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AM572x AVS and IO delay recalibration sequence

Other Parts Discussed in Thread: TPS659037, AM5728

Hi,

I have some question regarding the implementation of IO Delay Recalibration sequence after AVS setting of VD_CORE.

I already got some advices form other post ( https://e2e.ti.com/support/arm/sitara_arm/f/791/t/523714 ). And I was advised the below points.

* The AVS voltages should only be set once per boot-up cycle. 

* The basic configuration sequence is to set the AVS voltage and then perform the IO Delay Recalibration Sequence. This configuration would only have to happen once. 

My customer uses AVS voltage in their system. But customer does not implement IO Dealy Recalibration Sequence yet. So customer is considering to do it.

Customer's system is the below.

XLoader  - - - - - PAD configuration , clock setting, etc.

BOOT - - - - - I2C setting, AVS setting

If possible, customer does not want big change for loader and boot.

Questions are below.

1.From the description of IO Delay Recalibration sequence in TRM, I2C interface setting (for PMIC) is required prior to PAD configuration. In other words, AVS setting must be completed before the PAD cofiguration. Is my understanding right?

2.   The below sequence is allowed?

      1) I/O Delay Recalibration Sequence is executed (Including PAD configuration) in xloader.

      2) AVS is set in BOOT.

      3) After AVS completion, IO Delay Recalibration Sequence is executed again (except for Step6 (PAD configuration)).

I appreciate your quick reply.

Best regards,

Michi

  • Hi,

    I will forward this to the factory team.
  • Hi Yama-san,


    Unfortunately the boot sequence you described is not allowed.  As detailed in the IO Delay Recalibration section of the TRM, the following sequences is needed when performing AVS:

    1. Set the voltage
    2. Do the calibration
    3. Configure the pads

    The reason is that each step in the sequence is dependent on the previous step in order to ensure the device IO timings are met.

    Regards,

    Melissa

  • Dear Melissa-san,

    Thank you for your reply.

    I have one more question.

    As you know, customer uses PMIC TPS659037 with AM5728. And PMIC is connected to AM5728 via I2C interface.
    So customer needs to configure PAD for I2C setting before AVS is set to PMIC. This means "PAD configuration" is executed before set the voltage. Is the pad configuration allowed for only I2C I/F before IO Delay recalibration sequence?

    I appreciate your quick reply.

    Best regards,
    Michi
  • Hi Michi-san,

    Yes, the I2C pad is allowed to be configured before AVS.  After voltage is set, the IO Delay recalibration sequence should be run and other IOs configured.

    The u-boot code in the Processor SDK can be used as reference.  See the early_system_init() routine in u-boot/arch/arm/cpu/armv7/omap-common/hwinit-common.c. 

    Regards,

    Melissa