usb hub 3.0 for macbook pro

USB HUB 3.0 System Description

USB HUB 3.0 is a physical SuperSpeed bus combined in parallel with a physical USB 2.0 bus.

USB HUB 3.0 Devices Compatibility

The mechanical and electrical backward/forwards compatibility for USB 3.0 is accomplished via a composite cable and associated connector assemblies that form the dual-bus architecture. USB 3.0 devices accomplish backward compatibility by including both SuperSpeed and non-SuperSpeed bus interfaces. USB 3.0 hosts also include both SuperSpeed and non-SuperSpeed bus interfaces, The USB 3.0 connection model accommodates backwards and forward compatibility for connecting USB 3.0 or USB 2.0 devices into a USB 3.0 bus. Similarly, USB 3.0 devices can be attached to a USB 2.0 bus.

USB HUB 3.0 System Configuration

USB HUB 3.0 supports USB devices (all speeds) attaching and detaching from the USB 3.0 at any time. Consequently, system software must accommodate dynamic changes in the physical bus topology. The architectural elements for the discovery of attachment and removal of devices on USB 3.0 are identical to those in USB 2.0. There are enhancements provided to manage the specifics of the SuperSpeed bus for configuration and power management. The independent, dual-bus architecture allows for activation of each of the buses independently and provides for the attachment of USB devices to the highest speed bus available for the device.

USB 3.0 Cable

USB HUB 3.0 Connector

USB HUB 3.0 Standard-A Connector Color Coding Since both the USB 2.0 Standard-A and USB 3.0 Standard-A receptacles may co-exist on a host, color coding is recommended for the USB 3.0 Standard-A connector (receptacle and plug) housings to help users distinguish it from the USB 2.0 Standard-A connector.

Robustness

There are several attributes of SuperSpeed USB HUB 3.0 that contribute to its robustness: • Signal integrity using differential drivers, receivers, and shielding • CRC protection for header and data packets • Link level header packet retries to ensure their reliable delivery • End-to-end protocol retries of data packets to ensure their reliable delivery • Detection of attach and detach and system-level configuration of resources • Data and control pipe constructs for ensuring independence from adverse interactions between functions

Error Detection

The USB SuperSpeed physical layer bit error rate is expected to be less than one in 1012 bits. Each packet includes a CRC to provide error detection of multiple bit errors. When data integrity is required an error recovery procedure may be invoked in hardware or software. The protocol includes separate CRCs for headers and data packet payloads. Additionally, the link control word (in each packet header) has its own CRC. A failed CRC in the header or link control word is considered a serious error which will result in a link level retry to recover from the error. A failed CRC in a data packet payload is considered to indicate corrupted data and can be handled by the protocol layer with a request to resend the data packet.

Error Handling

Errors may be handled in hardware or software. Hardware error handling includes reporting and retrying of failed header packets. A USB host controller will try a transmission that encounters errors up to three times before informing the client software of the failure. The client software can recover in an implementation-specific way.

USB HUB 3.0 and USB HUB 2.0 Interoperability

Power Distribution

The power source and sink requirements of different device classes can be simplified with the introduction of the concept of a unit load. A unit load for SuperSpeed has been redefined to be 150 mA. The USB supports a range of power sourcing and power consuming agents; these include the following: Root port hubs: Are directly attached to the USB Host Controller. Hub power is derived from the same source as the Host Controller. Systems that obtain operating power externally, either AC or DC, must be capable of supplying at least six unit loads to each port. Such ports are called high-power ports. Battery-powered systems may supply either one or six unit loads. Ports that can supply only one unit load are termed low-power ports.