cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 46

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

2.0 Architecture Overview
2.3 Automated Segmentation Engine
2-12
VCC table located in SEG 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:
nine cells deep in order to optimize the balance between Cell Delay Variation
(CDV), which increases with longer transmit FIFO buffer depth, and PCI latency
protection, which decreases with shorter transmit FIFO buffer depth.
(or Virtual FIFO buffer). This is intended for circuit-based CBR traffic such as
voice channel(s).
independent parallel segmentation status queues. The CN8237 writes
segmentation status queue entries on either PDU boundaries or buffer boundaries,
selectable on a per-VCC basis. PDU boundary status reporting is called Message
Mode, while buffer status reporting is called Streaming Mode.
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
• 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
The system designer can set the depth of the transmit FIFO buffer from one to
The CN8237 provides a method to segment traffic from a fixed PCI address
The CN8237 reports segmentation status to the host on one of a set of 32
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.
coprocessor segments the Service Data Unit (SDU) to ATM cell payload
boundaries and generates ATM cell headers, but generates no other
overhead fields.
segmentation, wherein 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 OC-12 ServiceSAR Plus with xBR Traffic Management
™
28237-DSH-001-C
CN8237