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参数资料
型号： M7020R-050ZA1T
厂商： 意法半导体
英文描述： CAP TANT 22UF 10V 20% POLY SMD
中文描述： 32K的× 68位进入网络搜索引擎
文件页数： 66/150页
文件大小： 996K
代理商： M7020R-050ZA1T
M7020R
66/150
136-bit Search on Tables Configured as x136 Using Up to Eight M7020R Devices
The hardware diagram of the search subsystem of
eight devices is shown in Figure 44, page 67. The
following are parameters programmed into the
eight devices:
– First seven devices (devices 0–6):
CFG = 01010101, TLSZ = 01, HLAT = 010,
LRAM = 0, and LDEV = 0.
– Eighth device (device 7):
CFG = 01010101, TLSZ = 01, HLAT = 010,
LRAM = 1, and LDEV = 1.
Note:
All eight devices must be programmed with
the same value of TLSZ and HLAT. Only the last
device in the table must be programmed with
LRAM = 1 and LDEV = 1 (Device 7 in this case).
All other upstream devices must be programmed
with LRAM = 0 and LDEV = 0 (Devices 0 through
6 in this case).
Figure 46, page 69 shows the timing diagram for a
SEARCH command in the 136-bit-configured ta-
ble of eight devices for Device 0. Figure 47, page
70 shows the timing diagram for a SEARCH com-
mand in the 136-bit-configured table consisting of
eight devices for Device 1. Figure 48, page 71
shows the timing diagram for a SEARCH com-
mand in the 136-bit configured table consisting of
eight devices for Device 7 (the last device in this
specific table). For these timing diagrams, four
136-bit searches are performed sequentially, and
the following HIT/MISS assumptions were made
(see Table 35)
The following is the sequence of operation for a
single 136-bit SEARCH command (see COM-
MAND CODES AND PARAMETERS, page 29).
–
Cycle A:
The host ASIC drives CMDV high and
applies SEARCH command code ('10') on
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[8:7] signals must
be driven with the same bits that will be driven
by this device on SADR[21:20] if it has a hit.
DQ[67:0] must be driven with the 68-bit data
([135:68]) in order to be compared against all
even locations. The CMD[2] signal must be driv-
en to a logic '0.'
–
Cycle B:
The host ASIC continues to drive
CMDV high and to apply the command code for
SEARCH command ('10') on CMD[1:0].
CMD[5:2] must be driven by the index of 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 with the
SSR Index that will be used for storing the
address of the matching entry and the Hit
Flag (see
SEARCH-Successful
(SSR[0:7]), page 23). The DQ[67:0] is driven
with 68-bit data ([67:0]) compared against all
odd locations.
The logical 136-bit search operation is shown in
Figure 45, page 68. The entire table (eight devices
of 136-bit entries) is compared to a 136-bit word K
(presented on the DQ Bus in Cycles A and B of the
command) using the GMR and local mask bits.
The GMR is the 136-bit word specified by the even
and odd global mask pair selected by the GMR In-
dex in the command’s Cycle A.
The 136-bit word K (presented on the DQ Bus in
Cycles A and B of the command) is also stored in
the even and odd comparand registers specified
by the Comparand Register Index in the com-
mand’s Cycle B. In x136 configurations, the even
and odd comparand registers can subsequently
be used by the LEARN command in only one of
the devices (the first non-full device). The word K
(presented on the DQ Bus in Cycles A and B of the
command) is compared to each entry in the table
starting at location “0.” The first matching entry’s
location, “L,” is the winning address that is driven
as part of the SRAM address on the SADR[21:0]
lines (see SRAM ADDRESSING, page 126). The
global winning device will drive the bus in a specif-
ic cycle. On global miss cycles the device with
LRAM = 1 (the default driving device for the SRAM
Bus) and LDEV = 1 (the default driving device for
SSF and SSV signals) will be the default driver for
such missed cycles.
Note:
During 136-bit searches of 136-bit-config-
ured tables, the search hit will always be at an
even address.
The SEARCH command is a pipelined operation
and executes a search at half the rate of the fre-
quency of CLK2X for 136-bit searches in x136-
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 36, page 72.
For one to eight devices in the table and
TLSZ = 01, the latency of a SEARCH from com-
mand to SRAM access cycle is 5. In addition, SSV
and SSF shift further to the right for different val-
ues of HLAT as specified in Table 37, page 72.
Registers
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