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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
490
Order Number: 306262-004US
• Abort of pending complete-splits
— EOF
— Idle for more than 4 micro-frames
USB 2.0 – 11.18.[7-8]
• Transaction tracking for up to 16 data pipes.
— Some applications may not require transaction tracking up to a maximum of 16
periodic data pipes. The option to limit the tracking to only 4 periodic data
pipes exists in the by changing the configuration constant
VUSB_HS_TT_PERIODIC_CONTEXTS to 4. The result is a significant gate count
savings to the core given the limitations implied.
Warning:
Limiting the number of tracking pipes in the EMBedded –TT to four will impose the
restriction that no more than four periodic transactions (INTERRUPT/ISOCHRONOUS)
can be scheduled through the embedded-tt per frame. the number 16 was chosen in
the USB specification because it is sufficient to ensure that the high-speed to full-speed
periodic pipeline can remain full. Keeping the pipeline full puts no constraint on the
number of periodic transactions that can be scheduled in a frame and the only limit
becomes the flight time of the packets on the bus.
• Complete-split transaction searching.
Note:
There is no data schedule mechanism for these transactions other than the micro-
frame pipeline. The embedded TT assumes the number of packets scheduled in a frame
does not exceed the frame duration (1 ms) or else undefined behavior may result.
9.15.1.5.5
Multiple Transaction Translators
The maximum number of embedded Transaction Translators that is currently supported
is one as indicated by the N_TT field in
Table 131, “HCSPARAMS – Host Control
Structural Parameters” on page 371
.
9.15.2
Device Operation
The co-existence of a device operational controller within the host controller has little
effect on EHCI compatibility for host operation except as noted in this section.
9.15.2.1
USBMODE Register
Given that the dual-role controller is initialized in neither host nor device mode, the
USBMODE register must be programmed for host operation before the EHCI host
controller driver can begin EHCI host operations.
9.15.2.2
EHCI Reserved Fields
Some of the reserved fields and reserved addresses in the capability registers and
operational register are used in device mode, therefore you must adhere to the
following:
• Write operations to all EHCI reserved fields (some of which are device fields) with
the operation registers should always be written to zero. This is an EHCI
requirement of the device controller driver that must be adhered to.
• Read operations by the host controller must properly mask EHCI reserved fields
(some of which are device fields) because fields that are used exclusively for the
device are undefined in host mode.