MPC8280 datasheet(1066/1386 Pages) FREESCALE

1066 / 1386 page

ATM AAL1 Circuit Emulation Service

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

32-6

Freescale Semiconductor

Figure 32-4. AAL1 CES Receiver Data flow

32.4

Interworking Functions

The MPC8280 supports the interworking of ATM and TDM. The TDM data processing is done by the

MCC and the SI (refer to Chapter 29, “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

32.4.1

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

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