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.
36
Figure 5
- Construction of Search Keys
S
B
,L
B
CONFIGURATION
REGISTERS
S
A
,L
A
Field B
Location
Registers
Field A
Location
Registers
Field B Size & Location
V/P
FB
F
PHY ID
PRIMARY
SEARCH KEY
SECONDARY
SEARCH KEY
ROUTING
WORD
Field A Size
& Location
VPI/VCI
Once the search keys are assembled, the Primary Search Key is first used to
address an external direct look-up table (Primary Table). This table occupies 2n
memory locations where n = LP + LA, i.e. the length of the Primary Search Key.
The result of this direct look up is the address of a root node of a search tree.
From this root node, the Secondary Search Key is used by a patented search
algorithm to find the cell's VC Table address (held in external SRAM.) The
RCMP-200 requires this table address for cell processing. Table 1 provides a
description of the VC Table. If the search process does not lead to the successful
identification of the cell concerned (contents of the VC table address returned do
not match the Secondary Search Key contents), the cell is discarded as invalid.
Optionally, the cell is routed to the microprocessor cell interface for header error
logging.
The length of time required to perform the VC search is variable. Since the
Primary Search Key is used in a direct look up, only one cycle is required to
process the Primary Key. The Secondary Search Key processing time is highly
dependent on the key's contents, but the maximum number of processing cycles