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DS125DF410: about register address 0x33.

akihiro maeda
Prodigy 10 points
Part Number: DS125DF410

Tool/software:

Hi,Ti-team

Please tell me about register address 0x33.

[Question]
1. Is it correct to understand that this register is enabled when ADAPT_MODE is set to “11”?

2. Both HEO and VEO are 4-bit settings and the default value is 8, but what is the unit of this register?

3. For example, if the input eye pattern aperture is ±0.1UI and there is a signal with a lot of jitter,

   is it better to change the HEO_THRESH setting from the default value of 8 to 15 so that it can be locked?

Regards,

  • +1
    TI__Mastermind 24292 points

    Hi Akihiro-san,

    First, please note that adapt mode 3 is generally not our recommended adapt mode.  We generally see better high speed performance using adapt mode 2 than adapt mode 3.

    Adapt mode 3 emphasizes using DFE for equalization compared to adapt mode 2.  More details on this are in the section "Set Receiver Adapt Mode" of our programming guide.

    Regarding your questions:

    1. Yes, this register is enabled when using adapt mode 3.
    2. The HEO/VEO values are scaled by the HEO/VEO scalers used when reading HEO/VEO from registers 0x27, 0x28.
      • HEO [UI] = 0x33[7:4] / 64
      • VEO [mV] = 0x33[3:0] * 3.125
    3. Register 0x33 establishes a minimum "lock" threshold that the DS125DF410 will achieve in adapt mode 3 by automatically adapting CTLE.  After meeting this threshold, it will adapt DFE taps until it reaches optimal HEO/VEO, then will re-adapt CTLE until optimal HEO/VEO are reached.  Increasing the values in this register will place more emphasis on the initial CTLE adaptation in adapt mode 3.

      However, you might alternatively consider adapt mode 2.  Adapt mode 2 will first adapt CTLE until is reaches optimal HEO/VEO, then adapt DFE until it reaches optimal HEO/VEO.

    Thanks,

    Drew