CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 40

• 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

2.0 Architecture Overview
2.2 High Performance Host Architecture with Buffer Isolation
2.2.3 Buffer Isolation Utilizing Descriptor-Based Buffer Chaining
Figure 2-4. Reassembly Buffer Isolation—Data Buffers Separated from Descriptors
2-6
LEGEND:
Data Buffers
2
Associations (Pointing Function)
Data Writes
Host Actions
SAR Actions
1
3
The CN8237 uses buffer structures for reassembly and segmentation. The buffer
structures maximize the flexibility of the system architecture by isolating the data
buffers from the mechanisms that handle buffer allocation and linking. This
allows the data buffers to contain only payload data, and no control fields or other
user fields. The user can store the data buffers separately from the buffer
descriptors and implement a minimum data copy architecture.
chained together and manipulated by the ServiceSAR.
Figure 2-4
1.
2.
3.
4.
The host creates a link between a reassembly data buffer and a buffer
descriptor by writing in the buffer descriptor entry, a pointer to the data
buffer.
The host then formats a free buffer queue entry, which includes pointers to
both the data buffer and buffer descriptor, and writes this message to the
free buffer queue.
The reassembly coprocessor reads this free buffer queue entry and uses the
pointer to the reassembly data buffer as the memory location to write the
PDU being reassembled.
As reassembly of that PDU progresses, the reassembly coprocessor chains
together the necessary number of additional buffer descriptors (and thus
their associated reassembly data buffers) to complete reassembly of the PDU.
Mindspeed Technologies
(Write)
Host Memory
illustrates how reassembly data buffers and buffer descriptors are
RSM Buffer
Descriptors
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
1
2
3
(SAR
Links
Buffer
Descriptors
for the
PDU.)
™
PCI
(Write)
(Write)
RSM Coprocessor
Free Buffer
Queues
(32)
(Read)
28237-DSH-001-C
RSM Memory
CN8237
CN8237
8237_017