Cirrus Logic EP93xx User Manual

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DS785UM1

Universal Serial Bus Host Controller
EP93xx User’s Guide

CLF: ControlListFilled:

This bit is used to indicate whether there are any TDs on
the Control list. It is set by HCD whenever it adds a TD to
an ED in the Control list. When HC begins to process the
head of the Control list, it checks CLF. As long as
ControlListFilled is 0, HC will not start processing the
Control list. If CF is 1, HC will start processing the Control
list and will set ControlListFilled to 0. If HC finds a TD on
the list, then HC will set ControlListFilled to 1 causing the
Control list processing to continue. If no TD is found on the
Control list, and if the HCD does not set ControlListFilled,
then ControlListFilled will still be 0 when HC completes
processing the Control list and Control list processing will
stop.

BLF: BulkListFilled:

This bit is used to indicate whether there are any TDs on
the Bulk list. It is set by HCD whenever it adds a TD to an
ED in the Bulk list. When HC begins to process the head
of the Bulk list, it checks BF. As long as BulkListFilled is 0,
HC will not start processing the Bulk list. If BulkListFilled is
1, HC will start processing the Bulk list and will set BF to 0.
If HC finds a TD on the list, then HC will set BulkListFilled
to 1 causing the Bulk list processing to continue. If no TD
is found on the Bulk list, and if HCD does not set
BulkListFilled, then BulkListFilled will still be 0 when HC
completes processing the Bulk list and Bulk list processing
will stop.

OCR: OwnershipChangeRequest:

This bit is set by an OS HCD to request a change of
control of the HC. When set HC will set the
OwnershipChange field in HcInterruptStatus. After the
changeover, this bit is cleared and remains so until the
next request from OS HCD.

SOC: SchedulingOverrunCount:

These bits are incremented on each scheduling overrun
error. It is initialized to 00b and wraps around at 11b. This
will be incremented when a scheduling overrun is detected
even if SchedulingOverrun in HcInterruptStatus has
already been set. This is used by HCD to monitor any
persistent scheduling problems.