RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 38

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

2.0 Architecture Overview
2.2 High Performance Host Architecture with Buffer Isolation
2.2.3 Buffer Isolation Using Descriptor-Based Buffer Chaining
Figure 2-4. Reassembly Buffer Isolation — Data Buffers Separated from Descriptors
2-6
LEGEND:
Host Memory
Data Buffers
2
Associations (Pointing Function)
Data Writes
Host Actions
SAR Actions
1
3
The RS8234 employs 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, 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
Host (or optionally Local) Memory
(Write)
illustrates how reassembly data buffers and buffer descriptors are
RSM Buffer
Descriptors
1
2
3
ATM ServiceSAR Plus with xBR Traffic Management
(SAR
Links
Buffer
Descriptors
for the
PDU.)
™
PCI
(Write)
(Write)
RSM Coprocessor
Free Buffer
Queues
(32)
(Read)
28234-DSH-001-B
SAR-Shared
RS8234
Memory
RS8234
100074_005