In this article, we will be talking about the logical operations in the 8051 microcontroller. We would recommend that you go through our previous articles on data transfer and arithmetic instructions to better understand this topic.
Contents
List of logical instructions in 8051
Logical operations in 8051 perform bitwise operations between the accumulator and data stored in a memory location, register, or data given by the programmer. The result of a logical operation is stored in the accumulator itself. The table given below lists the logical operations which can be performed by the 8051. [A]=Accumulator; [Rn]= register in register bank of RAM space.
| Operation | Mnemonics | Description |
|
AND
|
ANL A, Rn | [A]<-[A] AND [Rn] |
| ANL A, Address | [A]<-[A] AND [Data at Address] | |
| ANL A, @Rn | [A]<-[A] AND [Data at Address in Rn] | |
| ANL A, #data | [A]<-[A] AND [Data] | |
| ANL Address, A | [Data at Address]<-[Data at Address] AND [A] | |
| ANL Address, #data | [Data at Address]<-[Data at Address] AND [Data] | |
|
OR
|
ORL A, Rn | [A]<-[A] OR [Rn] |
| ORL A, Address | [A]<-[A] OR [Data at Address] | |
| ORL A, @Rn | [A]<-[A] OR [Data at Address in Rn] | |
| ORL A, #data | [A]<-[A] OR [Data] | |
| ORL Address, A | [Data at Address]<-[Data at Address] OR [A] | |
| ORL Address, #data | [Data at Address]<-[Data at Address] OR [Data] | |
|
XOR
|
XRL A, Rn | [A]<-[A] XOR [Rn] |
| XRL A, Address | [A]<-[A] XOR [Data at Address] | |
| XRL A, @Rn | [A]<-[A] XOR [Data at Address in Rn] | |
| XRL A, #data | [A]<-[A] XOR [Data] | |
| XRL Address, A | [Data at Address]<-[Data at Address] XOR [A] | |
| XRL Address, #data | [Data at Address]<-[Data at Address] XOR [Data] | |
| Clear | CLR A | [A]<-0 |
| Complement | CPL A | [A]<-[A]’ |
|
Rotate left
|
RL A | Shifts the value in accumulator to the left |
| RLC A | Shifts the value in accumulator to the left through the accumulator | |
|
Rotate right
|
RR A | Shifts the value in accumulator to the right |
| RRC A | Shifts the value in accumulator to the right through the accumulator | |
| Swap | SWAP A | Swaps the upper nibble of the accumulator with the lower nibble |
AND operation
The AND instructions compare the bits in the source and the destination operand and then store the result in the accumulator after performing the AND operation.
|
Opcode
|
Operand
|
Description
|
Size
|
Execution Time
|
Flags affected | ||
| Carry | Overflow | Auxilary carry | |||||
|
ANL
|
A, Rn | Performs the AND operation on the data stored in the accumulator and the register Rn. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no |
| A, Address | Performs the AND operation on the data stored at the given address and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| A, @Rn | Uses the data stored in the register as an address and performs the AND operation on the data stored at that address and the accumulator. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no | |
| A, #data | Performs the AND operation on the data given by the programmer and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| Address, A | Performs the AND operation on the data stored at the given address and the accumulator. The result is then stored at the given address | 2 bytes | 12 clock cycles | no | no | no | |
| Address, #data | Performs the AND operation on the data stored at the given address and the data given by the programmer. The result is then stored at the given address | 3 bytes | 24 clock cycles | no | no | no | |
Example
MOV A, #35H; Moves 35H into the accumulator ANL A, #0FH; Performs AND operation between the data stored in the accumulator and 0FH. ;Then the result is stored in the accumulator (A=O5H)
OR Operation
The OR instructions compare the bits in the source and the destination operand and then store the result in the accumulator after performing the OR operation.
|
Opcode
|
Operand
|
Description
|
Size
|
Execution Time
|
Flags affected | ||
| Carry | Overflow | Auxilary carry | |||||
|
ORL
|
A, Rn | Performs the OR operation on the data stored in the accumulator and the register Rn. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no |
| A, Address | Performs the OR operation on the data stored at the given address and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| A, @Rn | Uses the data stored in the register as an address and performs the OR operation on the data stored at that address and the accumulator. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no | |
| A, #data | Performs the OR operation on the data given by the programmer and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| Address, A | Performs the OR operation on the data stored at the given address and the accumulator. The result is then stored at the given address | 2 bytes | 12 clock cycles | no | no | no | |
| Address, #data | Performs the OR operation on the data stored at the given address and the data given by the programmer. The result is then stored at the given address | 3 bytes | 24 clock cycles | no | no | no | |
Example
MOV A, #04H; Moves 04H into the accumulator ANL A, #30H; Performs AND operation between the data stored in the accumulator and 30H. ;Then the result is stored in the accumulator (A=34H)
XOR Operation
These instructions compare the bits in the source and the destination operand and then store the result in the accumulator after performing the XOR operation.
|
Opcode
|
Operand
|
Description
|
Size
|
Execution Time
|
Flags affected | ||
| Carry | Overflow | Auxilary carry | |||||
|
XRL
|
A, Rn | Performs the XOR operation on the data stored in the accumulator and the register Rn. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no |
| A, Address | Performs the XOR operation on the data stored at the given address and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| A, @Rn | Uses the data stored in the register as an address and performs the XOR operation on the data stored at that address and the accumulator. The result is then stored in the accumulator | 1 byte | 12 clock cycles | no | no | no | |
| A, #data | Performs the XOR operation on the data given by the programmer and the accumulator. The result is then stored in the accumulator | 2 bytes | 12 clock cycles | no | no | no | |
| Address, A | Performs the XOR operation on the data stored at the given address and the accumulator. The result is then stored at the given address | 2 bytes | 12 clock cycles | no | no | no | |
| Address, #data | Performs the XOR operation on the data stored at the given address and the data given by the programmer. The result is then stored at the given address | 3 bytes | 24 clock cycles | no | no | no | |
MOV A, #54H; Moves 54H into the accumulator XRL A, #78H; Performs AND operation between the data stored in the accumulator and 78H. ;Then the result is stored in the accumulator (A=2CH)
Clear operation
The CLR instruction is used to clear the data stored in the accumulator.
Example
MOV A, #50H; Moves 50H into the accumulator CLR A; Clears the data stored in the accumulator ; the contents of the accumulator are now 00H
Compliment operation
The CPL instruction inverts all the bits stored in the accumulator.
Example
MOV A, # 0100 1100B; Loads the value (0100 1100B) into the accumulator CPL A; Complements the value stored in the accumulator (A=1011 0011B)
Swap operation
Swaps the data in the upper nibble with the lower nibble of the accumulator.
Example
MOV A, #0110 0111B ;Loads the value (0110 0111B) into the accumulator SWAP A ;Swaps the data stored in the accumulator (A= 0111 0110B)
Rotate right operation
The RR instruction shifts the data stored in the accumulator to the right in a bit by bit fashion. The data in the LSB is shifted to the MSB.
Rotate right with carry operation
The RRC command performs the same operation but includes the carry bit in the operation as well. It is used for serial transmission of data to any external port.
Rotate left operation
The RL instruction shifts the data stored in the accumulator to the left in a bit by bit fashion. The data in the MSB is shifted to the LSB.
Rotate left with carry operation
The RLC command performs the same operation but includes the carry bit in the operation as well. It is used for serial transmission of data to any external port.
We hope that reading this article made you understand logical instruction in 8051. If you have any doubts regarding the same feel free to reach us through the comments section.
