cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 82

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

4.0 Segmentation Coprocessor
4.2 Segmentation Functional Description
4.2.2 Submitting Segmentation Data
Table 4-1. Segmentation PDU Delineation
4-4
BOM
4.2.2.1 User Data
0
0
1
1
4.2.2.2 Buffer
Descriptors
Format
EOM
0
1
0
1
Once the host establishes a connection, it supplies data for segmentation. The host
submits full or partial PDUs, either one at a time or in batches, for individual
VCCs. The SAR accepts PDUs at any time, regardless of the state of the
connection, and segments data on each VCC independently.
The CN8236 accepts user PDUs as sequences of data buffers. SAR-shared
memory resident segmentation buffer descriptors (SBDs) provide the address,
length and control information for buffers. The host forms PDU buffer sequences
by linking buffer descriptors. The data buffers themselves contain only user data
and reside in host (or optionally SAR-shared) memory. Host data buffers contain
the bulk of segmentation data, and can begin on any byte-aligned address in the
SAR’s PCI address space.
NOTE:
The host submits data using the following process sequence. First, the host
allocates an SBD for each buffer in a message. SBDs reside in SAR-shared
memory, and must begin on word-aligned addresses. Then, the host describes the
buffers in the SBD. This description includes the address and length of the buffer,
as well as control fields for the SAR during buffer segmentation. These control
fields specify the VCC_INDEX, the AAL type, and header override information
for the buffer.
host forms the buffer sequence by linking a list of buffer descriptors using the
SBD’s NEXT field. Two bits in the SBD control fields delineate the beginning
and end of messages. One bit, BOM, specifies that the buffer contains the
beginning of a message. The second bit, EOM, notifies the SAR that the buffer
contains the end of the current message. The host identifies the end of the SBD
chain by terminating the list with a NULL (0) NEXT pointer.
how to use these bits.
Segment as Continuation of Message (COM).
Terminate current CPCS-PDU at end of buffer (EOM).
Restart CPCS-PDU generation (BOM). Wait for EOM for termination.
Buffer contains complete message. Restart/terminate CPCS-PDU.
The host then creates PDU message sequences by concatenating buffers. The
SAR-shared memory data buffer segmentation should be limited to low
bandwidth applications, such as Signalling, OAM, and ILMI.
Mindspeed Technologies
Buffer to Message Adaptation
ATM ServiceSAR Plus with xBR Traffic Management
™
Table 4-1
28236-DSH-001-B
describes
CN8236