PM3351-SW datasheet(87/268 Pages) PMC

87 / 268 page

PM3351 ELAN 1X100

DATA SHEET

PMC-970113

ISSUE 3

SINGLE PORT FAST ETHERNET SWITCH

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE

DDRINGst

Element 0

Element 1

Element 2

Transfer Ring 0

Element 3

Element (N-1)

DDRINGst + 16*N

Element 0

Element 1

Element 2

Transfer Ring 1

Element 3

Element (N-1)

DDRINGst + 32*N

DDRINGst + 112*N

Element 0

Element 1

Element 2

Transfer Ring 7

Element 3

Element (N-1)

Each transfer ring consists of

N elements, where N is a power of 2. (The actual value of

N is an implementation parameter, and is determined at system initialization time by

configuration parameters in the boot image.) Each element in a transfer ring is

formatted as a data descriptor structure; the NextDD field in each data descriptor is set

up by the bootstrap firmware to point to the next consecutive element in the same

transfer ring, with the last element in a transfer ring being set up to point back to the

first. The elements in a given transfer ring therefore create a closed linked-list; if the

NextDD pointers are followed starting from any element in the ring, the path followed

will eventually return to the starting point. The remainder of the fields in each element

(beyond the NextDD pointer) are left uninitialized at system startup.

PM3351-SW Datasheet(PDF) 87 Page - PMC-Sierra, Inc