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Universal Serial Bus: Universal Serial Bus Specification
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The Enhanced Host Controller Interface (EHCI) specification describes the register-level interface for a Host Controller for the Universal Serial Bus (USB) Revision 2.0. The specification includes a description of the hardware/software interface between system software and the host controller hardware. This specification is intended for hardware component designers, system builders and device driver (software) developers.
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Windows CE 2.10 supports all four types of data transfers as required by the Universal Serial Bus Specification, Revision 1.0, to support a variety of devices. Device drivers for USB devices can use any of these transfer types that may be appropriate for the device:
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USB is ... faster than older ports, such as serial and parallel ports. The USB 1.1 specification supports data transfer rates of up to 12Mb/sec and USB 2.0 has a maximum transfer rate of 480 Mbps. Though USB was introduced in 1997, the technology didn't really take off until the introduction of the Apple iMac (in late 1998) which used USB ports exclusively. It is somewhat ironic, considering USB was created and designed by Intel, Compaq, Digital, and IBM. Over the past few years, USB has become a widely-used cross-platform interface for both Macs and PCs.
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While this compliance testing goes a long way toward ensuring device compatibility, there are no guarantees... that all USB certified devices will be able to work together compatibly over a particular USB bus. This is not only because of differences in interpreting and implementing the USB standard and failure by some manufacturers to adhere to the standards, but also because of the rapid development of technology itself. For example, because of the limited bandwidth of the USB 1.x standard, care must be exercised when combining devices compliant with that specification where data receipt is time-sensitive -- such as several devices on one bus that all transfer video simultaneously.
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There are two major versions of the Universal Serial Bus specification - USB 1.0 and USB 2.0. Amongst other things such as better power management and higher signal integrity, USB 2.0 has a data transfer rate of 20 Mbps which is a vast improvement over the 1.2 Mbps of USB 1.0.
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The specification provides for no more than 5.25V and no less than 4.75V (5V±5%) between the positive and negative bus power lines. Initially, a device is only allowed to draw 100mA. It may request more current from the upstream device in units of 2mA up to a maximum of 500mA.
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Universal Serial Bus Specification