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4-bit ALU
Yamei Li,Yuping Liang
Hua Qu,James Hsu
Advisor: Dave Parent12/6/2005
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Agenda• Introduction• Project (Experimental) Details
– ALU– Adder– DFF– MUX
• Summary– Project result– Lesson learned
• Acknowledgement
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Introduction
• The 4-bit ALU that our group designed can perform the following functions:– Adder, NOR, OR, and AND.
• The 4-bit ALU operates at 200 MHz and use 5.8mW of Power and occupied an area of 600m x 280m.
• The 4-bit ALU is made up of 4 identical 1-bit ALU, and 14 DFFs.
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Project Description and ALU schematic
• The 4-bit ALU is broken down into sub blocks consisting of:– 4 1-bit Adders– 4 4to1 MUXs– 4 AND, 4 NOR and 4 OR
gate– 10 input DFFs and 4 output
DFFs
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Logic Level
Gate Cg to Drive
#CDNs (N)
#CDP (M)
#LNs #LPs WN (H.C)
WP (H.C)
Cg of gate
DFFin(2)
NAND Master Mux Master
27 11
1 2
2 2
1 2
2 2
2.4 1.65
1.95 2.85
11 16
INV2 7 1 1 1 1 1.5 2.85 7 AOI2 7 2 2 3 3 2.7 4.8 20 AOI1 27 2 2 2 2 2.4 4.2 12
4 Adders (2+2+2+3=9)
INV1 12 1 1 1 1 2 3.3 10 MUX1 6.128 4 4 2 2 1.5 2.25 6.386 INV2 6.386 1 1 1 1 1.5 2.1 6.128 MUX3 8.43 4 4 2 2 1.5 2.25 6.386
MUX (4)
INV3 20 1 1 1 1 1.95 3 8.43 DFFout (2)
NAND Slave Mux Slave
27 20
1 1
2 3
1 2
2 2
4.05 2.85
3.45 4.95
20 27
nsns
PHL 294.17
5 Note: All widths are in microns
and capacitances in fF
Longest Path Calculations
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4-bit ALU Layout and LVS
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ALU Simulations and Power test
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DFF schematic & LVS report
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DFF layout
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DFF Hold Time Fall& Rise
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DFF Setup Time Rise & Fall
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1 Bit Adder Schematic,Layout & LVS
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1 Bit Adder Post Simulation
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4 Bit Adder Schematic and Simulation
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MUX schematics
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MUX layout and LVS
• Size of one MUX = 28m x 70m
• Size of 4 MUX = 5% of ALU area
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MUX Simulation Before Extraction
• Simulation results before extraction TPHL=1.0383 ns , TPLH=1.045 nsPropagation delay < 4 LL x 0.294ns=1.177ns
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MUX Post Simulation
• Results from Post Extraction Simulation
TPHL=0.758 ns , TPLH=0.755 ns
27% faster
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Summary• After this project, we became familiar with
Cadence tool and the fundamental concepts of IC design.
• Our project has 338 transistors and 18 terminals.
• The total area is =280m x 600m
• The power is=3.4W/cm2
• Lessons learned • how to fix the LVS error
• Learn how to work in a team
• Learn how to make trade offs
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Acknowledgements
• Thanks to Professor D. Parent guidance and unlimited patience.
• Thanks to Cadence Design Systems for the VLSI lab