2. Integer and Logic Unit
Used for Integer and Logic Operations on
Microprocessor
In our project:
1. Arithmetic- Addition and Multiplication
2. Logic- OR and AND
Addition using Carry Save Adder
Issue- 3 inputs
Multiplication using Booth Multiplier
High speed
2Seer Akademi (2011-13)
3. What is ALU?
• ALU stands for: Arithmetic Logic Unit.
ALU is a digital circuit that performs
Arithmetic (Add, Sub . . .) and Logical
(AND, OR, NOT) operations.
• John Von Neumann proposed the ALU in
1945 when he was working on EDVAC.
3Seer Akademi (2011-13)
7. Carry Save Adder:
• The basic CSA (carry save adder) is similar to the full
adder but the architecture is different.
• The operation and the principle of CSA is based on
formulae
A + B + C= SUM+2*CARRY
SUM=(A+B+C)mod2 and COUNT=((A+B+C)-
SUM)/2)
• For example if we add three numbers
X=0101,Y=0011,Z=0100.
• Sum=0010 and Saved Carry= 1010 was calculated in
CSA and next in the carry look adder/ ripple carry
adder the output new sum= 1100 and here new carry
is 0.
7Seer Akademi (2011-13)
9. Booth Multiplier –
Operation (step by step)
• mr-Multiplier,md-Multiplicand
• Shift md
• 2’s Complemet the md
• Shift md
• Encode the mr
• Partial product generation by addiing
shifting bits of md bits with respect to mr bits
• Final 3 stages of partial product generated
bits are added in end
Seer Akademi (2011-13) 9
10. 10
OR & AND
INPUT
A B
OUTPU
T
A + B
0 0 0
0 1 1
1 0 1
1 1 1
INPUT
OUTPU
T
A B
A AND
B
0 0 0
0 1 0
1 0 0
1 1 1
Seer Akademi (2011-13)
