This document summarizes arithmetic and logical instructions for the 8051 microcontroller. It describes addition, subtraction, multiplication, and division instructions that perform operations on registers and memory. It also covers increment, decrement, and logical instructions like AND, OR, and XOR that operate on registers and memory locations using bitwise operations. Flags are updated based on arithmetic results.

1. Arithmetic Logical Instructions
for
8051 Microcontroller
-A.Usha Rani,
-Lecturer, Department of Physics and Electronics,
-St.Ann’s College for Women

2. ARITHMETIC INSTRUCTIONS
These instructions perform arithmetic operations.
The arithmetic operations modify Carry, Overflow
and Auxiliary carry flags based on the result of the
operation
The status of the flags can be used a test conditions.

3. ADDITION
The mnemonic for addition is ADD.
ADD A, source //Add contents of A with operand
source and store result in A
All addressing modes can be used for this instruction.
The register A is always the destination as well as one of
the source operands.

4. ADD A, # data //Add contents of A with immediate data
and store result in A
ADD A, #10H // Add the value 10H to the contents of A
and store the result in A
ADD A,Rn //Add contents of A with contents of Rn
and store result in A
ADD A, R3 //Add contents of A with contents of
register R3 and store result in A

5. ADD A, direct //Add contents of A with contents of
address direct and store result in A
ADD A, 45H //Add contents of A with contents of
address 45 H and store result in A
ADD A, @Ri // Add contents of A with contents of
address in Ri
ADD A, @R0 // Add contents of A with contents of
address in R0

6. SUBTRACTION
The mnemonic is SUBB
SUBB A, Source //Subtract the operand source
from contents of A and store result in A

7. SUBB A, # data // Subtract immediate data and carry
from A and store result in A
SUBB A, #10H // Subtract immediate data 10H and
carry from A and store result in A
SUBB A,Rn //Subtract contents of Rn and carry
from A and store result in A
SUBB A, R3 //Subtract contents of R3 and
carry from A and store result in A

8. SUBB A, direct // Subtract contents of address direct
and carry from A and store result in A
SUBB A, 45H // Subtract contents of address 45H and
carry from A and store result in A
SUBB A, @Ri //Subtract contents and carry of address
in Ri from A and store result in A
SUBB A, R0 //Subtract contents and carry of address
in R0 from A and store result in A

9. MULTIPLICATION
Multiplication uses only the registers A and B as source
and destination.
MULAB //Multiply the contents of A with B
and put lower byte of result in A
and higher byte of result in B.

10. DIVISION
Division uses only the registers A and B as source and
destination.
 The number in A is divided by the number in B.
Quotient is placed in A and remainder is placed in B.
DIV AB // Divide the contents of A with
contents of B and result (quotient)in
A and remainder in B.

11. INCREMENT
Used to add 1 to a operand.
Supports all addressing modes.
No flags are effected.
Useful to repeat the operations i.e to increment
till the desired result is obtained.
INC destination // Add 1 to the destination
operand.

12. INC A //Increment the contents of A by 1
INC A //Increment the contents of A by 1
INC Rn // Increment the contents of Rn by 1
INC R3 // Increment the contents of R3 by 1
INC @Ri // Increment the contents of address
pointed by Ri by1
INC @R0 // Increment the contents of address
pointed by R0 by1

13. INC Direct //Increment the contents of direct
address by 1
INC 45H //Increment the contents of direct
address 45H by 1
INC DPTR //Increment the contents of DPTR by 1
INC DPTR //Increment the contents of DPTR by 1

14. DECREMENT
Used to subtract 1 from a operand.
Supports all addressing modes.
No flags are effected.
Useful to repeat the operations i.e to
increment till the desired result is obtained.
DEC destination //Subtract 1 from
destination operand

15. DEC A // Decrement the contents of A by 1
DEC A // Decrement the contents of A by 1
DEC Rn // Decrement the contents of Rn by 1
DEC R3 // Decrement the contents of R3 by 1
DEC @Ri // Decrement the contents of address
pointed by Ri by1
DEC @R0 // Decrement the contents of address
pointed by R0 by1

16. DEC Direct // Decrement the contents of direct
address by 1
DEC 45H // Decrement the contents of direct
address by 1
DEC DPTR //Decrement the contents of DPTR by 1
DEC DPTR //Decrement the contents of DPTR by 1

17. LOGICAL INSTRUCTIONS
8051 supports the following logical operations
AND
OR
EX_OR
 NOT

18. AND Operation
ANLA,#data //Bitwise AND operation of A with data
ANLA,Rn // Bitwise AND operation of A with Rn
ANLA,@Ri //Bitwise AND operation of A with data
pointed by Ri
ANLA,direct // Bitwise AND operation of A with data
in direct
ANL direct, #data // Bitwise AND operation of data in
direct with immediate data
ANL direct, A // Bitwise AND operation of data in
address direct with A

19. OR Operation
ORLA,#data // Bitwise OR operation of A with data
ORLA,Rn // Bitwise OR operation of A with Rn
ORLA,@Ri // Bitwise OR operation of A with data
pointed by Ri
ORLA,direct // Bitwise OR operation of A with data
in direct
ORL direct, #data // Bitwise OR operation of data in
direct with immediate data
ORL direct, A // Bitwise OR operation of data in
address direct with A

20. Ex-OR Operation
XRLA,#data // Bitwise X-OR operation of A with data
XRLA,Rn // Bitwise X-OR operation of A with Rn
XRLA,@Ri // Bitwise X-OR operation of A with data
pointed by Ri
XRLA,direct // Bitwise X-OR operation of A with data
in direct
XRL direct, #data // Bitwise X-OR operation of data in
direct with immediate data
XRL direct, A // Bitwise X-OR operation of data in
address direct with A

21. UNARY OPERATIONS
XRLA,#data //Bitwise X-OR operation of A with data
XRLA,Rn // Bitwise X-OR operation of A with Rn
XRLA,@Ri //Bitwise X-OR operation of A with data
pointed by Ri
XRLA,direct // Bitwise X-OR operation of A with
data in direct
XRL direct, #data //Bitwise X-OR operation of data
in direct with immediate data
XRL direct, A // Bitwise X-OR operation of data in
address direct with A