Home > Articles > Engineering > Communications Engineering

  • Print
  • + Share This
This chapter is from the book

Power On

The first set of boards came back from assembly and performed admirably on the bench top. The hardware team did their job measuring thermal characteristics, calculating power draw, and capturing bus transaction traces on the logic analyzer. Programmers sifted through register dumps and debugged their code. Knowing there was a possible exposure to crosstalk problems, Anne probed around the board while the other team members were out for a caffeine break. She found low levels of quiet line noise—for example, 200 mV on a 2.5 V signal. No cause for alarm. After two weeks of intense work, the development team declared the board ready for pre-production testing, and everyone left work early to celebrate.

The first sign of trouble arose in the final days of pre-production testing. A set of boards was in the thermal chamber undergoing stress testing at temperature and voltage corners when one of them crashed during a boot cycle, leaving little useful information in the registers. They pulled the board out of the chamber and attempted to repeat the fail on the bench top. No luck. The experienced engineers on the team collectively cringed, remembering painful 14-hour days on another project with a similar irreproducible error. Back to the chamber and still no luck. How worried should they be about this phantom error? It only occurred once while stressing voltage beyond design limits in an attempt to emulate the spectrum of silicon processing variations they expected to see in manufacturing. One could make a strong argument that silicon and voltage stresses produce different failure mechanisms. Are the test results truly representative of actual operating conditions?

Then the phantom reappeared, this time on the bench top while someone happened to be watching the console. The processor had just finished loading boot code and was passing control to the bridge chip to initialize the PCI Express interface. This serial number failed more than once, although not on every boot. The next morning during the daily meeting, the team discussed their options. Hearing the words "PCI Express initialization" reminded Anne of the design review and the I2C clock. She convinced the team to set up two parallel tests probing the I2C clock and its PCI Express neighbor using a glitch detect trigger. They repeatedly booted each board watching for the telltale crosstalk signature.

Their persistence and patience finally paid off when the gremlin surfaced again several days later during the middle of the graveyard shift around 3:00 am. Since I2C and PCI Express are asynchronous to one another, the board only crashed when timing conditions were exactly right for the PCI Express crosstalk to superimpose on the I2C clock while it was passing through the threshold region. The sharp, low-amplitude crosstalk caused a brief slope reversal in the slower I2C clock edge—just enough to clock the input latch twice and upset the state machine.

For a while, the engineers on the development team were elated at having found clear evidence pointing to the origin of the fault. Then reality set in: There was little to be done about it. It is not possible to slow down the edge rate on a PCI Express net. Someone would need to notify management, and that unpleasant job fell to Anne as the signal integrity engineer. They did not receive the news well but were at least decent enough to realize that they had set the stage by proceeding with an extremely aggressive project without gathering input from those responsible for making it happen. Management asked development engineering for a recovery plan.

The following day, the team isolated themselves in a conference room with a white board, pizza, caffeinated beverages, and mandatory cell phone silence. Adding layers to the board and rerouting did not appeal to anyone. Just when they had run out of ideas, Bob the veteran popped his head in the door because word of their dilemma had reached him and he was curious about how things were proceeding. Not very well, they explained, and invited him to listen in for a few minutes. Bob had earned a great deal of respect among his colleagues by observing intently, listening thoughtfully, and not opening his mouth until he had formed a well-founded opinion. When he finally spoke, people's ears perked up.

"What kind of package does your I2C buffer use?"

"TSSOP."

"Good. I was hoping you wouldn't say BGA. Why don't you lift the lead of the clock output pin and insert a snappy little high-bandwidth FET? This will sharpen up the I2C clock so the crosstalk will simply roll off the edge a bit rather than cause a slope reversal."

It may look good on the balance sheet to hand out pink slips to experienced engineers like Bob from time to time, but when they walk out the door, their experience goes with them. After implementing Bob's fix, the gremlin disappeared for good. Project Coyote was out of the ditch—for the time being.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020