Motorola PowerQUICC II MPC8280 Series Reference Manual page 1135

Freescale Semiconductor, Inc.
Interworking Functions
super-frame (multi-frame) SYNC from the external framer. The incoming CAS block
should be captured by the MCC only once for each super frame (on the last frame).
The user may use external logic to convert the framer super-frame SYNC to trigger the
MCC. The MCC captures the CAS block from the external framer and copies it
transparently into one of four internal CAS blocks. Each byte in the CAS block contains a
nibble of valid CAS information (depicted in Figure 32-8).
Note that the buffer data size should not include the CAS octets.
32.4.7.2.1 CAS Mapping Using the Core (Optional)
To avoid using another TDM dedicated to CAS information, the user can use a parallel
interface (controlled by the core) to deliver the CAS information from the framer to the
incoming CAS block. In this case, the core service routine reads the CAS information from
the external framer and writes it to the incoming CAS block. To optimize the process, the
framer can interrupt the core only when new information is received.
32.4.7.3 ATM-to-TDM CAS Support
During the reassembly process, the AAL1 CES receiver unpacks the signaling information
from the end of an AAL1 super frame (depicted in Figure 32-3) and places it in the internal
CAS block (using the receive CAS routing table). All AAL1 functions operate normally
(AAL1 PDU-header verification, bit count integrity, 3-step-SN algorithm, etc.). Each
common (MCC, ATM) BD table should point to buffers that can contain a whole number
of super
frames. The last buffer of the super frame is marked with EOSF. After closing a buffer with
an EOSF indication, the ATM receiver processes the CAS data (copies it to the internal
CAS block from the AAL1 cell payload at the receive side). The EOSF indication in the BD
is statically set by the CPU while initializing the BD table. See Figure 32-13.
MOTOROLA Chapter 32. ATM AAL1 Circuit Emulation Service 32-15
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