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ComputerAided Verification of Electronic Circuits and Systems

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... the design description as either clocked element or zero-delay combinational logic ... Only evaluate on the clock edge. First: evaluate all combinational logic ... – PowerPoint PPT presentation

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Title: ComputerAided Verification of Electronic Circuits and Systems


1
Computer-Aided Verification of Electronic
Circuits and Systems
  • EE219A Fall 2002
  • Professor Prof. Alberto Sangiovanni-Vincentelli
  • Instructor Alessandra Nardi

2
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

3
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

4
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

5
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
6
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?

7
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

8
Digital Systems Verification Hierarchy
9
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

10
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

11
Simulation Perfomance vs Abstraction
Cycle-based Simulator
Event-driven Simulator
Abstraction
SPICE
Performance and Capacity
12
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

13
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

14
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
15
Boolean Simulation Hardware Acceleration
  • Quickturn-IBM (Cobalt) type
  • 1M Event/sec.
  • Requires fairly long compilation time

16
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.

17
Prototyping Techniques in Design Stages
Hardware Design Changes
Emulation
Cost
Software Simulation
Performance
Prototype Replication
Flexibility
time
18
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)

19
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

20
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)

21
More on Verification.
  • System-on-Chip (SoC) Hardware/Software
    Co-Verification
  • Mixed-Signal Verification
  • Physical Issues introduced by DSM technologies

22
Classes at Berkeley
23
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

24
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

25
Analog Circuit Simulation
  • AC Analysis and Noise
  • Simulation Techniques for RF
  • Shooting-Newton
  • Harmonic-Balance

26
Digital Systems Verification
  • Overview
  • Cycle-based and event-driven simulation
  • Formal methods
  • Timing Analysis
  • Hardware Description Languages (Verilog-VHDL)
  • System C

27
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

28
Physical issues verification (DSM)
  • Interconnects
  • Signal Integrity
  • P/G integrity
  • Substrate coupling
  • Crosstalk
  • Parasitic Extraction
  • Reduced Order Modeling
  • Manufacturability and Reliability
  • Power Estimation

29
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)

30
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
31
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!

32
Physical issues verification (DSM)Parasitic
Extraction
  • Parasitics play a major role in DSM technologies
  • Need to properly extract their value and model

33
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

34
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!

35
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?

36
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

37
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
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