Split Transaction, Isochronous Scheduling Boundary Conditions - Intel IXP45X Developer's Manual

USB 2.0 Host Controller—Intel
complete-splits (respectively). The H-Frame boundaries are marked with a large, solid
bold vertical line. The B-Frame boundaries are marked with a large, bold, dashed line.
The bottom of the figure illustrates the relationship of an siTD to the H-Frame.
Figure 72.

Split Transaction, Isochronous Scheduling Boundary Conditions

When the endpoint is an isochronous OUT, there are only start-splits, and no complete-
splits. When the endpoint is an isochronous IN, there is at most one start-split and one
to N complete-splits. The scheduling boundary cases are:
• Case 1: The entire split transaction is completely bounded by an H-Frame. For
example: the start-splits and complete-splits are all scheduled to occur in the same
H-Frame.
• Case 2a: This boundary case is where one or more (at most two) complete-splits of
a split transaction IN are scheduled across an H-Frame boundary. This can only
occur when the split transaction has the possibility of moving data in B-Frame,
micro-frames 6 or 7 (H-Frame micro-frame 7 or 0). When an H-Frame boundary
wrap condition occurs, the scheduling of the split transaction spans more than one
location in the periodic list. (e.g. it takes two siTDs in adjacent periodic frame list
locations to fully describe the scheduling for the split transaction).
Although the scheduling of the split transaction may take two data structures, all of the
complete-splits for each full-speed IN isochronous transaction must use only one data
pointer. For this reason, siTDs contain a back pointer, the use of which is described
below.
Software must never schedule full-speed isochronous OUTs across an H-Frame
boundary.
August 2006
Order Number: 306262--, Revision: 004US
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IXP45X and Intel IXP46X Product Line of Network Processors
Intel
® ®
IXP45X and Intel IXP46X Product Line of Network Processors
B4519-01
Developer's Manual
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