PXB4330 Datasheet, PDF (39/201 Pages) Infineon Technologies AG – ICs for Communications

PXB 4330
Functional Description
3.1.2 The Scheduler
The basic building block of the ABM is the Scheduler. A Scheduler is a cascade of two
multiplexers: a Weighted Fair Queuing (WFQ) Multiplexer, and a Priority Multiplexer, as
shown in Figure 3-3. The inputs of the multiplexers are connected to a programmable
number of queues.
real time queue
queues for
non-real time
connections
W₁
W₂
W
F
W_n-1 ^Q
W_n
output rate
W_n = weight factor of non real time queue n
Figure 3-3 Scheduler Structure
One single queue is provided for all real-time connections. It is connected directly to the
high-priority input of the Priority Multiplexer (marked with the arrow symbol). The 2-input
Priority Multiplexer first takes a cell from the high-priority input; and, only if there is no
cell here, then looks at the low-priority input where the WFQ Multiplexer is connected.
Thus, real-time traffic is always prioritized. As the output rate of the Scheduler is limited
- as denoted in Figure 3-3 with the bubble symbol at the Priority Multiplexer output - the
non-real-time connections share the remaining bandwidth. This behavior is shown in
Figure 3-4.
bandwidth
output rate
non-real time
connections
(low priority)
real time connections
(high priority)
Figure 3-4 Scheduler Behavior
Data Sheet
3-39
09.99