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TUSB212: Eye Diagram Testing Issue

CK Ho
Expert 1780 points
Part Number: TUSB212


Dear sir,

Our customer is using TUSB212 builded on AMD platform.

And they have an eye diagram testing issue.

When they transmit the test pattern to USB port first time, the eye diagram can pass.

But if they transmit the test pattern to USB port second time, the eye diagram will fail. It looks like the TUSB212 doesn't work.

And if after measuring the eye diagram of port A, then switch the host testing tool to the other port B, and then switch back to port A to measure port A again, the result is pass.

Do you know why this is the case?? Customer wants to know how to explain this phenomenon??

Thank you very much.

  • 0
    TI__Guru**** 179131 points
    CK

    Have you looking at this app note: www.ti.com/.../slla392.pdf

    USB 2.0 High Speed Downstream Signal Quality Testing

    When performing USB 2.0 compliance eye-diagram testing with a host or the downstream port of a HUB
    with the TUSB2XX, a scenario can occur where the TUSB2XX signal boosting is not enabled. This can
    occur when the test packets are being transmitted before the USB test fixture is connected to the
    TUSB2XX. This scenario does not occur during device compliance eye-diagram testing as the USB test
    fixture must always be connected while testing a device. This scenario only occurs during the compliance
    testing with the USB test fixtures and does not affect normal operation with a host, HUB, or device.
    To avoid this scenario, follow the test procedures provided by the scope equipment vendor and USB-IF
    (links provided in Section 5.2). Specifically, the USB HS test fixture should be connected prior to executing
    the TEST PACKETS command using the HSETT test tool. Alternatively, if the test fixture is hot-plugged to
    the host or downstream HUB port after the command to send test packets has already been entered using
    the HSETT tool, it is necessary to select TEST PACKETS and click “Execute” again after the test fixture is
    connected to ensure the TUSB2XX detects a compliance test set-up.
    The following generic procedure can be used to take the USB 2.0 compliance eye-diagrams (refer to
    Section 5.4 for details):
    1. Connect the USB test fixture to the host, downstream HUB (+ TUSB2XX) port or device under test.
    2. Configure the host, or HUB, or device using xHSETT or HSETT to send test packets using the
    procedure detailed in the HSETT documentation.
    3. Start sending test packets
    4. Capture test packet on scope to display eye (running compliance software on the scope)
    USB 2.0 compliance eye-diagrams can be taken on host, device, and HUB platform ports configured with
    the TUSB2XX using the EHCI and xHCI High-speed Electrical Test Tool Setup Instruction document
    provided by the USB Implementers Forum.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 1780 points

    Dear David,

    Yes, we had followed the procedure.

    The test packets are being transmitted after the USB test fixture is connected.

    But if we click "Execute" twice, the eye diagram will fail.

    Customers want to know why??

  • 0 in reply to CK Ho
    TI__Guru**** 179131 points
    CK

    The host behavior between the test packet is system dependent, most likely the system will exit and re-enter test packet mode when test packet command is executed twice. When exit and re-enter test packet mode while the test fixture is still plugged in, TUSB212 signal boosting will not work properly.

    Thanks
    David