Computer-Aided Verification of Electronic Circuits and Systems

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Computer-Aided Verification of Electronic
Circuits and Systems

• EE219A Fall 2002
• Professor Prof. Alberto Sangiovanni-Vincentelli
• Instructor Alessandra Nardi

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Administration

• Office Hours Th 11.30-13.00 in 545H
• Course mailing list send e-mail to
  nardi_at_eecs.berkeley.edu
• Course website http//www-cad.eecs.berkeley.edu/
  nardi/EE219A

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Grading

• Grading will be assigned on
• Project (? 50 )
• Homework (? 20 )
• Midterm (? 30 )
• There will be approximately 5 bi-weekly homework
  and a take-home midterm
• No final

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Projects

• Groups of 2 people are strongly recommended
• Tentative schedule
• Make your choice by October 21
• First update October 31
• Second update November 21
• Final presentation December 3 and 5
• May be shared with other classes you are taking

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Major Verification Tasks
Design Concept
Is what I asked for what I want?
Design Verification
Design Description
Is what I asked for what I got?
Synthesis
Implementation Verification
Design Implementation
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Functional Verification

• Specification Validation Are the specifications
  consistent? Are they complete, i.e. if the design
  satisfies them are we sure that it is correct?
• Design Verification Is the entry level
  description of my design correct? Most common
  reason for chip failure.
• Implementation Verification Are the different
  levels of abstractions generated by the design
  process equivalent?

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Multi-Million-Gate Verification

• Moores Law
• Faster and more complex designs
• Test-vector size grows even faster than design
  size
• Time-to-market pressures will certainly not abate
• Clearly conflicts with the need to exhaustively
  verify a design before sign-off

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Digital Systems Verification Hierarchy
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Verification Techniques
Goal Ensure the design meets its functional (F)
and timing (T) requirements at each of those
levels of abstraction

• Simulation (FT)
• Build a mathematical model of the components of
  the design, submit test vectors and solve the
  equations that give the output as a function of
  the input and of the models on a computer
• Formal Verification (F)
• Prove mathematically that
• A description has a set of properties
• Two descriptions at different levels of
  abstraction are functionally equivalent

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Verification Techniques
Goal Ensure the design meets its functional (F)
and timing (T) requirements at each of those
levels of abstraction

• Static Timing Analysis (T)
• Analyze circuits topological paths and check
  their timing properties and their impact on
  circuit delay
• Emulation (F)
• Map the design onto the components of the
  emulation machine, submit test vectors and check
  the outputs of the machine possibly physically
  connecting them to a system
• Prototyping (F)
• Build a hardware implementation of the design
  and operate it

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Simulation Perfomance vs Abstraction
Cycle-based Simulator
Event-driven Simulator
Abstraction
SPICE
Performance and Capacity
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Boolean Simulation Single-Processor

• Event-driven ("time-wheel" or static-ordered)
• Delay Model Emphasis (Inertial or Transport) is
  major differentiator.
• Today about 20-50K events/sec/Mip
• Cycle-based

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Cycle-based simulation

• Cycle-based simulators work off of a control and
  data-flow representation
• Treats everything in the design description as
  either clocked element or zero-delay
  combinational logic
• Advantages
• exceptionally fast
• same internal representation for both simulation
  and synthesis
• predicted results same as synthesized logic

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Cycle-based Algorithm

• Input design must be completely synchronous
• Only evaluate on the clock edge
• First evaluate all combinational logic
• Next latch values into state registers
• Repeat on next clock edge

clock
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Boolean Simulation Hardware Acceleration

• Quickturn-IBM (Cobalt) type
• 1M Event/sec.
• Requires fairly long compilation time

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Emulation

• Based on re-programmable FPGA technology.
• Only functional verification (no timing
  verification yet).
• Close to implementation performance.
• Can boot operating system, give look and feel for
  final implementation.
• Allows hardware-software co-design.

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Prototyping Techniques in Design Stages
Hardware Design Changes
Emulation
Cost
Software Simulation
Performance
Prototype Replication
Flexibility
time
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Board Level Rapid-Prototyping Environment

• Early feedback on customers requirements
• Early system integration
• In-field test on vehicle
• Virtual prototyping (co-simulation) and physical
  prototyping (emulation board)

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Simulation vs Formal Methods

• Degree of confidence in simulation depends on
  test vectors selected by the designers
• Formal methods most important for implementation
  verification
• Simulation cannot be replaced by formal
  verification especially for design verification
  specifications are often not given in rigorous
  terms and are not complete

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Analog Circuits A World Apart

• Analog circuits behavior specified in terms of
  complex functions time-domain, frequency-domain,
  distorsion, noise, power spectra.
• Required accuracy of models much higher than
  digital
• emerging paradigm Field Programmable Analog
  Array for prototyping (and more)

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More on Verification.

• System-on-Chip (SoC) Hardware/Software
  Co-Verification
• Mixed-Signal Verification
• Physical Issues introduced by DSM technologies

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Classes at Berkeley
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219A Course Overview

• Fundamentals of Circuit Simulation
• Approximately 12 lectures
• Analog Circuits Simulation 
• Approximately 4 lectures
• Digital Systems Verification 
• Approximately 3 lectures
• Physical Issues Verification 
• Approximately 6 lectures

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Circuit Simulation

• Formulation of circuit equations
• STA, MNA
• Solution of linear equations
• LU factorization, QR factorization, Krylov
  Methods
• Solution of nonlinear equations
• Newtons method
• Solution of ordinary differential equations
• One-step and Multi-step methods

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Analog Circuit Simulation

• AC Analysis and Noise
• Simulation Techniques for RF
• Shooting-Newton
• Harmonic-Balance

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Digital Systems Verification

• Overview
• Cycle-based and event-driven simulation
• Formal methods
• Timing Analysis
• Hardware Description Languages (Verilog-VHDL)
• System C

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Digital Systems Verification Timing Analysis

• Not only has the design to function
  properly.it also has always tighter timing
  constraints
• Design timing properties have
• to be verified
• ? Static Timing Analysis is the main method

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Physical issues verification (DSM)

• Interconnects
• Signal Integrity
• P/G integrity
• Substrate coupling
• Crosstalk
• Parasitic Extraction
• Reduced Order Modeling
• Manufacturability and Reliability
• Power Estimation

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Physical issues verification (DSM)Interconnects

• Scaling technology
• They get longer and longer
• Increasing complexity
• New materials for low resistivity
• ? Inductance and capacitance become more
  relevant
• Larger and larger impact on the design
• ? Need to model them and include them in the
  design choices (gate-centric to
  interconnect-centric paradigm)

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Physical issues verification (DSM)P/G and
Substrate

• Analog and Digital blocks may share supply
  network and substrate
• Can I just plug them together on the same chip?
  Will it work?
• The switching activity of digital blocks injects
  noise current that may kill analog sensitive
  blocks

Digital IP
Analog
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Physical issues verification (DSM)Crosstalk

• In DSM technologies, coupling capacitance
  dominates interlayer capacitance
• ? there is a bridge between interconnects on
  the same layer.they interfere with each other!

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Physical issues verification (DSM)Parasitic
Extraction

• Parasitics play a major role in DSM technologies
• Need to properly extract their value and model

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Physical issues verification (DSM)Reduced Order
Modeling

• Increasing complexity ?? bigger and more complex
  models
• E.g. supply grid, parasitics
• Need to find a reduced model so that
• Still good representation
• Manageable size

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Physical issues verification (DSM)Manufacturabili
ty

• Design a chip
• Send it to fabrication
• .
• Did I account for the fabrication process
  variations?
• How many of my chips will work?
• Just one? All? Most of them?
• How good is my chips performance?
• ?Design and verification need to account for
  process variations!

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Physical issues verification (DSM)Reliability

• Design a chip
• Send it to fabrication
• .
• Did I test my design for different kinds of
  stress?
• Is it going to work even in the worst case?
• Can I sell it both in Alaska and Louisiana?

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Physical issues verification (DSM)Power
Estimation

• Advent of portable and high-density circuits
• ? power dissipation of VLSI circuits becomes a
  critical concern
• ?Accurate and efficient power
• estimation techniques are required

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Emerging Paradigm

• Design and Verification Integration (Correct by
  Construction Paradigm)
• Hardware and Software Co-verification
• ltGone are the days of throwing code "over the
  wall" to another group. Productive verification
  requires tearing down the wall between design and
  verification and between hardware and software.gt
• By Tom Fitzpatrick, Co-Design Automation, Inc.,
  Los Altos, CA
• EETimes, May 28, 2002