gbz80 man page
gbz80 — CPU opcode reference
Description
This is the list of opcodes supported by rgbasm(1), including a short description, the number of bytes needed to encode them and the number of CPU cycles at 1MHz (or 2MHz in GBC dual speed mode) needed to complete them.
Note: All arithmetic/logic operations that use register A as destination can omit the destination as it is assumed it's register A. The following two lines have the same effect:
OR A,B
OR B
Legend
List of abbreviations used in this document.
 r8
Any of the 8bit registers (A, B, C, D, E, H, L).
 r16
Any of the generalpurpose 16bit registers (BC, DE, HL).
 n8
8bit integer constant.
 n16
16bit integer constant.
 e8
8bit offset (

128 to 127). u3
3bit unsigned integer constant (0 to 7).
 cc

Condition codes:
 Z:
Execute if Z is set.
 NZ:
Execute if Z is not set.
 C:
Execute if C is set.
 NC:
Execute if C is not set.
 vec
One of the RST vectors (0x00, 0x08, 0x10, 0x18, 0x20, 0x28, 0x30 and 0x38).
Instruction Overview
8bit Arithmetic and Logic Instructions
 ADC A,r8
 ADC A,[HL]
 ADC A,n8
 ADD A,r8
 ADD A,[HL]
 ADD A,n8
 AND A,r8
 AND A,[HL]
 AND A,n8
 CP A,r8
 CP A,[HL]
 CP A,n8
 DEC r8
 DEC [HL]
 INC r8
 INC [HL]
 OR A,r8
 OR A,[HL]
 OR A,n8
 SBC A,r8
 SBC A,[HL]
 SBC A,n8
 SUB A,r8
 SUB A,[HL]
 SUB A,n8
 XOR A,r8
 XOR A,[HL]
 XOR A,n8
16bit Arithmetic Instructions
 ADD HL,r16
 DEC r16
 INC r16
Bit Operations Instructions
 BIT u3,r8
 BIT u3,[HL]
 RES u3,r8
 RES u3,[HL]
 SET u3,r8
 SET u3,[HL]
 SWAP r8
 SWAP [HL]
Bit Shift Instructions
 RL r8
 RL [HL]
 Rla
 RLC r8
 RLC [HL]
 Rlca
 RR r8
 RR [HL]
 Rra
 RRC r8
 RRC [HL]
 Rrca
 SLA r8
 SLA [HL]
 SRA r8
 SRA [HL]
 SRL r8
 SRL [HL]
Load Instructions
 LD r8,r8
 LD r8,n8
 LD r16,n16
 LD [HL],r8
 LD [HL],n8
 LD r8,[HL]
 LD [r16],A
 LD [n16],A
 LD [$FF00+n8],A
 LD [$FF00+C],A
 LD A,[r16]
 LD A,[n16]
 LD A,[$FF00+n8]
 LD A,[$FF00+C]
 LD [HL+],A
 LD [HL],A
 LD A,[HL+]
 LD A,[HL]
Jumps and Subroutines
 CALL n16
 CALL cc,n16
 JP HL
 JP n16
 JP cc,n16
 JR e8
 JR cc,e8
 RET cc
 Ret
 Reti
 RST vec
Stack Operations Instructions
 Add Hl,Sp
 ADD SP,e8
 Dec SP
 Inc SP
 LD SP,n16
 LD [n16],SP
 LD HL,SP+e8
 LD Sp,Hl
 POP Af
 POP r16
 Push Af
 PUSH r16
Miscelaneous Instructions
 CCF
 CPL
 Daa
 Di
 Ei
 Halt
 Nop
 SCF
 Stop
Instruction Reference
ADC A,r8
Add the value in r8 plus the carry flag to A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: Set if overflow from bit 3.
 C: Set if overflow from bit 7.
Adc a,[Hl]
Add the value pointed by HL plus the carry flag to A.
Cycles: 2
Bytes: 1
Flags: See ADC A,r8
ADC A,n8
Add the value n8 plus the carry flag to A.
Cycles: 2
Bytes: 2
Flags: See ADC A,r8
ADD A,r8
Add the value in r8 to A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: Set if overflow from bit 3.
 C: Set if overflow from bit 7.
Add a,[Hl]
Add the value pointed by HL to A.
Cycles: 2
Bytes: 1
Flags: See ADD A,r8
ADD A,n8
Add the value n8 to A.
Cycles: 2
Bytes: 2
Flags: See ADD A,r8
ADD HL,r16
Add the value in r16 to HL.
Cycles: 2
Bytes: 1
Flags:
 N: 0
 H: Set if overflow from bit 11.
 C: Set if overflow from bit 15.
Add Hl,Sp
Add the value in SP to HL.
Cycles: 2
Bytes: 1
Flags: See ADD HL,r16
ADD SP,e8
Add the signed value e8 to SP.
Cycles: 4
Bytes: 2
Flags:
 Z: 0
 N: 0
 H: Set if overflow from bit 3.
 C: Set if overflow from bit 7.
AND A,r8
Bitwise AND between the value in r8 and A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: 1
 C: 0
And a,[Hl]
Bitwise AND between the value pointed by HL and A.
Cycles: 2
Bytes: 1
Flags: See AND A,r8
AND A,n8
Bitwise AND between the value in n8 and A.
Cycles: 2
Bytes: 2
Flags: See AND A,r8
BIT u3,r8
Test bit u3 in register r8, set the zero flag if bit not set.
Cycles: 2
Bytes: 2
Flags:
 Z: Set if the selected bit is 0.
 N: 0
 H: 1
BIT u3,[HL]
Test bit u3 in the byte pointed by HL, set the zero flag if bit not set.
Cycles: 3
Bytes: 2
Flags: See BIT u3,r8
CALL n16
Call address n16.
Cycles: 6
Bytes: 3
Flags: None affected.
CALL cc,n16
Call address n16 if condition cc is met.
Cycles: 6/3
Bytes: 3
Flags: None affected.
CCF
Complement Carry Flag.
Cycles: 1
Bytes: 1
Flags:
 N: 0
 H: 0
 C: Complemented.
CP A,r8
Subtract the value in r8 from A and set flags accordingly, but don't store the result.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 1
 H: Set if no borrow from bit 4.
 C: Set if no borrow (set if r8 > A).
CP a,[Hl]
Subtract the value pointed by HL from A and set flags accordingly, but don't store the result.
Cycles: 2
Bytes: 1
Flags: See CP A,r8
CP A,n8
Subtract the value n8 from A and set flags accordingly, but don't store the result.
Cycles: 2
Bytes: 2
Flags: See CP A,r8
CPL
Complement accumulator (A = ~A).
Cycles: 1
Bytes: 1
Flags:
 N: 1
 H: 1
Daa
Decimal adjust register A to get a correct BCD representation after an arithmetic instruction.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 H: 0
 C: Set or reset depending on the operation.
DEC r8
Decrement value in register r8 by 1.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 1
 H: Set if no borrow from bit 4.
Dec [Hl]
Decrement the value pointed by HL by 1.
Cycles: 3
Bytes: 1
Flags: See DEC r8
DEC r16
Decrement value in register r16 by 1.
Cycles: 2
Bytes: 1
Flags: None affected.
Dec SP
Decrement value in register SP by 1.
Cycles: 2
Bytes: 1
Flags: None affected.
Di
Disable Interrupts.
Cycles: 1
Bytes: 1
Flags: None affected.
Ei
Enable Interrupts.
Cycles: 1
Bytes: 1
Flags: None affected.
Halt
Enter CPU low power mode.
Cycles: 
Bytes: 1
Flags: None affected.
INC r8
Increment value in register r8 by 1.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: Set if overflow from bit 3.
Inc [Hl]
Increment the value pointed by HL by 1.
Cycles: 3
Bytes: 1
Flags: See INC r8
INC r16
Increment value in register r16 by 1.
Cycles: 2
Bytes: 1
Flags: None affected.
Inc SP
Increment value in register SP by 1.
Cycles: 2
Bytes: 1
Flags: None affected.
JP n16
Absolute jump to address n16.
Cycles: 4
Bytes: 3
Flags: None affected.
JP cc,n16
Absolute jump to address n16 if condition cc is met.
Cycles: 4/3
Bytes: 3
Flags: None affected.
JP HL
Jump to address in HL, that is, load PC with value in register HL.
Cycles: 1
Bytes: 1
Flags: None affected.
JR e8
Relative jump by adding e8 to the current address.
Cycles: 3
Bytes: 2
Flags: None affected.
JR cc,e8
Relative jump by adding e8 to the current address if condition cc is met.
Cycles: 3/2
Bytes: 2
Flags: None affected.
LD r8,r8
Store value in register on the right into register on the left.
Cycles: 1
Bytes: 1
Flags: None affected.
LD r8,n8
Load value n8 into register r8.
Cycles: 2
Bytes: 2
Flags: None affected.
LD r16,n16
Load value n16 into register r16.
Cycles: 3
Bytes: 3
Flags: None affected.
LD [HL],r8
Store value in register r8 into byte pointed by register HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD [HL],n8
Store value n8 into byte pointed by register HL.
Cycles: 3
Bytes: 2
Flags: None affected.
LD r8,[HL]
Load value into register r8 from byte pointed by register HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD [r16],A
Store value in register A into address pointed by register r16.
Cycles: 2
Bytes: 1
Flags: None affected.
LD [n16],A
Store value in register A into address n16.
Cycles: 4
Bytes: 3
Flags: None affected.
LD [$FF00+n8],A
Store value in register A into high RAM or I/O registers.
The following synonym forces this encoding: LDH [$FF00+n8],A
Cycles: 3
Bytes: 2
Flags: None affected.
LD [$Ff00+C],a
Store value in register A into high RAM or I/O registers.
Cycles: 2
Bytes: 1
Flags: None affected.
LD A,[r16]
Load value in register A from address pointed by register r16.
Cycles: 2
Bytes: 1
Flags: None affected.
LD A,[n16]
Load value in register A from address n16.
Cycles: 4
Bytes: 3
Flags: None affected.
LD A,[$FF00+n8]
Load value in register A from high RAM or I/O registers.
The following synonym forces this encoding: LDH A,[$FF00+n8]
Cycles: 3
Bytes: 2
Flags: None affected.
LD a,[$Ff00+C]
Load value in register A from high RAM or I/O registers.
Cycles: 2
Bytes: 1
Flags: None affected.
LD [Hl+],a
Store value in register A into byte pointed by HL and postincrement HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD [Hl],a
Store value in register A into byte pointed by HL and postdecrement HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD a,[Hl+]
Load value into register A from byte pointed by HL and postincrement HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD a,[Hl]
Load value into register A from byte pointed by HL and postdecrement HL.
Cycles: 2
Bytes: 1
Flags: None affected.
LD SP,n16
Load value n16 into register SP.
Cycles: 3
Bytes: 3
Flags: None affected.
LD [n16],SP
Store SP into addresses n16 (LSB) and n16 + 1 (MSB).
Cycles: 5
Bytes: 3
Flags: None affected.
LD HL,SP+e8
Add the signed value e8 to SP and store the result in HL.
Cycles: 3
Bytes: 2
Flags:
 Z: 0
 N: 0
 H: Set if overflow from bit 3.
 C: Set if overflow from bit 7.
LD Sp,Hl
Load register HL into register SP.
Cycles: 2
Bytes: 1
Flags: None affected.
Nop
No operation.
Cycles: 1
Bytes: 1
Flags: None affected.
OR A,r8
Bitwise OR between the value in r8 and A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: 0
Or a,[Hl]
Bitwise OR between the value pointed by HL and A.
Cycles: 2
Bytes: 1
Flags: See OR A,r8
OR A,n8
Bitwise OR between the value in n8 and A.
Cycles: 2
Bytes: 2
Flags: See OR A,r8
POP Af
Pop register AF from the stack.
Cycles: 3
Bytes: 1
Flags: None affected.
POP r16
Pop register r16 from the stack.
Cycles: 3
Bytes: 1
Flags: None affected.
Push Af
Push register AF into the stack.
Cycles: 4
Bytes: 1
Flags: None affected.
PUSH r16
Push register r16 into the stack.
Cycles: 4
Bytes: 1
Flags: None affected.
RES u3,r8
Set bit u3 in register r8 to 0.
Cycles: 2
Bytes: 2
Flags: None affected.
RES u3,[HL]
Set bit u3 in the byte pointed by HL to 0.
Cycles: 4
Bytes: 2
Flags: None affected.
Ret
Return from subroutine.
Cycles: 4
Bytes: 1
Flags: None affected.
RET cc
Return from subroutine if condition cc is met.
Cycles: 5/2
Bytes: 1
Flags: None affected.
Reti
Return from subroutine and enable interrupts.
Cycles: 4
Bytes: 1
Flags: None affected.
RL r8
Rotate register r8 left through carry.
C < [7 < 0] < C
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
RL [Hl]
Rotate value pointed by HL left through carry.
C < [7 < 0] < C
Cycles: 4
Bytes: 2
Flags: See RL r8
Rla
Rotate register A left through carry.
C < [7 < 0] < C
Cycles: 1
Bytes: 1
Flags:
 Z: 0
 N: 0
 H: 0
 C: Set according to result.
RLC r8
Rotate register r8 left.
C < [7 < 0] < [7]
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
RLC [Hl]
Rotate value pointed by HL left.
C < [7 < 0] < [7]
Cycles: 4
Bytes: 2
Flags: See RLC r8
Rlca
Rotate register A left.
C < [7 < 0] < [7]
Cycles: 1
Bytes: 1
Flags:
 Z: 0
 N: 0
 H: 0
 C: Set according to result.
RR r8
Rotate register r8 right through carry.
C > [7 > 0] > C
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
RR [Hl]
Rotate value pointed by HL right through carry.
C > [7 > 0] > C
Cycles: 4
Bytes: 2
Flags: See RR r8
Rra
Rotate register A right through carry.
C > [7 > 0] > C
Cycles: 1
Bytes: 1
Flags:
 Z: 0
 N: 0
 H: 0
 C: Set according to result.
RRC r8
Rotate register r8 right.
[0] > [7 > 0] > C
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
RRC [Hl]
Rotate value pointed by HL right.
[0] > [7 > 0] > C
Cycles: 4
Bytes: 2
Flags: See RRC r8
Rrca
Rotate register A right.
[0] > [7 > 0] > C
Cycles: 1
Bytes: 1
Flags:
 Z: 0
 N: 0
 H: 0
 C: Set according to result.
RST vec
Call restart vector vec.
Cycles: 4
Bytes: 1
Flags: None affected.
SBC A,r8
Subtract the value in r8 and the carry flag from A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 1
 H: Set if no borrow from bit 4.
 C: Set if no borrow (set if r8 > A).
SBC a,[Hl]
Subtract the value pointed by HL and the carry flag from A.
Cycles: 2
Bytes: 1
Flags: See SBC A,r8
SBC A,n8
Subtract the value n8 and the carry flag from A.
Cycles: 2
Bytes: 2
Flags: See SBC A,r8
SCF
Set Carry Flag.
Cycles: 1
Bytes: 1
Flags:
 N: 0
 H: 0
 C: 1
SET u3,r8
Set bit u3 in register r8 to 1.
Cycles: 2
Bytes: 2
Flags: None affected.
SET u3,[HL]
Set bit u3 in the byte pointed by HL to 1.
Cycles: 4
Bytes: 2
Flags: None affected.
SLA r8
Shift left arithmetic register r8.
C < [7 < 0] < 0
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
Sla [Hl]
Shift left arithmetic value pointed by HL.
C < [7 < 0] < 0
Cycles: 4
Bytes: 2
Flags: See SLA r8
SRA r8
Shift right arithmetic register r8.
[7] > [7 > 0] > C
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
Sra [Hl]
Shift right arithmetic value pointed by HL.
[7] > [7 > 0] > C
Cycles: 4
Bytes: 2
Flags: See SRA r8
SRL r8
Shift right logic register r8.
0 > [7 > 0] > C
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: Set according to result.
SRL [Hl]
Shift right logic value pointed by HL.
0 > [7 > 0] > C
Cycles: 4
Bytes: 2
Flags: See SRA r8
Stop
Enter CPU very low power mode. Also used to switch between doube speed and normal CPU modes in GBC.
Cycles: 
Bytes: 2
Flags: None affected.
SUB A,r8
Subtract the value in r8 from A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 1
 H: Set if no borrow from bit 4.
 C: Set if no borrow (set if r8 > A).
Sub a,[Hl]
Subtract the value pointed by HL from A.
Cycles: 2
Bytes: 1
Flags: See SUB A,r8
SUB A,n8
Subtract the value n8 from A.
Cycles: 2
Bytes: 2
Flags: See SUB A,r8
SWAP r8
Swap upper 4 bits in register r8 and the lower ones.
Cycles: 2
Bytes: 2
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: 0
Swap [Hl]
Swap upper 4 bits in the byte pointed by HL and the lower ones.
Cycles: 4
Bytes: 2
Flags: See SWAP r8
XOR A,r8
Bitwise XOR between the value in r8 and A.
Cycles: 1
Bytes: 1
Flags:
 Z: Set if result is 0.
 N: 0
 H: 0
 C: 0
Xor a,[Hl]
Bitwise XOR between the value pointed by HL and A.
Cycles: 2
Bytes: 1
Flags: See XOR A,r8
XOR A,n8
Bitwise XOR between the value in n8 and A.
Cycles: 2
Bytes: 2
Flags: See XOR A,r8
See Also
History
rgbds was originally written by Carsten Sørensen as part of the ASMotor package, and was later packaged in RGBDS by Justin Lloyd. It is now maintained by a number of contributors at https://github.com/rednex/rgbds.
Referenced By
rgbasm(1), rgbasm(5), rgbds(5), rgbds(7), rgbgfx(1).