Emma 02

aaa	12 bit address
kk	8 bit constant
n	4 bit constant
x	Register number Vx (x = 0 to F)
y	Register number Vy (y = 0 to F)
I	Register I (12 bit)
[I]	Memory value of address in register I
NH	Bit 0-3 Horizontal Location Bit 4-7, Horizontal width
NV	Bit 0-3 Vertical Location Bit 4-7, Vertical height
1..9, A..F	Hexadecimal digits

Opcode	Mnemonic	Parameter	Definition
Fx1E	ADD	I, Vx	I = I + Vx
7xkk	ADD	Vx, kk	Vx = Vx + kk
8xy4	ADD	Vx, Vy	Vx = Vx + Vy, VF = carry
8xy2	AND	Vx, Vy	Vx = Vx AND Vy, VF undefined
2aaa	CALL	aaa	Call subroutine at aaa (16 levels)
00E0	CLS		Clear display
Dxyn	DRW	Vx, Vy, n	Draw n byte sprite stored at [I] at Vx, Vy. Set VF = collision
1aaa	JP	aaa	Jump to address aaa
Baaa	JP	V0, aaa	Jump to address aaa + V0
Fx33	LD	B, Vx	Store BCD value of Vx in [I], [I+1], [I+2]
Fx15	LD	DT, Vx	Delaytimer = Vx
Fx29	LD	F, Vx	Point I to 5 byte numeric sprite for value in Vx
Aaaa	LD	I, aaa	I = aaa
Fx18	LD	ST, Vx	Soundtimer = Vx
Fx07	LD	Vx, DT	Vx = Delaytimer
Fx0A	LD	Vx, K	Vx = key, wait for keypress
6xkk	LD	Vx, kk	Vx = kk
8xy0	LD	Vx, Vy	Vx = Vy, VF undefined
Fx65	LD	Vx, [I]	Read V0 .. Vx from [I] .. [I+x]
Fx55	LD	[I], Vx	Store V0 .. Vx in [I] .. [I+x]
8xy1	OR	Vx, Vy	Vx = Vx OR Vy, VF undefined
00EE	RETURN		Return from subroutine (16 levels)
Cxkk	RND	Vx , kk	Vx = random AND kk
3xkk	SE	Vx , kk	Skip next instruction if Vx == kk
5xy0	SE	Vx , Vy	Skip next instruction if Vx == Vy
8xxE	SHL	Vx	Vx = Vx << 1, VF = carry
8xyE	SHL	Vx , Vy	Vx = Vy << 1, VF = carry
8xx6	SHR	Vx	Vx = Vx >> 1, VF = carry
8xy6	SHR	Vx , Vy	Vx = Vy >> 1, VF = carry
Ex9E	SKP	Vx	Skip next instruction if key Vx down
ExA1	SKNP	Vx	Skip next instruction if key Vx up
4xkk	SNE	Vx, kk	Skip next instruction if Vx != kk
9xy0	SNE	Vx, Vy	Skip next instruction if Vx != Vy
8xy5	SUB	Vx, Vy	Vx = Vx - Vy, VF = !borrow
8xy7	SUBN	Vx, Vy	Vx = Vy - Vx, VF = !borrow
0aaa	SYS	aaa	Call CDP1802 code at aaa
8xy3	XOR	Vx, Vy	Vx = Vx XOR Vy, VF undefined

All of the instruction from Chip-8, except 'Baaa: JP V0, aaa' are valid for Chip-8X. Chip-8X offers the following additional instructions:

Opcode	Mnemonic	Parameter	Definition
5xy1	ADD8	Vx, Vy	Vx = Vx + Vy (hex digits 00 to 77, mainly for manipulating the NH and NV parameters)
02A0	CLR	B BACK	Step background 1 colour (-> blue, -> black, -> green, -> red ->)
Bxy0	CLR CLRL	Vx, Vy Vx/Vz, Vy	Set Vy colour @ Vx (NH), Vz (Vz has to be V(x+1)) (NV)
Bxyn	CLR CLRH	Vx, Vy, n Vx/Vz, Vy, n	Set Vy colour @ Vx, Vz (Vz has to be V(x+1)) byte, n bytes vertically, n != 0
FxFB	INP1	Vx	Input port 1 to Vx (waits for EF4=1)
FxF8	OUT3	Vx	Vx to output port 3 (used for simple sound)
ExF2	SKP2	Vx	Skip next instruction if key Vx on keypad 2 is down
ExF5	SKNP2	Vx	Skip next instruction if key Vx on keypad 2 is up

All of the instruction from Chip-8 are valid for the TI-660 Chip-8 variant. ETI-660 Chip-8 offers the following additional instruction:

Opcode	Mnemonic	Parameter	Definition
Fx00	LD	P, Vx	Set the pitch (frequency) of the tone generator (beeper) to Vx

EMMA 02