CPU Instruction Set
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Tables below specify the mnemonic, opcode bytes, clock cycles, affected flags (ordered as znhc), and explanatation. The timings assume a CPU clock frequency of 4.194304 MHz (or 8.4 MHz for CGB in double speed mode), as all gameboy timings are divideable by 4, many people specify timings and clock frequency divided by 4.
Contents
GMB 8bit-Loadcommands
ld r,r xx 4 ---- r=r ld r,n xx nn 8 ---- r=n ld r,(HL) xx 8 ---- r=(HL) ld (HL),r 7x 8 ---- (HL)=r ld (HL),n 36 nn 12 ---- ld A,(BC) 0A 8 ---- ld A,(DE) 1A 8 ---- ld A,(nn) FA 16 ---- ld (BC),A 02 8 ---- ld (DE),A 12 8 ---- ld (nn),A EA 16 ---- ld A,(FF00+n) F0 nn 12 ---- read from io-port n (memory FF00+n) ld (FF00+n),A E0 nn 12 ---- write to io-port n (memory FF00+n) ld A,(FF00+C) F2 8 ---- read from io-port C (memory FF00+C) ld (FF00+C),A E2 8 ---- write to io-port C (memory FF00+C) ldi (HL),A 22 8 ---- (HL)=A, HL=HL+1 ldi A,(HL) 2A 8 ---- A=(HL), HL=HL+1 ldd (HL),A 32 8 ---- (HL)=A, HL=HL-1 ldd A,(HL) 3A 8 ---- A=(HL), HL=HL-1
GMB 16bit-Loadcommands
ld rr,nn x1 nn nn 12 ---- rr=nn (rr may be BC,DE,HL or SP) ld SP,HL F9 8 ---- SP=HL push rr x5 16 ---- SP=SP-2 (SP)=rr (rr may be BC,DE,HL,AF) pop rr x1 12 (AF) rr=(SP) SP=SP+2 (rr may be BC,DE,HL,AF)
GMB 8bit-Arithmetic/logical Commands
add A,r 8x 4 z0hc A=A+r add A,n C6 nn 8 z0hc A=A+n add A,(HL) 86 8 z0hc A=A+(HL) adc A,r 8x 4 z0hc A=A+r+cy adc A,n CE nn 8 z0hc A=A+n+cy adc A,(HL) 8E 8 z0hc A=A+(HL)+cy sub r 9x 4 z1hc A=A-r sub n D6 nn 8 z1hc A=A-n sub (HL) 96 8 z1hc A=A-(HL) sbc A,r 9x 4 z1hc A=A-r-cy sbc A,n DE nn 8 z1hc A=A-n-cy sbc A,(HL) 9E 8 z1hc A=A-(HL)-cy and r Ax 4 z010 A=A & r and n E6 nn 8 z010 A=A & n and (HL) A6 8 z010 A=A & (HL) xor r Ax 4 z000 xor n EE nn 8 z000 xor (HL) AE 8 z000 or r Bx 4 z000 A=A | r or n F6 nn 8 z000 A=A | n or (HL) B6 8 z000 A=A | (HL) cp r Bx 4 z1hc compare A-r cp n FE nn 8 z1hc compare A-n cp (HL) BE 8 z1hc compare A-(HL) inc r xx 4 z0h- r=r+1 inc (HL) 34 12 z0h- (HL)=(HL)+1 dec r xx 4 z1h- r=r-1 dec (HL) 35 12 z1h- (HL)=(HL)-1 daa 27 4 z-0x decimal adjust akku cpl 2F 4 -11- A = A xor FF
GMB 16bit-Arithmetic/logical Commands
add HL,rr x9 8 -0hc HL = HL+rr ;rr may be BC,DE,HL,SP inc rr x3 8 ---- rr = rr+1 ;rr may be BC,DE,HL,SP dec rr xB 8 ---- rr = rr-1 ;rr may be BC,DE,HL,SP add SP,dd E8 16 00hc SP = SP +/- dd ;dd is 8bit signed number ld HL,SP+dd F8 12 00hc HL = SP +/- dd ;dd is 8bit signed number
GMB Rotate- und Shift-Commands
rlca 07 4 000c rotate akku left rla 17 4 000c rotate akku left through carry rrca 0F 4 000c rotate akku right rra 1F 4 000c rotate akku right through carry rlc r CB 0x 8 z00c rotate left rlc (HL) CB 06 16 z00c rotate left rl r CB 1x 8 z00c rotate left through carry rl (HL) CB 16 16 z00c rotate left through carry rrc r CB 0x 8 z00c rotate right rrc (HL) CB 0E 16 z00c rotate right rr r CB 1x 8 z00c rotate right through carry rr (HL) CB 1E 16 z00c rotate right through carry sla r CB 2x 8 z00c shift left arithmetic (b0=0) sla (HL) CB 26 16 z00c shift left arithmetic (b0=0) swap r CB 3x 8 z000 exchange low/hi-nibble swap (HL) CB 36 16 z000 exchange low/hi-nibble sra r CB 2x 8 z00c shift right arithmetic (b7=b7) sra (HL) CB 2E 16 z00c shift right arithmetic (b7=b7) srl r CB 3x 8 z00c shift right logical (b7=0) srl (HL) CB 3E 16 z00c shift right logical (b7=0)
GMB Singlebit Operation Commands
bit n,r CB xx 8 z01- test bit n bit n,(HL) CB xx 12 z01- test bit n set n,r CB xx 8 ---- set bit n set n,(HL) CB xx 16 ---- set bit n res n,r CB xx 8 ---- reset bit n res n,(HL) CB xx 16 ---- reset bit n
GMB CPU-Controlcommands
ccf 3F 4 -00c cy=cy xor 1 scf 37 4 -001 cy=1 nop 00 4 ---- no operation halt 76 N*4 ---- halt until interrupt occurs (low power) stop 10 00 ? ---- low power standby mode (VERY low power) di F3 4 ---- disable interrupts, IME=0 ei FB 4 ---- enable interrupts, IME=1
GMB Jumpcommands
jp nn C3 nn nn 16 ---- jump to nn, PC=nn jp HL E9 4 ---- jump to HL, PC=HL jp f,nn xx nn nn 16;12 ---- conditional jump if nz,z,nc,c jr PC+dd 18 dd 12 ---- relative jump to nn (PC=PC+/-7bit) jr f,PC+dd xx dd 12;8 ---- conditional relative jump if nz,z,nc,c call nn CD nn nn 24 ---- call to nn, SP=SP-2, (SP)=PC, PC=nn call f,nn xx nn nn 24;12 ---- conditional call if nz,z,nc,c ret C9 16 ---- return, PC=(SP), SP=SP+2 ret f xx 20;8 ---- conditional return if nz,z,nc,c reti D9 16 ---- return and enable interrupts (IME=1) rst n xx 16 ---- call to 00,08,10,18,20,28,30,38
