cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 88

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

4.0 Segmentation Coprocessor
4.2 Segmentation Functional Description
4.2.3 CPCS-PDU Processing
Figure 4-5. AAL5 CPCS-PDU Generation
4-8
PHY Interface
H
4.2.3.1 AAL5
(1-9 Cells)
TX_FIFO
The buffers submitted by the user contain only user data, the CPCS Service Data
Unit (CPCS-SDU). The CN8237 adds the CPCS-PDU protocol fields to the
CPCS-SDU. The SAR supports two AAL levels: AAL5 and a transparent
adaptation layer (AAL0).
OAM generation in detail.
For AAL5, the SAR generates the CPCS-PDU trailer and pads the CPCS-SDU to
align the PDU to a cell boundary. The CN8237 generates the PAD, Length (LEN),
Common Part Indicator (CPI), and Cyclic Redundancy Check (CRC) fields
according to I.363. The host supplies the CPCS User-to-User Indication (UU)
field in the first buffer descriptor in a message, and the CN8237 transmits it
following I.363.
the VCC table entry. The CN8237 terminates AAL5 PDUs by setting bit 0 of the
Payload Type Identifier field, PTI[0] = 1.
activates this by setting the following fields in the SEG buffer descriptor entry to
these values: AAL_MODE = AAL5 (b00), and AAL_OPT = ABORT (b01).
uses internal circuits to generate and store PDU length and CRC-32 in the SEG
VCC table. The CN8237 transmits these fields within the EOM cell. The PAD
and CPI fields are generated internally.
Specific features also allow the generation of OAM cells.
The SAR generates the ATM header according to host-initialized settings in
The host aborts PDUs by activating an EOM SBD abort option. The host
Figure 4-5
Byte Length Counter
CRC Accumulator
H
Mindspeed Technologies
Internal
Circuits
USER DATA BUFFER(S)
illustrates the CN8237’s AAL5 PDU generation scheme. The SAR
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
SEG VCC Table Entry
(Set PTI[0] = 1)
ATM_HEADER
™
CRC_REM
PDU_LEN
UU
H
PAD UU CPI LEN CRC-32
Chapter 7.0
28237-DSH-001-C
CN8237
covers
8237_032