PTM defines the following: • PTM Requester - A Function capable of using PTM as a consumer associated with an Endpoint or an Upstream Port. • PTM Responder - A Function capable of using PTM to supply PTM Master Time associated with a Port or an RCRB. • Time Source - A local clock associated with a PTM Responder. • PTM Root - The source of PTM Master Time for a PTM Hierarchy. A PTM Root must also be a Time Source and is typically also a PTM Responder. Each PTM Root supplies a single PTM Master Time to all of the PTM Hierarchy: a set of PTM Requesters associated with a single PTM Root. Figure 6-23 illustrates some example system topologies using PTM. These are only illustrative examples, and are not intended to imply any limits or requirements.翻译一下

PTM 定义了以下概念:
• PTM 请求者 - 一种能够使用 PTM 作为消费者与端口或上游端口关联的功能。
• PTM 响应者 - 一种能够使用 PTM 提供与端口或 RCRB 关联的 PTM 主时间的功能。
• 时间源 - 与 PTM 响应者关联的本地时钟。
• PTM 根 - PTM 层次结构的 PTM 主时间来源。 PTM 根必须也是时间源，通常也是 PTM 响应者。每个 PTM 根向所有 PTM 层次结构提供单个 PTM 主时间：与单个 PTM 根相关联的一组 PTM 请求者。图 6-23 展示了使用 PTM 的一些示例系统拓扑结构。这些仅是说明性的示例，不意味着任何限制或要求。

相关问题

In addition to the requirements listed above for the PTM Requester and PTM Responder Roles, Switches must follow these requirements: • When the Upstream Port is associated with a Multi-Function Device, only a single Function associated with that Upstream Port is permitted to implement the PTM Extended Capability structure. For Switches, all PTM functionality associated with the Switch must be controlled through that structure. It is not required that the Function implementing the PTM Extended Capability structure be the Switch Upstream Port Function. • The PTM Extended Capability structure for a Switch must indicate support for both the PTM Requester and PTM Responder roles. • The PTM Extended Capability in the Upstream Port controls all Switches in that Upstream Port. • A Switch is permitted to act as a PTM Root, or to issue PTM Requests on its Upstream Port to obtain the PTM Master Time for use in fulfilling PTM Requests received at its Downstream Ports. In the latter case the Switch must account for any internal delays within the Switch. 翻译

除了 PTM 请求者和 PTM 响应者角色的要求之外，交换机必须遵循以下要求：
• 当上行端口与多功能设备相关联时，只允许与该上行端口相关联的单个功能实现 PTM 扩展能力结构。对于交换机，所有与交换机相关的 PTM 功能必须通过该结构进行控制。实现 PTM 扩展能力结构的功能不必是交换机上行端口功能。
• 交换机的 PTM 扩展能力结构必须指示支持 PTM 请求者和 PTM 响应者角色。
• 上行端口中的 PTM 扩展能力控制该上行端口中的所有交换机。
• 交换机可以作为 PTM 根，或者在其上行端口发出 PTM 请求以获取用于满足其下行端口接收的 PTM 请求的 PTM 主时间。在后一种情况下，交换机必须考虑交换机内部延迟。

• Once having issued a PTM Request Message, the Upstream Port must not issue another PTM Request Message prior to the receipt of a PTM Response Message, PTM ResponseD Message, Reset, or the passage of 100 μs without a corresponding PTM Message from the Downstream Port. • Upon receiving a PTM Response, the Upstream Port must wait at least 1 μs before issuing another PTM Request Message. • For Multi-Function Devices (MFDs) containing multiple PTM Requesters, the Upstream Port associated with that MFD must issue a single PTM dialog during each PTM context refresh. PTM Requesters within the MFD maintain their individual PTM contexts using this one, Device-wide PTM dialog. The mechanism for refreshing multiple PTM contexts from one PTM dialog is implementation specific. 翻译一下

• 一旦发出PTM请求消息，上游端口在收到PTM响应消息、PTM ResponseD消息、复位或100μs内没有来自下游端口的相应PTM消息之前，不能再发出另一个PTM请求消息。
• 收到PTM响应后，上游端口必须等待至少1μs才能再次发出PTM请求消息。
• 对于包含多个PTM请求者的多功能设备（MFDs），与该MFD相关联的上游端口必须在每个PTM上下文刷新期间发出单个PTM对话框。 MFD内的PTM请求者使用此单个设备范围的PTM对话框维护其各自的PTM上下文。从一个PTM对话框中刷新多个PTM上下文的机制是实现特定的。