CSE464 Digital Systems Engineering L0: Logistics and Introduction David M. Zar Computer Science and Engineering Washington University dzar@wustl.edu (Based on Original Work of Fred Rosenberger) - PowerPoint PPT Presentation

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CSE464 Digital Systems Engineering L0: Logistics and Introduction David M. Zar Computer Science and Engineering Washington University dzar@wustl.edu (Based on Original Work of Fred Rosenberger)

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Title: CSE464 Digital Systems Engineering L0: Logistics and Introduction David M. Zar Computer Science and Engineering Washington University dzar@wustl.edu (Based on Original Work of Fred Rosenberger)


1
CSE464 Digital Systems EngineeringL0 Logistics
and Introduction David M. ZarComputer Science
and EngineeringWashington Universitydzar_at_wustl.e
du(Based on Original Work of Fred Rosenberger)
2
Logistics EE464, Spring 2009
  • Lectures MW 230-400 in Urbauer 116
  • Textbook Dally and Poulton, Digital Systems
    Engineering
  • Grading Approximate weighting for grade
    determination 25 Homework (exams based on
    homework)
  • 35 First midterm exam 45 Final exam
  • Collaboration Academic integrity will be taken
    seriously. You may collaborate on homework with
    other students, use solutions from last year, or
    get help from anyone but you are to state who you
    worked with or got help from, and give an
    estimate of contribution from other sources to
    what you submit. This is just acknowledgement of
    source of material, and recognition of the work
    contributed by others, it has no effect on your
    grade. Exceptions to this rule will be specified
    in the assignments. Tests and projects are to be
    entirely your own work.

3
More Logistics
  • Exams Closed book. One handwritten (no
    photocopies) sheet (both
  • sides) allowed on first exam, two sheets final
    exam.
  • Homework Usually due in class (230 p.m.) on
    assigned date.
  • Instructor David M. Zar Bryan 307C GPS N38
    38.979' W90 18.360' Elevation 550'
  • Office Hours by appointment. dzar_at_wustl.edu
    (best contact method) http//www.cse.wustl.edu/d
    zar
  • Attendance Class attendance is important,
    material will covered in class that is not in
    text. You will wish to get copies of notes from
    classmate if you miss class.

4
Discussion Topics
  • Class attendance
  • Class participation (please!)
  • Dally (Dally, not Daily) lecture notes
  • Textbook cost, errata, etc.
  • Homework length and style
  • EE314 Engineering Electromagnetics 1
    Fundamentals
  • Goal Extremely practical backed up by theory
    and analysis

5
Interesting Links and Sources
  • Links
  • http//www.signalintegrity.com/
  • http//www.nesa.com/
  • http//www.sigrity.com/
  • http//www.ultracad.com/ (careful here)
  • http//www.automata.com/ (careful here, some
    calculations are wrong)
  • http//groups.yahoo.com/group/si-list (this is
    the signal integrity mailing list archive lots
    here, good and bad)
  • Books
  • High-Speed Digital Design, A Handbook of Black
    Magic, Howard W. Johnson and Martin Graham,
    Prentice Hall, ISBN 0-13-395724-1, 1993.
  • High-Speed Signal Propagation, Advanced Black
    Magic, Howard W. Johnson and Martin Graham, ISBN
    0-13-084408-X, 2003
  • Brooks, Bogatin, Ritchey, Granberg, ...
  • Transmission Lines with Pulse Excitation, Georges
    Metzger and Jean-Paul Vabre, Academic Press, New
    York, NY, 1969. (Bergeron Diagrams)

6
Todays Assignment
  • Reading
  • Complete before Wednesday, Jan 14 class
  • Preface, Chapter 1
  • Complete before Wednesday, Jan 21 class
  • Chapter 2
  • Complete before Monday, Jan 26 class
  • Chapter 3, Sections 3.1 through 3.3.3

7
Digital Systems Engineering
  • From Dally
  • noise management
  • keeping signals clean
  • signaling
  • moving bits from here to there
  • timing
  • how we know when a new bit is here
  • power distribution
  • DC voltage with AC current
  • Signal integrity
  • High-Speed signals
  • low speed signals
  • reset
  • All Signals
  • Signaling (electrical representation
    of signals)
  • Timing/Clocking
  • Power distribution
  • Cooling/Packaging as part of above

Rules of Thumb (e.g. C/inch, L/inch) Analytical/C
alculation Simulation (HSPICE) Measurement Tools
(dont be a tool driver)
8
Wires
  • Advanced components Wires
  • Care and feeding of wires
  • Wires can be expensive, even if its a scam
  • http//www.monstercable.com
  • http//www.jpslabs.com/aluminata.shtml (they
    claim Pricing- If you have to ask.)
  • "The shear mass of the particle shield alone
    proves that JPS has the transfer of noise taken
    care of- Nothing gets through this cable's shield
    and into the conductors beneath- NOTHING... "

9
Why is Digital Systems Engineering/Design Harder
Now Than Previously?
  • Wires are not ideal (never were, but valid
    approximation sometimes) !!!
  • Gross Simplification here Long wires or
    High-Speed Design (delay gt 0.1 Clock Period)
  • 1968 1 MHz gt40 ft
  • 1978 10 Mhz gt4 ft
  • 1988 100 Mhz gt5 inches
  • 1998 1 GHz gt0.5 inch
  • 2008 10 GHz??? gt0.05 inch
  • 2018 ?????
  • Overall size of system? approximately constant
  • Ad hoc methods that worked in the past now fail
  • To paraphrase Roy Jewell, President of TMA The
    rules of physics dont change for high-speed
    design, they are just more strictly enforced.
  • The fact that long wires are harder to deal with
    does not imply short ones are easy, nor that they
    can be ignored.
  • The fact that high-speed signals are harder to
    deal with does not imply that slow ones are easy,
    nor that they can be ignored (e.g. Reset).
  • EMI Even harder, we will not deal with this in
    CSE464.

10
Outrageous Statements
  • Propagation delay to closer device is longer
  • Slower is better (and faster)
  • A capacitor is an inductor unless you want
    inductor
  • Converse for inductor (or resistor)
  • Short wire is worse than long one (e.g. probe)
  • Negative characteristic impedance?
  • Square corners on PC traces are bad?
  • Vias on PC traces are bad?
  • Resistor networks Bad?
  • We could not use perfect logic (Midas touch)!
  • Tune your absurdity detector!!!

11
Thoughts to Remember (Models)
  • A model is an artifice to make you think you
    understand a problem better than you actually do.
  • All models are wrong, but some models are useful.
  • Make everything as simple as possible, but no
    simpler (A. Einstein).
  • In theory there is no difference between practice
    and theory, but in practice there is!
  • An approximate answer to the right question is
    worth a good deal more than the exact answer to
    an approximate problem. John Tukey (FFT Fame)
  • Models are a really dangerous (and necessary)
    tool
  • Example ground, ideal ground, logic ground,
    safety ground,

12
Ground is Fiction
  • At low frequency and low accuracy ground is a
    convenient model
  • Be very careful
  • What is ideal ground (see si-list)? What you
    draw with chalk on a blackboard!

13
Bonus Safety Ground
14
What is Wrong Here?
15
Lots!!!Try to avoid surprises!!!What worked
last time may not work this time!
What is Wrong Here?
16
Surprises
  • Invalid Assumptions
  • Individual effects dont add linearly
  • Consider effects one at a time, not the sum
  • Coupling from multiple sources (lines)
  • PS noise
  • Reflection noise
  • Component tolerances
  • Temperature
  • Process
  • PC board noise
  • Package noise
  • Connectors
  • Vias

17
More Surprises
  • Multiple backward xtalk coupling, increased V
  • Unaccounted for parasitics
  • Inductance
  • Resistance
  • Capacitance
  • ESR, ESL
  • Nonlinearities
  • Series termination with Capacitance load
  • Driver resistance when switching (1/4 wave)

18
Still More
  • Transmission line
  • Manufacturer data sheets
  • Stubs
  • Split load and standing wave
  • Layout rules/communication/slip-up
  • Tolerances
  • T-line traces, return currents
  • R and C functions of frequency

19
Last of Surprises?
  • System cost
  • Vs. Design time
  • Vs. Manufacturing time
  • Vs. Reliability
  • Metastability

20
Digital Systems Engineering
  • Designing systems that work by design, not by
    trial and error, with reasonable cost (dollars,
    time, effort, ). Using appropriate tools
    (analysis, simulation, measurement) to insure
    correct operation. Avoiding surprises.
  • Question which is better?
  • Guess/Estimate?
  • Analysis (e.g. equations and calculation)?
  • Simulation (e.g. HSPICE)?
  • Measurement (e.g. oscilloscope, TDR)?
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