Motorola MPC8260 - Manual (Page 803)

29-23 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Figure 29-12. ABR Transmit Flow (Continued)
RM/DATA In Rate Cell Tx
Count >= Nrm
or (Count > Mrm
and Now ³
(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 ÒTime-Out FactorÓ Max time
allowed between RM Cells before a rate
Decrease is required.
Time >ADTF
ACR = ICR
ACR is too high
Idle adjust (Òuse it or loose itÓ)
Unack ³Crm
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