1. ARITHMETIC MICRO OPERATIONS
Department of Computer Engineering,
M.S.P.V.L Polytechnic College,
Pavoorchatram.

2. Introduction The basic arithmetic micro operations are Addition
Subtraction
Increment
And decrement

3. Add Micro Operations
The arithmetic add micro operation is given by the statement,
R3  R1+ R2
It states that the contents of register R1 are added with the contents of register R2 and the result will be transferred to register R3.

4. Subtract Micro Operation
The arithmetic subtract micro operation is given by the statement,
R3  R1 + R2+ 1
Where R2 denotes the 1’s complement of R2. adding 1 to the 1’s complement produces the 2’s complement of R2.
Then adding the contents of R1 with the 2’s complement of R2 is equivalent to R1 – R2.

5. Increment Micro Operation
The increment micro operation is given by the statement,
R1  R1 + 1
The contents of register R1 are incremented by one.

6. Decrement Micro operation
The decrement micro operation is given by the statement
R1  R1 – 1
The contents of register R1 are decremented by one.

7. Binary Adder
Binary adder is used to generate the arithmetic sum of two binary numbers of any length. A binary adder can be constructed in cascade, i.e., the output carry from each full adder is connected to the input carry of the next high order full adder.

8. Circuit Diagram

9. Binary Adder- Subtractor
The addition and subtraction operations are performed in one common circuit by including an exclusive-OR gate with each full adder.

10. Cont.., The mode input M controls the operation.
When M=0 => B  0 = B and C0 = 0
The full adders receive the value of B, the input carry is 0.
Then the circuit performs A plus B. Therefore, when M = 0, the circuit behaves as a binary adder.
When M = 1 => B  1 = B

11. Binary Incrementer
Binary Incrementer is used to add one to a number in a register. A binary incrementer can be constructed using half adder circuits connected in cascade.

12. Cont..,
One input of the least significant half adder is connected to logic 1.
The other input is connected to the least significant of the number to be incremented.
The output carry from one half adder is connected to one of the inputs of the next higher order half adder.

13. ARITHMETIC CIRCUIT
The basic arithmetic micro operations (addition, subtraction, increment and decrement) can be performed in one composite arithmetic circuit.

14. 4 bit Arithmetic Circuit Diagram

15. Arithmetic Circuit Function Table

16. The End
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