Hardware Reference
In-Depth Information
USB cables, connectors, hubs, and peripherals can also be identified by icons, as shown
in
Figure 14.6
. The plus (+) symbol added to the upper icon indicates that port or device
would support USB 2.0 (Hi-Speed USB) in addition to the standard 1.1 support.
Figure 14.6
These icons identify USB 1.x and 2.x devices.
Note that these icon guidelines do not apply to USB cables or connectors because the
cable and connector design did not change from USB 1.1 to 2.0. Cables are supposed to
use the standard icon (without the plus symbol), and all cables that support USB 1.1 also
support 2.0.
USB 1.1/2.0 Connectors
The USB 1.1 and 2.0 family of specifications has included numerous connector styles
since it was introduced. Initially, four main styles of connectors were specified: Series
A, Series B, Mini-A, and Mini-B. The A connectors are used for upstream connections
between a device and the host or a hub. The USB ports on motherboards and hubs are
usually Series A connectors. USB 3.0 extends several of these connectors with additional
sections and/or pins, which are shown in the following section covering USB 3.0.
Series B connectors are designed for the downstream connection to a device that has de-
tachable cables. The Mini connector is simply a smaller version of the larger ones, in a
physically smaller form factor for smaller devices, such as digital cameras, PDAs, and
media players. For USB On-The-Go devices, a Mini-AB connector was developed to per-
mitadevicetoactaseitheranupstreamoradownstreamdeviceinrelationshiptoanother
device.
InApril2006,theMicro-BandMicro-ABconnectorswereaddedasapprovedconnectors,
and in May 2007, the Mini-A and Mini-AB connectors were removed from the approved
listofUSBconnectors.Therefore,asofmid-2007,newandforthcomingUSBdevicescan
use only the following connectors: Series A, Series B, Mini-B, Micro-B, and Micro-AB.
(Micro-AB is used only by On-The-Go products.)
The physical USB plugs are small (especially the Mini and Micro plugs) and, unlike a
typical serial or parallel cable, the plug is not attached by screws or thumbscrews. There
arenopinstobendorbreak,makingUSBdevicesuserfriendlytoinstallandremove.The
USB plugs shown in
Figure 14.7
connect to the corresponding USB sockets.
Figure 14.7
USB plugs and sockets.
