M7010R datasheet(16/67 Pages) STMICROELECTRONICS

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M7010R

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OPERATION

Command Bus and DQ Bus

CMD[8:0] carries the command and its associated

parameter. DQ[67:0] is used for data transfer to,

and from the data base entries. The database en-

tries are comprised of a data field and a mask field

which are organized as a data array and a mask

array. The DQ Bus carries the SEARCH data dur-

ing the SEARCH command as well as the address

and data during Pipelined I/O (PIO) READ/WRITE

operations, of the data array, mask array, and in-

ternal registers. The DQ Bus also can carry the ad-

dress information for the PIO accesses to the

SRAM.

Database Entry (Data Array and Mask Array)

Each database entry comprises a data field and a

mask field. The resultant value of the entry is a log-

ical AND of the corresponding data and mask bits

and can take logical values of '1,' '0' and 'X' (don’t

care), depending on the value in the mask bit. The

on-chip priority encoder selects the first matching

entry in the database which is nearest to location

Arbitration Logic

When multiple (Silicon) Search Engines are cas-

caded to create large databases, the data being

searched is presented to all Search processors si-

multaneously in the cascaded system. When more

than one device has duplicate entries, the arbitra-

tion logic on the Search Engine with the matching

entry which is closest to address 0 of the cascaded

database, will be selected to drive the SRAM Bus.

Pipeline and SRAM Control

Pipeline latency is added to give enough time to

the arbitration logic in a cascaded system to deter-

mine the index with the highest priority. The pipe-

line logic adds latency to the SRAM access cycles

and the SSF and SSV signals to align them to the

host ASIC receiving the associated data. Refer to

Table 27, page 36 for details.

Full Logic

Bit[0] in each of the 68-bit entries has a special

purpose for the LEARN command (0 = empty, 1 =

full). When all the data entries have Bit[0] set to '1,'

the database asserts the FULL flag, indicating that

all the Search Engines in the depth-cascaded ar-

ray are full.

Connections Descriptions

Master Clock (CLK2X). The M7010R samples

all of the control and data signals on the positive

edge of CLK2X when PHS_L is low.

Phase (PHS_L). This signal runs at half the fre-

quency of CLK2X and generates an internal clock

from CLK2X (see Figure 12, page 18).

Reset (RST_L). Driving RST low initializes the

device to a known state.

Command Bus (CMD[8:0]. [1:0]

specifies

the

command; [8:2] contains the command parame-

ters. The descriptions of individual commands ex-

plains the details of the parameters. The encoding

of commands based on the [1:0] field are:

– 00: PIO READ

– 01: PIO WRITE

– 10: SEARCH

– 11: LEARN

Command Valid (CMDV). Qualifies the CMD bus

as follows:

– 0: No Command

– 1: Command

Address/Data Bus (DQ[67:0]). Carries the READ

and WRITE address as well as the data during

ries the compare data during SEARCH opera-

tions. It also carries the SRAM address during

SRAM PIO accesses.

READ Acknowledge (ACK). Indicates that valid

data is available on the DQ Bus during register,

data, and mask array READ operations, or the

data is available on the SRAM data bus during

SRAM READ operations.

Note: ACK Signals require a pull-down resistor of

Ω.

End of Transfer (EOT). Indicates

the

end

burst transfer during READ or WRITE burst oper-

ations.

Note: EOT Signals require a pull-down resistor of

47 ohms.

SEARCH Successful Flag (SSF). When assert-

ed, this signal indicates that the device is the glo-

bal winner in a SEARCH operation.

SEARCH Successful Flag Valid (SSV). When

asserted, this signal qualifies the SSF signal.

SRAM Address (SADR[21:0]). This

bus

con-

tains address lines to access off-chip SRAMs that

contain associative data. See Table 35, page 61

for the details of the generated SRAM address.

SRAM Chip Enable (CE_L). This is Chip Enable

control for external SRAMs. When more than one

device is cascaded, CE_L of all devices must be

connected.

SRAM WRITE Enable (WE_L). This is WRITE

Enable control for external SRAMs. When more

than one device is cascaded, WE_L of all devices

must be connected.

SRAM Output Enable (OE_L). This

Output

Enable control for external SRAMs. Only the last

device drives this signal (with the LRAM Bit set).

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