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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
483
USB 2.0 Host Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
call (DPC) which will execute later. The DPC routine processes the results of the
schedule execution. The precise mechanisms used are beyond the scope of this
document.
Note: the host controller is not required to de-assert a currently active interrupt
condition when software sets the interrupt enables (in the USBINR register, see
) to a zero. The only reliable method software should
use for acknowledging an interrupt is by transitioning the appropriate status bits in the
USBSTS register (
Section 9.12.2, “USBSTS” on page 375
) from a one to a zero.
9.14.15.1 Transfer/Transaction Based Interrupts
These interrupt sources are associated with transfer and transaction progress. They are
all dependent on the next interrupt threshold.
9.14.15.1.1 Transaction Error
A transaction error is any error that caused the host controller to think that the transfer
did not complete successfully.
lists the events/responses that the host can
observe as a result of a transaction. The effects of the error counter and interrupt
status are summarized in the following paragraphs. Most of these errors set the XactErr
status bit in the appropriate interface data structure.
There is a small set of protocol errors that relate only when executing a queue head
and fit under the umbrella of a WRONG PID error that are significant to explicitly
identify. When these errors occur, the XactErr status bit in the queue head is set and
the CErr field is decremented. When the PIDCode indicates a SETUP, the following
responses are protocol errors and result in XactErr bit being set to a one and the CErr
field being decremented.
• EPS field indicates a high-speed device and it returns a Nak handshake to a SETUP.
• EPS field indicates a high-speed device and it returns a Nyet handshake to a SETUP.
• EPS field indicates a low- or full-speed device and the complete-split receives a Nak
handshake.
Serial Bus Babble
When a device transmits more data on the USB than the host controller is expecting for
this transaction, it is defined to be babbling. In general, this is called a Packet Babble.
When a device sends more data than the Maximum Length number of bytes, the host
controller sets the Babble Detected bit to a one and halts the endpoint if it is using a
Table 185.
Summary of Transaction Errors
Event /
Result
Queue Head/qTD/iTD/siTD Side-effects
USB Status Register
(USBSTS)
Cerr
Status Field
USBERRINT
CRC
-1
XactErr set to a one.
Timeout
-1
XactErr set to a one.
-1
XactErr set to a one.
Babble N/A
“Serial Bus Babble” on page 483
1
Buffer Error
N/A
“Data Buffer Error” on page 484
Notes:
1.
If occurs in a queue head, then USBERRINT is asserted only when CErr counts down from a one
to a zero. In addition the queue is halted, see
“Halting a Queue Head” on page 447
2.
The host controller received a response from the device, but it could not recognize the PID as a
valid PID.