PM3350-SW datasheet(72/224 Pages) PMC

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ELAN 8X10

PM3350 ELAN 8 X10

DATA SHEET

PMC-970109

ISSUE 3

8 PORT ETHERNET SWITCH

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY

Data Descriptors

Ethernet packets being buffered within the ELAN 8x10 system are tracked by means of

16-byte

data descriptors. Data descriptors form the primary queuing element in the

ELAN 8x10 device: they are used to form receive, transmit and expansion port queues,

as well as to hold message information and special packet handling queues. All data

descriptors have the same general format, and contain pointers to the first and last

packet buffer of a packet buffer chain holding an Ethernet packet, flags fields that

indicate the processing to be performed on the packet, and other information

associated with the packet.

Data descriptors are formatted as follows:

24 23

16 15

8 7

0 Byte Offset

Flags

NextDD

NumPBs

FirstPB

SrcPort

LastPB

SrcChip

HashBkt

NextDD:

24-bit pointer to next data descriptor in linked-list of data descriptors forming

queue.

Flags:

8-bit data descriptor flags field, formatted as below.

FirstPB:

24-bit pointer to first packet buffer in linked-list of packet buffers containing

frame data. If NULL (zero), no packet buffer chain exists for this data

descriptor; this is only valid for special message data descriptors.

NumPBs:

8-bit count of packet buffers in chain pointed to by FirstPB.

LastPB:

24-bit pointer to last packet buffer in linked-list of packet buffers pointed to by

FirstPB.

SrcPort:

8-bit source port index within device: indicates the MAC channel upon which

the packet was received. For the ELAN 8x10, this ranges from 0 through 7.

HashBkt:

24-bit pointer to source or destination hash bucket.

PM3350-SW Datasheet(PDF) 72 Page - PMC-Sierra, Inc

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