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 2-30. Handled Standard Requests
RequestDefinition
GET_DESCRIPTORReturns the current device configuration value
SET_ADDRESSSets the device address for all future device accesses
SET_CONFIGURATIONSets the device configuration
GET_CONFIGURATIONReturns the current device configuration value
GET_STATUSReturns status for the specified recipient
SET_FEATUREUsed to set or enable a specific feature
CLEAR_FEATUREUsed to clear or disable a specific feature

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

Table 2-31. Handled Class Requests
RequestDefinition
SET_LINE_CODINGConfigures DTE rate, stop bits, parity and number of character bits
GET_LINE_CODINGRequests current DTE rate, stop bits, parity and number of character bits
SET_CONTROL_LINE_STATERS-232 signal used to indicate to the DCE device that the DTE device is now present

Unhandled requests are stalled.