# nlitsme/AVRInstructionSet

Investigating the AVR / Arduino instruction set
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# investigating the AVR instruction set.

## Unallocated opcodes

There are some unallocated opcodes, they are listed at the bottom of the instruction table below. I used this python script to verify that the table below has all possible bit combinations listed.

Then i investigated the unallocated codes using this arduino project

## conditions

Test Boolean Mnemonic Complementary Boolean Mnemonic Comment
Rd > Rr Z & (N ^ V) = 0 BRLT(1) Rd <= Rr Z+(N ^ V) = 1 BRGE* Signed
Rd >= Rr (N ^ V) = 0 BRGE Rd < Rr (N ^ V) = 1 BRLT Signed
Rd = Rr Z=1 BREQ Rd != Rr Z=0 BRNE Signed
Rd <= Rr Z+(N ^ V) = 1 BRGE(1) Rd > Rr Z & (N ^ V) = 0 BRLT* Signed
Rd < Rr (N ^ V) = 1 BRLT Rd >= Rr (N ^ V) = 0 BRGE Signed
Rd > Rr C+Z=0 BRLO(1) Rd <= Rr C+Z=1 BRSH* Unsigned
Rd >= Rr C=0 BRSH/BRCC Rd < Rr C=1 BRLO/BRCS Unsigned
Rd = Rr Z=1 BREQ Rd != Rr Z=0 BRNE Unsigned
Rd <= Rr C+Z=1 BRSH(1) Rd > Rr C+Z=0 BRLO* Unsigned
Rd < Rr C=1 BRLO/BRCS Rd >= Rr C=0 BRSH/BRCC Unsigned
Carry C=1 BRCS No carry C=0 BRCC Simple
Negative N=1 BRMI Positive N=0 BRPL Simple
Overflow V=1 BRVS No overflow V=0 BRVC Simple
Zero Z=1 BREQ Not zero Z=0 BRNE Simple

## instructions

A prettier table can be found here

Opcode Mnemonics Operands Description Operation Flags #Clocks #Clocks XMEGA Note Remarks
Arithmetic and Logic Instructions
0000 11rd dddd rrrr ADD Rd, Rr Add without Carry Rd ← Rd+Rr Z,C,N,V,S,H 1 -
0001 11rd dddd rrrr ADC Rd, Rr Add with Carry Rd ← Rd+Rr+C Z,C,N,V,S,H 1 -
1001 0110 KKdd KKKK ADIW Rd, K Add Immediate to Word Rd ← Rd+1:Rd+K Z,C,N,V,S 2 - (1) d in {24,26,28,30}
0001 10rd dddd rrrr SUB Rd, Rr Subtract without Carry Rd ← Rd-Rr Z,C,N,V,S,H 1 -
0101 KKKK dddd KKKK SUBI Rd, K Subtract Immediate Rd ← Rd-K Z,C,N,V,S,H 1 -
0000 10rd dddd rrrr SBC Rd, Rr Subtract with Carry Rd ← Rd-Rr-C Z,C,N,V,S,H 1 -
0100 KKKK dddd KKKK SBCI Rd, K Subtract Immediate with Carry Rd ← Rd-K-C Z,C,N,V,S,H 1 - d=16..31
1001 0111 KKdd KKKK SBIW Rd, K Subtract Immediate from Word Rd+1:Rd ← Rd+1:Rd-K Z,C,N,V,S 2 - (1) d in {24,26,28,30}
0010 00rd dddd rrrr AND Rd, Rr Logical AND Rd ← Rd & Rr Z,N,V,S 1 -
0111 KKKK dddd KKKK ANDI Rd, K Logical AND with Immediate Rd ← Rd & K Z,N,V,S 1 - d = 16..31
0010 10rd dddd rrrr OR Rd, Rr Logical OR Rd ← Rd Rr Z,N,V,S 1 -
0110 KKKK dddd KKKK ORI Rd, K Logical OR with Immediate Rd ← Rd K Z,N,V,S 1 -
0010 01rd dddd rrrr EOR Rd, Rr Exclusive OR Rd ← Rd^Rr Z,N,V,S 1 -
1001 010d dddd 0000 COM Rd One's Complement Rd ← \$FF-Rd Z,C,N,V,S 1 -
1001 010d dddd 0001 NEG Rd Two's Complement Rd ← \$00-Rd Z,C,N,V,S,H 1 -
0110 KKKK dddd KKKK SBR Rd,K Set Bit(s) in Register Rd ← Rd or K Z,N,V,S 1 - alias for ORI Rd,K
0111 KKKK dddd KKKK CBR Rd,K Clear Bit(s) in Register Rd ← Rd & (\$FFh-K) Z,N,V,S 1 - alias
1001 010d dddd 0011 INC Rd Increment Rd ← Rd+1 Z,N,V,S 1 -
1001 010d dddd 1010 DEC Rd Decrement Rd ← Rd-1 Z,N,V,S 1 -
0010 00dd dddd dddd TST Rd Test for Zero or Minus Rd ← Rd & Rd Z,N,V,S 1 - alias for AND Rd,Rd
0010 01dd dddd dddd CLR Rd Clear Register Rd ← Rd xor Rd Z,N,V,S 1 - alias for EOR Rd,Rd
1110 1111 dddd 1111 SER Rd Set Register Rd ← \$FF None 1 - alias for LDI Rd,0xFF
1001 11rd dddd rrrr MUL Rd,Rr Multiply Unsigned R1:R0 ← Rd x Rr (UU) Z,C 2 - (1)
0000 0010 dddd rrrr MULS Rd,Rr Multiply Signed R1:R0 ← Rd x Rr (SS) Z,C 2 - (1) d,r=16..31
0000 0011 0ddd 0rrr MULSU Rd,Rr Multiply Signed with Unsigned R1:R0 ← Rd x Rr (SU) Z,C 2 - (1) d,r=16..23
0000 0011 0ddd 1rrr FMUL Rd,Rr Fractional Multiply Unsigned R1:R0 ← Rd x Rr<<1 (UU) Z,C 2 - (1) r,d = 16..23
0000 0011 1ddd 0rrr FMULS Rd,Rr Fractional Multiply Signed R1:R0 ← Rd x Rr<<1 (SS) Z,C 2 - (1) r,d = 16..23
0000 0011 1ddd 1rrr FMULSU Rd,Rr Fractional Multiply Signed with Unsigned R1:R0 ← Rd x Rr<<1 (SU) Z,C 2 - (1) r,d = 16..23
1001 0100 KKKK 1011 DES K Data Encryption if (H = 0) then R15:R0 ← Encrypt(R15:R0, K) else if (H = 1) then R15:R0 ← Decrypt(R15:R0, K) - - 1/2
Branch Instructions
1100 kkkk kkkk kkkk RJMP k Relative Jump PC ← PC+k+1 None 2 -
1001 0100 0000 1001 IJMP Z Indirect Jump to (Z) PC(15:0) ← Z, PC(21:16) ← 0 None 2 - (1)
1001 0100 0001 1001 EIJMP EIND:Z Extended Indirect Jump to (Z) PC(15:0) ← Z, PC(21:16) ← EIND None 2 - (1)
1001 010k kkkk 110k K JMP k Jump PC ← k None 3 - (1) two words
1101 kkkk kkkk kkkk RCALL k Relative Call Subroutine PC ← PC+k+1 None 3 / 4(3)(5) 2 / 3(3)
1001 0101 0000 1001 ICALL Z Indirect Call to (Z) PC(15:0) ← Z, PC(21:16) ← 0 None 3 / 4(3) 2 / 3(3) (1)
1001 0101 0001 1001 EICALL EIND:Z Extended Indirect Call to (Z) PC(15:0) ← Z, PC(21:16) ← EIND None 4 (3) 3 (3) (1)
1001 010k kkkk 111k K CALL k call Subroutine PC ← k, STACK ← PC, SP ← SP-2 None 4 / 5(3) 3 / 4(3) (1) two words
1001 0101 0000 1000 RET - Subroutine Return PC ← STACK None 4 / 5(3) -
1001 0101 0001 1000 RETI - Interrupt Return PC ← STACK I 4 / 5(3) -
0001 00rd dddd rrrr CPSE Rd,Rr Compare, Skip if Equal if(Rd=Rr)PC ← PC+2or3 None 1/2/3 -
0001 01rd dddd rrrr CP Rd,Rr Compare Rd - Rr Z,C,N,V,S,H 1 -
0000 01rd dddd rrrr CPC Rd,Rr Compare with Carry Rd - Rr - C Z,C,N,V,S,H 1 -
0011 KKKK dddd KKKK CPI Rd,K Compare with Immediate Rd - K Z,C,N,V,S,H 1 - d = 16..31
1111 110r rrrr 0bbb SBRC Rr, b Skip if Bit in Register Cleared if(Rr(b)=0)PC ← PC+2or3 None 1/2/3 -
1111 111r rrrr 0bbb SBRS Rr, b Skip if Bit in Register Set if(Rr(b)=1)PC ← PC+2or3 None 1/2/3 -
1001 1001 AAAA Abbb SBIC A, b Skip if Bit in I/O Register Cleared if(I/O(A,b)=0)PC ← PC+2or3 None 1/2/3 2/3/4
1001 1011 AAAA Abbb SBIS A, b Skip if Bit in I/O Register Set If(I/O(A,b)=1)PC ← PC+2or3 None 1/2/3 2/3/4
1111 00kk kkkk k000 BRCS k Branch if Carry Set if(C=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k000 BRLO k Branch if Lower if(C=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k001 BREQ k Branch if Equal if(Z=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k010 BRMI k Branch if Minus if(N=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k011 BRVS k Branch if Overflow Flag is Set if(V=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k100 BRLT k Branch if Less Than, Signed if(N^V=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k101 BRHS k Branch if Half Carry Flag Set if(H=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k110 BRTS k Branch if T Flag Set if(T=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk k111 BRIE k Branch if Interrupt Enabled if(I=1)thenPC ← PC+k+1 None 1/2 - alias
1111 00kk kkkk ksss BRBS s, k Branch if Status Flag Set if(SREG(s)=1)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k000 BRCC k Branch if Carry Cleared if(C=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k000 BRSH k Branch if Same or Higher if(C=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k001 BRNE k Branch if Not Equal if(Z=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k010 BRPL k Branch if Plus if(N=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k011 BRVC k Branch if Overflow Flag is Cleared if(V=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k100 BRGE k Branch if Greater or Equal, Signed if(N^V=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k101 BRHC k Branch if Half Carry Flag Cleared if(H=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k110 BRTC k Branch if T Flag Cleared if(T=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk k111 BRID k Branch if Interrupt Disabled if(I=0)thenPC ← PC+k+1 None 1/2 - alias
1111 01kk kkkk ksss BRBC s, k Branch if Status Flag Cleared if(SREG(s)=0)thenPC ← PC+k+1 None 1/2 - alias
Data Transfer Instructions
0010 11rd dddd rrrr MOV Rd, Rr Copy Register Rd ← Rr None 1 -
0000 0001 dddd rrrr MOVW Rd, Rr Copy Register Pair Rd+1:Rd ← Rr+1:Rr None 1 - (1)
1110 KKKK dddd KKKK LDI Rd, K Load Immediate Rd ← K None 1 - d=16..31
1001 000d dddd 0000 K LDS Rd, k Load Direct from data space Rd ← (k) None 1(5)/2(3) 2(3)(4) (1) attiny only, two words
1010 0kkk dddd kkkk LDS Rd, k Load Direct from data space Rd ← (k) None 1(5)/2(3) 2(3)(4) (1)
1001 000d dddd 1100 LD Rd, X Load Indirect Rd ← (X) None 1(5)2(3) 1(3)(4) (2)
1001 000d dddd 1101 LD Rd, X+ Load Indirect and Post-Increment Rd ← (X) X←X+1 None 2(3) 1(3)(4) (2)
1001 000d dddd 1110 LD Rd, -X Load Indirect and Pre-Decrement X←X-1, ← X-1 Rd←(X) ← (X) None 2(3)/3(5) 2(3)(4) (2)
1000 000d dddd 1000 LD Rd, Y Load Indirect Rd←(Y) ← (Y) None 1(5)/2(3) 1(3)(4) (2) alias for LDD Rd,Y+0
1001 000d dddd 1001 LD Rd, Y+ Load Indirect and Post-Increment Rd ← (Y) Y←Y+1 None 2(3) 1(3)(4) (2)
1001 000d dddd 1010 LD Rd, -Y Load Indirect and Pre-Decrement Y←Y-1 Rd ← (Y) None 2(3)/3(5) 2(3)(4) (2)
10q0 qq0d dddd 1qqq LDD Rd, Y+q Load Indirect with Displacement Rd ← (Y+q) None 2(3) 2(3)(4) (1)
1000 000d dddd 0000 LD Rd, Z Load Indirect Rd ← (Z) None 1(5)/2(3) 1(3)(4) (2) alias for LDD Rd,Z+0
1001 000d dddd 0001 LD Rd, Z+ Load Indirect and Post-Increment Rd ← (Z), Z ← Z+1 None 2(3) 1(3)(4) (2)
1001 000d dddd 0010 LD Rd, -Z Load Indirect and Pre-Decrement Z ← Z-1, Rd ← (Z) None 2(3)/3(5) 2(3)(4) (2)
10q0 qq0d dddd 0qqq LDD Rd, Z+q Load Indirect with Displacement Rd ← (Z+q) None 2(3) 2(3)(4) (1)
1001 001d dddd 0000 K STS k, Rr Store Direct to Data Space (k) ← Rd None 1(5)/2(3) 2(3) (1) attiny only, two words
1010 1kkk dddd kkkk STS k, Rr Store Direct to Data Space (k) ← Rd None 1(5)/2(3) 2(3) (1)
1001 001r rrrr 1100 ST X, Rr Store Indirect (X) ← Rr None 1(5)/2(3) 1(3) (2)
1001 001r rrrr 1101 ST X+, Rr Store Indirect and Post-Increment (X) ← Rr, X←X+1 None 1(5)/2(3) 1(3) (2)
1001 001r rrrr 1110 ST -X, Rr Store Indirect and Pre-Decrement X ← X-1, (X) ← Rr None 2(3) 2(3) (2)
1000 001r rrrr 1000 ST Y, Rr Store Indirect (Y) ← Rr None 1(5)/2(3) 1(3) (2) alias for STD Y+0,Rr
1001 001r rrrr 1001 ST Y+, Rr Store Indirect and Post-Increment (Y) ← Rr, Y←Y+1 None 1(5)/2(3) 1(3) (2)
1001 001r rrrr 1010 ST -Y, Rr Store Indirect and Pre-Decrement Y ← Y-1, (Y) ← Rr None 2(3) 2(3) (2)
10q0 qq1r rrrr 1qqq STD Y+q, Rr Store Indirect with Displacement (Y+q) ← Rr None 2(3) 2(3) (1)
1000 001r rrrr 0000 ST Z, Rr Store Indirect (Z) ← Rr None 1(5)/2(3) 1(3) (2) alias for STD Z+0,Rr
1001 001r rrrr 0001 ST Z+, Rr Store Indirect and Post-Increment (Z) ← Rr Z←Z+1 None 1(5)/2(3) 1(3) (2)
1001 001r rrrr 0010 ST -Z, Rr Store Indirect and Pre-Decrement Z←Z-1 None 2(3) 2(3) (2)
10q0 qq1r rrrr 0qqq STD Z+q,Rr Store Indirect with Displacement (Z+q) ← Rr None 2(3) 2(3) (1)
1001 0101 1100 1000 LPM - Load Program Memory R0 ← (Z) None 3 3 (1)(2)
1001 000d dddd 0100 LPM Rd, Z Load Program Memory Rd ← (Z) None 3 3 (1)(2)
1001 000d dddd 0101 LPM Rd, Z+ Load Program Memory and Post- Increment Rd ← (Z), Z←Z+1 None 3 3 (1)(2)
1001 0101 1101 1000 ELPM R0,Z Extended Load Program Memory R0 ← (RAMPZ:Z) None 3 - (1)
1001 000d dddd 0110 ELPM Rd, Z Extended Load Program Memory Rd ← (RAMPZ:Z) None 3 - (1)
1001 000d dddd 0111 ELPM Rd, Z+ Extended Load Program Memory and Post-Increment Rd ← (RAMPZ:Z), Z←Z+1 None 3 - (1)
1001 0101 1110 1000 SPM Z Store Program Memory (RAMPZ:Z) ← R1:R0 None - - (1)
1001 0101 1111 1000 ESPM Z+ Store Program Memory and Post- Increment by 2 (RAMPZ:Z) ← R1:R0, Z←Z+2 None - - (1)
1011 0AAd dddd AAAA IN Rd, A In From I/O Location Rd ← I/O(A) None 1 -
1011 1AAr rrrr AAAA OUT A, Rr Out To I/O Location I/O(A) ← Rr None 1 -
1001 001d dddd 1111 PUSH Rr Push Register on Stack STACK ← Rr None 2 1(3) (1)
1001 000d dddd 1111 POP Rd Pop Register from Stack Rd ← STACK None 2 2(3) (1)
1001 001r rrrr 0100 XCH Z, Rd Exchange (Z) ← Rd, Rd ← (Z) None 1 -
1001 001r rrrr 0101 LAS Z, Rd Load and Set (Z) ← Rd (Z) Rd ← (Z) None 1 -
1001 001r rrrr 0110 LAC Z, Rd Load and Clear (Z) ← (\$FF - Rd) & (Z) Rd ← (Z) None 1 -
1001 001r rrrr 0111 LAT Z, Rd Load and Toggle (Z) ← Rd^(Z) Rd ← (Z) None 1 -
Bit and Bit-test Instructions
0000 11dd dddd dddd LSL Rd Logical Shift Left Rd(n+1) ← Rd(n), Rd(0) ← 0, C ← Rd(7) Z,C,N,V,H 1 - alias for ADD Rd,Rd
1001 010d dddd 0110 LSR Rd Logical Shift Right Rd(n) ← Rd(n+1), Rd(7) ← 0, C ← Rd(0) Z,C,N,V 1 -
0001 11dd dddd dddd ROL Rd Rotate Left Through Carry Rd(0) ← C, Rd(n+1) ← Rd(n), C ← Rd(7) Z,C,N,V,H 1 - alias for ADC Rd,Rd
1001 010d dddd 0111 ROR Rd Rotate Right Through Carry Rd(7) ← C, Rd(n) ← Rd(n+1), C ← Rd(0) Z,C,N,V 1 -
1001 010d dddd 0101 ASR Rd Arithmetic Shift Right Rd(n) ← Rd(n+1), n=0..6, Rd(7) ← Rd(7), C ← Rd(0) Z,C,N,V 1 -
1001 010d dddd 0010 SWAP Rd Swap Nibbles Rd(3..0) ↔ Rd(7..4) None 1 -
1001 0100 0sss 1000 BSET s Flag Set SREG(s) ← 1 SREG(s) 1 -
1001 0100 1sss 1000 BCLR s Flag Clear SREG(s) ← 0 SREG(s) 1 - s = 0-7 = C,Z,N,V,S,H,T,I
1001 1010 AAAA Abbb SBI A, b Set Bit in I/O Register I/O(A,b) ← 1 None 1(5)2 1
1001 1000 AAAA Abbb CBI A, b Clear Bit in I/O Register I/O(A,b) ← 0 None 1(5)/2 1
1111 101d dddd 0bbb BST Rr, b Bit Store from Register to T T ← Rr(b) T 1 -
1111 100d dddd 0bbb BLD Rd, b Bit load from T to Register Rd(b) ← T None 1 -
1001 0100 0000 1000 SEC - Set Carry C←1 C 1 - alias
1001 0100 1000 1000 CLC - Clear Carry C←0 C 1 - alias
1001 0100 0010 1000 SEN - Set Negative Flag N←1 N 1 - alias
1001 0100 1010 1000 CLN - Clear Negative Flag N←0 N 1 - alias
1001 0100 0001 1000 SEZ - Set Zero Flag Z←1 Z 1 - alias
1001 0100 1001 1000 CLZ - Clear Zero Flag Z←0 Z 1 - alias
1001 0100 0111 1000 SEI - Global Interrupt Enable I←1 I 1 - alias
1001 0100 1111 1000 CLI - Global Interrupt Disable I←0 I 1 - alias
1001 0100 0100 1000 SES - Set Signed Test Flag S←1 S 1 - alias
1001 0100 1100 1000 CLS - Clear Signed Test Flag S←0 S 1 - alias
1001 0100 0011 1000 SEV - Set Two's Complement Overflow V←1 V 1 - alias
1001 0100 1011 1000 CLV - Clear Two's Complement Overflow V←0 V 1 - alias
1001 0100 0110 1000 SET - Set T in SREG T←1 T 1 - alias
1001 0100 1110 1000 CLT - Clear T in SREG T←0 T 1 - alias
1001 0100 0101 1000 SEH - Set Half Carry Flag in SREG H←1 H 1 - alias
1001 0100 1101 1000 CLH - Clear Half Carry Flag in SREG H←0 H 1 - alias
MCU Control Instructions
1001 0101 1001 1000 BREAK - Break (See specific descr. for BREAK) None 1 - (1)
0000 0000 0000 0000 NOP - No Operation - None 1 -
1001 0101 1000 1000 SLEEP - Sleep (see specific descr. for Sleep) None 1 -
1001 0101 1010 1000 WDR - Watchdog Reset (see specific descr. for WDR) None 1 -
unallocated codes
0000 0000 xxxx xxxx NOP (7) x!=0
1001 000x xxxx 0011 NOP (7)
1001 000x xxxx 1000 NOP (7)
1001 000x xxxx 1011 NOP (7)
1001 001x xxxx 0011 NOP (7)
1001 001x xxxx 1000 NOP (7)
1001 001x xxxx 1011 NOP (7)
1001 0101 xxxx 1001 (E)ICALL (7) x!={0,1}
1001 0101 0xxx 1000 (I)RET (7) x!={0,1}
1001 0101 1011 1000 NOP (7)
1001 010x xxxx 0100 NOP (7)
1001 0101 xxxx 1011 NOP (7)
1001 0100 xxxx 1001 (E)IJMP (7) x!={0,1}
1111 100x xxxx 1xxx BLD Rd,b (7)
1111 101x xxxx 1xxx BST Rd,b (7)
1111 110x xxxx 1xxx SBRC Rr,b (7)
1111 111x xxxx 1xxx SBRS Rr,b (7)
1. This instruction is not available in all devices. Refer to the device specific instruction set summary.

2. Not all variants of this instruction are available in all devices. Refer to the device specific instruction set summary.

3. Cycle times for Data memory accesses assume internal memory accesses, and are not valid for accesses via the external RAM interface.

4. One extra cycle must be added when accessing Internal SRAM.

5. Number of clock cycles for Reduced Core tinyAVR®.

6. SPM should be called ESPM, since it addresses through RAMPZ

7. Some of the unallocated codes are actually aliases for existing instructions.