Sunday, February 26, 2012

8051 Instruction Set:

Instructions by OPCODE

0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
0x08
0x09
0x0a
0x0b
0x0c
0x0d
0x0e
0x0f
0x00
NOP
AJMP
LJMP
RR
INC
INC
INC
INC
INC
INC
INC
INC
INC
INC
INC
INC
0x10
JBC
ACALL
LCALL
RRC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
DEC
0x20
JB
AJMP
RET
RL
ADD
ADD
ADD
ADD
ADD
ADD
ADD
ADD
ADD
ADD
ADD
ADD
0x30
JNB
ACALL
RETI
RLC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
ADDC
0x40
JC
AJMP
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
ORL
0x50
JNC
ACALL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
ANL
0x60
JZ
AJMP
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
XRL
0x70
JNZ
ACALL
ORL
JMP
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
0x80
SJMP
AJMP
ANL
MOVC
DIV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
0x90
MOV
ACALL
MOV
MOVC
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
SUBB
0xa0
ORL
AJMP
MOV
INC
MUL
?
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
0xb0
ANL
ACALL
CPL
CPL
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
CJNE
0xc0
PUSH
AJMP
CLR
CLR
SWAP
XCH
XCH
XCH
XCH
XCH
XCH
XCH
XCH
XCH
XCH
XCH
0xd0
POP
ACALL
SETB
SETB
DA
DJNZ
XCHD
XCHD
DJNZ
DJNZ
DJNZ
DJNZ
DJNZ
DJNZ
DJNZ
DJNZ
0xe0
MOVX
AJMP
MOVX
MOVX
CLR
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
0xf0
MOVX
ACALL
MOVX
MOVX
CPL
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV


Alphabetical List of Instructions:

ACALL 
 Absolute Call
ADD, ADDC 
 Add Accumulator (With Carry)
AJMP 
 Absolute Jump
ANL 
 Bitwise AND
CJNE 
 Compare and Jump if Not Equal
CLR 
 Clear Register
CPL 
 Complement Register
DA 
 Decimal Adjust
DEC 
 Decrement Register
DIV 
 Divide Accumulator by B
DJNZ 
 Decrement Register and Jump if Not Zero
INC 
 Increment Register
JB 
 Jump if Bit Set
JBC 
 Jump if Bit Set and Clear Bit
JC 
 Jump if Carry Set
JMP 
 Jump to Address
JNB 
 Jump if Bit Not Set
JNC 
 Jump if Carry Not Set
JNZ 
 Jump if Accumulator Not Zero
JZ 
 Jump if Accumulator Zero
LCALL 
 Long Call
LJMP 
 Long Jump
MOV 
 Move Memory
MOVC 
 Move Code Memory
MOVX 
 Move Extended Memory
MUL 
 Multiply Accumulator by B
NOP 
 No Operation
ORL 
 Bitwise OR
POP 
 Pop Value From Stack
PUSH 
 Push Value Onto Stack
RET 
 Return From Subroutine
RETI 
 Return From Interrupt
RL 
 Rotate Accumulator Left
RLC 
 Rotate Accumulator Left Through Carry
RR 
 Rotate Accumulator Right
RRC 
 Rotate Accumulator Right Through Carry
SETB 
 Set Bit
SJMP 
 Short Jump
SUBB 
 Subtract From Accumulator With Borrow
SWAP 
 Swap Accumulator Nibbles
XCH 
 Exchange Bytes
XCHD 
 Exchange Digits
XRL 
 Bitwise Exclusive OR
Undefined 
 Undefined Instruction


8051 Instruction Set: ACALL

Operation:
ACALL
Function:
Absolute Call Within 2K Block
Flags
None
Syntax:
ACALL code address

Instructions
OpCode
Bytes
Flags
ACALL page0
0x11
2
None
ACALL page1
0x31
2
None
ACALL page2
0x51
2
None
ACALL page3
0x71
2
None
ACALL page4
0x91
2
None
ACALL page5
0xB1
2
None
ACALL page6
0xD1
2
None
ACALL page7
0xF1
2
None
Description: ACALL unconditionally calls a subroutine at the indicated code address. ACALL pushes the address of the instruction that follows ACALL onto the stack, least-significant-byte first, most-significant-byte second. The Program Counter is then updated so that program execution continues at the indicated address.
The new value for the Program Counter is calculated by replacing the least-significant-byte of the Program Counter with the second byte of the ACALL instruction, and replacing bits 0-2 of the most-significant-byte of the Program Counter with 3 bits that indicate the page. Bits 3-7 of the most-significant-byte of the Program Counter remain unchanged.
Since only 11 bits of the Program Counter are affected by ACALL, calls may only be made to routines located within the same 2k block as the first byte that follows ACALL.
See Also: LCALL, RET

8051 Instruction Set: ADD

Operation:
ADD, ADDC
Function:
Add Accumulator, Add Accumulator With Carry
Flags
OV, AC, CY
Syntax:
ADD A, operand
ADDC A, operand

Instructions
OpCode
Bytes
Flags
ADD A,#data
0x24
2
C, AC, OV
ADD A,iram addr
0x25
2
C, AC, OV
ADD A,@R0
0x26
1
C, AC, OV
ADD A,@R1
0x27
1
C, AC, OV
ADD A,R0
0x28
1
C, AC, OV
ADD A,R1
0x29
1
C, AC, OV
ADD A,R2
0x2A
1
C, AC, OV
ADD A,R3
0x2B
1
C, AC, OV
ADD A,R4
0x2C
1
C, AC, OV
ADD A,R5
0x2D
1
C, AC, OV
ADD A,R6
0x2E
1
C, AC, OV
ADD A,R7
0x2F
1
C, AC, OV
Instructions
OpCode
Bytes
Flags
ADDC A,#data
0x34
2
C, AC, OV
ADDC A,iram addr
0x35
2
C, AC, OV
ADDC A,@R0
0x36
1
C, AC, OV
ADDC A,@R1
0x37
1
C, AC, OV
ADDC A,R0
0x38
1
C, AC, OV
ADDC A,R1
0x39
1
C, AC, OV
ADDC A,R2
0x3A
1
C, AC, OV
ADDC A,R3
0x3B
1
C, AC, OV
ADDC A,R4
0x3C
1
C, AC, OV
ADDC A,R5
0x3D
1
C, AC, OV
ADDC A,R6
0x3E
1
C, AC, OV
ADDC A,R7
0x3F
1
C, AC, OV
Description: Description: ADD and ADDC both add the value operand to the value of the Accumulator, leaving the resulting value in the Accumulator. The value operand is not affected. ADD and ADDC function identically except that ADDC adds the value of operand as well as the value of the Carry flag whereas ADD does not add the Carry flag to the result.
The Carry bit (C) is set if there is a carry-out of bit 7. In other words, if the unsigned summed value of the Accumulator, operand and (in the case of ADDC) the Carry flag exceeds 255 Carry is set. Otherwise, the Carry bit is cleared.
The Auxillary Carry (AC) bit is set if there is a carry-out of bit 3. In other words, if the unsigned summed value of the low nibble of the Accumulator, operand and (in the case of ADDC) the Carry flag exceeds 15 the Auxillary Carry flag is set. Otherwise, the Auxillary Carry flag is cleared.
The Overflow (OV) bit is set if there is a carry-out of bit 6 or out of bit 7, but not both. In other words, if the addition of the Accumulator, operand and (in the case of ADDC) the Carry flag treated as signed values results in a value that is out of the range of a signed byte (-128 through +127) the Overflow flag is set. Otherwise, the Overflow flag is cleared.
See Also: SUBB, DA, INC, DEC
Example:

MOV A, #55H                        ; A=55H
ADD A, #3FH                        ; A=94H

Here    A=94H (55H + 3FH) and CY= 0, AC=1

8051 Instruction Set: AJMP

Operation:
AJMP
Function:
Absolute Jump Within 2K Block
Flags:
None
Syntax:
AJMP code address

Instructions
OpCode
Bytes
Flags
AJMP page0
0x01
2
None
AJMP page1
0x21
2
None
AJMP page2
0x41
2
None
AJMP page3
0x61
2
None
AJMP page4
0x81
2
None
AJMP page5
0xA1
2
None
AJMP page6
0xC1
2
None
AJMP page7
0xE1
2
None
Description: AJMP unconditionally jumps to the indicated code address. The new value for the Program Counter is calculated by replacing the least-significant-byte of the Program Counter with the second byte of the AJMP instruction, and replacing bits 0-2 of the most-significant-byte of the Program Counter with 3 bits that indicate the page of the byte following the AJMP instruction. Bits 3-7 of the most-significant-byte of the Program Counter remain unchanged.
Since only 11 bits of the Program Counter are affected by AJMP, jumps may only be made to code located within the same 2k block as the first byte that follows AJMP.
See Also: LJMP, SJMP

8051 Instruction Set: ANL

Operation:
ANL
Function:
Bitwise AND
Flags
None
Syntax:
ANL operand1, operand2

Instructions
OpCode
Bytes
Flags
ANL iram addr,A
0x52
2
None
ANL iram addr,#data
0x53
3
None
ANL A,#data
0x54
2
None
ANL A,iram addr
0x55
2
None
ANL A,@R0
0x56
1
None
ANL A,@R1
0x57
1
None
ANL A,R0
0x58
1
None
ANL A,R1
0x59
1
None
ANL A,R2
0x5A
1
None
ANL A,R3
0x5B
1
None
ANL A,R4
0x5C
1
None
ANL A,R5
0x5D
1
None
ANL A,R6
0x5E
1
None
ANL A,R7
0x5F
1
None
ANL C,bit addr
0x82
2
C
ANL C,/bit addr
0xB0
2
C
Description: ANL does a bitwise "AND" operation between operand1 and operand2, leaving the resulting value in operand1. The value of operand2 is not affected. A logical "AND" compares the bits of each operand and sets the corresponding bit in the resulting byte only if the bit was set in both of the original operands, otherwise the resulting bit is cleared.
See Also: ORL, XRL

8051 Instruction Set: CJNE

Operation:
CJNE
Function:
Compare and Jump If Not Equal
Flags:
CY
Syntax:
CJNE operand1,operand2,reladdr

Instructions
OpCode
Bytes
Flags
CJNE A,#data,reladdr
0xB4
3
C
CJNE A,iram addr,reladdr
0xB5
3
C
CJNE @R0,#data,reladdr
0xB6
3
C
CJNE @R1,#data,reladdr
0xB7
3
C
CJNE R0,#data,reladdr
0xB8
3
C
CJNE R1,#data,reladdr
0xB9
3
C
CJNE R2,#data,reladdr
0xBA
3
C
CJNE R3,#data,reladdr
0xBB
3
C
CJNE R4,#data,reladdr
0xBC
3
C
CJNE R5,#data,reladdr
0xBD
3
C
CJNE R6,#data,reladdr
0xBE
3
C
CJNE R7,#data,reladdr
0xBF
3
C
Description: CJNE compares the value of operand1 and operand2 and branches to the indicated relative address if operand1 and operand2 are not equal. If the two operands are equal program flow continues with the instruction following the CJNE instruction.
The Carry bit © is set if operand1 is less than operand2, otherwise it is cleared.

8051 Instruction Set: CLR

Operation:
CLR
Function:
Clear Register
Flags:
None
Syntax:
CLR register

Instructions
OpCode
Bytes
Flags
CLR bit addr
0xC2
2
None
CLR C
0xC3
1
C
CLR A
0xE4
1
None
Description: CLR clears (sets to 0) all the bit(s) of the indicated register. If the register is a bit (including the carry bit), only the specified bit is affected. Clearing the Accumulator sets the Accumulator's value to 0.

8051 Instruction Set: CPL

Operation:
CPL
Function:
Complement Register
Flags:
-
Syntax:
CPL operand

Instructions
OpCode
Bytes
Flags
CPL A
0xF4
1
None
CPL C
0xB3
1
C
CPL bit addr
0xB2
2
None
Description: CPL complements operand, leaving the result in operand. If operand is a single bit then the state of the bit will be reversed. If operand is the Accumulator then all the bits in the Accumulator will be reversed. This can be thought of as “Accumulator Logical Exclusive OR 255” or as “255-Accumulator.” If the operand refers to a bit of an output Port, the value that will be complemented is based on the last value written to that bit, not the last value read from it.
See Also: CLR, SETB

8051 Instruction Set: DA

Operation:
DA
Function:
Decimal Adjust Accumulator
Flags:
CY
Syntax:
DA A

Instructions
OpCode
Bytes
Flags
DA
0xD4
1
C
Description: DA adjusts the contents of the Accumulator to correspond to a BCD (Binary Coded Decimal) number after two BCD numbers have been added by the ADD or ADDC instruction. If the carry bit is set or if the value of bits 0-3 exceed 9, 0x06 is added to the accumulator. If the carry bit was set when the instruction began, or if 0x06 was added to the accumulator in the first step, 0x60 is added to the accumulator.
The Carry bit (C) is set if the resulting value is greater than 0x99, otherwise it is cleared.
See Also: ADD, ADDC

8051 Instruction Set: DEC

Operation:
DEC
Function:
Decrement Register
Flags:
None
Syntax:
DEC register

Instructions
OpCode
Bytes
Flags
DEC A
0x14
1
None
DEC iram addr
0x15
2
None
DEC @R0
0x16
1
None
DEC @R1
0x17
1
None
DEC R0
0x18
1
None
DEC R1
0x19
1
None
DEC R2
0x1A
1
None
DEC R3
0x1B
1
None
DEC R4
0x1C
1
None
DEC R5
0x1D
1
None
DEC R6
0x1E
1
None
DEC R7
0x1F
1
None
Description: DEC decrements the value of register by 1. If the initial value of register is 0, decrementing the value will cause it to reset to 255 (0xFF Hex). Note: The Carry Flag is NOT set when the value “rolls over” from 0 to 255.
See Also: INC, SUBB

8051 Instruction Set: DIV

Operation:
DIV
Function:
Divide Accumulator by B
Flags:
CY and OV
Syntax:
DIV AB

Instructions
OpCode
Bytes
Flags
DIV AB
0x84
1
C, OV
Description: Divides the unsigned value of the Accumulator by the unsigned value of the "B" register. The resulting quotient is placed in the Accumulator and the remainder is placed in the "B" register.
The Carry flag (C) is always cleared.
The Overflow flag (OV) is set if division by 0 was attempted, otherwise it is cleared.
See Also: MUL AB

8051 Instruction Set: DJNZ

Operation:
DJNZ
Function:
Decrement and Jump if Not Zero
Flags:
None
Syntax:
DJNZ register, reladdr

Instructions
OpCode
Bytes
Flags
DJNZ iram addr, reladdr
0xD5
3
None
DJNZ R0,reladdr
0xD8
2
None
DJNZ R1,reladdr
0xD9
2
None
DJNZ R2,reladdr
0xDA
2
None
DJNZ R3,reladdr
0xDB
2
None
DJNZ R4,reladdr
0xDC
2
None
DJNZ R5,reladdr
0xDD
2
None
DJNZ R6,reladdr
0xDE
2
None
DJNZ R7,reladdr
0xDF
2
None
Description: DJNZ decrements the value of register by 1. If the initial value of register is 0, decrementing the value will cause it to reset to 255 (0xFF Hex). If the new value of register is not 0 the program will branch to the address indicated by relative addr. If the new value of register is 0 program flow continues with the instruction following the DJNZ instruction.
See Also: DEC, JZ, JNZ

8051 Instruction Set: INC

Operation:
INC
Function:
Increment Register
Flags:
None
Syntax:
INC register

Instructions
OpCode
Bytes
Flags
INC A
0x04
1
None
INC iram addr
0x05
2
None
INC @R0
0x06
1
None
INC @R1
0x07
1
None
INC R0
0x08
1
None
INC R1
0x09
1
None
INC R2
0x0A
1
None
INC R3
0x0B
1
None
INC R4
0x0C
1
None
INC R5
0x0D
1
None
INC R6
0x0E
1
None
INC R7
0x0F
1
None
INC DPTR
0xA3
1
None
Description: INC increments the value of register by 1. If the initial value of register is 255 (0xFF Hex), incrementing the value will cause it to reset to 0. Note: The Carry Flag is NOT set when the value "rolls over" from 255 to 0.
In the case of "INC DPTR", the value two-byte unsigned integer value of DPTR is incremented. If the initial value of DPTR is 65535 (0xFFFF Hex), incrementing the value will cause it to reset to 0. Again, the Carry Flag is NOT set when the value of DPTR "rolls over" from 65535 to 0.
See Also: ADD, ADDC, DEC

8051 Instruction Set: JB

Operation:
JB
Function:
Jump if Bit Set
Flags:
None
Syntax:
JB bit addr, reladdr

Instructions
OpCode
Bytes
Flags
JB bit addr,reladdr
0x20
3
None
Description: JB branches to the address indicated by reladdr if the bit indicated by bit addr is set. If the bit is not set program execution continues with the instruction following the JB instruction.
See Also: JBC, JNB

8051 Instruction Set: JBC

Operation:
JBC
Function:
Jump if Bit Set and Clear Bit
Flags:
None
Syntax:
JB bit addr, reladdr

Instructions
OpCode
Bytes
Flags
JBC bit addr,reladdr
0x10
3
None
Description: JBC will branch to the address indicated by reladdr if the bit indicated by bit addr is set. Before branching to reladdr the instruction will clear the indicated bit. If the bit is not set program execution continues with the instruction following the JBC instruction.
See Also: JB, JNB

8051 Instruction Set: JC

Operation:
JC
Function:
Jump if Carry Set
Flags:
None
Syntax:
JC reladdr

Instructions
OpCode
Bytes
Flags
JC reladdr
0x40
2
None
Description: JC will branch to the address indicated by reladdr if the Carry Bit is set. If the Carry Bit is not set program execution continues with the instruction following the JC instruction.

8051 Instruction Set: JMP

Operation:
JMP
Function:
Jump to Data Pointer + Accumulator
Flags:
None
Syntax:
JMP @A+DPTR

Instructions
OpCode
Bytes
Flags
JMP @A+DPTR
0x73
1
None
Description: JMP jumps unconditionally to the address represented by the sum of the value of DPTR and the value of the Accumulator.
See Also: LJMP, AJMP, SJMP

8051 Instruction Set: JNB

Operation:
JNB
Function:
Jump if Bit Not Set
Flags:
None
Syntax:
JNB bit addr,reladdr

Instructions
OpCode
Bytes
Flags
JNB bit addr,reladdr
0x30
3
None
Description: JNB will branch to the address indicated by reladdress if the indicated bit is not set. If the bit is set program execution continues with the instruction following the JNB instruction.
See Also: JB, JBC

8051 Instruction Set: JNC

Operation:
JNC
Function:
Jump if Carry Not Set
Flags:
None
Syntax:
JNC reladdr

Instructions
OpCode
Bytes
Flags
JNC reladdr
0x50
2
None
Description: JNC branches to the address indicated by reladdr if the carry bit is not set. If the carry bit is set program execution continues with the instruction following the JNB instruction.

8051 Instruction Set: JNZ

Operation:
JNZ
Function:
Jump if Accumulator Not Zero
Flags:
None
Syntax:
JNZ reladdr

Instructions
OpCode
Bytes
Flags
JNZ reladdr
0x70
2
None
Description: JNZ will branch to the address indicated by reladdr if the Accumulator contains any value except 0. If the value of the Accumulator is zero program execution continues with the instruction following the JNZ instruction.

8051 Instruction Set: JZ

Operation:
JZ
Function:
Jump if Accumulator Zero
Flags:
None
Syntax:
JNZ reladdr

Instructions
OpCode
Bytes
Flags
JZ reladdr
0x60
2
None
Description: JZ branches to the address indicated by reladdr if the Accumulator contains the value 0. If the value of the Accumulator is non-zero program execution continues with the instruction following the JNZ instruction.

8051 Instruction Set: LCALL

Operation:
LCALL
Function:
Long Call
Flags:
None
Syntax:
LCALL code addr

Instructions
OpCode
Bytes
Flags
LCALL code addr
0x12
3
None
Description: LCALL calls a program subroutine. LCALL increments the program counter by 3 (to point to the instruction following LCALL) and pushes that value onto the stack (low byte first, high byte second). The Program Counter is then set to the 16-bit value which follows the LCALL opcode, causing program execution to continue at that address.
See Also: ACALL, RET

8051 Instruction Set: LJMP

Operation:
LJMP
Function:
Long Jump
Flags:
None
Syntax:
LJMP code addr

Instructions
OpCode
Bytes
Flags
LJMP code addr
0x02
3
None
Description: LJMP jumps unconditionally to the specified code addr.
See Also: AJMP, SJMP, JMP

8051 Instruction Set: MOV

Operation:
MOV
Function:
Move Memory
Flags:
None
Syntax:
MOV operand1,operand2

Instructions
OpCode
Bytes
Flags
MOV @R0,#data
0x76
2
None
MOV @R1,#data
0x77
2
None
MOV @R0,A
0xF6
1
None
MOV @R1,A
0xF7
1
None
MOV @R0,iram addr
0xA6
2
None
MOV @R1,iram addr
0xA7
2
None
MOV A,#data
0x74
2
None
MOV A,@R0
0xE6
1
None
MOV A,@R1
0xE7
1
None
MOV A,R0
0xE8
1
None
MOV A,R1
0xE9
1
None
MOV A,R2
0xEA
1
None
MOV A,R3
0xEB
1
None
MOV A,R4
0xEC
1
None
MOV A,R5
0xED
1
None
MOV A,R6
0xEE
1
None
MOV A,R7
0xEF
1
None
MOV A,iram addr
0xE5
2
None
MOV C,bit addr
0xA2
2
C
MOV DPTR,#data16
0x90
3
None
MOV R0,#data
0x78
2
None
MOV R1,#data
0x79
2
None
MOV R2,#data
0x7A
2
None
MOV R3,#data
0x7B
2
None
MOV R4,#data
0x7C
2
None
MOV R5,#data
0x7D
2
None
MOV R6,#data
0x7E
2
None
MOV R7,#data
0x7F
2
None
MOV R0,A
0xF8
1
None
MOV R1,A
0xF9
1
None
MOV R2,A
0xFA
1
None
MOV R3,A
0xFB
1
None
MOV R4,A
0xFC
1
None
MOV R5,A
0xFD
1
None
MOV R6,A
0xFE
1
None
MOV R7,A
0xFF
1
None
MOV R0,iram addr
0xA8
2
None
MOV R1,iram addr
0xA9
2
None
MOV R2,iram addr
0xAA
2
None
MOV R3,iram addr
0xAB
2
None
MOV R4,iram addr
0xAC
2
None
MOV R5,iram addr
0xAD
2
None
MOV R6,iram addr
0xAE
2
None
MOV R7,iram addr
0xAF
2
None
MOV bit addr,C
0x92
2
None
MOV iram addr,#data
0x75
3
None
MOV iram addr,@R0
0x86
2
None
MOV iram addr,@R1
0x87
2
None
MOV iram addr,R0
0x88
2
None
MOV iram addr,R1
0x89
2
None
MOV iram addr,R2
0x8A
2
None
MOV iram addr,R3
0x8B
2
None
MOV iram addr,R4
0x8C
2
None
MOV iram addr,R5
0x8D
2
None
MOV iram addr,R6
0x8E
2
None
MOV iram addr,R7
0x8F
2
None
MOV iram addr,A
0xF5
2
None
MOV iram addr,iram addr
0x85
3
None
Description: MOV copies the value of operand2 into operand1. The value of operand2 is not affected. Both operand1 and operand2 must be in Internal RAM. No flags are affected unless the instruction is moving the value of a bit into the carry bit in which case the carry bit is affected or unless the instruction is moving a value into the PSW register (which contains all the program flags).
** Note: In the case of "MOV iram addr, iram addr", the operand bytes of the instruction are stored in reverse order. That is, the instruction consisting of the bytes 0x85, 0x20, 0x50 means "Move the contents of Internal RAM location 0x20 to Internal RAM location 0x50" whereas the opposite would be generally presumed.
See Also: MOVC, MOVX, XCH, XCHD, PUSH, POP

8051 Instruction Set: MOVC

Operation:
MOVC
Function:
Move Code Byte to Accumulator
Flags:
None
Syntax:
MOVC A, @A+register

Instructions
OpCode
Bytes
Flags
MOVC A,@A+DPTR
0x93
1
None
MOVC A,@A+PC
0x83
1
None
Description: MOVC moves a byte from Code Memory into the Accumulator. The Code Memory address from which the byte will be moved is calculated by summing the value of the Accumulator with either DPTR or the Program Counter (PC). In the case of the Program Counter, PC is first incremented by 1 before being summed with the Accumulator.
See Also: MOV, MOVX

8051 Instruction Set: MOVX

Operation:
MOVX
Function:
Move Data To/From External Memory (XRAM)
Flags:
None
Syntax:
MOVX operand1,operand2

Instructions
OpCode
Bytes
Flags
MOVX @DPTR,A
0xF0
1
None
MOVX @R0,A
0xF2
1
None
MOVX @R1,A
0xF3
1
None
MOVX A,@DPTR
0xE0
1
None
MOVX A,@R0
0xE2
1
None
MOVX A,@R1
0xE3
1
None
Description: MOVX moves a byte to or from External Memory into or from the Accumulator.
If operand1 is @DPTR, the Accumulator is moved to the 16-bit External Memory address indicated by DPTR. This instruction uses both P0 (port 0) and P2 (port 2) to output the 16-bit address and data. If operand2 is DPTR then the byte is moved from External Memory into the Accumulator.
If operand1 is @R0 or @R1, the Accumulator is moved to the 8-bit External Memory address indicated by the specified Register. This instruction uses only P0 (port 0) to output the 8-bit address and data. P2 (port 2) is not affected. If operand2 is @R0 or @R1 then the byte is moved from External Memory into the Accumulator.
See Also: MOV, MOVC

8051 Instruction Set: MUL

Operation:
MUL
Function:
Multiply Accumulator by B
Flags:
CY and OV
Syntax:
MUL AB

Instructions
OpCode
Bytes
Flags
MUL AB
0xA4
1
C, OV
Description: Multiples the unsigned value of the Accumulator by the unsigned value of the "B" register. The least significant byte of the result is placed in the Accumulator and the most-significant-byte is placed in the "B" register.
The Carry Flag (C) is always cleared.
The Overflow Flag (OV) is set if the result is greater than 255 (if the most-significant byte is not zero), otherwise it is cleared.

8051 Instruction Set: NOP

Operation:
NOP
Function:
None, waste time
Flags:
None
Syntax:
No Operation

Instructions
OpCode
Bytes
Flags
NOP
0x00
1
None
Description: NOP, as it's name suggests, causes No Operation to take place for one machine cycle. NOP is generally used only for timing purposes. Absolutely no flags or registers are affected.

8051 Instruction Set: ORL

Operation:
ORL
Function:
Bitwise OR
Flags:
None
Syntax:
ORL operand1,operand2

Instructions
OpCode
Bytes
Flags
ORL iram addr,A
0x42
2
None
ORL iram addr,#data
0x43
3
None
ORL A,#data
0x44
2
None
ORL A,iram addr
0x45
2
None
ORL A,@R0
0x46
1
None
ORL A,@R1
0x47
1
None
ORL A,R0
0x48
1
None
ORL A,R1
0x49
1
None
ORL A,R2
0x4A
1
None
ORL A,R3
0x4B
1
None
ORL A,R4
0x4C
1
None
ORL A,R5
0x4D
1
None
ORL A,R6
0x4E
1
None
ORL A,R7
0x4F
1
None
ORL C,bit addr
0x72
2
C
ORL C,/bit addr
0xA0
2
C
Description: ORL does a bitwise "OR" operation between operand1 and operand2, leaving the resulting value in operand1. The value of operand2 is not affected. A logical "OR" compares the bits of each operand and sets the corresponding bit in the resulting byte if the bit was set in either of the original operands, otherwise the resulting bit is cleared.
See Also: ANL, XRL

8051 Instruction Set: POP

Operation:
POP
Function:
Pop Value From Stack
Flags:
None
Syntax:
POP

Instructions
OpCode
Bytes
Flags
POP iram addr
0xD0
2
None
Description: POP "pops" the last value placed on the stack into the iram addr specified. In other words, POP will load iram addr with the value of the Internal RAM address pointed to by the current Stack Pointer. The stack pointer is then decremented by 1.

8051 Instruction Set: PUSH

Operation:
PUSH
Function:
Push Value Onto Stack
Flags:
None
Syntax:
PUSH

Instructions
OpCode
Bytes
Flags
PUSH iram addr
0xC0
2
None
Description: PUSH "pushes" the value of the specified iram addr onto the stack. PUSH first increments the value of the Stack Pointer by 1, then takes the value stored in iram addr and stores it in Internal RAM at the location pointed to by the incremented Stack Pointer.

8051 Instruction Set: RET

Operation:
RET
Function:
Return From Subroutine
Flags:
None
Syntax:
RET

Instructions
OpCode
Bytes
Flags
RET
0x22
1
None
Description: RET is used to return from a subroutine previously called by LCALL or ACALL. Program execution continues at the address that is calculated by popping the topmost 2 bytes off the stack. The most-significant-byte is popped off the stack first, followed by the least-significant-byte.
See Also: LCALL, ACALL, RETI

8051 Instruction Set: RETI

Operation:
RETI
Function:
Return From Interrupt
Flags:
None
Syntax:
RETI

Instructions
OpCode
Bytes
Flags
RETI
0x32
1
None
Description: RETI is used to return from an interrupt service routine. RETI first enables interrupts of equal and lower priorities to the interrupt that is terminating. Program execution continues at the address that is calculated by popping the topmost 2 bytes off the stack. The most-significant-byte is popped off the stack first, followed by the least-significant-byte.
RETI functions identically to RET if it is executed outside of an interrupt service routine.

8051 Instruction Set: RL

Operation:
RL
Function:
Rotate Accumulator Left
Flags:
None
Syntax:
RL A

Instructions
OpCode
Bytes
Flags
RL A
0x23
1
C
Description: Shifts the bits of the Accumulator to the left. The left-most bit (bit 7) of the Accumulator is loaded into bit 0.
See Also: RLC, RR, RRC

8051 Instruction Set: RLC

Operation:
RLC
Function:
Rotate Accumulator Left Through Carry
Flags:
CY
Syntax:
RLC A

Instructions
OpCode
Bytes
Flags
RLC A
0x33
1
C
Description: Shifts the bits of the Accumulator to the left. The left-most bit (bit 7) of the Accumulator is loaded into the Carry Flag, and the original Carry Flag is loaded into bit 0 of the Accumulator. This function can be used to quickly multiply a byte by 2.
See Also: RL, RR, RRC

8051 Instruction Set: RR

Operation:
RR
Function:
Rotate Accumulator Right
Flags:
None
Syntax:
RR A

Instructions
OpCode
Bytes
Flags
RR A
0x03
1
None
Description: Shifts the bits of the Accumulator to the right. The right-most bit (bit 0) of the Accumulator is loaded into bit 7.
See Also: RL, RLC, RRC

8051 Instruction Set: RRC

Operation:
RRC
Function:
Rotate Accumulator Right Through Carry
Flags:
CY
Syntax:
RRC A

Instructions
OpCode
Bytes
Flags
RRC A
0x13
1
C
Description: Shifts the bits of the Accumulator to the right. The right-most bit (bit 0) of the Accumulator is loaded into the Carry Flag, and the original Carry Flag is loaded into bit 7. This function can be used to quickly divide a byte by 2.
See Also: RL, RLC, RR

8051 Instruction Set: SETB

Operation:
SETB
Function:
Set Bit
Flags:
CY
Syntax:
SETB bit addr

Instructions
OpCode
Bytes
Flags
SETB C
0xD3
1
C
SETB bit addr
0xD2
2
None
Description: Sets the specified bit.

8051 Instruction Set: SJMP

Operation:
SJMP
Function:
Short Jump
Flags:
None
Syntax:
SJMP reladdr

Instructions
OpCode
Bytes
Flags
SJMP reladdr
0x80
2
None
Description: SJMP jumps unconditionally to the address specified reladdr. Reladdr must be within -128 or +127 bytes of the instruction that follows the SJMP instruction.
See Also: LJMP, AJMP

8051 Instruction Set: SUBB

Operation:
SUBB
Function:
Subtract from Accumulator With Borrow
Flags:
OV , CY, AC
Syntax:
SUBB A, operand

Instructions
OpCode
Bytes
Flags
SUBB A, #data
0x94
2
C, AC, OV
SUBB A, iram addr
0x95
2
C, AC, OV
SUBB A,@R0
0x96
1
C, AC, OV
SUBB A,@R1
0x97
1
C, AC, OV
SUBB A,R0
0x98
1
C, AC, OV
SUBB A,R1
0x99
1
C, AC, OV
SUBB A,R2
0x9A
1
C, AC, OV
SUBB A,R3
0x9B
1
C, AC, OV
SUBB A,R4
0x9C
1
C, AC, OV
SUBB A,R5
0x9D
1
C, AC, OV
SUBB A,R6
0x9E
1
C, AC, OV
SUBB A,R7
0x9F
1
C, AC, OV
Description: SUBB subtract the value of operand from the value of the Accumulator, leaving the resulting value in the Accumulator. The value operand is not affected.
The Carry Bit © is set if a borrow was required for bit 7, otherwise it is cleared. In other words, if the unsigned value being subtracted is greater than the Accumulator the Carry Flag is set.
The Auxillary Carry (AC) bit is set if a borrow was required for bit 3, otherwise it is cleared. In other words, the bit is set if the low nibble of the value being subtracted was greater than the low nibble of the Accumulator.
The Overflow (OV) bit is set if a borrow was required for bit 6 or for bit 7, but not both. In other words, the subtraction of two signed bytes resulted in a value outside the range of a signed byte (-128 to 127). Otherwise it is cleared.
See Also: ADD, ADDC, DEC

8051 Instruction Set: SWAP

Operation:
SWAP
Function:
Swap Accumulator Nibbles
Flags:
None
Syntax:
SWAP A

Instructions
OpCode
Bytes
Flags
SWAP A
0xC4
1
None
Description: SWAP swaps bits 0-3 of the Accumulator with bits 4-7 of the Accumulator. This instruction is identical to executing "RR A" or "RL A" four times.
See Also: RL, RLC, RR, RRC

8051 Instruction Set: Undefined Instruction

Operation:
Undefined Instruction
Function:
Undefined
Flags:
-
Syntax:
???

Instructions
OpCode
Bytes
Flags
???
0xA5
1
C
Description: The "Undefined" instruction is, as the name suggests, not a documented instruction. The 8051 supports 255 instructions and OpCode 0xA5 is the single OpCode that is not used by any documented function. Since it is not documented nor defined it is not recommended that it be executed. However, based on my research, executing this undefined instruction takes 1 machine cycle and appears to have no effect on the system except that the Carry Bit always seems to be set.
Note: We received input from an 8052.com user that the undefined instruction really has a format of Undefined bit1,bit2 and effectively copies the value of bit2 to bit1. In this case, it would be a three-byte instruction. We haven't had an opportunity to verify or disprove this report, so we present it to the world as "additional information."
Note: It has been reported that Philips 8051 model P89C669 uses instruction prefix 0xA5 to let the user access a different (extended) SFR area.

8051 Instruction Set: XCH

Operation:
XCH
Function:
Exchange Bytes
Flags:
None
Syntax:
XCH A, register

Instructions
OpCode
Bytes
Flags
XCH A,@R0
0xC6
1
None
XCH A,@R1
0xC7
1
None
XCH A,R0
0xC8
1
None
XCH A,R1
0xC9
1
None
XCH A,R2
0xCA
1
None
XCH A,R3
0xCB
1
None
XCH A,R4
0xCC
1
None
XCH A,R5
0xCD
1
None
XCH A,R6
0xCE
1
None
XCH A,R7
0xCF
1
None
XCH A, iram addr
0xC5
2
None
Description: Exchanges the value of the Accumulator with the value contained in register.

8051 Instruction Set: XCHD

Operation:
XCHD
Function:
Exchange Digit
Flags:
None
Syntax:
XCHD A,[@R0/@R1]

Instructions
OpCode
Bytes
Flags
XCHD A,@R0
0xD6
1
None
XCHD A,@R1
0xD7
1
None
Description: Exchanges bits 0-3 of the Accumulator with bits 0-3 of the Internal RAM address pointed to indirectly by R0 or R1. Bits 4-7 of each register are unaffected.

8051 Instruction Set: XRL

Operation:
XRL
Function:
Bitwise Exclusive OR
Flags:
None
Syntax:
XRL operand1,operand2

Instructions
OpCode
Bytes
Flags
XRL iram addr,A
0x62
2
None
XRL iram addr,#data
0x63
3
None
XRL A,#data
0x64
2
None
XRL A,iram addr
0x65
2
None
XRL A,@R0
0x66
1
None
XRL A,@R1
0x67
1
None
XRL A,R0
0x68
1
None
XRL A,R1
0x69
1
None
XRL A,R2
0x6A
1
None
XRL A,R3
0x6B
1
None
XRL A,R4
0x6C
1
None
XRL A,R5
0x6D
1
None
XRL A,R6
0x6E
1
None
XRL A,R7
0x6F
1
None
Description: XRL does a bitwise "EXCLUSIVE OR" operation between operand1 and operand2, leaving the resulting value in operand1. The value of operand2 is not affected. A logical "EXCLUSIVE OR" compares the bits of each operand and sets the corresponding bit in the resulting byte if the bit was set in either (but not both) of the original operands, otherwise the bit is cleared.
See Also: ANL, ORL

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