Appendix B: Hub Requests

Over-Current Indicator Change

This field only applies to hubs that report over-current conditions on a per port basis. If the hub does not report over-current on a per port hub basis, then this field is RESERVED and returns zero.

This field reports whether or not a change has occurred on the port’s over-cur- rent indicator.

•0 = No over-current indicator change for this port has occurred

•1 = The over-current indicator for this port has changed

Reset Complete

This field is set when reset processing for this port has completed. Reset complete also causes the port enable status bit to be set, and the suspend change field is reset.

•0 = No change

•1 = Reset complete

Set/Clear Port Feature

The set and clear feature requests may specify a given hub feature or may be associated with an individual port. Hub feature requests are differentiated from port feature requests by the “index” field value of the setup transaction. The index field identifies the port number (port #) that the request applies to. Note that a port number of zero is not permissible, since a hub would interpret the request as a hub-specific rather than a port-specific request. Table B-10 lists the individual port features that can be set or cleared.

Table B-10: Feature Selector and Index Values for Port Specific Requests

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Table B-10: Feature Selector and Index Values for Port Specific Requests

The section entitled “Get Port Status Request” on page 456, defined the status and indicator bits and the status and indicator change bits that are maintained by the hub for each port and returned when a “Get Port Status” request is made. These bits reflect the various port features supported by a hub. The “Set” and “Clear Port Feature” requests provide a method of enabling and disabling particular features and also allow software to acknowledge changes that are detected when the “Get Port Status” request is performed.

Port Test Modes

These requests on valid only for high-speed devices. A device is placed in the test mode via a “Set Port Feature” request as defined in Tab leB-11 on page462.

Table B-11: Set Port Test Feature

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Appendix B: Hub Requests

Table B-12 defines the tests and the corresponding selector value used to invoke a particular test.

Table B-12: Test Selector Values

Get Bus State

This request is no longer defined by the USB 2.0 specification. The description of this request is included here for legacy purposes The “Get Bus State” request was designed to facilitate diagnosis of problems by providing bus state information on a port-by-port basis. The information returned is sampled at the last EOF2 point detected at the selected port. Bus state information is returned in a single byte during the data stage of the transfer. The bit definition is shown in Table B-13 on page 463.

Table B-13: Format of the Bus State Returned During the Get Bus State Request

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