USB 3.0

A SuperSpeed link is a logical and physical connection of two ports. The connected ports are called link partners. A port has a physical part and a logical part. The link layer defines the logical portion of a port and the communications between link partners.

The logical portion of a port has:

>> State machines for managing its end of the physical connection. These include physical layer initialization and event management, i.e., connect, removal, and power management.

>> State machines and buffering for managing information exchanges with the link partner. It implements protocols for flow control, reliable delivery (port to port) of packet headers, and link power management.

>> Buffering for data and protocol layer information elements.

The logical portion of a port also:

Ø Provides correct framing of sequences of bytes into packets during transmission; e.g., insertion of packet delimiters

Ø Detects received packets, including packet delimiters and error checks of received header packets (for reliable delivery).

Ø Provides an appropriate interface to the protocol layer for pass-through of protocol-layer packet information exchanges.

The physical layer provides the logical port an interface through which it is able to:

Ø Manage the state of its PHY (i.e., its end of the physical connection), including power management and events (connection, removal, and wake).

Ø Transmit and receive byte streams, with additional signals that qualify the byte stream as control sequences or data. The physical layer includes discrete transmit and receive physical links, therefore, a port is able to simultaneously transmit and receive control and data information.

The protocol between link partners uses specific encoded control sequences. Note that control sequences are encoded to be tolerant to a single bit error. Control sequences are used for port-to- port command protocol, framing of packet data (packet delimiters), etc. There is a link-partner protocol for power management that uses packet headers.