Hardware Reference
In-Depth Information
Figure 14.4. A typical PC with USB devices can use multiple USB hubs to support a variety of
peripherals, connected to whichever hub is most convenient.
Note
A USB 1.1 hub supports both 12Mbps (Full-Speed) and 1.5Mbps (Low-Speed) peripherals. A
USB 2.0 hub supports USB 1.1 12Mbps and 1.5Mbps speeds and the 480Mbps (Hi-Speed)
used by native USB 2.0 devices. A USB 3.0 hub supports 5Gbps (SuperSpeed) devices as
well as any slower USB 2.0 and 1.1 devices.
The maximum cable length between two USB 2.0 480Mbps (Hi-Speed) or USB 1.1 12Mbps (Full-
Speed) devices, or between a device and a hub, is 5 meters using twisted-pair shielded cable with
20-gauge wire. The maximum cable length for USB 3.0 SuperSpeed (5Gbps) connections, as well as
any Low-Speed (1.5Mbps) devices using non-twisted-pair wire, is 3 meters. These distance limits
are shorter if smaller gauge wire is used (see Table 14.1 ).
Table 14.1. Maximum Cable Lengths Versus Wire Gauge
USB 2.0
USB 2.0 (also called Hi-Speed USB ) is a backward-compatible extension of the USB 1.1
specification that uses the same cables, connectors, and software interfaces but that runs 40 times
faster than the original 1.0 and 1.1 versions. The higher speed enables higher-performance
 
 
 
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