Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 4/01/2024
Public

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5.1.6.9.2. Peer-to-Peer PTP Transparent Clock Message Support

The IEEE 1588-2008 supports peer-to-peer PTP (Pdelay) message in addition to the SYNC, Delay Request, Follow-up, and Delay Response messages. The following figure shows the method to calculate the propagation delay in clocks supporting peer-to-peer path correction.

Figure 76. Propagation Delay Calculation in Clocks Supporting Peer-to-Peer Path Correction
The propagation delay is calculated in the following way:
  1. Port 1 issues a Pdelay_Req message and generates a timestamp (t1) for the Pdelay_Req message.
  2. Port 2 receives the Pdelay_Req message and generates a timestamp (t2) for this message.
  3. Port 2 returns a Pdelay_Resp message and generates a timestamp (t3) for this message. To minimize errors because of any frequency offset between the two ports, Port 2 returns the Pdelay_Resp message as quickly as possible after the receipt of the Pdelay_Req message. Port 2 returns any one of the following:
    • Difference between the timestamps t2 and t3 in the Pdelay_Resp message
    • Difference between the timestamps t2 and t3 in the Pdelay_Resp_Follow_Up message
    • Timestamps t2 and t3 in the Pdelay_Resp and Pdelay_Resp_Follow_Up messages, respectively
  4. Port 1 generates a timestamp (t4) on receiving the Pdelay_Resp message.
  5. Port 1 uses all four timestamps to compute the mean link delay.