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TUSB8041A: Regarding the USB 2.0 compliance test

Kyohei
Expert 1490 points
Part Number: TUSB8041A
Other Parts Discussed in Thread: TUSB8044RGCEVM, TUSB8041

Tool/software:

Hi team,

We conducted a USB 2.0 compliance test on a prototype board equipped with the TUSB8041A for one of our customers, and confirmed failures in the following two items:

  • EL_21 Sync Field Length Test
  • EL_22 Inter-packet Gap Between Host And Device Packet Test

We also performed a compliance test using the TUSB8041A evaluation board (TUSB8044RGCEVM) with a different model from our company, and observed failures in the same items.

However, when we conducted the compliance test directly on the port to which the evaluation board was connected, all items passed.

We would appreciate it if you could confirm the following two points:

  1. Has TI conducted USB 2.0/3.0 compliance testing for the TUSB8041A?
  2. For compliance testing, there are HUB and HOST settings. When performing compliance testing with the TUSB8041A mounted onboard (on the same board as the CPU), is it correct to use the HOST setting?

Best regards,

Kyohei

  • 0
    TI__Guru*** 146535 points

    Hi Kyohei:

      We did compliance test  directly on the port of hub EVM.

       

    Kyohei said:
    For compliance testing, there are HUB and HOST settings. When performing compliance testing with the TUSB8041A mounted onboard (on the same board as the CPU), is it correct to use the HOST setting?

         if you test hub downstream port , then you should use host setting. but you need to add more bits for hub 

    Best

    Brian

  • 0 in reply to Brian Zhou
    Expert 1490 points

    Hi Brian,

    Thank you for your response.

    Understood that the host setting should be used and that an additional bit needs to be set for the hub.

    Is it correct to understand that TI has not conducted USB 2.0/3.0 compliance testing for the TUSB8041A?

    Also, could you please provide the URL of the document that references the statement about adding the bit?

    Best regrads,

    Kyohei

  • 0 in reply to Kyohei
    TI__Guru*** 146535 points

    Kyohei:

         TUSB8041A is same die as TUSB8041, it did pass USBIF compliance test.

      Attached is document for the test.

          USB_2_0_Electrical_Compliance_Specificationv1.06.pdf

    Best

    Brian

  • 0 in reply to Brian Zhou
    Expert 1490 points

    Hi Brian,

    Thank you for your reply.

    I understand EL_22. Do you have any comments regarding EL_21?

    Best regards,

    Kyoehi

  • +1 in reply to Kyohei
    TI__Guru*** 146535 points

    For EL-21, did customer use  32 bit SYNC field?

    Best

    Brian

  • 0 in reply to Brian Zhou
    Expert 1490 points

    Hi Brian,

    Thank you for your support.

    ■ Inquiry Cases:
    EL_21 and EL_22 are failing.

    ■ EL_21 Failure Details:
    Please refer to the table below. (Same results observed with the manufacturer's evaluation board.)

    ■ Our Interpretation Based on USB Specification Review:
    According to the USB Specification (Universal Serial Bus Specification Revision 2.0, April 27, 2000),
    the judgment criterion for EL_21 is 32 bits. However, when passing through a hub, a drop of up to 4 bits is allowed.
    Therefore, the acceptable range becomes 28 to 32 bits.

    Based on this, when converted to time (480 Mbps), the following range applies:
    58.3 ns ≦ Measured Value (62.8 ns) ≦ 67.7 ns

    ■ Excerpt from USB Specification:
    [Excerpt not provided in original text]

    7.1.10 Sync Pattern

    The SYNC pattern used for low-/full-speed transmission is required to be 3 KJ pairs followed by 2 K’s for a total

    of eight symbols. Figure 7-35 shows the NRZI bit pattern, which is prefixed to each low-/full-speed packet.

    The SYNC pattern used for high-speed transmission is required to be 15 KJ pairs followed by 2 K’s, for a total

    of 32 symbols. Hubs are allowed to drop up to 4 bits from the start of the SYNC pattern when repeating

    packets. Hubs must not corrupt any repeated bits of the SYNC field, however. Thus, after being repeated by

    5 hubs, a packet’s SYNC field may be as short as 12 bits.

    Best regards,

    Kyohei

  • 0 in reply to Kyohei
    TI__Guru*** 146535 points

    Hi Kyohei:

      Thanks for the information.

    Best

    Brian

  • 0 in reply to Brian Zhou
    Expert 1490 points

    Hi Brian,

    Could you please confirm whether the customer's interpretation above is correct?

    Best regards,

    Kyohei

  • +1 in reply to Kyohei
    TI__Guru*** 146535 points

    Hi Kyohie:

      customer's interpretation is correct, SYNC bits are dropped by hub.

    Best

    Brian