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Module Operation
Device Request
clear_feature
Request processor clears the feature specified by the feature selector parameter. Currently,
remote wakeup and endpoint halt are the only features defined by the USB specification. If
the feature to be cleared is remote wakeup, the USB block disables the remote wakeup
functionality. If the feature to be cleared is endpoint halt, the request processor activates the
selected endpoint. The user is notified when the remote wakeup is disabled or an endpoint
halt is cleared.
get_configuration
Returns the current configuration as set by a previous
notification is provided. No user action required.
get_descriptor
Reads the specified device or configuration descriptor from the configuration RAM and
transfers it to the host. Requests for a configuration descriptor returns all of the descriptors
associated with a given configuration including interface, endpoint, and class-specific
descriptors. This request fails if the configuration RAM has not been initialized. No user
notification is provided.
The optional requests for string descriptors are not handled automatically by the request
processor.
vendor specific request. The string descriptors must be stored in external memory and not
the configuration RAM.
get_interface
Returns the selected alternate setting for the specified interface. No user notification is
provided.
get_status
Returns the current status of the specified device, endpoint or interface. No user notification
is provided, no user action required.
set_address
Loads the specified address into USBFAR. The control logic begins responding to the new
address once the status stage of the request completes successfully. No user notification is
provided unless debug mode is enabled.
set_configuration
Reads the configuration RAM. If the configuration is cleared, the USB module is placed into
the unconfigured state. If a valid configuration is selected, the appropriate endpoint
controllers are activated. An invalid configuration number or error in the configuration
descriptor causes the USB module to return a STALL response to the host. The user is
notified when this request completes successfully and must initialize the active endpoint
controllers.
set_descriptor
Not supported. Returns request error.
set_feature
Sets the specified feature. Remote wakeup and endpoint halt are the only features defined in
the USB Specification, Revision 1.0. If the specified feature is remote wakeup, the USB
enables the remote wakeup functionality. If the specified feature is endpoint halt, the USB
request processor halts the selected endpoint. A halted endpoint returns a STALL response
to any requests.
set_interface
Allows the host to select an alternate setting for the specified interface. If a valid alternate
setting is selected, the appropriate endpoint controllers are activated. The user is notified
upon successful completion of this request and must reinitialize the affected endpoint
controllers.
NOTE: The user must read the descriptor structure to determine which endpoints correspond
to a given interface.
sync_frame
Passed to the user as a vendor specific request.
12-6
Table 12-1. USB Device Requests
USB Request Processor Action
_
requests for string descriptors are passed to the user as a
GET
DESCRIPTOR
MCF5272 User's Manual
_
request. No user
SET
CONFIGURATION
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