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Intel® PXA26x Processor Family Developer’s Manual 12-9
Universal Serial Bus Device Controller
• Data transfer direction: host to device, device to host
• Data transfer type: standard, class, vendor
• Data recipient: device, interface, endpoint, other
• Number of bytes to transfer
• Index or offset
• Value: used to pass a variable-sized data parameter
• Device request
Table 12-11 shows a summary of all device requests. Refer to the Universal Serial Bus
Specification Revision 1.1 for a full description of host device requests.
The UDC decodes most standard device commands with no intervention required by the user. The
following commands are not passed to the user are: Set Address, Set Feature, Clear Feature, Get
Configuration, Get Status, Get Interface, and Sync Frame. The Set Configuration and Set Interface
commands are passed to the user to indicate that the host set the specified configuration or interface
and the software must take any necessary actions. Alternate interfaces settings are not supported;
the host mus
t set the alternate settings field in SET_INTERFACE requests to zero. If the UDC
receives a SET_INTERFACE request with the alternate settings field non-zero, the UDC responds
with a STALL. The Get Descriptor and Set Descriptor commands are passed to the user to be
decoded.
Because the Set Feature and Clear Feature commands are not passed on, the user is not able to
decode the device-remote-wake-up-feature commands. To solve this problem, the status bit
UDCCS0:DRWF indicates whether or not the device-remote-wake-up feature is enabled.
UDCCS0: DRWF is a read-only bit. When the bit is set to 1, the device-remote-wake-up feature is
enabled. When the bit is set to 0, the feature is not enabled.
Table 12-11. Host Device Request Summary
Request Name
SET_FEATURE Enables a specific feature such as device remote wake-up or endpoint stalls.
CLEAR_FEATURE Clears or disables a specific feature.
SET_CONFIGURATION
Configures the UDC for operation. Used after a reset of the core or after a
reset has been signalled via the USB.
GET_CONFIGURATION Returns the current UDC configuration to the host.
SET_DESCRIPTOR
Sets existing descriptors or add new descriptors. Existing descriptors include:
device, configuration, string, interface, and endpoint.
GET_DESCRIPTOR Returns the specified descriptor, if it exists.
SET_INTERFACE Selects an alternate setting for the UDC’s interface.
GET_INTERFACE Returns the selected alternate setting for the specified interface.
GET_STATUS
Returns the UDC’s status including: remote wake-up, self-powered, data
direction, endpoint number, and stall status.
SET_ADDRESS Sets the UDC’s 7-bit address value for all future device accesses.
SYNCH_FRAME Sets then reports an endpoint’s synchronization frame.