User`s guide

Appendix A

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15. USB Device: Also called a USB function. This is a logical or physical entity on the bus that contains

one or more USB interfaces. It possesses one upstream-capable USB connector.

16. USB Hub: A device that provides communication between one upstream connector and multiple

downstream connectors, allowing more USB devices to be attached to a host. In any given bus

configuration, a device is either a host, device, or hub.

17. USB Interface: A logical USB entity that performs a particular function. An interface is typically

associated with a particular device class – for example, a "CDC interface".

18. USB Descriptors: Data structures contained within a physical USB device that describe the device

(including the interfaces it supports) and its capabilities. The host reads these during enumeration.

19. USB Serial Number: A unique string that allows a host to differentiate between devices attached to it

that contain the same VID and PID values.

20. USB speeds: A USB connection is characterized by one of four speeds: low-speed (1.5 Mbps), full-

speed (12 Mbps), high-speed (480 Mbps), or super-speed (4.8 Gbps). MSP430 MCUs are USB 2.0

full-speed devices. All MSP430 USB traffic is full-speed.

21. VBUS: The host is required to make 5-V power available to the device through the USB cable. The

name of this power rail is VBUS. In addition to sourcing power, the USB device uses VBUS to

determine whether or not an active host is present. Devices often respond to a VBUS-on event by

asserting their presence to the host by pulling up the D+ signal.

22. Vendor ID (VID): A unique 16-bit value assigned by the USB Implementers Forum to a particular

USB hardware vendor.

Starting a USB Design Using MSP430™ MCUs SLAA457A–September 2013–Revised May 2014

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