Vendors Elaborate on HSIO Test Products and Strategies

High-speed I/O (HSIO) is presenting significant measurement challenges as fourth-generation standards emerge, as detailed in EE-Evaluation Engineering's January special report on serial-bus test. That report describes the relevant offerings of companies including Agilent Technologies, Anritsu, Rohde & Schwarz, Tektronix, and Teledyne LeCroy. Relevant products include bit error rate testers and oscilloscopes. Providing detailed insight to the latter is our January special report on oscilloscopes and the companion online exclusive on the topic. The following online exclusive article offers elaboration on HSIO test and provides links to additional resources to facilitate additional research.

Hiroshi Goto, business development manager at Anritsu, elaborated on his company's new high-sensitivity error detector (ED) and PAM converter, as well as enhanced its MP1825B 4Tap Emphasis, which extends the performance of the MP1800 Signal Quality Analyzer BERT to support accurate signal integrity analysis of high-speed interconnects.

“The new ED delivers a wideband bit rate from 2.4 to 32.1 Gb/s and offers Rx sensitivity of typically 10 mV to enable BER measurement for the closed eye of high bit-rate data transmission,” he said. “An Auto Adjust function detects the optimum BER voltage threshold and phase level in less than one second simultaneously for up to eight channels in order to improve test efficiency and lower cost-of-test.”

Goto added, “Combining the 4PAM/8PAM converters with the MP1800A supports generation of both 4PAM and 8PAM signals for R&D high-speed backplane and 400 GbE R&D. The high-quality NRZ waveform from the MP1800A and wideband passive PAM converter together generate best-in-class PAM signals with assured S/N.

“The MP1825B 4Tap Emphasis supports easy changes to the pre-emphasis waveform amplitude, offset, and amplitude of each tap, so signal integrity engineers can more effectively evaluate high-speed interface characteristics. Unlike other solutions, each tap can be changed independently on the MP1825B. This allows the effect of pre-emphasis to be confirmed with higher precision.”

Chris Loberg, senior technical marketing manager at Tektronix, elaborated on how Tektronix help customers solve fixturing and probing issues. “Tektronix provides a high level of support for customers trying to access their devices for successful serial bus measurements,” he said, citing three examples of support the company provides:

Industry Plugfests. “Tektronix actively runs golden test suites at over a dozen industry plugfests annually,” Loberg said. “These plugfests are sponsored by the standards industry (e.g., PCI-SIG, USB-IF, SATA-IO), and Tektronix provides equipment and consultation at each of them, trying to assist customers seeking compliance advice for their devices.”

Meet The Experts Seminars. “Tektronix hosts a bimonthly series at its Santa Clara, CA, campus featuring half-day seminars on how to test and probe/connect to devices for different standards,” Loberg said.

Field Application Engineers. “Tektronix has apps engineers stationed in the field at key locations around the US/World,” Loberg said. “These FAEs have years of experience in guiding customers on interconnect issues and prescribing proper probing/de-embedding techniques for specific needs.”

Product innovations have helped, too, Loberg said. “Tektronix released SDLA-64bit software for our DPO/MSO70000 Series oscilloscopes,” he said. “This enables a more precise measurement from the transmit pins of a chip or board by extraction of measurement artifacts from cable/connector/boards that interfere with the signal path. In addition, the continued leadership in high-bandwidth probing is evidenced in the P7633 Probing System. This product features a remote-head probing technique, which places the calibrated measurement source as close as possible to the device under test, enabling a greater degree of confidence for signal fidelity in these new high-frequency signaling environments.”

Chris Busso, senior product marketing manager at Teledyne LeCroy, elaborated on the HDO oscilloscopes. “The underpinning of the HDO’s serial decode capabilities lies in Teledyne LeCroy’s ProtoBus MAG (Measure, Analyze, Graph) serial debug toolkit, the basic building block upon which many other serial trigger and decoder options can then be added,” he said. “It significantly extends the trigger and decode functionalities of these other packages by providing tools for more complete and faster validation and debugging of embedded designs.” Supported protocols extend from I²C to InfiniBand.

“All protocol decoding is shown directly on the waveform with an intuitive, color-coded overlay and presented in binary, hex or ASCII,” he said. “Decoding on the HDO is fast even with long memory, and zooming in to the waveform shows precise byte-by-byte decoding.”

Busso added, “To further simplify the debug process all decoded data can be displayed in a table below the waveform grid. Selecting an entry in the table with the touch screen will display just that event. Additionally, built-in search functionality will find specific decoded values.”

Busso also commented on configurable Manchester/NRZ decode. “Many of today's serial data-communication protocols are built on Manchester or NRZ encoding,” he said. “Such protocols range from specialized buses such as Digital Addressable Lighting Interface (DALI) for control of building lighting and the Peripheral Sensor Interface 5 (PSI5) used to connect sensors to controllers in automotive applications, to proprietary, custom buses used for non-standardized applications. In all of these cases, the basic Manchester and NRZ schemes are modified to create the more complex, specialized protocols. Designers around the globe are developing and debugging systems with these protocols and looking for bus analysis tools to simplify the process.”

Teledyne LeCroy's Manchester and NRZ protocol decoders, Busso said, help engineers design and debug such custom protocols by providing broad flexibility in terms of physical layer characteristics, protocol word and frame structure, and other parameters. “Users may specify bit rates from 10 bits/s to 10 Gb/s,” he said. Idle states, sync bits, and header and footer information can all be configured to decode custom preambles or CRC details. “Decoding is highly flexible,” he added. Data mode can be in bits or words with viewing in hex, ASCII, or decimal. Further, bit order may be either LSB or MSB. “Decoded information is displayed with a color-coded overlay,” he said, “which expands or contracts as the user adjusts the oscilloscope timebase or zooms in on the waveform for more details.”

He added, “Powerful search capabilities allow users to quickly search long captures of decoded Manchester and NRZ waveforms for specific bus details such as data, sync, or interframe gap. Decoded data is conveniently displayed in an interactive table. Clicking on any line in the table opens a zoomed view of that instance in the waveform.”

To help customers contend with fixture and probing issues, Teledyne LeCroy offers the Virtual Probe software option, which permits the viewing of waveforms as they would appear other than at the probing point. “It is very useful in circumstances where a user wants to understand the characteristics of signals at a point in the circuit where a physical probe cannot be placed, such as inside of a chip package or at the end of an interconnect that does not physically exist,” Busso said. “Users can remove effects caused by elements such as fixtures that will not be present when the DUT is in its final configuration, or add the effects of a device that is to be included but for which only an S-parameter model exists.”

As for physical probing, Busso said, “A common issue for oscilloscope users is that of probe loading and its effects on the DUT. Our WaveLink medium- (8-13 GHz) and high-bandwidth (13-25 GHz) differential probing systems are carefully designed to mitigate AC loading and to deliver superior noise performance.”

The WaveLink medium-bandwidth probes provide high dynamic range of 3.5 V_PK-PK and a ±4-V offset range. “As a result,” Busso said, “they’re a suitable choice for DDR probing applications, not to mention a wide variety of related differential and single-ended signals. Such signals have widely varying voltage swings, often accompanied by high overshoot. They also can be seen with high offset levels.”

Busso added, “Many of the same issues that worry users of differential probes also plague users of single-ended probes. The effects of probe loading on the DUT can impact its performance and cause skewed test results. To that end, the ZS4000 single-ended probe extends the ZS probe family’s bandwidth to 4 GHz.”

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