- 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 Instructionsby 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.
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 anded 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 xored 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. |
TBD
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