MPC8280 datasheet(1166/1386 Pages) FREESCALE

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Inverse Multiplexing for ATM (IMA)

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

34-20

Freescale Semiconductor

34.3.3.3

Cell Processing Task

The cell processing task is triggered by the cell processing activation function. When the cell processing

task is triggered, it will extract cells in-order from the delay compensation buffers. Cells extracted from

the delay compensation buffers are processed per the standard MPC8280 ATM operation (i.e. mapped into

ATM channels and processed per the appropriate AAL or OAM function).

If the on-demand cell processing activation function is used, then when the cell processing task is

triggered, it will extract cells in-order from the delay compensation buffers until either (1) no more are

available, or (2) four cells have been extracted. The purpose of limiting the cell processing task to a

maximum of four cells is to limit the maximum latency of servicing requests from the external PHYs. Note

that, on the average, the receive process will deliver one cell to the ATM layer per cell reception.

If the IDCR-regulated processing activation function is used, then one cell will be extracted from the delay

compensation buffers of a particular IMA group per timeout of that group’s IDCR timer.

34.4

IMA Programming Model

34.4.1

Data Structure Organization

Figure 34-12 shows the organization of IMA data structures.

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