HS_USB2.0 host
RM0082
444/844
Doc ID 018672 Rev 1
to the Host Controller without concern for corrupting previously issued commands. The Host
Controller Driver has normal read access to all bits.
The SchedulingOverrunCount field indicates the number of frames with which the Host
Controller has detected the scheduling overrun error. This occurs when the Periodic list
does not complete before EOF. When a scheduling overrun error is detected, the Host
Controller increments the counter and sets the SchedulingOverrun field in the
HcInterruptStatus register.
Table 368.
HcCommandStatus register bit assignments
Bits
Name
Reset
Read/Write
Description
HCD
HC
[31:18]
Reserved
[17:16]
SOC
00b
R
R/W
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.
[15:04]
Reserved
[03]
OCR
00b
R/W
R/R
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.
[02]
BLF
0b
R/W
R
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.