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AM2432: SORTE Time Synchronization

Part Number: AM2432

[日本語]

設計ガイドTIDUCK4の2.2.3.6 Time Synchronizationについて4つ質問があります。

私は、Figure 13. Line Delay Measurementを見て、Device Nが、Device NとDevice N+1の間のLine delayを計算することを理解しました。

それと同時に、私は、Device N+1も、このLine delayの値を知っている必要があると思いました。

Q1)Device Nが計算したLine delayの値は、Device N+1に保存されるでしょうか?

Q2)Device N自身は、Line delayの値を保存するでしょうか?
  それとも、保存しないでしょうか?

Q3)Device Nが計算したLine delayの値は、どのようにしてDevice N+1に渡されるのでしょうか?
  Device Nから直接Device N+1に、専用のパケットで送られるのでしょうか?
  それとも、まずDevice NからSORTE_G Controllerに送られ、その後でSORTE_G ControllerからDevice N+1に送られるのでしょうか?

Q4)Device Nが計算したLine delayの値は、SORTE_G Controllerにも保存されるでしょうか?

[English]
I have four questions about 2.2.3.6 Time Synchronization in the design guide TIDUCK4.

I see in Figure 13. Line Delay Measurement that Device N calculates the Line delay between Device N and Device N+1.

At the same time, I thought that Device N+1 must also know the value of this line delay.

Q1) Will the line delay value calculated by Device N be stored in Device N+1?

Q2) Will Device N itself store the line delay value?
  Or does it not?

Q3) How is the line delay value calculated by Device N passed to Device N+1?
  Is it sent directly from Device N to Device N+1 in a dedicated packet?
  Or is it first sent from Device N to SORTE_G Controller and then from SORTE_G Controller to Device N+1?

Q4) Will the line delay value calculated by Device N also be stored in SORTE_G Controller?

TIDUCK4_page19.pdf

  • Hello Katsufumi-san,

    We use a two step approach in the synchronization state. This happens in source code files line_delay_g and sync_g, when referring to the source code.

    To answer Q1 to Q3:

    1st the device N measures the line delay (PHY and cable delay) to device N+1. This is repeated a couple of times and an average is calculated and stored in device N. Also, device N+1 measures the line delay to device N+2. At the end, each device (and the controller) know the line delay towards it next device.

    2nd the controller sends out the sync frame. The controller inserts the time-triggered send (TTS) time into the sync frame. The device N reads this value, and stores it locally. Before forwarding the sync frame to the next device N+1, device N sums up its bridge delay (fixed and known by design) and the line delay (measured in 1st step) to the next device N+2. This procedure repeats in each device. After sync is completed, each device knows the delay time from controller to device N.

    Q4: The controller does know know the line delay value of any device.

    I hope this answers your question.

    Regards,

     Thomas

  • [日本語]
    Thomasさん
    回答いただき、ありがとうございます。

    回答の内容について、3つ質問します。

    Q5)2ndステップにおいて、SORTE_G Controllerが送信するsync frame内の時間の値は、Controllerの送信時刻とControllerと最初のDeviceの間のline delayを足したものですか?

    Q6)Device Nがsync frame内の時間の値に加算するline delayは、Device NとDevice N+1の間のline delayですか?

    Q7)Device N+1が受信するsync frame内の時間の値は、Device N+1がIO Exchange stateにおいてOUTパケットを受信する予定の時刻を意味していますか?

    [English]
    Mr. Thomas.
    Thank you for your answer.

    I have three questions regarding your answer.

    Q5) In the 2nd step, Is the time value in the sync frame sent by the SORTE_G Controller the sum of the Controller's transmission time and the line delay between the Controller and the first device?

    Q6) Is the line delay that Device N adds to the time value in the sync frame the line delay between Device N and Device N+1?

    Q7) Does the time value in the sync frame received by Device N+1 mean the time when Device N+1 is scheduled to receive OUT packets in the IO Exchange state?

  • Hi Miyaji-san,

    Q5: Yes, correct. Controller sends with 500ns, and he adds the line delay time he measured in first step. This accumulated value is sent.

    Q6: Yes, correct. It also adds its own bridge delay of 160ns. This is a constant known to the device.

    Q6: Yes, correct. Device N+1 used this value and compares it in IO-EX state to the time stamp of the received IO EX frame. Then, based on the difference, Device N+1 adjusts its IEP timer to compensate its local drift.

    Regards,

     Thomas

  • Mr. Thomas.
    Thank you for your answer.

    I was able to understand how Time Synchronization works.