cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 46

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

2.0 Architecture Overview
2.3 Automated Segmentation Engine
2-12
2.3 Automated Segmentation Engine
The CN8236 can segment up to 64 K VCCs simultaneously. The segmentation
coprocessor block independently segments each channel and multiplexes the
VCCs onto the line with cell level interleaving. For each cell transmission
opportunity, the xBR Traffic Manager tells the segmentation coprocessor which
VCC to send.
transparent or NULL adaptation layer, AAL0.
VCC table located in SAR-shared memory. A VCC specifies a single VC or VP
in the ATM network. These VCC table entries define the negotiated or contracted
characteristics of the traffic for that channel, and are initialized by the host either
during system initialization or on-the-fly during operation. An initialized
segmentation VCC table entry effectively establishes a connection on which data
can be segmented.
NOTE:
point to the buffers containing the PDU to be transmitted, and then submitting
that chained message to the SAR by writing to one of 32 independent circular
transmit queues.
cells on each channel according to the host-defined segmentation VCC table
entries for each channel. The formatting functions include the following:
The CN8236 provides full support of the AAL5 and AAL3/4 protocols and a
Each segmentation channel is specified as a single entry in the segmentation
The host submits data for segmentation by first linking buffer descriptors that
The segmentation coprocessor then operates autonomously, formatting the
• The segmentation coprocessor formats the ATM cell header for each cell,
• The segmentation coprocessor also generates the CPCS-PDU header and
• For AAL5 traffic, the SEG coprocessor also generates the PDU-specific
• Each AAL3/4 cell carries 44 octets of payload and four octets (in five
• AAL0 is intended for client-proprietary use. For AAL0, the segmentation
• The user has per-channel, per-PDU control of Raw Cell Mode
• The formatted cells are passed through the transmit FIFO buffer to the
ABR VCCs occupy two table entries.
based on the settings in the segmentation VCC table entry for that VCC.
trailer fields in the first and last cell of the segmented PDU.
fields in the trailer of the CPCS-PDU, and places these in the last cell (the
End of Message [EOM] cell) for the PDU.
fields) of header and trailer information. The SAR performs the formatting
steps necessary to create AAL3/4 cells.
coprocessor segments the Service Data Unit (SDU) to ATM cell payload
boundaries and generates ATM cell headers, but generates no other
overhead fields.
segmentation, where the segmentation coprocessor reads the entire
52-octet ATM cell from the segmentation buffer and does not generate the
ATM headers for the cells.
PHY interface for transmission.
Mindspeed Technologies
ATM ServiceSAR Plus with xBR Traffic Management
™
28236-DSH-001-B
CN8236