Motorola PowerQUICC II MPC8280 Series Reference Manual page 1226

IMA Microcode Architecture
TRL stuff event occurs
and this link is not given
a cell during a round
robin pass.
Depth decreases to 2.x
"imminent stuff" flagged
Before stuff event can
happen, queue depth
creeps down below 2.x
threshold to 1.x
Stuff event occurs,
bringing queue depth
back to 2.x
"imminent stuff'
remains flagged, but
is held off for minimum
5 frames.
Holdoff expires and
stuff event occurs,
bringing queue depth
back to normal depth
of 3.x
Figure 34-9. Transmit Queue Behavior: Link Clock Rate Faster than TRL,
34.3.2.4 Differences in CTC Operation
Overall, CTC operation is similar to ITC operation in task partitioning and overall
structure. Differences are as follows:
1. Transmit buffers are still maintained for the non-TRL links, but these buffers will
not 'jitter', since the transmit clocks are all the same. However, queue depths may
vary slightly because PHY requests, while synchronous, will not necessarily come
in simultaneously (i.e. may have constant offsets) and will definitely not be serviced
simultaneously.
34-16
Freescale Semiconductor, Inc.
Tx Queue
Tx Queue
Tx Queue
Tx Queue
Worst-Case Event Sequence
MPC8280 PowerQUICC II Family Reference Manual
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Normal 'Wander zone'
Queue extraction pointer
(Transmitted by non-TRL task)
Normal 'Wander zone'
Queue extraction pointer
(Transmitted by non-TRL task)
Normal 'Wander zone'
Queue extraction pointer
(Transmitted by non-TRL task)
Normal 'Wander zone'
Queue extraction pointer
(Transmitted by non-TRL task)
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