• 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。