What Are the Principles of the HEO and VEO Measurements with the Advanced Cable Tester?

Question from the Customer:

I need to test cables that are in development. Before I get started, I have some questions about the Advanced Cable Tester:

  1. How does the Advanced Cable Tester obtain the HEO and VEO measurements of the eye diagram? What test principles are used?
  2. What are the units of HEO & VEO? When I use an oscilloscope to view an eye diagram, the horizontal axis unit represents time, and the vertical axis unit represents voltage or power.
  3. Can I run tests on cables that do not have an E-Marker chip?  I’m testing new cable designs, and they don’t yet have an E-Marker chip. Can I still run the SI test?

Response from Technical Support:

Thank for your questions! We’ll start with an overview of what the Advanced Cable Tester does, and then we’ll answer your questions.

Overview of the Advanced Cable Tester

The Advanced Cable Tester supports testing both full-featured and USB 2.0 Type-C cables. Adapter cards are available for legacy connectors, which supports testing additional types of cables:

  • Standard-A to Micro-B (USB 2.0 and USB 3.1)
  • Standard-A to Type-C (USB 2.0 and USB 3.1)
  • Standard-A to Lightning (USB 2.0)
  • Type-C to Micro-B (USB 2.0 and USB 3.1)

Note – the Advanced Cable Tester must be installed on the Promira™ Serial Platform.

How Are Tests Run?

HEO and VEO measurements are related to the signal integrity tests. For signal integrity, the Advanced Cable Tester transmits a high-speed differential signal at an assigned rate. A pseudo random binary sequence (PRBS) is used to simulate traffic.

The default speeds for USB cables are 518 Mbps (High-speed), 5 Gbps (SuperSpeed Gen1), and 10 Gbps (SuperSpeed Gen2). You can also customize the test rates between 518 Mbps and 12.8 Gbps.

There are other tests available for DCR resistance, IR Drop, digital pins, E-Marker and cable shield.  For more information, please refer to the Detailed Test information section of the Advanced Cable Tester User Manual.

What Are HEO and VEO Units?

HEO and VEO units are used for pass/fail criteria. Both HEO and VEO are measured in internal units (UI).

  • The HEO (Horizontal Eye Opening) is a value from 0 to 63. Each unit represents 1/64 of the UI.
  • The VEO (Vertical Eye Opening) is a value from 0 to 150, which represents the vertical opening of the recovered eye diagram.

For more information, please refer to the Profiles Option and Detailed Test information sections of the Advanced Cable Tester User Manual.

Does the Advanced Cable Tester Work with Cables without E-Marker Chips?

All the tests are independent of each other. The absence of the E-Marker chip will not cause any issues for testing the prototype cables.  The Advanced Cable Tester supports cables both with and without E-Markers.

Additional resources that you may find helpful include the following:

We hope this answers your question. Need more information? You can contact us and request a demo that applies to your application, as well as ask questions about our Advanced Cable Testers and other Total Phase products.