Motorola PowerQUICC II MPC8280 Series Reference Manual page 1015

Chapter 31
ATM Controller and
AAL0, AAL1, and AAL5
The functionality described in this chapter is not available on
the MPC8270.
The ATM controller provides the ATM and AAL layers of the ATM protocol using the
universal test and operations physical layer (PHY) interface for ATM (UTOPIA level II)
for both master and slave modes. It performs segmentation and reassembly (SAR)
functions of AAL5, AAL1 circuit emulation service (CES), AAL2, and AAL0, and most of
the common parts of the convergence sublayer (CP-CS) of these protocols.
For each virtual channel (VC), the controller's ATM pace control (APC) unit generates a
cell transmission rate to implement constant bit rate (CBR), variable bit rate (VBR),
available bit rate (ABR), unspecified bit rate (UBR) or UBR+ traffic. To regulate VBR
traffic, the APC unit performs a continuous-state leaky bucket algorithm. The APC unit
also uses up to eight priority levels to prioritize real-time ATM channels, such as CBR and
real-time VBR, over non-real-time ATM channels such as VBR, ABR and UBR.
The ATM controller performs the ATM Forum (UNI-4.0) ABR flow control. To perform
feedback rate adaptation, it supports forward and backward resource management (RM)
cell generation and ATM Forum floating-point calculation. ABR flow control is
implemented in hardware and firmware (without software intervention) to prevent potential
delays during backward RM cell processing and feedback rate adaptation.
The MPC8280 supports a special mode for ATM/TDM interworking. The CPM performs
automatic data forwarding between ATM channels and the MCCs' TDM channels without
core intervention.
The MPC8280 ATM SAR controller applications are as follows:
• ATM line card controllers
• ATM-to-WAN interworking (frame relay, T1/E1 circuit emulation)
• Residential broadband network interface units (NIU) (ATM-to-Ethernet)
• High-performance ATM network interface cards (NIC)
MOTOROLA Chapter 31. ATM Controller and AAL0, AAL1, and AAL5
Freescale Semiconductor, Inc.
NOTE
For More Information On This Product,
Go to: www.freescale.com
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