USB2 and USB1.1 Interoperability

http://www.siliconimaging.com/universal_serial_bus.htm

The new USB 2.0 expansion hub design manages the transition of the data rates between the high speed host and lower speed USB peripherals, while maintaining full bandwidth utilization.

The USB 2.0 specification extends the maximum speed of the connection from 12 Mbps on USB 1.1 up to 480 Mbps (60MBytes/sec). This enables the transfer of 1920x1080 images at 24fps (frames per second) for high-definition video conferencing or 320x240 images at 500fps for high speed video motion analysis. The transition to USB 2.0 will be seamless, since USB 2.0 is both forward and backward compatible with USB 1.1. Older peripherals will simply plug into new USB 2.0 capable PCs and Hubs. The USB connectors and cables are even identical. It is even possible for a high speed USB 2.0 device to plug into a legacy USB1.1 port and simply operate at reduced throughput. Both Hi-Speed USB 2.0 and original USB 1.1 peripherals can operate on a computer at the same time. The new USB 2.0 expansion hub design manages the transition of the data rates between the high speed host and lower speed USB peripherals, while maintaining full bandwidth utilization. Up to 127 USB peripherals with 5 levels of hubs can be connected to a single USB host controller. With 5 Meters (16.4 feet) of cabling between devices, a network of cameras, sensors, data acquisition, and I/O devices can physically extend up to 30 Meters (98 feet) from the PC. A peripheral can either be self-powered or bus-powered, with up to 500mA of consumption. To satisfy the needs of low-power embedded and portable computer applications, a power-management mechanism is also incorporated.