Motorola PowerQUICC II MPC8280 Series Reference Manual page 1140

ATM-to-TDM Adaptive Slip Control
MCC Tx pointer
MCC Tx pointer
MCC Tx pointer
32-20
Freescale Semiconductor, Inc.
ATM-to-TDM
BD table
0 BD 1 ATM Rx pointer
0 BD 2
MCC_Start
0 BD 3
0 BD 4
0 BD 5
0 BD 6
0 BD 7 W
ATM-to-TDM
BD table
1 BD 1
1 BD 2
MCC_Start
1 BD 3
0 BD 4 ATM Rx pointer
0 BD 5
0 BD 6
0 BD 7 W
ATM-to-TDM
BD table
0 BD 1
0 BD 2
0 BD 3
0 BD 4
1 BD 5 ATM Rx pointer
0 BD 6
0 BD 7 W MCC_Start
Figure 32-16. Pre-Underrun Sequence
MPC8280 PowerQUICC II Family Reference Manual
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Step 1:
Initialize the MCC and ATM pointers
to the same BD table.
CESAC=0
MCC_Start=3, MCC_Stop=1
ATM_Start=5, ATM_Stop=7-1=6
Step 2:
When CESAC reaches MCC_Start,
the MCC starts transmitting.
CESAC=3
MCC_Start=3, MCC_Stop=1
ATM_Start=5, ATM_Stop=7-1=6
Step 3:
Because the MCC is reading the data
faster than the ATM, CESAC falls to the
MCC_Stop threshold. The MCC pointer
then freezes, and the current buffer
retransmitted for a multiple of the frame
size. (The buffer size should be a multiple
of the frame size.)
CESAC=1
MCC_Start=3, MCC_Stop=1
ATM_Start=5, ATM_Stop=7-1=6
1
The MCC can optionally transmit
the underrun template.
Step 4:
The MCC switches to pre-underrun
state and continues to send the current
buffer (the last buffer that was sent).
When CESAC reaches MCC_Start and
a multiple of complete frames has been
sent, the MCC starts to transmit again
(returns to Step 2 in this flow).
1
is
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