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VLSI Design
System-on-Chip Design
Overview of System on a Chip
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System on Chip Design
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System on Chip Design

A complete System on a Chip (SoC)
design flow beginning with a design
specification and ending with a working
SoC. Creation of RTL level modules
designed for reuse, integration of
Intellectual Property (IP) for both RTL
level and physical level IP, IC
verification, and the creation of selfchecking test benches for SoC designs.
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System on Chip Design

System-on-a-chip (SoC) is a major
revolution taking place in the design of
integrated circuits due to the
unprecedented levels of integration
possible. As a result, new methodologies
and tools are demanded to address
design, verification and test problems
presented by SoCs in this rapidly
evolving area.
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System on Chip Design

The key concept in SoC/IP design is that
a chip can be constructed rapidly using
third-party and internal IP, where IP
refers to a pre-designed behavioral or
physical descriptions of a standard
component.
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System on Chip Design

According to the International
Technology Roadmap for
Semiconductors, "Innovation in the
techniques used in circuit and system
design will be essential to maintain the
historical trends in performance
improvement."
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SOC example and VLSI system
For DSM, Interconnects between chips and within chips
dominate the performance of your system !!
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SOC example

General purpose processor and DSP
processor are hard cores (Hard IP)
– A pre-designed layout
– Programmed, Interface to standard buses

Bus interface unit (Soft IP)
– A synthesizable module in Verilog, VHDL, C
– Internal buses, External buses (PCI, ISA,
etc)

Glue Logic
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SOC Example
Analog: A/D and RF circuitry
 MEMS: Micro-Electrical Mechanical
Systems
 Sensors

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An Example: System on A Chip Architecture
from Palmchip corporation
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A BUS ARCHITECTURE FOR SYSTEM-ON-CHIP DESIGNS
from Atmel corporation
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SOC Applications
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Our Course: System on Chip
Design and Architecture
1.
2.
VLSI Integrated Circuit Design: A Design
Perspective, emphasis on system performance.
Materials mainly from the textbook, some from
other books or papers
System Introduction
Multimedia Application, Wireless Application
Telecommunications, Computer Arithmetic, and
others
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Why VLSI?
Integration improves the design:
 lower parasitics = higher speed;

– lower power;
– physically smaller = higher speed.

Integration reduces manufacturing cost
(almost) no manual assembly.
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VLSI and you

Microprocessors:
–
–
–
–
desktop personal computers;
notebook computers
microcontrollers.
pocket PCs/games
DRAM/SRAM/Flash Memory/EEPROM.
 Special-purpose processors.

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Moore’s Law
Gordon Moore: co-founder of Intel.
 Predicted that number of transistors per chip
would grow exponentially (double every 18
months).
 Exponential improvement in technology is a
natural trend: steam engines, dynamos,
automobiles.

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Moore’s Law plot
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The cost of fabrication
Current cost: $2-3 billion.
 Typical fab line occupies about 1 city block,
employs a few hundred people.
 Most profitable period is first 18 months-2
years.

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Cost factors in ICs

For large-volume ICs:
– packaging is largest cost;
– testing is second-largest cost.

For low-volume ICs, design costs may
swamp all manufacturing costs.
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The VLSI design process
May be part of larger product design.
 Major levels of abstraction:

–
–
–
–
–

specification;
architecture;
logic design;
circuit design;
layout.
The VLSI design process = SOC design
process
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Challenges in VLSI design
Multiple levels of abstraction: transistors to
CPUs.
 Multiple and conflicting constraints: low
cost and high performance are often at odds.
 Short design time: Late products are often
irrelevant.

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Dealing with complexity
Divide-and-conquer: limit the number of
components you deal with at any one time.
 Group several components into larger
components:

–
–
–
–
transistors form gates;
gates form functional units;
functional units form processing elements;
etc.
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Layout and its abstractions

Layout for dynamic latch:
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Stick diagram
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Transistor schematic
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Mixed schematic
inverter
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Levels of abstraction
Specification: function, cost, etc.
 Architecture: large blocks.
 Logic: gates + registers.
 Circuits: transistor sizes for speed, power.
 Layout: determines parasitics.

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Circuit abstraction

Continuous voltages and time:
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Digital abstraction
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Discrete levels, discrete time:
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Register-transfer abstraction

Abstract components, abstract data types:
0010
+
0001
+
0111
0100
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Top-down vs. bottom-up design

Top-down design adds functional detail.
– Create lower levels of abstraction from upper
levels.
Bottom-up design creates abstractions from
low-level behavior.
 Good design needs both top-down and
bottom-up efforts.

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Design abstractions
English
Executable
program
function
Sequential
machines
Logic gates
specification
behavior
Throughput,
design time
registertransfer
Function units,
clock cycles
logic
cost
Literals,
logic depth
transistors
circuit
nanoseconds
rectangles
layout
microns
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Design validation
Must check at every step that errors haven’t
been introduced - the longer an error
remains, the more expensive it becomes to
remove it.
 Forward checking: compare results of lessand more-abstract stages.
 Back annotation: copy performance
numbers to earlier stages.

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Manufacturing test
Not the same as design validation: just
because the design is right doesn’t mean
that every chip coming off the line will be
right.
 Must quickly check whether manufacturing
defects destroy function of chip.
 Must also speed-grade.
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