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
other channel that is destined for an end-station on the flow-controlled channel), the
MAC channel will cease transmitting the backpressure pattern, wait for a normal
interframe gap, and then transmit the desired frame(s). After all the pending frames
have been transmitted, the MAC logic will resume backpressuring the channel.
The backpressure mechanism described above is an optional feature that may be
enabled on a per-port basis by means of configuration parameters in the boot image. It
should be noted that the backpressure method will result in the complete shutdown of
the MAC channel (i.e., even local segment traffic will not be allowed to proceed), and so
it is recommended that backpressure be enabled only on ports that are connected to a
small number of end-stations.
The ELAN 8x10 MAC channels also provide a frame type filtering feature that extracts
the 16-bit EtherType fields of incoming frames (occupying the portion of the Ethernet
frame header immediately after the destination and source MAC addresses), compares
it to a programmable 16-bit value, and signals the Switch Processor firmware if a match
is found. This facility may be used, for example, to quickly identify MAC Control frames
(defined in IEEE 802.3x) or Address Resolution Protocol frames belonging to the
TCP/IP protocol. The Switch Processor firmware may then handle such marked frames
in a special manner.
Each MAC channel maintains a pair of control and status registers that allow the Switch
Processor to monitor and manage the state of the MAC channels. The MAC interfaces
are configurable (as a group) by a set of configuration registers that are loaded at
initialization time. The following parameters are configurable:
Parameter
Interframe spacing, Part 1
Interframe spacing, Part 2
Transmitted preamble length (not
including SFD byte)
Jam length (after collision)
Maximum frame size
Minimum frame size
Late collision threshold
Receiver blind time
EtherType comparison value
Min
Max
0
255
0
255
0
255
1
255
1
4095
1
255
0
1024
0
255
0
65535
Units
bit times
bit times
bits
bit times
bytes
bytes
bit times
bit times
N/A
It should be noted that the Part 1 interframe spacing may be set to zero, in which case
the interframe behavior of the ELAN 8x10 MAC defaults to that specified by the
Ethernet V2.0 standard. If the Part 1 interframe spacing is non-zero, then the minimum
interframe gap that can be tolerated by the MAC port during back-to-back frame receive
will be the greater of the Part 1 interframe spacing and the receiver blind time.
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY
47
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