
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 de
fi
ned in Chapter 9 of the
USB Specification.
See beginning
of Page 12-1.
Table 12-1. USB Device Requests
Device Request
USB Request Processor Action
clear_feature
Request processor clears the feature speci
fi
ed by the feature selector parameter. Currently,
remote wakeup and endpoint halt are the only features de
fi
ned by the USB speci
fi
cation. 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 noti
fi
ed when the remote wakeup is disabled or an endpoint
halt is cleared.
get_con
fi
guration
Returns the current con
fi
guration as set by a previous
SET
_
CONFIGURATION
request. No user
noti
fi
cation is provided. No user action required.
get_descriptor
Reads the speci
fi
ed device or con
fi
guration descriptor from the con
fi
guration RAM and
transfers it to the host. Requests for a con
fi
guration descriptor returns all of the descriptors
associated with a given con
fi
guration including interface, endpoint, and class-speci
fi
c
descriptors. This request fails if the con
fi
guration RAM has not been initialized. No user
noti
fi
cation 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 speci
fi
c request. The string descriptors must be stored in external memory and not
the con
fi
guration RAM.
get_interface
Returns the selected alternate setting for the speci
fi
ed interface. No user noti
fi
cation is
provided.
get_status
Returns the current status of the speci
fi
ed device, endpoint or interface. No user noti
fi
cation
is provided, no user action required.
set_address
Loads the speci
fi
ed address into USBFAR. The control logic begins responding to the new
address once the status stage of the request completes successfully. No user noti
fi
cation is
provided unless debug mode is enabled.
set_con
fi
guration
Reads the con
fi
guration RAM. If the con
fi
guration is cleared, the USB module is placed into
the uncon
fi
gured state. If a valid con
fi
guration is selected, the appropriate endpoint
controllers are activated. An invalid con
fi
guration number or error in the con
fi
guration
descriptor causes the USB module to return a STALL response to the host. The user is
noti
fi
ed when this request completes successfully and must initialize the active endpoint
controllers.
set_descriptor
Not supported. Returns request error.
set_feature
Sets the speci
fi
ed feature. Remote wakeup and endpoint halt are the only features de
fi
ned in
the USB Speci
fi
cation, Revision 1.0. If the speci
fi
ed feature is remote wakeup, the USB
enables the remote wakeup functionality. If the speci
fi
ed 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 speci
fi
ed interface. If a valid alternate
setting is selected, the appropriate endpoint controllers are activated. The user is noti
fi
ed
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 speci
fi
c request.