PM3350-SW datasheet(74/224 Pages) PMC

74 / 224 page

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

information carried by the data descriptor, or the purpose for which the data

descriptor is being used. In the case of message descriptors, this field is used

carry a code that identifies the type of message being sent from one chip to

another. For normal data descriptors that point to frame data being

processed, this field is usually set to zero. The mark-and-sweep algorithm

used to maintain the transmit queues will also utilize this field to determine

when a particular transmit queue has been excessively blocked.

The FirstPB and LastPB fields contain the 24-bit addresses of the head and tail,

respectively, of the linked-list of packet buffers that are associated with this data

descriptor. If only one packet buffer is present in the linked-list, then the FirstPB and

LastPB pointers contain the same value. It is an error for the FirstPB field to be zero in

any valid data descriptor that points to an Ethernet frame; however, message data

descriptors (i.e., those used for exchanging messages between ELAN 8x10 devices)

may optionally have the FirstPB field set to zero, if the entire content of the message

can be placed in unused fields of the data descriptor. The NumPBs field contains the

count of the number of packet buffers contained within the linked-list of packet buffers,

and may range between 1 and 255.

The SrcPort and SrcChip fields indicate the source port index and the source device

index, respectively, on which the Ethernet frame entered the system. The values in the

SrcPort field are directly derived from the hardware indices assigned to the various

physical MAC channels of the ELAN 8x10; the value placed in the SrcChip field by any

ELAN 8x10 device is assigned as a system parameter during the device boot-up and

initialization process, using data obtained from the boot image. If the Learn bit is set in

the data descriptor Flags field, then both of these fields are used to associate the

source MAC address within the Ethernet frame with a particular device and physical

port.

The HashBkt field holds the 24-bit local memory address of the address hash bucket

associated with either the source or destination MAC address in the Ethernet frame

header. If the Ethernet frame is to be broadcast (or the Learn bit is set, and the frame

must be flooded), the HashBkt field holds the memory address of the hash bucket

corresponding to the source MAC address in the source device's address space; if, on

the other hand, the frame is a unicast, then the HashBkt field contains the memory

address of the hash bucket for the destination MAC address in the destination device's

address space. (The distinction between the source and destination device address

spaces only applies to frame transfers across the PCI expansion bus; if the frame is

being switched locally, or there is only one ELAN 8x10 device in the system, then the

source and destination address spaces are the same.) The HashBkt field has a dual

purpose: it is used to learn the memory address of a source hash bucket during

broadcasts and floods, and is also used to indicate a target destination hash bucket to

use in switching unicast frames once address learning is complete. More details on the

use of the HashBkt field in various situations will be provided in subsequent sections.

PM3350-SW Datasheet(PDF) 74 Page - PMC-Sierra, Inc

PM3350-SW Datasheet(HTML) 74 Page - PMC-Sierra, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL