PCI Express® Transmitter Compliance/Debug Solution

The PCI-SIG 6.0 specification has introduced PAM4 signaling to achieve 64 GT/s while maintaining NRZ signaling for backwards compatibility. The multilevel (PAM4) approach brings new signal integrity challenges to adopters and validation teams. Tektronix PCI Express 6.0 software minimizes this new complexity to automate testing and ensures measurement accuracy and repeatability.

The Tektronix Option PCE6 (Gen6), Option PCE5 (Gen5), Option PCE4 (Gen4), and PCE3 (Gen 1/2/3) applications provide the most comprehensive solution for PCI Express Transmitter and Reference Clock compliance testing as well as debug and validation of PCI Express devices against the PCI-SIG® specifications.

Features and benefits

Applications

Tektronix provides the most comprehensive solutions for validation and compliance of PCI Express transmitters at the Base (silicon) and system level including support for CEM, U.2, and M.2 interfaces. Numerous protocols utilizing the PCI Express physical layer including NVMe and CXL can take advantage of the transmitter and reference clock automation under TekExpress software solution.

The Tektronix Option PCE3 (Gen1/2/3), PCE4 (Gen4) and PCE5 (Gen5) includes compliance and debug testing and electrical validation for the following:

• Root complex base Tx jitter and voltage
• Endpoint base Tx jitter and voltage
• Switches
• Bridges
• Add-In cards
• System boards
• Embedded systems
• Express module

The Tektronix Option PCE3, PCE4 and PCE5 applications include a TekExpress™ compliance automation solution that integrates SigTest from the PCI-SIG as well as Tektronix DPOJET-based PCI Express Jitter and Eye Diagram analysis tools for debug purposes in a single software package.

The Tektronix Option PCE6 (Gen6) includes the following signal quality measurements:

• Unit Interval
• V-TX-DIFF-PP
• V-TX-EIEOS-FS
• T-TX-UTJ
• T-TX-UDJDD
• T-TX-RJ
• RLM-TX
• SNDR
• PS21 TX
• V-TX-BOOST
• T-TX-UPW-TJ
• T-TX-UPW-DJDD
• V-TX-AC-CM-PP
• V-TX-AC-CM-PP-Filtered

The PCIe Gen6 has two pre-shoot and one de-emphasis value for each preset complicating the preset test algorithm. The Tektronix PCE6 also comes with Tektronix Preset test tool, which can be used either by TekExpress or manually.

TekExpress compliance automation is available now for PCIe Gen 1-3 CEM and Gen 3 Base via Option PCE3, Gen4 CEM and Gen4 Base via Option PCE4, and Gen5 CEM and Gen5 Base via Option PCE5.

The Tektronix Option PCE3, Option PCE4, and Option PCE5 applications are compatible with Tektronix DPO/MSO70000 series oscilloscopes that are designed to meet the challenges of the next generation of serial data standards such as PCI Express. These oscilloscopes provide industry competitive vertical noise performance with the flattest frequency response for oscilloscopes in their class. The Tektronix DPO/MSO70000 series of oscilloscopes have been approved by PCI-SIG for compliance testing.

Compliance testing

The PCI-SIG provides PCI Express compliance tests for testing PCI Express systems and add-in cards. For a PCI Express system or a device to be placed on the Integrators List, the system or device must pass interoperability and compliance testing. For electrical validation, the PCI-SIG uses SigTest Post Capture Analysis Software that uses acquisitions from an oscilloscope connected to the PCI-SIG's CBB (main board + riser) test fixture for add-in cards or CLB test fixture for systems to perform the analysis. Manually capturing the required waveforms and analyzing them is tedious, time consuming, and error prone.

The Tektronix Option PCE3, Option PCE4, and Option PCE5 TekExpress Automation for PCI Express Transmitter Compliance reduces the effort and accelerates the compliance testing for PCI Express systems and devices with several unique and innovative capabilities. These options ultimately allow the testing of devices that support various technologies, such as NVMe, which is supported as an add-in card device, or through a U.2 or M.2 connector.

The Tektronix Option PCE3, Option PCE4, and Option PCE5 TekExpress Automation software can control the DUT using selected models of a Tektronix AFG or AWG, GRL PCIE 3/4 Controller or NI USB6501 CBB controller to toggle DUT and automatically cycle it through various speeds, de-emphasis, and presets that are necessary for the compliance test. This eliminates the error-prone manual push button approach normally used for DUT control on the CBB and CLB test fixtures.

A complete test run requires multiple waveforms to be acquired at different DUT settings per lane. This waveform set will increase by the number of lanes that need to be analyzed. The ability to manage and store the required data for analysis and future reference is an important criterion for any compliance solution. The Option PCE3, Option PCE4 and Option PCE5 TekExpress automation software, apart from adjusting the horizontal and vertical settings as well as the acquisition depth for optimal signal quality for accurate analysis, provides easy analysis to manage multiple acquired waveforms.

This makes use of the PCI-SIG's SigTest EXE to analyze the acquired waveforms. Thus makes the results of the analysis consistent with the SigTest post-capture analysis software used at PCI-SIG workshops for compliance testing.

The Option PCE3, Option PCE4 and Option PCE5 TekExpress automation software provides flexibility in selecting data rates, voltage swing, presets, and the tests to run. It also provides the option to de-embed the effects of the channel and the test fixtures and provide an accurate representation of the signal at the pins as required by the specification.

TekExpress uses Tektronix next generation PAM4 tool PAMJET for the measurement. During analysis, TekExpress will automatically set up the tool as per the specification, capture results, and report them to the user. PAMJET also allows expert users to configure the PAMJET tool to test the DUT in non-specification settings for debugging purposes.

PAMJET introduces the Signal to Noise Distortion Ratio (SNDR) measurements with measurement methodology updated to support the latest PCI Express 6.0 Base Specification. Support for instrument noise compensation is integrated to improve measurement accuracy.

All the analysis results are compiled in a PDF/HTML/CSV formatted report that can include pass/fail summary, eye diagrams, setup configuration, and user comments. The contents of the report can be customized to include information of interest such as append results and custom report generation based on test name/pass fail/equalization.

Reference Clock Testing with TekExpress

Reference Clock testing has moved from optional to required for many designs due to the jitter limit decrease driven by the highest data rates supported by the PCI-SIG standards. Additionally, with the removal of dual-port (data and clock Tx testing) for Gen5 systems, compliance is required on the reference clock. The TekExpress PCIe solution has now integrated the SkyWorks Clock Jitter Tool to allow an automated hassle-free Reference Clock testing. Once the user connects the Reference Clock output to the oscilloscope, the TekExpress PCIe software will acquire the signal, invoke the SkyWorks Clock Jitter Tool, and provide Reference Clock test results from Gen1 to Gen5. Instrument noise compensations is supported with the Skyworks Clock Jitter Tool.

Switch Matrix automation

Switch Matrix application allows to configure and setup automated multi-lane testing using RF switch. The solution allows you to map each of the several transmitter signals and forward the selected input either to another relay or to the oscilloscope channel. Option SWX-PCE supports x12 and x16 lanes using Keithley and Gigatronics switches respectively, and enhances throughput and automated test speed.

Debug and validation

If a DUT or Add-In card fails any portion of the compliance test, the application includes a DPOJET-based debug and analysis tool kit customized for debug and validation of PCI Express interfaces.

The new jitter measurements introduced with PCIe Gen3 and Gen 4 provide separate limits for data dependent (DDJ) and uncorrelated deterministic jitter (UDJDD). It is important to separate DDJ (which can be compensated with transmitter and receiver equalization) and UDJDD (which can be caused by effects such as crosstalk and power supply noise).

Apart from the above Jitter measurements, Pulse Width Jitter (PWJ) is a new measurement that addresses the increased channel loss at 8 to 16 Gb/s. The purpose of the PWJ measurement is to ensure that lone bits meet minimum pulse width requirements. All new jitter measurements implement Q-scale extrapolation as defined in the base specification. The Tektronix Option PCE3, Option PCE4, and Option PCE5 provide the complete set of PCI Express 3.0, 4.0, and 5.0 Base Spec jitter measurements enabling silicon designers to verify that their silicon meets the base specification requirements.

Furthermore, the base specification requirements are defined at the pins of the transmitter. Before the measurements are computed the test channel must be de-embedded. De-embed filters can be easily created using the Tektronix Option SDLA64 Serial Data Link Analysis software and then quickly entered into the Option PCE3 and Option PCE4 base specification measurement setup and saved for future use. In addition to jitter, Option PCE3 and Option PCE4 also provide voltage, package loss, and transmitter equalization measurements.

Option PCE3 and Option PCE4 leverage the channel modeling and receiver equalization functionality of the Tektronix Option SDLA64 software to support CEM measurements. Unlike other solutions, Option PCE3 and Option PCE4 provide full visibility to the signal as it has been modified to embed the compliance channel and provide receiver equalization. Eye diagrams and measurements can be set up to visually see the results of channel embedding, CTLE application, and DFE. For example, when determining the optimal Rx Equalization settings (CTLE setting and DFE tap value) the resulting eye diagrams and measurements show the effects of post processing on the acquired signal. Compliance measurements can then be taken on the waveform.

PAMJET for GEN6 Base Measurements

Tektronix has created a next generation PAM4 tool named PAMJET, which is used for Gen6 Base measurement. This PAMJET tool can configure the measurement and can perform Bessel Thompson filtering, configure Gen6 clock recovery, configure CTLE, and report the results. These built-in functions are specifically designed to aid Gen6 Base testing.

DPOJET based Reference Clock measurements

The Tektronix DPOJET based RefClock measurements provide a reliable way to implement the Reference clock specifications described in the PCI Express Base Specification Rev 1.0 for Gen1, Gen2, Gen3, Gen4 and Gen5.

Comprehensive programmatic interface

You can use Standard Commands for Programmable Instruments (SCPI) to communicate with the TekExpress application. The Online Help document of TekExpress application describes the steps for TCPIP socket configuration and TekVISA configuration to execute the SCPI commands.

PCI Express Decoder for Gen 1 - 4 (Option SR-PCIe)

Decode and Display of PCIe data in a protocol-aware view with the characters and names that are familiar from the standard such as the ordered sets: SKP, Electrical Idle, and EIEOS. A time correlated event table view with waveform allows for quickly searching through events of interest simultaneously. All decoding features support PCIe generations 1 - 4. The PCIe trigger is easily configured through Bus Setup under the oscilloscope's Vertical menu with a variety of user-adjustable settings. The PCIe data stream is integrated with serial bus trigger and search for PCIe gen 1 and 2 allows for triggering on information of interest.

Comprehensive measurements for PCIe validation, debug, and precompliance

Tektronix Option PCE3, Option PCE4 and Option PCE5 provide measurements that span multiple test points and versions of the PCIe specification. All PCIe specifications, test points, and measurements supported are listed in the following sections.

SignalConnect™ software and TCS70902 Calibration Source