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NUC970 Technical Reference Manual
Publication Release Date: Dec. 15, 2015
- 731 -
Revision V1.30
NUC97
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CHNIC
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[4]
HSERR
Host System Error (R/WC)
The Host Controller sets this bit to 1 when a serious error occurs during a host system
access involving the Host Controller module.
[3]
FLR
Frame List Rollover (R/WC)
The Host Controller sets this bit to a one when the Frame List Index rolls over from its
maximum value to zero. The exact value at which the rollover occurs depends on the
frame list size. For example, if the frame list size (as programmed in the Frame List Size
field of the USBCMD register) is 1024, the Frame Index Register rolls over every time
FRINDEX[13] toggles. Similarly, if the size is 512, the Host Controller sets this bit to a one
every time FRINDEX[12] toggles.
[2]
PCD
Port Change Detect (R/WC)
The Host Controller sets this bit to a one when any port for which the Port Owner bit is set
to zero has a change bit transition from a zero to a one or a Force Port Resume bit
transition from a zero to a one as a result of a J-K transition detected on a suspended port.
This bit will also be set as a result of the Connect Status Change being set to a one after
system software has relinquished ownership of a connected port by writing a one to a
port's Port Owner bit.
This bit is allowed to be maintained in the Auxiliary power well. Alternatively, it is also
acceptable that on a D3 to D0 transition of the EHCI HC device, this bit is loaded with the
OR of all of the PORTSC change bits (including: Force port resume, over-current change,
enable/disable change and connect status change).
[1]
UERRINT
USB Error Interrupt (USBERRINT) (R/WC)
The Host Controller sets this bit to 1 when completion of a USB transaction results in an
error condition (e.g., error counter underflow). If the TD on which the error interrupt
occurred also had its IOC bit set, both this bit and USBINT bit are set.
[0]
USBINT
USB Interrupt (USBINT) (R/WC)
The Host Controller sets this bit to 1 on the completion of a USB transaction, which results
in the retirement of a Transfer Descriptor that had its IOC bit set.
The Host Controller also sets this bit to 1 when a short packet is detected (actual number
of bytes received was less than the expected number of bytes).