Freescale Semiconductor MPC8260 - Manual (Page 1022)

ATM AAL1 Circuit Emulation Service
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
31-6 Freescale Semiconductor
Figure 31-4. AAL1 CES Receiver Data flow
31.4 Interworking Functions
The PowerQUICC II supports the interworking of ATM and TDM. The TDM data processing is done by
the MCC and the SI (refer to
Chapter 28, “Multi-Channel Controllers (MCCs),” and Chapter 15, “Serial
Interface with Time-Slot Assigner,” for further information). The ATM controller processes the ATM data.
Data forwarding between the ATM controller and the MCC can be done in two ways:
• Automatic data forwarding. This mode enables automatic data forwarding between AAL1 and
transparent mode over a TDM.
• Core intervention. When an MCC receive buffer is full and its RxBD is closed, the MCC interrupts
the core. The core copies the MCC’s receive buffer pointer to an ATM TxBD and sets the ready bit
(TxBD[R]). Similarly, when an ATM receive buffer is full and its RxBD is closed, the core services
the ATM controller’s interrupt by copying the ATM receive buffer pointer to an MCC TxBD and
setting TxBD[R]. This mode is useful when additional core processing is required.
Possible interworking applications are as follows:
• Circuit emulation service (CES)
• Carrying voice over ATM
• Multiplexing low speed services, such as voice and data, onto one ATM connection
31.4.1 Automatic Data Forwarding
The basic concept of automatic data forwarding is to program the ATM controller and the MCC to process
the same BD table (ring).
The MCC and ATM receivers must be programmed to operate in opposite E-bit polarity. That is, both
receivers receive into buffers in which RxBD[E] = 0 and then set RxBD[E] when the buffer is full. For the
Bit count integrity
User information
3-step SN algorithm
Drop cell
Pointer verification
Valid/dummy/drop
SN/SNP verification
Invalid SN
Process payload
Valid SN
Valid cell
Cell size
Tag cell
Unstructured
data format
AAL1 cell stream