Presentation on ILU

Group - P Integer and Logic Unit by

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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

Seer Akademi (2011-13)

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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.


Seer Akademi (2011-13) 4

Bus Concept


I/O Representation


Interaction with Other Units


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.


Carry Save Adder


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


OR & AND INPUTA B

OUTPUT

A + B

0 0 0

0 1 1

1 0 1

1 1 1

INPUT OUTPUT

A B A AND B

0 0 0

0 1 0

1 0 0

1 1 1

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Timing Diagram



Queries

Presentation on ILU

Design

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