CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 81

• Manufacturer Part Number: CN8237EBGB
• Description: ATM SAR 622Mbps 3.3V ABR/CBR/GFR/UBR/VBR 456-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8237EBGB

• Package: 456BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 622 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.135 V

4.2.1 Segmentation VCCs
28237-DSH-001-C
4.0 Segmentation Coprocessor
4.1 Overview
ATM’s cell transport mechanism enables large numbers of virtual channels or
VCCs to be multiplexed onto a single PHY interface. The segmentation process
converts user data (typically Ethernet, Token Ring, or Frame Relay packets) into
ATM cells.
coprocessor block independently segments each channel and multiplexes the
VCCs onto the line with cell level interleaving. The CN8237 xBR Traffic
Manager determines the order of execution of these independent processes to
ensure the requested QoS for every channel. For each cell transmission
opportunity, the xBR Traffic Manager tells the segmentation coprocessor which
VCC to send. Therefore, the segmentation coprocessor acts as a slave to the xBR
Traffic Manager.
generates all AAL overhead for AAL5, or optionally uses a null adaptation layer,
AAL0. The CN8237 also generates the ATM cell header, as defined by the host,
for each VCC. Furthermore, the segmentation coprocessor and xBR Traffic
Manager together provide service-specific features to enhance the performance of
Frame Relay internetworking and LAN Emulation.
4.2 Segmentation Functional Description
A VCC specifies a single VC or VP in the ATM network. The CN8237 supports
up to 64 K segmentation VCCs, referenced by a unique index, VCC_INDEX. The
VCC_INDEX identifies a location in the Segmentation VCC table, an array of
10-word segmentation VCC channel descriptors.
single descriptor in the table (10 words). Due to the large number of specified
parameters for ABR traffic, ABR VCCs occupy two descriptors (20 words) in the
Segmentation VCC table. The VCC_INDEX for ABR VCCs points to the first of
the two descriptors, and must be evenly divisible by two.
The CN8237 can segment 64 K VCCs simultaneously. The segmentation
In addition to converting blocked user data into ATM cells, the CN8237
Except for ABR service category VCCs, each segmentation VCC occupies a
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