Motorola PowerQUICC II MPC8280 Series Reference Manual page 1128

Interworking Functions
TDM
interface
UTOPIA
interface
32.4.1.2 TDM-to-ATM
When going from TDM to ATM (depicted in Figure 32-6), the MCC receiver routes data
from the TDM line to a specific BD table. The ATM transmitter is programmed to operate
on the same BD table. When the MCC fills a receive buffer, the ATM controller sends it.
The two controllers synchronize on the MCC's RxBD[E] and the ATM controller's
TxBD[R].
In a CES application, first initialize the ATM transmitter, then initialize the MCC receiver
and set CHAMR[EP].
In order to prevent an overrun condition on the MCC receiver, the ATM transmitter should
be programmed to work at a faster rate than the MCC super channel. This ensures that the
ATM channel polls the common BD table at a higher rate than it is being filled by the MCC.
In CES mode, the ATM controller ignores BSY (busy) events when the ATM tries to open
a buffer that is not yet full; it continues polling the BD until the buffer is filled by the MCC
receiver and then updates the relevant statistics; see Section 32.15, "Internal AAL1 CES
Statistics Tables."
Note that if an overrun condition occurs on the MCC, despite the above mechanism,
software should restart the MCC and ATM channels in order to recover.
32-8
Freescale Semiconductor, Inc.
MCC
MCC
Tx pointer
Tx
ATM
ATM
Rx pointer
Rx
Note: The ATM Rx should be programmed to operate in
inverted polarity E (Empty) bit.
Figure 32-5. ATM-to-TDM Interworking
MPC8280 PowerQUICC II Family Reference Manual
For More Information On This Product,
Go to: www.freescale.com
BD table
0 BD 1
1 BD 2
1 BD 3
0 BD 4
0 BD 5
Buffer 1
Buffer 2
Buffer 3
Buffer 4
Buffer 5
MOTOROLA