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DS160PT801: Equalization Control and Tuning Guide

Igor Aleinikov
Prodigy 20 points
Part Number: DS160PT801


Do you have a tuning guide for the DS160PT801? The required speeds are Gen1, Gen2, and Gen3. The link width is x8.  

We must disable equalization on the upstream side and use fixed TX preset, CTLE, and gain settings. Ideally, equalization should be enabled on the downstream side, but fixed settings will work. Can you provide guidance on configuring the DS160PT801 with the following settings?

  1. Disable equalization on the upstream side.
  2. TX preset – 4
  3. Minimum or no CTLE – what the CTLE index in the channel registers means.
  4. Minimum gain – what the RX VGA index in the channel registers means.
  5. Enable or disable equalization on the downstream side. If equalization is disabled, we will use fixed settings similar to the upstream side.

We use initialization values described in the datasheet and provided in the EEPROM images. In addition, we set 0x9D=0x44 (requested Gen3 TX preset value for retimer) and 0xB6=0x08 (Disable DFE) in the channel registers. The link works, but the retimer initiates equalization, although the equalization is disabled in the upstream and downstream components. As a result, the link does not tune to the optimal values and results in RX and DLL errors on the PCIe link.  

  • 0
    TI__Mastermind 20711 points

    Hi Igor,

    Thank you for reaching out. Could you please specify the reasoning to desire the adaptive equalization on the retimer RX? Typically, the adaptive CTLE, VGA, and DFE blocks of the retimer allow for the optimal equalization settings to be selected and can adapt to varying link conditions.

    These modes can be supported if desired. Additional clarifications to your questions may be answered in the DS160PT801 Configuration Guide, which is available only on the TI Secure Resources portal. I have just granted you access to the folder containing this document for the DS160PT801, you will receive an email within the next 30 minutes with instructions on how to access the folder.

    If you have additional follow-up questions related to content in the Configuration Guide, please send me a private message on E2E, as the content in the Configuration Guide cannot be discussed on our public E2E forum.

    Best,
    David

  • 0 in reply to David Waier
    Prodigy 20 points

    Hi David,

    We use a cable with buffers between the upstream component and the DS160PT801. So, the link is split into 3 segments, and the standard equalization does not work. We must disable it.

    I do the configuration guide and have access to the document folder. However, the guide does not address the question I ask. Half of the registers are not described at all. I can extract some information from SigCon Acritect, but I still need to guess. For instance, how are the CTLE or VGA indexes mapped to dB? The register which controls Forwarding and Execution modes is not described in the guide.

    Best Regards,

    Igor   

  • 0 in reply to Igor Aleinikov
    TI__Mastermind 20711 points

    Hi Igor,

    I have sent you an E2E friend request so we can discuss your configuration requirements in more detail. Please accept this request so that I can provide some additional clarifications to you.

    Best,
    David