M7010R
38/67
136-bit Configuration
Figure 28, page 39 shows the timing diagram for
the SEARCH operation in the 136-bit table (CFG =
01010101) consisting of a single device for one set
of parameters: TLSZ = 00, HLAT = 001, LRAM =
1, and LDEV = 1. The hardware diagram for the
search subsystem is shown in Figure 27.
The following is the operation sequence for a sin-
gle, 136-bit SEARCH command.
–
Cycle A:
The host ASIC drives the CMDV high
and applies the SEARCH command code (10)
to CMD[1:0] signals. CMD[5:3] signals must be
driven with the index to the GMR pair for use in
this SEARCH operation. CMD[8:6] signals must
be driven with the same bits that will be driven
on SADR[21:19] by this device if it has a hit.
DQ[67:0] must be driven with the 68-bit data
([135:68]) to be compared against all even loca-
tions. The CMD[2] signal must be driven to logic
'0.'
–
Cycle B:
The host ASIC continues to drive the
CMDV high and applies SEARCH command
code (10) on CMD[1:0]. CMD[5:2] must be driv-
en by the index to the comparand register pair
for storing the 136-bit word presented on the DQ
Bus during Cycles A and B. CMD[8:6] signals
must be driven by the index of the SSR that will
be used for storing the address of the matching
entry and hit flag. The DQ[67:0] is driven with
68-bit data ([67:0]), compared to all odd loca-
tions.
Note:
For 136-bit searches, the host ASIC must
supply two distinct, 68-bit data words on
DQ[67:0] during Cycles A and B. The even-
numbered GMR of the pair specified by the
GMR Index is used for masking the word in Cy-
cle A. The odd-numbered GMR of the pair spec-
ified by the GMR Index is used for masking the
word in Cycle B.
The SEARCH command is a pipelined operation
that executes searches at half the rate of the fre-
quency of CLK2X for 136-bit searches in x136-bit-
configured tables. The latency of SADR, CE_L,
ALE_L, WE_L, SSV, and SSF from the 136-bit
SEARCH command cycle (two CLK2X cycles) is
shown in Table 30, page 40.
The timing diagram for all SRAM interface signals,
SSV, and SSF shift to the right for different values
of TLSZ, as specified in Table 28, page 40.
In addition, SSV and SSF shift to the right for dif-
ferent values of HLAT, as specified in Table 29,
page 40.
The result of the SEARCH operation appears as
an SRAM READ Cycle with a pipelined latency. It
is specified as shown in Table 30, page 40.
Figure 27. Hardware Diagram for a Table with One Device (136-bit Operation)
DQ[67:0]
CMDV, CMD[8:0]
SSF, SSV
SRAM
LHO[1]
BHI[2:0]
BHI[2:0]
LHI
3
2
1
0
M7010R
LHO[0]
6
5
4
AI07040