MT90883 Zarlink Semiconductor, MT90883 Datasheet - Page 58

• Manufacturer Part Number: MT90883
• Description: (MT90880 - MT90883) TDM to Packet Processors
• Manufacturer: Zarlink Semiconductor

Once a successful match is established, the characteristics of each traffic class may be determined by a
look-up process. If the matched class contains TDM traffic, the context descriptor is retrieved from a
pre-determined position. This indicates the identity of the context to which the packet belongs, which is used to
place the packet into the appropriate queue. More than one traffic class can be designated as TDM traffic,
allowing the context descriptor to be retrieved from a different position for each class. This may be useful when
the MT9088x device received traffic from multiple sources, each of which may be using a different protocol
stack.
CPU traffic can be allocated to one of four queues waiting for DMA transfer up to the host. Therefore the
classifier can be used to pre-sort the traffic destined for the CPU. This can be used either to direct traffic to
different destination devices (e.g. packets for the control CPU, and packets for a DSP or local resource pool), or
to separate high priority control traffic from lower priority maintenance information.
Mask Stage
Comparison Stage
Look-up Stage
Masked
Header
Comparison
Header
result 1
Comparator
Figure 26 - Packet Classification Process
Look-up Context
Mask 1
Pattern 1
Descriptor
Incoming packet for classification
Masked
Header
Zarlink Semiconductor Inc.
MT90880/1/2/3
TDM traffic
Comparison
result 2
Comparator
Match Result
Payload
Mask 2
Pattern 2
58
Pattern
Priority Encoder
Succesful
Traffic
Class
Masked
Match
Header
Comparison
result 3
Y
Comparator
N
CPU Traffic
Mask 3
Pattern 3
Look up CPU queue
FCS
Masked
Header
Comparison
CPU queue 0
result 4
Forward to
Comparator
Mask 4
Pattern 4
Data Sheet