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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
419
USB 2.0 Host Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
The end of the periodic schedule is identified by a next link pointer of a schedule data
structure having its T-bit set to a one. When the host controller encounters a T-Bit set
to a one during a horizontal traversal of the periodic list, it interprets this as an End-Of-
Periodic-List mark. This causes the host controller to cease working on the periodic
schedule and transitions immediately to traversing the asynchronous schedule. Once
this transition is made, the host controller executes from the asynchronous schedule
until the end of the micro-frame.
When the host controller determines that it is time to execute from the asynchronous
list, it uses the operational register ASYNCLISTADDR to access the asynchronous
schedule, see
Figure 55, “General Format of Asynchronous Schedule List” on page 419
.
The ASYNCLISTADDR register contains a physical memory pointer to the next queue
head. When the host controller makes a transition to executing the asynchronous
schedule, it begins by reading the queue head referenced by the ASYNCLISTADDR
register. Software must set queue head horizontal pointer T-bits to a zero for queue
heads in the asynchronous schedule. See
Section 9.14.8, “Asynchronous Schedule” on
for complete operational details.
Figure 54.
Derivation of Pointer into Frame List Array
B4472-01
DWord-aligned
Periodic Frame List Element
Address
Periodic Frame List Base
Address
Frame Index Register
Periodic Frame
List
31
12 11
2
1 0
31
12
1 3 1 2 1 1 10 9 8 7 6 5 4 3 2 1 0
Figure 55.
General Format of Asynchronous Schedule List
B4473-01