CHIP-8 Instructions

Instructions are divided by Nibble.

Structure

• First Nibble: Instruction type
• Second Nibble (X): one of the registers V0-VF
• Third Nibble (Y): one of the registers V0-VF
• Fourth Nibble (N): A 4-bit number
• Fourth + Fifth Nibble (NN): A 8-bit immediate number
• Fourth + Fifth + Sixth Nibble (NNN): A 12-bit memory address

Instructions Table

Code	Description
00E0	Clear screen
1NNN	Jump, or set PC to NNN
6XNN	Set register VX
7XNN	Add value to register VX. Overflow Flag not affected
ANNN	Set memory register I to NNN
DXYN	Display/Draw N pixel tall sprite from memory location at Index Register I at coordinate VX,VY. All pixels that are 1 in the original sprite will turn the same pixels on at the memory location. If any pixels were turned off, set VF flag to 1. Sprite image should not wrap.
0NNN	Execute subroutine at address NNN
00EE	Return from subroutine by popping last address from stack
2NNN	Call subroutine at memory location NNN
3XNN	Branch statement if VX = NN
4XNN	Branch statement if VX != NN
5XY0	Branch statement if VX = VY
9XY0	Branch statement if VX != VY
8XY0	Set the value VX to VY
8XY1	Set VX to Bitwise OR of VX, VY
8XY2	Set VX to Bitwise AND of VX, VY
8XY3	Set VX to Bitwise XOR of VX, VY
8XY4	Set VX to addition of VX, VY. Affects Carry Flag
8XY5	Set VX to subtraction VX - VY. Set VF to 1 if we have a natural remainder Set VF to 0 if we underflow
8XY7	Set VX to subtraction VY - VX Set VF to 1 if we have a natural remainder Set VF to 0 if we underflow
8XY6	Put value of VY into VX, then Bitwise Right Shift by one Set VF to the bit that was shifted out.
8XYE	Put value of VY into VX, then Bitwise Left Shift by one Set VF to the bit that was shifted out.
BNNN	Jump with offset NNN + V0 used as Jump Table
CXNN	Generate a random number, Bitwise AND with NN and store result in VX
EX9E	Skip instruction (increment PC by 2) if pressing a key corresponding to VX
EXA1	Skip instruction (increment PC by 2) if key in VX is not pressed.
FX07	Set VX to current value of CHIP-8 Delay Timer
FX15	Set CHIP-8 Delay Timer to value in VX
FX18	Set CHIP-8 Sound Timer to value in VX
FX1E	Set Index Register I adds value in VX. Triggers Overflow Flag
FX0A	Yield until key at VX is pressed. Decrements PC if PC is incremented during fetch of Sec-Fetch-Dest
FX29	Index register I set to address of hexadecimal character in VX
FX33	Binary-coded decimal conversion. Takes number in VX and converts it into 3 decimal digits at Index Register I. E.g: VX = 153. Then, I = 1, I+1 = 5, I+2 = 3
FX55	Store all register values up to VX (V0-VX) at I. So: I : V0 I+1 : V1 … I+X : VX
FX65	Load all register values up to VX (V0-VX) starting from I. So: V0 : I … VX : I+X