Universal Serial Bus (USB) is the most successful peripheral interface in the history of the personal computer. USB is a standard connection interface between computers and digital devices. It enables the easy transfer of data through a direct connection or cable. USB was created with simplicity of use in mind, and thus “plug-and-play” became the expectation as drivers loaded themselves and printers, external hard drives, and other peripherals “just worked.”
USB has other features that make it attractive for product designs. It provides a small current available to the peripheral, and so USB became a standard for recharging and data transfer in one cable. USB 3.0 ups that current to 900 mA from 500 mA (in 2.0).
The USB 3.0 bus and the USB 2.0 bus operate separately in the same USB 3.0 cable and thus USB 3.0 is backwards compatible with USB 2.0 products by inclusion, with the right cable. SuperSpeed traffic travels in both directions simultaneously, referred to as “full duplex.” The SuperSpeed portion of USB 3.0 hubs do not poll device endpoints to check for ready data; devices operating at SuperSpeed initiate communication with the USB 3.0 hub only when they need it. USB 3.0 also provides for more aggressive power savings modes.
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SuperSpeed now enables streaming video and mass storage at a new level of performance with much faster data transmission rates. Much of USB 3.0 is the same as USB 2.0 from a software standpoint in terms of device classes, data transfer types, and descriptors. Hardware is affected by differential signaling at significantly higher frequencies, however, which can present new challenges to designers in terms of increased signal loss or degraded signal integrity.
Note that USB 3.0 systems cannot utilize both USB 2.0 and 3.0 busses simultaneously; they are mutually exclusive. This holds true with device power consumption as well. Therefore, don’t expect to draw 900mA with a low-, full-, or high-speed USB device. With the largest installed base for interfaces (of USB 2.0) combined with backwards compatibility (of USB 3.0), the new USB is sure to be a winner.
Cypress Semiconductor EZ-USB® FX3 SuperSpeed USB Controllers
EZ-USB® FX3 SuperSpeed USB Controller enables developers to add USB 3.0 functionality to any system. EZ-USB FX3 has a fully configurable, parallel, General Programmable Interface (GPIF II™) which can connect to any processor, ASIC, or FPGA. Integrating USB 3.0 and USB 2.0 physical layers with a 32-bit ARM926EJ-S processor, the FX3 provides exceptional processing power, great flexibility, and data transfers as high as 320 MBps from GPIF II™ to USB.