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IEEE 1588 Related

Naveen M94353
Prodigy 90 points

Other Parts Discussed in Thread: AM3356

AM3356 supports PTP. The controller has inbuilt functionality of IEEE 1588.

Is there any advantage on using an Ethernet PHY which is also supporting IEEE 1588?

or

AM3356 with Normal MII interfaced PHY transceiver is enough to implement IEEE1588 Feature in my Project?

  • 0
    TI__Intellectual 1835 points

    Yes, AM3356 has IEEE1588 support. It is advisable to analyze your application and think through the procedure and steps that must be taken to make your application work. Each step of your analysis should be mapped to respective hardware/software resources in the TI device you are considering and ensure it will work.

    AM3356 has a IEEE1588 v2 implementation. So, transmit and receive frames with PTP headers will get time stamps. Annex D and Annex F of IEEE1588 are also supported to enable IP based PTP.

    Note that there is a software algorithm required that will actually calculate the clock adjustments to be made and also make such adjustments.

    Note that the AM3356 does not offer a way to adjust its source clock frequency but it does offer a way to overwrite the timers that maintain the clock.

    Thanks.

  • 0 in reply to Maneesh
    Prodigy 150 points
    Can you explain your statement "AM3356 does not offer a way to adjust its source clock frequency but it does offer a way to overwrite the timers that maintain the clock".
  • 0 in reply to Joaquin Domingo
    TI__Guru 64655 points
    The AM335x internal clocks are based on crystal oscillators. The crystal reference clock is used for some logic functions and sources various PLLs that lock their output frequency to a fixed ratio of the crystal reference clock. The PLLs do not support small incremental frequency increases or decreases that allow their outputs to be adjusted to track the IEEE1588 master clock. However, the RTC provides a crystal compensation feature that allows software to adjust the RTC based on information received via IEEE1588.

    If the crystal reference clock is running 80 PPM fast, all logic functions operating on this clock will be running 80 PPM fast since there is no way to apply an incremental adjustment. This would cause the RTC or any other software implemented clock to increment time faster than IEEE1588 master clock. Software would need to occasionally adjust the RTC or software implemented clock so it track the IEEE1588 master clock.

    If you need all AM335x clocks to track the IEEE1588 master, one option would be to use an external reference clock source that supports small incremental frequency increases or decreases via software control over I2C.

    Regards,
    Paul
  • 0 in reply to peaves
    Prodigy 150 points

    I need, besides having Time of Day synchronized by IEEE1588, to have a precise 10 MHz output .

    Does the AM437x support adjusting the internal PLL to track the IEEE1588 master? If so, what do you think it is better to have a precise 10 MHz output signal, using a eCAP in PWM or a eHRPWM?

    Regards,

    Joaquin

  • 0 in reply to Joaquin Domingo
    TI__Guru 64655 points
    No. You would need to use an external VCXO clock source to source AM437x such that software could compare the RTC being sourced by the VCXO with the IEEE1588 time stamp and adjust the VCXO to track the IEEE1588 master clock. Then you could use a divided down version of the VCXO clock to generate the 10MHz reference.