• 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。