Explains the mnemonics for arithmetic and logical instructions in 8051 microcontroller

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