CSE464 Digital Systems Engineering L0: Logistics and Introduction David M. Zar Computer Science and Engineering Washington University [e-mail] (Based on Original Work of Fred Rosenberger)

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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)
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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.

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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.

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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

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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)

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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

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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)
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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... "

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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.

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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!!!

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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,

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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!

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Bonus Safety Ground
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What is Wrong Here?
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Lots!!!Try to avoid surprises!!!What worked
last time may not work this time!
What is Wrong Here?
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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

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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)

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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

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Last of Surprises?

• System cost
• Vs. Design time
• Vs. Manufacturing time
• Vs. Reliability
• Metastability

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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)?