PM3350-SW View Datasheet(PDF) - PMC-Sierra
Part Name
Description
MFG CO.
'PM3350-SW' PDF : 224 Pages View PDF
ELAN 8X10
DATA SHEET
PMC-970109
ISSUE 3
PM3350 ELAN 8 X10
8 PORT ETHERNET SWITCH
control is set to the default of zero, indicating no byte swap, the packet buffers have the
following format (where 'N' is the total size of the packet buffer in bytes):
31
24 23
16 15
87
0 Byte Offset
Size
NextPB
0
LastSize
RefCount
unused, reserved
4
PayloadByte0
PayloadByte1
PayloadByte2
PayloadByte3
8
PayloadByte4
PayloadByte5
PayloadByte6
PayloadByte7
12
....
....
PayloadByte(n-4) PayloadByte(n-3) PayloadByte(n-2) PayloadByte(n-1) (N-4)
If the MAC channel is set up to swap the incoming frame bytes, then the payload field
of the packet buffers will be byte-swapped, but the headers will be left unchanged, as
shown below:
31
24 23
16 15
87
0 Byte Offset
Size
NextPB
0
LastSize
RefCount
unused, reserved
4
PayloadByte3
PayloadByte2
PayloadByte1
PayloadByte1
8
PayloadByte7
PayloadByte6
PayloadByte5
PayloadByte4
12
....
....
PayloadByte(n-1) PayloadByte(n-2) PayloadByte(n-3) PayloadByte(n-4) (N-4)
NextPB:
24-bit pointer to next packet buffer in linked-list of packet buffers constituting
a frame. If no next packet buffer exists (i.e., this is the tail of the linked-list),
then this field is NULL (all-zeros).
Size:
8-bit size of packet buffer payload (excludes the 8-byte header), in bytes.
RefCount:
8-bit reference count associated with packet: gives the number of queues that
are pointing to this packet buffer.
LastSize:
8-bit count of total number of valid bytes (including the 8-byte header) in the
last packet buffer in the linked-list of buffers. Only valid if this is the first
packet buffer in the linked-list, and there is more than one packet buffer in the
linked-list.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY
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