Motorola MPC8260 User Manual

29-22

MOTOROLA

3. The CCR and MCR Þelds are taken from the F-RM and is not changed.

4. The CI bit of the B-RM cell is set if the previous data cell arrived with EFCI = 1 

(congestion bit in the ATM cell header).

5. The ER Þeld of the turn around B-RM cells is limited by TCTE[ER-BRM].

6. If a F-RM cell arrives before the previous F-RM cell was turned around (for the same 

connection), the new RM cell overwrites the old RM cell.

The MPC8260Õs ABR transmit and receive flow control is described in the following
ßowcharts. See Figure 29-11, Figure 29-12, Figure 29-13, and Figure 29-14.

 Start Channel Tx

ACR < TCR

Send RM (DIR = forward, CCR = ACR, ER = PCR, CI = NI = 0, CLP =1)

               Schedule: Time_to_send = now+1/TCR

ACR is low sent only 

   EXIT

 RM/DATA In Rate Cell Tx

ACR>=TCR

 out-of-rate cells at TCR

Yes

No