Freescale Semiconductor TWR-MCF52259-Ethenet - Manual (Page 96)

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The General USB Process
How Does the Host Know a Device’s Requirements?
When a USB device is plugged into a USB port the host communicates
with the device and configures each device according its unique
requirements such
as:
1. Type of transfer required (interrupt, bulk, isochronous, or control
2. Who supplies the power (host or device)
3. Maximum packet size
4. The number of configurations (e.g., a single device can be
configured to use its own power or power from the host)
5. Manufacturer’s product ID and registration information
6. Etc.
This configuration process is called enumeration. Enumeration
is be covered in greater detail later in this presentation