Freescale Semiconductor MPC8260 - Manual (Page 943)

ATM Controller and AAL0, AAL1, and AAL5
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 30-23
Figure 30-12. 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
No
Yes
No
Yes
No