Ensuring that All Things Digital Play Well Together

Think of all the high-speed digital devices in your life. The ones you see, like your smartphone or your laptop, and the ones you don't see, like all those computer servers that make up the so-called cloud. Think about the little things you hardly notice, like the high-speed cables that transfer movies from your DVR to your HDTV, or the thumb-sized memory stick that holds copies of all your files.

"High-speed digital—anything that goes faster than 5 gigabits per second—constitutes a major focus for engineers," says Shamree Howard, the cross-divisional lead for high-speed digital marketing operations at Keysight.

Digital designers play a vital role in helping to ensure that all the digital devices we take for granted actually work they way they're supposed to—with each other.

"That's what high-speed digital is all about," Shamree says. "It's making sure all things digital play well together. When you plug your USB stick into your computer, you want those two things to talk to each other, so there's a standard they both have to meet to ensure that interoperability is seamless. When you take your SD card out of your digital camera and put it into your laptop to download your pictures, you don't want to see: ‘Device Not Recognized.' The cables that connect your iPhone to your computer or to the wall outlet? Those have to be tested. The HDMI cables to your high-def television? Those have to be tested. You need to know that, regardless of whether you get them from Verizon or Best Buy, they're going to work."

Interoperability doesn't just happen. It happens because of thousands of industry standards and the oscilloscopes, logic analyzers, network analyzers, bit error ratio testers and simulation programs that ensure compliance.

"High-Speed digital designers have signal integrity issues from simulation through compliance testing," Shamree says. "They start testing for these issues in the design layout long before any silicon is created."

Plus, there are high-speed digital functions within devices that we never see but must meet exacting standards or they won't work.

"The faster these things go, the greater the chance something could go wrong," Shamree says.

Remember when the Internet was referred to as the information superhighway? It's an apt analogy, especially useful in describing what's happening with high-speed digital technology today, like PCI Express.

"You can either increase the efficiency of the highway with things like metered on-ramps, or you can add lanes, but the more lanes, the more chances of accidents happening," Shamree explains. "You can also increase the speed limit, but that too increases the risk that accidents will happen."

Whatever the approach, it will only work if everyone plays by the same rules.

"Some people create individual parts, and some people put all the parts together within a device." Shamree says. "So companies of all kinds have to be able to check interoperability, and we can help them do that."

To that end, the industry has long focused on industry standards. Some industry standards bodies, such as PCI-SIG, actually create the tests required to gain certification; other organizations, such as JEDEC, create new standards and leave it up to individual companies to determine how to test them.The table below will help you compare some of the predominant high-speed digital standards committees:

Organization	Standards	Compliance Certification required?	Where to gain certification	Website
JEDEC	DDR, GDDR, LPDDR, e.MMC, etc.	No	NA	www.jedec.org
PCI-SIG	PCIe, PCI-X, I/O Virtualization	Yes	Plugfests	www.pci-sig.com
VESA	DisplayPort	Yes	Authorized Test Center, self-test	www.vesa.org
HDMI	HDMI	Yes	Authorized Test Center, self-test	www.hdmi.org
USB	USB	Yes	Workshops, Authorized Test Center, self-test	www.usb.org
Serial ATA	SATA	Yes	Authorized Test Centers	http://www.sata-io.org/
SCSI Trade Association	SAS, SCSI Express	No	NA	http://www.scsita.org/

 

Keysight sits on these committees to help ensure that the new standards coming out can be tested. "We're not just waiting for new standards to come out," Shamree says. "We're helping to define them. This enables us to bring the right solutions to market when customers need them."

Anything faster than 5 gigabits per second starts to get tricky, she says, but it's not just the increased speed that makes things harder. Devices are getting smaller all the time—crowded with tiny circuits—and they need to use as little power as possible so their batteries don't run out so fast.

"At slower speeds, customers could easily ignore things like receiver testing and simulation. Now, as we're getting beyond 5 gigabits per second—to 8 or 12 or whatever it may be—they're starting to realize they can't skip those steps anymore," Shamree says. "Now more and more customers have to worry about simulation and receiver testing as well as all the stuff they used to do. Moving forward, having one company that can take you from simulation through the debugging process to receiver testing to verifying compliance with relevant standards is going to be increasingly important."

In fact, a big trend now, across a lot of different standards, is receiver equalization. That is, giving the receiver a standardized way to talk back to the transmitter and ask for clarification, if needed.

As a commonplace example of transmitting and receiving, think about digital images moving from your smartphone over a cable to your computer. All three of those things need to be tested. First, you need an oscilloscope to test the transmission of information. Using oscilloscopes that are exceptionally quiet is extremely important. Why? "You do not want to be creating more noise than the device you're trying to test," Shamree explains. "Having equipment with the lowest noise floor means you can actually measure what's happening on your device, not the equipment you are using to make your tests.

At high speeds, you can no longer assume the receiver understood what you transmitted. Imagine listening to a person talking very fast, in a crowded room where everyone else is talking, too, and that person's whispering because he wants to conserve his voice. If you couldn't hear what the person was saying you'd ask for clarification. In the same way designers need a smart receiver, one that can say, in essence: "Wait a minute. What? Can you repeat that?" It needs to be a dynamic relationship, like two people talking.

Below is a list of commonly used test equipment for high-speed digital testing. Designers are using any combination of these products to create the latest smartphones, tablets, desktop computers, HDTVs, and cables to connect them. Just like the standards organizations, these test solutions help ensure all things digital play well together.

Simulation programs are used to design, simulate and optimize the performance of electronic circuits on a chip or printed circuit board. With Keysight's electronic design automation software, engineers accelerate the design and validation of their designs before building the first prototype.

Oscilloscopes observe and measure changing electrical signals, monitor input and output, and test for compliance to specific standards. Electronics companies use Keysight's high-speed real-time oscilloscopes to validate and debug integrated circuits and computer chips.

Logic analyzers capture and display multiple signals from a digital system or circuit. Keysight logic analyzers help minimize project risk by providing the most reliable, accurate measurements and the most complete view of system behavior.

Network analyzers characterize the response of devices within electrical networks to verify simulation models or actual hardware. Keysight's PNA-X network analyzers provide the broadest range of measurements through a single set of connections to a device under test, allowing manufacturers to reduce test time.

Bit error ratio testers measure the number of received bits of data that have been altered due to noise, interference, distortion or synchronization errors. Keysight's BERT solutions allow the most accurate and efficient design verification, characterization, compliance and quality testing of high-speed communication ports for today's integrated circuits, components and modules.

Keysight's high-speed digital solutions offer a wide range of essential tools to help engineers design and simulate, analyze, debug and achieve compliant designs while cutting through the challenges of gigabit digital designs. For additional information visit www.keysight.com/find/hsd.