CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 85

• 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

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
Figure 4-2. Segmentation Buffer Descriptor Chaining
4.2.2.4 Transmit Queues
28237-DSH-001-C
Segmentation Buffer
4.2.2.3 Host Linked
Descriptors
SAR SEG-Shared Memory
VCC_INDEX = 4
VCC_INDEX = 4
VCC_INDEX = 4
BUFF_PNTR
BUFF_PNTR
BUFF_PNTR
CONTROL
CONTROL
CONTROL
Figure 4-2
three-buffer message by linking three SBDs. In this example, the SAR transmits a
message sequence of buffer A, then buffer B, and finally buffer C as the end of
message.
Once the linked list of SBDs is complete, the host submits the chained message to
the SAR for segmentation. The host uses one of the 32 transmit queues for this
purpose. Each transmit queue is a circular queue of two-word entries. The host
identifies the next available transmit queue entry according to the write-only host
interface specification described in
pointer to the SAR SEG-shared memory SBD onto the next available transmit
queue entry. During this write, the host also sets the VLD bit to indicate the entry
is valid.
accesses. When a write occurs to any of the transmit queues, the CN8237 marks
that queue as pending. Once every cell slot, the CN8237 services one queue entry
from one Transmit Queue. The system designer selects one of two service order
priority schemes. With the SEG_CTRL(TX_RND) bit set to 1, the CN8237
services queues in round-robin order (that is, one entry per queue in transmit
queue sequence for all active queues). With the SEG_CTRL(TX_RND) bit set to
0, the CN8237 services the queues in fixed priority order (that is, entries from
higher priority active queues are serviced before lower priority queue entries, with
transmit queue 31 having highest priority).
<BOM>
<COM>
<EOM>
(NULL)
NEXT
NEXT
NEXT
SBDs
The CN8237 detects this write by snooping SAR SEG-shared memory
Mindspeed Technologies
illustrates an example of SBD chaining. The host has formed a
Host (or SAR SEG-Shared) Memory
Section
™
3.3.1. The host processor writes a
4.2 Segmentation Functional Description
Buffers
A
C
B
4.0 Segmentation Coprocessor
8237_029
4-5