USB is a very popular serial interface especially for PCs. As well known, the interface is used to connect to a PC such equipments as a keyboard, a mouse, a printer, a Flash memory, a hard disk drive, a speaker, and so on.
USB has several speed versions, Low-Speed (1.5Mbps), Full-Speed (12Mbps), High-Speed (480Mbps) and so on.Toshiba TX03 series microprocessors support USB Full-Speed. A hierarchical structure is applied to USB interface. One “Host” dominates many “Devices” in a network. For example, a PC is a Host, and Devices are any apparatuses which are connected to the PC through USB cables, like a keyboard, a mouse and so on.
USB has a remarkable feature of plug-and-play. Switching off a PC is unnecessary when USB Devices are connected or removed. This is one of the reasons USB has become so popular.
The cable of USB has 4 wires; VDD, GND, signal D+, and signal D-. D+ and D- are complementary values each other for one transferred data. In the case that D+ is high and D- is low, the data is called “Differential 1”. And D+ is low and D- is high, “Differential 0”.The data format of USB is NRZI (non-return to zero inverted). This format defines data “1” when no change occurs in one clock interval, and data “0”, either high-to-low or low-to-high change occurs.
USB does not have any clock lines. So the Host and the Driver have to synchronize each other. 8 bit SYNC codes are transferred to synchronize a receiver to a transmitter in USB Full-Speed.
Microcontrollers products incorporating a USB interface are displayed.