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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262--, Revision: 004US
489
USB 2.0 Host Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Once periodic transfers are exhausted, any stored asynchronous transfer will be
moved. Asynchronous transfers are opportunistic in that they execute whenever
possible and their operation is not tied to H-frame and B-frame boundaries with the
exception that an asynchronous transfer cannot babble through the SOF (start of B-
frame 0.)
9.15.1.5.2
Split-State Machines
The start and complete split operational model differs from EHCI slightly because there
is no bus medium between the EHCI controller and the embedded Transaction
Translator. Where a start or complete-split operation would occur by requesting the
split to the HS hub, the start/complete split operation is simple an internal operation to
the embedded Transaction Translator.
summarizes the conditions where
handshakes are emulated from internal state instead of actual handshakes to HS split
bus traffic.
The unshaded cells represent Start-Splits and the shaded cells represent Complete-
Splits.
9.15.1.5.3
Asynchronous Transaction Scheduling and Buffer Management
The following USB 2.0 specification items are implemented in the embedded
Transaction Translator:
USB 2.0 – 11.17.3
• Sequencing is provided & a packet length estimator ensures no full-speed/low-
speed packet babbles into SOF time.
USB 2.0 – 11.17.4
• Transaction tracking for 2 data pipes.
USB 2.0 – 11.17.5
• Clear_TT_Buffer capability provided though the use of the register.
9.15.1.5.4
Periodic Transaction Scheduling and Buffer Management
The following USB 2.0 specification items are implemented in the embedded
Transaction Translator:
USB 2.0 – 11.18.6.[1-2]
• Abort of pending start-splits
— EOF (and not started in micro-frames 6)
— Idle for more than 4 micro-frames
Table 188.
Condition vs. Emulate TT Response
Condition
Emulate TT Response
Start-Split: All asynchronous buffers full.
NAK
Start-Split: All periodic buffers full.
ERR
Start-Split: Success for start of Async. Transaction.
ACK
Start-Split: Start Periodic Transaction.
No Handshake (Ok)
Complete-Split: Failed to find transaction in queue.
Bus Time Out
Complete-Split: Transaction in Queue is Busy.
NYET
Complete-Split: Transaction in Queue is Complete.
[Actual Handshake from LS/FS device]