• A PTM Responder must issue PTM ResponseD when it has stored copies of the values required to populate the PTM ResponseD Message: historical timestamps (t3 - t2) and the PTM Master Time at the receipt of the most recent PTM Request Message (time t2’). • A PTM Responder is permitted to issue PTM Response when it has stored copies of the historical timestamps (t3 - t2) but must request the PTM Master Time from elsewhere. In this case, it is permitted to issue PTM Response messages in response to PTM Request Messages while it retrieves the PTM Master Time if that retrieval is expected to take more than 10 μs. • The perceived granularity of the historical timestamps and PTM Master Time values transmitted by a PTM Responder must not exceed that reported in the Local Clock Granularity field of the PTM Capability register. 翻译

• 当 PTM 响应者已经存储了填充 PTM ResponseD 消息所需的值，包括历史时间戳（t3 - t2）和在收到最近的 PTM 请求消息时的 PTM 主时间（时间 t2'）时，必须发出 PTM ResponseD。
• 当 PTM 响应者已经存储了历史时间戳（t3 - t2），但需要从其他地方请求 PTM 主时间时，可以发出 PTM Response 消息。在这种情况下，如果检索所需的 PTM 主时间需要超过 10 微秒，则可以在响应 PTM 请求消息时发出 PTM Response 消息。
• PTM 响应者传输的历史时间戳和 PTM 主时间值的感知粒度不能超过 PTM Capability 寄存器中报告的本地时钟粒度字段。

相关问题

• Switch Downstream Ports and Root Ports acting as PTM Responders must respond to each PTM Request Message received at their Downstream Ports with either PTM Response or PTM ResponseD according to the following rules: ◦ A PTM Responder must not send a PTM Response or PTM ResponseD Message without first receiving a PTM Request Message. ◦ Upon receipt of a PTM Request Message, a PTM Responder must attempt to issue a PTM Response or PTM ResponseD Message within 10 μs. ◦ A PTM Responder must issue PTM Response when the Downstream Port does not have valid historical timestamps (t3 - t2) with which to fulfill a PTM Request Message. 翻译

• 作为 PTM Responders 的 Switch Downstream Ports 和 Root Ports 必须根据以下规则响应其收到的每个 PTM Request Message，使用 PTM Response 或 PTM ResponseD： ◦ PTM Responder 必须在先收到 PTM Request Message 后才能发送 PTM Response 或 PTM ResponseD Message。 ◦ 在收到 PTM Request Message 后，PTM Responder 必须在 10 微秒内尝试发出 PTM Response 或 PTM ResponseD Message。 ◦ 当 Downstream Port 没有有效的历史时间戳（t3 - t2）来满足 PTM Request Message 时，PTM Responder 必须发出 PTM Response。

A PTM Responder is permitted to issue PTM Response when it has stored copies of the historical timestamps (t3 - t2) but must request the PTM Master Time from elsewhere. In this case, it is permitted to issue PTM Response messages in response to PTM Request Messages while it retrieves the PTM Master Time if that retrieval is expected to take more than 10 μs. 这句话怎么理解

这句话是在讨论一个 PTM 响应器的行为。它的意思是，当 PTM 响应器存储了历史时间戳（t3 - t2）的副本时，可以在没有获得 PTM 主时间的情况下发出 PTM 响应。但是，如果检索 PTM 主时间需要超过 10 微秒，那么在检索 PTM 主时间的同时，该 PTM 响应器可以发出 PTM 响应消息以响应 PTM 请求消息。这意味着，如果 PTM 响应器需要从其他地方获取 PTM 主时间，而这个过程需要一定的时间，那么它可以在等待的同时回应 PTM 请求消息，以提高系统的响应速度。