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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—USB 2.0 Host Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
442
Order Number: 306262-004US
This traversal state machine applies to all queue heads, regardless of transfer type or
whether split transactions are required. The following sections describe each state.
Each state description describes the entry criteria. The Execute Transaction state
(
Section 9.14.10.3, “Execute Transaction” on page 444
) describes the basic
requirements for all endpoints.
Section 9.14.12.1, “Split Transactions for Asynchronous
and
Section 9.14.12.2, “Split Transaction Interrupt” on
describe details of the required extensions to the Execute Transaction
state for endpoints requiring split transactions.
Note: Prior to software placing a queue head into either the periodic or asynchronous
list, software must ensure the queue head is properly initialized. Minimally, the queue
head should be initialized to the following:
• Valid static endpoint state
Figure 65.
Host Controller Queue Head Traversal State Machine
4508-01
Fetch QH
Execute
Transaction
Write Back
QTd
Advance
Queue
Follow QH
Horizontal Pointer
S t a r t
Halted
.or.
!Active .AND. Ibit
!Active
!Active
Active
!Active
.AND.
!Halted
!Active .AND. !Halted
Active