CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 90

• 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

4.0 Segmentation Coprocessor
4.3 Segmentation Control and Data Structures
4.2.6 Virtual FIFO Buffers
4.3.1 Segmentation VCC Table Entry
4-10
Table 4-2. Segmentation VCC Table Entry—AAL5-AAL0 Format (1 of 2)
Word 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0
1
2
3
4
PM_INDEX
UU
PDU_LEN
In addition to gathering PDU data from buffers, the CN8237 provides an optional
method to segment from a fixed PCI address, or Virtual FIFO buffer. The
CN8237 supports AAL0, CBR Virtual FIFO buffer segmentation.
the CURR_PNTR and RUN fields to 0 in the SEG VCC table entry. The host
writes the FIFO buffer address to the FIFO_PNTR field in the VCC table entry.
The host also initially sets the SCH_MODE field = CBR.
buffer. Once the FIFO buffer is almost full, the host sets the RUN bit to a logic
high. The SAR will then start reading from the FIFO buffer. When the FIFO
buffer gets below almost empty, the host will set the SCH_OPT bit to a logic high.
The SAR will then skip a cell transmit opportunity in order to allow the FIFO
buffer to refill. After the SAR skips a cell, it will reset the SCH_OPT bit to a logic
low.
host FIFO buffer, and prepends (that is, attaches to the beginning) the
ATM_HEADER value in the VCC table entry. The host does not use the transmit
queue for Virtual FIFO buffers. The CN8237 transmits cell payloads from this
location indefinitely, with no status reporting.
4.3 Segmentation Control and Data Structures
Each Segmentation VCC table entry occupies one 10-word descriptor of the
Segmentation VCC table. The first 7 words are generic, independent of traffic
class. The last 3 or 13 words provide additional parameters specific to service
classes.
AAL5-AAL0 and Virtual FIFO buffer. Each completely describe the state of the
segmentation process for individual VCCs.
format of AAL5-AAL0 VCC table entries.
The host configures the channel for Virtual FIFO buffer operation by setting
At this point the host can start writing cells to the external host transmit FIFO
In this mode, the segmentation coprocessor reads 48 bytes of payload from the
There are two basic formats for the generic part of the VCC table entry:
PORT_ID
Mindspeed Technologies
ATM_HEADER
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
CRC_REM
™
LAST_PNTR
BOM_PNTR
Tables 4-2
BUFFER_LEN
and
4-3
28237-DSH-001-C
describe the
CN8237