MPC8280 datasheet(983/1386 Pages) FREESCALE

983 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

Freescale Semiconductor

31-23

Figure 31-12. ABR Transmit Flow (continued)

RM/DATA In Rate Cell Tx

Count >= Nrm

or (Count > Mrm

and Now

≥

(Last_RM+Trm))

Nrm=Number of data cells between every RM cell

Mrm=Fixed number=2

Trm=Max time between every F-RM Cells.

Count=Number of data cells from last F-RM.

Time = Now - Last_RM

Checking “Time-Out Factor” Max time

allowed between RM Cells before a rate

Decrease is required.

Time >ADTF

ACR = ICR

ACR is too high

Idle adjust (“use it or loose it”)

Unack

≥Crm

ACR = ACR-ACR

× CDF

ACR = max(ACR,MCR)

Unack=Number of F-RM cells sent

without any B-RM cell received.

Crm=Max number of F-RM cells without any

B-RM cell allowed before rate decrease

is required.

Send RM (DIR = forward, CCR = ACR, ER = PCR, CI = NI = CLP = 0)

Count=0

Last_RM = Now

First-turn = TRUE

Unack = Unack+1

EXIT

First-turn = Flag indicates first turn of RM cell

with priority over data cells.

B-RM/DATA In Rate Cell Tx

F-RM In Rate Cell Tx

Count = Count+1

Source End-Sys 3

Source End-Sys 4

Source End-Sys 7

Source End-Sys 8

Yes

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