19.1.5.3.3 Enumeration Process

The USB protocol is a host/client protocol. The host starts the enumeration, sending requests to the device through the control endpoint. The device handles standard requests as defined in the USB specification.

Table 19-7. Handled Standard Requests
Request Definition
GET_DESCRIPTOR Returns the current device configuration value
SET_ADDRESS Sets the device address for all future device accesses
SET_CONFIGURATION Sets the device configuration
GET_CONFIGURATION Returns the current device configuration value
GET_STATUS Returns status for the specified recipient
SET_FEATURE Used to set or enable a specific feature
CLEAR_FEATURE Used to clear or disable a specific feature

The device also handles some class requests defined in the CDC class.

Table 19-8. Handled Class Requests
Request Definition
SET_LINE_CODING Configures DTE rate, stop bits, parity and number of character bits
GET_LINE_CODING Requests current DTE rate, stop bits, parity and number of character bits
SET_CONTROL_LINE_STATE RS-232 signal used to indicate to the DCE device that the DTE device is now present

Unhandled requests are stalled.