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Incremental DDR3 leveling supported by AM335x hardware?

Carsten Hansen
Expert 1450 points

Hi,

The AM335x TRM (7.3.3.6 in my copy of the document) describes two types of DDR3 read-write leveling:

  1. Full leveling, to be performed once and for all on a given design
  2. Incremental leveling, to compensate for changes in temperature and voltage during operation

Advisory 1.0.19 in the errata for the AM335x however states that hardware leveling is unsupported, but does not specifically say whether that applies to full leveling, incremental leveling, or both.

From the description it would appear that it's talking about full leveling, but I'm a bit unsure what the situation is with incremental leveling.

Thus my question: is incremental leveling supported, in hardware, on the AM335x?

Thanks,
Carsten

  • 0
    TI__Guru**** 393215 points

    Hi Carsten,

    I will ask the factory team to clarify this.

  • 0 in reply to Biser Gatchev-XID
    TI__Genius 9655 points

    Carsten

    Incremental leveling is applied after full leveling for readjusting timings periodically. Since full leveling is not supported as per the Errata, incremental leveling is also not supported.

    Regards, Siva

  • 0 in reply to sivak
    Expert 1450 points
    Thank you Siva for clearing that up.

    I assume that means incremental leveling will have to be performed by software.

    Would you know if TI provides any guidelines on how to implement this?

    Searching through the forums I came across another request for documentation on the algorithm used in the DDR3_slave_ratio_search binary, but this was turned down as it would "not (be) used within your actual product".
    See: http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/717/t/184600

    The slave ratio search binary (obviously) runs the full leveling algorithm, so RandyP is correct that strictly speaking we could get by with just the binary.

    Incremental leveling however would have to be implemented in the shippable product, so it would be helpful if details were available on how to achieve this.

    Best regards,
    Carsten
  • 0 in reply to Carsten Hansen
    Expert 1450 points
    Hello,

    Since incremental leveling is not supported by AM335x, is there anyone who could comment on how to implement this in software?

    Or is this even possible to achieve without hardware support?

    Best regards,
    Carsten
  • 0 in reply to Carsten Hansen
    TI__Genius 9655 points

    Carsten

    For AM335x, a one time HW leveled value should suffice and has been tested to work across the recommended operating range of the device. Is there a reason why you are looking at incremental leveling?

    Regards, Siva

  • 0 in reply to sivak
    Expert 1450 points

    Thank you Siva, that is very useful information.

    The reason we were looking at incremental leveling was that we assumed it was required on the AM335x.

    Or put another way, we had not been able to find any mention of it not being necessary. The TRM does go to great lengths to describe this (non-functional, as it were) feature in the silicon.

    Cheers,
    Carsten