![](http://datasheet.mmic.net.cn/30000/MCF5272CVF66_datasheet_2373703/MCF5272CVF66_266.png)
12-6
MCF5272 User’s Manual
MOTOROLA
Module Operation
USB module responds with a request error when the SET_DESCRIPTOR request is issued.
These standard requests are dened in Chapter 9 of the USB Specication. See beginning
Table 12-1. USB Device Requests
Device Request
USB Request Processor Action
clear_feature
Request processor clears the feature specied by the feature selector parameter. Currently,
remote wakeup and endpoint halt are the only features dened by the USB specication. 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 notied when the remote wakeup is disabled or an endpoint
halt is cleared.
get_conguration
Returns the current conguration as set by a previous SET_CONFIGURATION request. No user
notication is provided. No user action required.
get_descriptor
Reads the specied device or conguration descriptor from the conguration RAM and
transfers it to the host. Requests for a conguration descriptor returns all of the descriptors
associated with a given conguration including interface, endpoint, and class-specic
descriptors. This request fails if the conguration RAM has not been initialized. No user
notication is provided.
The optional requests for string descriptors are not handled automatically by the request
processor. GET_DESCRIPTOR requests for string descriptors are passed to the user as a
vendor specic request. The string descriptors must be stored in external memory and not
the conguration RAM.
get_interface
Returns the selected alternate setting for the specied interface. No user notication is
provided.
get_status
Returns the current status of the specied device, endpoint or interface. No user notication
is provided, no user action required.
set_address
Loads the specied address into USBFAR. The control logic begins responding to the new
address once the status stage of the request completes successfully. No user notication is
provided unless debug mode is enabled.
set_conguration
Reads the conguration RAM. If the conguration is cleared, the USB module is placed into
the uncongured state. If a valid conguration is selected, the appropriate endpoint
controllers are activated. An invalid conguration number or error in the conguration
descriptor causes the USB module to return a STALL response to the host. The user is
notied when this request completes successfully and must initialize the active endpoint
controllers.
set_descriptor
Not supported. Returns request error.
set_feature
Sets the specied feature. Remote wakeup and endpoint halt are the only features dened in
the USB Specication, Revision 1.0. If the specied feature is remote wakeup, the USB
enables the remote wakeup functionality. If the specied 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 specied interface. If a valid alternate
setting is selected, the appropriate endpoint controllers are activated. The user is notied
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 specic request.