cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 42

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

2.0 Architecture Overview
2.2 High Performance Host Architecture with Buffer Isolation
2.2.4 Status Queue Relation to Buffers and Descriptors
Figure 2-6. Segmentation Status Queues Related to Data Buffers and Descriptors
2-8
LEGEND:
Host Memory
Buffer Descriptors
(Host Copy)
Associations (Pointing Function)
Host Actions
Data Buffers
SEG
The status queues employed by the CN8237 are written by the SAR and read by
the host. These status queue entries provide the data needed by the host in order to
further process the segmentation and reassembly data flow in progress or just
completed. Each status queue entry thus includes data (such as error flags and
status bits), which the host uses in its succeeding process steps. The SAR also
includes, in each status queue entry, a pointer to the first buffer descriptor of the
segmented or reassembled data buffer(s) which comprise a single PDU. This
accomplishes the other principal function of a status queue entry—to establish the
association from the SAR to the host of the successful or unsuccessful
segmentation or reassembly of a PDU.
and segmentation data buffers and descriptors. The figure shows one three-buffer
PDU on a single virtual channel, represented by a single entry in one of the
transmit queues and a single entry in one of the SEG status queues. The host links
the buffer descriptors pointing to the data buffers containing the PDU, makes a
host-only copy of the buffer descriptor, then writes the transmit queue entry. The
SAR performs segmentation processing on the PDU and writes a SEG status
queue entry informing the host of the status of the segmentation process.
SEG Status Queues
Figure 2-6
Mindspeed Technologies
illustrates the association between the segmentation status queues
Transmit Queue
Host Writes
Host Writes
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
Entry
SBD
PCI
™
SAR Writes
SEG Status Queue
Entry
SEG Buffer Descriptors (SBD)
Transmit Queues
(Buffer
Descriptors
Linked by Host)
28237-DSH-001-C
SEG Memory
CN8237
8237_019