USB3.2 packet type

时间：2023-07-03 13:37:01 lmp331液压变送器

Packet type	description
Link Management Packets (LMP)	travel between a pair of links; 2. used to manage that link
Transaction Packets (TP)	traverse all the links directly connecting the host to a device. They are used to control the flow of data packets, configure devices, and hubs, ect. Transaction Packets have no data payload
Data Packets (DP)	(DPP) traverse all the links directly connecting the host to a device, Data Packets have two parts: a Data Packet Header (DPH) and a Data Packet Payload
Isochronous Timestamp Packets (ITP)	multicast on all the active links

所有的pkt都包含一个14-byte的header 和 2-byte的 link control。共16-byte 4个dw。具体的格式如下所示：

note：1. 所有保留字段都不能用作vendor-specific manner。

2. 应采用保留字段tie 0，接收端需要忽略这些字段。

其中type类型如下：

Link control word描述如下：

Part one - LMP

1. link management packet are used to manage a signal link.

2. they carry no addressing information and not routable.

3. they may generate as the result of hub port commands.

4. they may be used to exchange port capability information .

5. they may be used for testing purposes.

subtype	value	description
Set Link Function	0001	be used to configure functionality that can be changed without leaving the active (U0) state. the Force_LinkPM_Accept bit asserted,the port shall accept all LGO_U1 and LGO_U2 Link Commands. The device must stay in U1 or U2 until the downstream port initiates exit to U0. During normal operation, this feature shall only be used if all other means of lowerng the link state from U0 to U1 or U2 fail.
U2 inactivity timeout	0010	The U2 Inactivity Timeout LMP shall be used to define the timeout from U1 to U2
Vendor device test	0011	Use of this LMP is intended for vendor-specific device testing and shall not be used duringnormal operation of the link
Port capability	0100	describes each port's link capabilities and is sent by both link partners after the successful completion of training and link initialization the device shall send a Port Capability LMP immediately upon entering U0
Port configuration	0101	All Enhanced SuperSpeed ports that support downstream port capability shall be capable of sending this LMP. A port configured in the downstream mode shall send the Port Configuration LMP to the upstream port.
Port configuration response	0110	This LMP is sent by the upstream port in response to a Port Configuration
Precision time management	0111	Precision Time Measurement consists of two separate mechanisms: Link Delay Measurement (LDM) and Hub Delay Measurement (HDM).

Precision time management

superspeedplus host and hub shall support PTM

superspeed host and hub optional support PTM

The PTM Clock has a period of tIsochTimestampGranularity units.

Part two - TP

subtype	value	description
ACK	0001	to acknowledge the previously received data packet data packet sent by the host, as well as to inform the host of the number of data packet buffers it has available after receipt of this packet For OUT endpoints, this TP is sent by a device to acknowledge receipt of the previous For IN endpoints, this TP is sent by the host to request data from a device as well as
NRDY	0010	1.This TP can only be sent by a device for a non-isochronous endpoint.
ERDY	0011	1.This TP can only be sent by a device for a non-isochronous endpoint. 2.It is used to inform the host that an endpoint is ready to send or receive data packets.
STATUS	0100	This TP can only be sent by the host. It is used to inform a control endpoint that the host has initiated the Status stage of a control transfer
STALL	0101	This TP can only be sent by an endpoint on the device
DEC_NOTIFACATION	0110	This TP can only be sent by a device
PING	0111	This TP can only be sent by the host.
PING_RESPONSE	1000	This TP can only be sent by a device in response to a PING TP sent by the host

Part three - DP

This packet can be sent by either the host or a device.

Part four - Isochronous Timestamp Packet (ITP)

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