USB SuperSpeed Dual Bus Architecture

Thu Apr 20 11:51:56 CST 2023

0_USB-SuperSpeed-Dual-Bus-Architecture-Hornmic

USB SuperSpeed Dual Bus Architecture

USB 3.0, whose USB speed mode is called "Super Speed", uses 8b/10b encoding and has a bandwidth of 5 Gbps.

USB 3.1 is called "Super Speed +" and features 128b/132b with 10 Gbps bandwidth.

USB 3.2 is the latest version of the USB connection interface announced by the USB Implementers Forum on July 25, 2017, based on USB 3.1 improvements. In addition to doubling the transfer speed from 10Gbps to 20Gbps, it is also recommended that devices be unified using Type-C as the primary terminals. In addition, USB 3.2 is also backward compatible with older specifications, whether the USB 3.2 devices plugged into the old terminal, or old devices plugged into the USB 3.2 terminal, can still operate normally at a lower speed.

1_USB-SuperSpeed-Main-Differences

The SuperSpeed USB system is functionally identical to previous versions of USB in that it connects USB host USB peripherals via USB cable for data interaction. The USB bus allows external devices to be accessed (attached), configured, used or removed.

USB 3.2 is a dual bus architecture, with one bus used for backward compatible USB 2.0 device data communication and the other named SuperSpeed bus architecture for super-speed device to host side data communication.

2_USB3.2-dual-BUS-architecture

USB3.2 interconnect refers to the way USB3.2 and USB2.0 devices connect to and communicate with USB3.2 hosts, i.e., USB3.2 interconnect consists of USB2.0 devices and USB3.2 SuperSpeed devices interconnecting with and reading data through to the USB3.2 SuperSpeed host side. USB3.2 interconnect inherits the core architecture elements of USB2.0, although some of these are expanded to accommodate the dual-bus architecture.

The topology of USB 3.2 SuperSpeed is defined in the same way as the topology of USB 2.0. It consists of a layered star topology with a host at layer 1, a hub (HUB) at a lower layer, and USB devices connected through the hub interface.

The USB3.2 connectivity model is forward and backward compatible. A USB 3.2 SuperSpeed device can be connected into a USB 2.0 connector, or a USB 2.0 device can be connected into a USB 3.2 SuperSpeed interface. This forward and backward compatibility is achieved through the dual bus body architecture of USB.

The USB 3.2 and bus system hosts both an enhanced SuperSpeed interface and a USB 2.0 interface, which are essentially parallel buses that can work simultaneously.

The USB 3.2 connectivity model allows devices, hubs and host-side support to be detected and configured at the highest possible signal rate.

USB 3.2 hubs are a special type of USB device whose purpose is to provide additional connection points to the bus beyond those provided by the host. In this specification, non-hub devices are referred to as peripheral devices in order to distinguish them from hub devices.

USB speed comparison by version:

3_USB-speed-data-chart

USB SuperSpeed Architecture

The USB SuperSpeed architecture is divided into a physical layer, a data link layer, and a protocol layer.

4_USB-enhanced-SuperSpeed-System

USB3.0 defines USB, and USB3.1/USB3.2 implements the SuperSpeed Plus architecture.

5_USB-SuperSpeed-Plus-architecture

Link Layer

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

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

- Manages the state of the PHY (i.e., the physical connection on its end), including power management and events (connect, remove, and wake).

- Transmit and receive byte streams, which have additional signals to qualify whether the byte stream is control sequences or data. The physical layer consists of discrete transmit and receive physical links, so that the port can send and receive both control and data information.

Protocol Layer

The protocol layer defines the rules for end-to-end communication between hosts and devices. The ultra-high-speed protocol provides for the exchange of application data information between the host and device endpoints. This communication relationship is called a pipe. This is a host-directed protocol, meaning that the host decides when application data is transferred between the host and the device. SuperSpeed is not a polled protocol because the device can request services from the host asynchronously on behalf of a specific endpoint.



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By HornmicLink_Henry @230420 14:30