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AM3703: SDRC_DDA_CTRL settings

Nomo
Guru 16800 points

Part Number: AM3703

Hello,

I have three questions for the SDRC_DLLA_CTRL settings of SDRC on AM3703.

1.Does the FIXEDDELAY field of SDRC_DLLA_CTRL work in TrackingDelay mode?
  My customers set DDR frequency as 200MHz and TrackingDelay mode; however, it seems that the FIXEDDELAY field affects AC timing.
  If the fields work in TrackingDelay mode and 200MHz operation, could you tell me the meaning of the field?
  My customers want to know the how is the delay caused for the setting.

2.What is the bit 0 of the SDRC_DLLA_CTRL register?
  In TRM, the description of this field is "RESERVED" and "Write 0s for future compatibility. Reads return zero".
  However, in the following URL, the typical value of SDRC_DLLA_CTRL is 0x0000000A (i.e. bit 0 is 1).
  Also, in BSP "72 deg phase" is described and it seems that this bit is set for a certain function for temperature.

3.How do you disable the function of adjusting the delay of DLL by according to voltage and temperature variations automatically?
  In room temperature, the read corruption is caused frequently; however, in low temperature, the issue doesn't cause.
  My customers assume that the read corruption issue may be affected of temperature.

Best Regards,
Nomo

  • 0
    TI__Genius 9655 points
    Nomo-san

    We apologize for the delay in the response on your issue. We have been trying to do some checks here on our HW/EVM, but is taking lot longer than we expected.

    Please find the responses to your questions:

    1. FIXEDDELAY controls the delay through the delay lines when in unlock mode. When it is set in lock mode i.e. TrackingDelay mode, this field should not have any impact. Can you elaborate more on when you say the "it seems that the FIXEDELAY field affects AC timing"? As mentioned in the TRM, the FIXEDDELAY setting should be used for a max. frequency of 83MHz

    2. bit0 is reserved in the SDRC_DLLA_CTRL and should write and a read should return a 0. You specified a URL in your post, but cannot find the URL. with a setting of 0x0000000A - bit 0 of SDRC_DLLA_CTRL is indeed a 0. bit 1 defines the DLLPHASE and a value of 0 is for phase for 72 degrees and value of 1 is for phase of 90 degrees. The bit is set to 1 for a 90 degree phase shift between DQS and incoming data. However, you can change this settings to 0 for a 72 degree phase shift to verify if that gives you the best performance for your application board. I'm not aware of any specific temperature setting that changes this setting to 72 vs. 90 degree phase shift. I also don't see any issue in changing the setting to 0 if that gives you the best performance in your system

    3. There are only 2 settings for the DLL i.e. DLL in lock mode and unlock mode. There is no other setting that disables the DLL by voltage and temperature automatically. You need to make sure the mDDR device connected along with the board layout is robust to meet all the input timings

    Let us know if you have any other additional questions

    Regards, Siva
  • 0 in reply to sivak
    Guru 16800 points

    Hello Siva-san,

    Thank you for your reply and I appreciate for your kind support.

    I have an additional question for 1.
    My customers know the FixedDelay mode shouldn't be used in 200MHz; however, they want to know the behavior of the FIXEDDELAY mode in 200MHz.
    (The "it seems that the FIXEDELAY field affects AC timing" intended to the FixedDelay mode.)
    In case of the FixedDelay mode and the 200MHz operation, how does the FIXEDDELAY field of SDRC_DLLA_CTRL work?

    Best Regards,
    Nomo

  • 0 in reply to sivak
    Guru 16800 points
    Hello sivak-san,

    Do you have any updates on my thread?

    Best Regards,
    Nomo
  • 0 in reply to Nomo
    TI__Genius 9655 points
    Nomo-san

    I'm confused about your question. As I mentioned earlier, FIXEDELAY mode is not supported for 200MHz. I'm unable to comment on what happens for an unsupported feature. Can you explain what is the AC timing impact you are noticing. Is this with FIXEDDELAY mode. If so, please use the lock mode or TrackingDelay mode and let me know if you have any other issues.

    Regards, Siva
  • 0 in reply to sivak
    Guru 16800 points
    Hello Siva-san,

    Thank you for your reply.
    I can understand about your suggestion.
    I appreciate your kind support.

    Best Regards,
    Nomo