RS8234 Mindspeed Technologies, RS8234 Datasheet - Page 87

• Manufacturer Part Number: RS8234
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

RS8234
ATM ServiceSAR Plus with xBR Traffic Management
28234-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 RS8234 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-zeros 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 four-byte CPCS-PDU trailer and
then fills octets with zeros 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 will pad the
SAR-PDU payload with 0 to 44 bytes.
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 shown in
The RS8234 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
LENGTH
BASIZE
Field
BTAG
ETAG
CPI
AL
Mindspeed Technologies
# Bits
16
16
8
8
8
8
Common Part Identifier; set to zero.
Beginning Tag; read from SEG VCC Table entry.
Buffer Allocation Size; read from SEG Buffer Descriptor 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.
™
4.2 Segmentation Functional Description
Function
4.0 Segmentation Coprocessor
Table
4-2.
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