![](http://datasheet.mmic.net.cn/330000/PM7323_datasheet_16444372/PM7323_48.png)
STANDARD PRODUCT
PM7323 RCMP-200
DATASHEET
PMC-960543
ISSUE 2
ROUTING CONTROL, MONITORING, & POLICING
200 MBPS
Proprietary and Confidential to PMC-Sierra, Inc.
and for its Customer’s Internal Use.
37
required is equal to the number of bits in the Secondary Search Key which must
the examined to make a unique identification. Some VPI and VCI bits may
always be zero; therefore, they need not be used in the search. In some
instances, the Primary Search Key may overlap the Secondary Search Key;
therefore, the intersecting bits are only required for the confirmation of a search
and will not be used as decision points by the binary search. If the number of
bits used by the binary search is no greater than 18, a sustained rate of
0.355x10
6
cell/s is guaranteed. The general expression for guaranteed
throughput is
Throughput
=
(17
+
max.binary tree 1
Note, however, if the binary tree depth is is less than 10, the throughput
becomes:
Throughput
=
(cell word length1
where the cell word length is the number of 8-bit words in the cell.
The first two words of each VC Table Record are reserved for the primary table
and the search table. The third word of the VC Table Record contains the
Secondary Search Key and an "NNI" bit in the most significant bit position. This
word is used to confirm whether the incoming cell belongs to a provisioned
virtual connection. Any unused bits within this word must be set to zero. The
NNI bit identifies if the VC belongs to a Network-Network Interface. If the NNI bit
is set to zero, the connection is part of a UNI which means that the four MSBs of
the VPI are excluded from the secondary key verification. If the VCI field in the
VC Table is all zeros, this signifies the connection is a VPC and that the VCI field
is to be ignored.
9.2.1 Search Table Data Structure
The Primary and Secondary Search Tables reside in external SRAM. The
Primary Search Table is located in the least significant 16 bits of RAM locations
with SA[19:16]=0001 and requires 2
(L
P
+ L
A
)
words of memory. The Secondary
Search Table resides in RAM locations with SA[19:16]=0000 and its size is
bounded by the number of virtual connections supported.