Spinpoint M8U-Internal Product Manual REV 3.4
68
INSTALLATION
recipient is an interface, and only endpoint feature selector values may be used when the recipient is an
endpoint.
Refer to Table 6-9 for a definition of which feature selector values are defined for which recipients. A
ClearFeature () request that references a feature that cannot be cleared, that does not exist, or that references
an interface or endpoint that does not exist, will cause the device to respond with a Request Error.
If
wLength
is non-zero, then the device behavior is not specified.
Default state
: Device behavior when this request is received while the device is in the Default state is not
specified.
Address state
: This request is valid when the device is in the Address state; references to interfaces or to
endpoints other than endpoint zero shall cause the device to respond with a Request Error.
Configured state
: This request is valid when the device is in the Configured state.
Note: The Test_Mode feature cannot be cleared by the ClearFeature () request.
6.3.6.3.3
Get Configuration (Request Code 8)
This request returns the current device configuration value.
If the returned value is zero, the device is not configured.
If
wValue
,
wIndex
, or
wLength
are not as specified above, then the device behavior is not specified.
Default state
: Device behavior when this request is received while the device is in the Default state
is not specified.
Address state
: The value zero must be returned.
Configured state
: The non-zero
bConfigurationValue
of the current configuration must be returned.
6.3.6.3.4
Get Descriptor (Request Code 6)
This request returns the specified descriptor if the descriptor exists.
The
wValue
field specifies the descriptor type in the high byte (refer to Table 9-8) and the descriptor index in
the low byte. The descriptor index is used to select a specific descriptor (only for configuration and string
descriptors) when several descriptors of the same type are implemented in a device. For example, a device can
implement several configuration descriptors. For other standard descriptors that can be retrieved via a
GetDescriptor() request, a descriptor index of zero must be used. The range of values used for a descriptor
index is from 0 to one less than the number of descriptors of that type implemented by the device. The
wIndex
field specifies the Language ID for string descriptors or is reset to zero for other descriptors. The
wLength
field specifies the number of bytes to return. If the descriptor is longer than the
wLength
field, only
the initial bytes of the descriptor are returned. If the descriptor is shorter than the
wLength
field, the device
indicates the end of the control transfer by sending a short packet when further data is requested. A short
packet is defined as a packet shorter than the maximum payload size or a zero length data packet.
The standard request to a device supports three types of descriptors: device (also device_qualifier),
configuration (also other_speed_configuration), and string. A high-speed capable device supports the
device_qualifier descriptor to return information about the device for the speed at which it is not operating
(including
wMaxPacketSize
for the default endpoint and the number of configurations for the other speed).
The other_speed_configuration returns information in the same structure as a configuration descriptor, but for
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