers `V0` through `VX`. `I` does not change.
FX75	DISP VX	CHIP-8E	Display the value of `VX` on the COSMAC Elf hex display.
FX75	LD R, VX	SCHIP-8	Store `V0` through `VX` to HP-48 RPL user flags (X <= 7).
FX85	LD VX, R	SCHIP-8	Read `V0` through `VX` to HP-48 RPL user flags (X <= 7)
FX94	LD I, VX	CHIP-8E	Load `I` with the address of the font sprite of the `ASCII` value found in `VX`.
FXFB	IN VX	CHIP-8X	Copy contents from `input port` to `VX`. (Waits for EF4=1)
FXF8	OUT VX	CHIP-8X	Output contents of `VX` to `output port`. Used to program simple sound.

Sound

TBD

Display

TBD

Control

TBD

chip-8/chip-8_documentation

ErrorLooks like something went wrong!

About

Resources

Uh oh!

Stars

Watchers

Forks

Releases

Packages 0

Error
Looks like something went wrong!

Packages