cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 87

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

CN8236
ATM ServiceSAR Plus with xBR Traffic Management
28236-DSH-001-B
4.2.3.2 AAL3/4
When a segmentation buffer descriptor’s AAL_MODE field is set to AAL3/4
(value = b10), the CN8236 generates the CPCS-PDU’s CPI, Btag, Etag, BASIZE,
Alignment (AL), and Length fields in the header and trailer of the CPCS-PDU
and pads the PDU to align to a cell boundary.
generates the CPCS-PDU header fields as the first four bytes of the first
SAR-PDU’s payload.
an all-0s PAD field after the end of the segmentation buffer data to complement
the CPCS-PDU payload to an integral number of four-byte words. The
segmentation coprocessor then adds the 4-byte CPCS-PDU trailer and fills octets
with 0s for the remainder of the SAR-PDU payload.
Table 4-2. AAL3/4 CPCS-PDU Field Generation
Number (SN), Message Identification (MID), Length Indication (LI), and CRC
fields in each segmented cell for that CPCS-PDU.
header and trailer information. On the last generated cell for a CPCS-PDU with
the EOM set in the buffer descriptor, the segmentation coprocessor pads the
SAR-PDU payload with 0 to 44 bytes.
CPI
BTAG
BASIZE
AL
ETAG
LENGTH
On the first cell of a buffer with BOM set, the segmentation coprocessor
On the last cell of a buffer with EOM set, the segmentation coprocessor writes
Each CPCS-PDU field is generated as described in
The CN8236 also generates the SAR-PDU’s Segment Type (ST), Sequence
Each AAL3/4 cell carries 44 octets of payload and four octets (five fields) of
Field
Mindspeed Technologies
# Bits
16
16
8
8
8
8
Common Part Identifier; set to 0.
Buffer Allocation Size; read from SEG Buffer Descriptor entry.
Beginning Tag; read from SEG VCC table entry.
Alignment Filler, aligns the trailer to fit a 32-bit word.
Ending Tag; read from SEG VCC table entry.
CPCS-PDU Length; the calculated size of the PDU’s payload.
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4.2 Segmentation Functional Description
Function
4.0 Segmentation Coprocessor
Table
4-2.
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