cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 109

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

28237-DSH-001-C
5.0 Reassembly Coprocessor
5.1 Overview
The reassembly (RSM) coprocessor processes cells received from the ATM PHY
Interface block. The coprocessor extracts the AAL SDU payload from the
received cell stream and reassembles this information into buffers supplied by the
host system. The CN8237 supports AAL5 and AAL0 reassembly, as well as cell
mode (1-cell PDUs through a Virtual FIFO buffer, for CBR voice traffic).
connections are identified through separate VPI and VCI Index table structures.
The VPI/VCI Index table mechanism provides very fast consistent channel
identification over the full range of VPI/VCI addresses.
assigned to each VCC. The host assigns each VCC to one or two of 32
independent buffer pools, from which the RSM coprocessor draws buffers as
needed.
host-supplied buffers, and performs all CPCS-PDU checks. The results of these
checks, as well as AAL information, are passed to the host on one of 32
independent status queues.
reassembly coprocessor. For detailed information on how the CN8237 handles
PM cells, deals with OAM functions and interacts with the segmentation
coprocessor in handling traffic management and scheduling, refer to
and 7.0.
5.2 Reassembly Functional Description
Each cell received from the ATM PHY Interface block belongs to any one of a
possible 64 K virtual channels, or simultaneous messages. Due to the
asynchronous nature of ATM, the cell contained in any incoming cell slot can
belong to any VCC. Thus, the reassembly coprocessor must assign each arriving
cell to the proper VCC, thereby demultiplexing the incoming messages.
Figure 5-1
The CN8237 reassembles up to 64 K VCCs simultaneously. Individual
CPCS-PDU payload data, the CPCS-SDU, fills the host-supplied data buffers
The CN8237 extracts the CPCS-SDU from the CPCS-PDU, writes the SDU to
This chapter provides information on the functions and data structures of the
Mindspeed Technologies
illustrates the basic reassembly process flow.
5
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Chapter 6.0
5-1