Logistics EE464, Spring 2011

1. CSE464 Digital Systems EngineeringL0: Logistics and Introduction David M. ZarComputer Science and EngineeringWashington Universitydzar@wustl.edu(Based on Original Work of Fred Rosenberger)

2. Logistics EE464, Spring 2011 Lectures: MW 2:30-4:00 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 (2:30 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@wustl.edu (best contact method)http://www.cse.wustl.edu/~dzar http://tinyurl.com/wucse464 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://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. Today’s Assignment • Reading • Complete before Wednesday, Jan 24 class • Preface, Chapter 1 • Complete before Wednesday, Jan 26 class • Chapter 2 • Complete before Monday, Jan 31 class • Chapter 3, Sections 3.1 through 3.3.3

7. 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 Digital Systems Engineering Rules of Thumb (e.g.: C/inch, L/inch) Analytical/Calculation Simulation (HSPICE) Measurement Tools (don’t be a “tool driver”):

8. Wires • Advanced components: Wires • Care and feeding of wires • Wires can be expensive, even if it’s 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... “ • The truth about Monster Cables

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 ~> 0.1 Clock Period) • 1968 1 MHz; >40 ft • 1978 10 Mhz; >4 ft • 1988 100 Mhz; >5 inches • 1998 1 GHz; >0.5 inch • 2008 10 GHz??? >0.05 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 don’t 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 don’t 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)?