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TMS320F28388D: EMAC PTP Offload feature

David M. Alter
Guru 61235 points
Part Number: TMS320F28388D
Other Parts Discussed in Thread: C2000WARE

C2000 Team,

A customer is using F2838x and having some unexpected behavior from the PTP offload feature of the ethernet MAC.   They are using the 802.1AS protocol.  Currently, they have enabled the offload feature, which allows them to automatically send the peer delay response message, but it is only the one-step response.

They had hoped that it would automatically do a 2-step response.

Also, they do not see timestamps properly in the one-step response that is sent out.

Can someone from the C2000 team comment on this?

Thank you,

David

  • 0
    TI__Expert 5391 points

    Hi David,

    Are they using C2000Ware? is there a PTP stack being used. 

    If they are using C2KWare? Did they get a chance to look into the ethernet_ex5_ptp_offload_slave example in C2000Ware? 

    Regards,

    Sudharsanan

  • 0 in reply to Sudharsanan
    Prodigy 90 points

    Sudharsanan,

    We took some elements of C2000Ware and some of our own software components, but the C2000Ware was our starting code.  The real question here, I believe, is "does the PTP Offload Engine support 802.1AS?".  It is my understanding that 802.1AS requires a 2-step response to a PeerDelay Request message.  We are using the offload engine (with auto PeerDelay Response Enabled), and have the 802.1AS bit enabled, but when we receive a PeerDelay Request, we only get a single response out of the device.  

    We have looked at the ptp slave offload example, but that code does not have 802.1AS enabled.  It may be worth a try to flip the bit in the example, but I believe that we would be in the same boat that we are in with our own code.  

    One last question.  Does the outbound PTP PeerDelay Response get tagged at the MAC level as the messages leaves the device (proper one-step response), or does this happen at a higher layer, requiring a two-step response?  This does not change the requirement of 802.1AS to have a two-step response, but I would like to understand how the device works.

    Thanks,

    Steve

  • 0 in reply to Stephen Strong
    TI__Expert 5391 points

    Hi,

    Sorry about the delay in responding, had a bunch of notes on this topic at office and due to prevailing situation couldn't visit office hence took some time to brush up on with available documentation remotely. 

    Stephen Strong said:
    "does the PTP Offload Engine support 802.1AS?".  It is my understanding that 802.1AS requires a 2-step response to a PeerDelay Request message.  We are using the offload engine (with auto PeerDelay Response Enabled), and have the 802.1AS bit enabled, but when we receive a PeerDelay Request, we only get a single response out of the device.  

    The PTP Offload engine is for IEEE1588 Timestamp related offload. Hope you are mentioning about the master side. When a PeerDelay request is received from slave only peer Delay response is generated automatically. I do not have access to 802.1AS specifications to help you out on the second message you are referring to. But if it is related to Time Sensitive Network profile. We do not have this supported on F2838x. 

    When you enable the AV8021ASMEN in MAC_Timestamp_Control register it only specifies whether the transportSpecific field of PTP message should be checked/generated for 802.1AS. It does not change the functionality of core PTP offload functioning. 

     

    Stephen Strong said:
    One last question.  Does the outbound PTP PeerDelay Response get tagged at the MAC level as the messages leaves the device (proper one-step response), or does this happen at a higher layer,

    Yes the timestamps tagged are at the MAC level using the MAC system time in hardware. 

    Hope it clarifies. 

    Regards,

    Sudharsanan