vlsi presentation on alu

EEE 416

V L S I

Design and Analysis of Arithmetic Logic Unit (ALU)

Submitted To:Dr. Ishfaqur Raza

Submitted by:Tawhid ReazwanMashfiqul IslamAsifur Rahman

FunctionsAdditionSubtractionMultiplicationComparison

Logic Functions

• Functions for Addition , multiplication , subtraction operations:

P1=A0S0’ + S1S0’B0’ + A0B0S1’S0 Q1=S0’ (S1’B0 + S1) P2=A1S0’ + S1S0’B1’ + A1B0S1’S0 Q2=S0’ (S1’B1+S1) + A0B2S1’S0 P3=A2S0’ + S1S0’B2’ + (A2B0+A1B1) S1’S0 Q3=S0’ (S1’B2+S1) + A0B2S1’S0 P4= A3S0’ + S1S0’B3’ + (A3B0+A2B1) S1’S0 Q4=S0’ (S1’B3+S1) + A0B3S1’S0

• Functions for Comparator operation: Pc1= (A0 + B0’)S1S0 Qc1=S1S0 Pc2= (A1 + B1’)S1S0 Qc2=S1S0 Pc1= (A2 + B2’)S1S0 Qc1=S1S0 Pc1= (A3 + B3’)S1S0 Qc1=S1S0

Schematic diagram

PLAN

•Logic gate design •Adder design•ALU construction•Spice extraction•Verification•Parameter determination

Parameters:

•Rise Time

•Fall Time

•PCO

•Frequency

So.S1

Operation

00 Addition

01 Multiplication

10 Subtraction

11 Comparison

Design in Magic

•Basic Element•Conversion to a single Element

2 input NAND

3 input NAND

4 input NAND

2 input NOR

3 input NOR

Change in plan

•Using Inverter•Using usual logic gate•Mirror of Logic Diagram

2 input AND

3 input AND

4 input AND

2 input OR

3 input OR

NOT

EXOR

1 bit ADDER

4 bit ADDER

ALU

Errors

•Error in magic labeling•Error in spice extraction•Error in spice file•Error in Hspice simulation

Advantages

•Less number of gates•Less number of transistors•0.2mm *0.3mm(approximately)•Simplicity in magic design

Conclusion

•After doing this project we have learnt how to construct and design an ALU. We tried a lot. Unfortunately we are not able to get the final output.