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Spinpoint M8U-Internal Product Manual REV 3.4
72
INSTALLATION
The wValue field specifies the descriptor type in the high byte (refer to Table 6-8) 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 set via a
SetDescriptor() 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 transfer from the host to the device.
The only allowed values for descriptor type are device, configuration, and string descriptor types.
If this request is not supported, the device will respond with a Request Error.
Default state: Device behavior when this request is received while the device is in the Default state is not
specified.
Address state: If supported, this is a valid request when the device is in the Address state.
Configured state: If supported, this is a valid request when the device is in the Configured state.
6.3.6.3.10 Set Feature (Request Code 3)
This request is used to set or enable a specific feature.
Feature selector values in wValue must be appropriate to the recipient. Only device feature selector values
may be used when the recipient is a device; only interface feature selector values may be used when the
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.
The TEST_MODE feature is only defined for a device recipient (i.e., bmRequestType = 0) and the lower byte
of wIndex must be zero. Setting the TEST_MODE feature puts the device upstream facing port into test mode.
The device will respond with a request error if the request contains an invalid test selector. The transition to
test mode must be complete no later than 3 ms after the completion of the status stage of the request. The
transition to test mode of an upstream facing port must not happen until after the status stage of the request.
The power to the device must be cycled to exit test mode of an upstream facing port of a d
evice. A
SetFeature() request that references a feature that cannot be set or that does not exist causes a STALL to be
returned in the Status stage of the request.
If the feature selector is TEST_MODE, then the most significant byte of wIndex is used to specify the specific
test mode. The recipient of a SetFeature(TEST_MODE…) must be the device; i.e., the lower byte of wIndex
must be zero and the bmRequestType must be set to zero. The device must have its power cycled to exit test
mode. The valid test mode selectors are listed in Table 6-10.