M7020R datasheet(99/150 Pages) STMICROELECTRONICS

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M7020R

Table 44. Latency of SEARCH from Cycles C and D to SRAM Access Cycle, 272-bit, Up to 8 Devices

Table 45. Shift of SSF and SSV from SADR

272-bit Search on Tables Configured as x272 Using Up to 31 M7020R Devices

The hardware diagram of the search subsystem of

31 devices is shown in Figure 71, page 101. Each

of the four blocks in the diagram represents a

block of eight M7020R devices, except the last

which has seven devices.The diagram for a block

of eight devices is shown in Figure 72, page 102.

The following are the parameters programmed

into the 31 devices.

– First thirty devices (devices 0–29):

CFG = 10101010, TLSZ = 10, HLAT = 000,

LRAM = 0, and LDEV = 0.

– Thirty-first device (device 30):

CFG = 10101010, TLSZ = 10, HLAT = 000,

LRAM = 1, and LDEV = 1.

Note: All 31 devices must be programmed with the

same value of TLSZ and HLAT. Only the last de-

vice in the table must be programmed with

LRAM = 1 and LDEV = 1 (Device 30 in this case).

All other upstream devices must be programmed

with LRAM = 0 and LDEV = 0 (Devices 0 through

29 in this case).

The timing diagrams referred to in this paragraph

reference the HIT/MISS assumptions defined in

Table 46, page 101. For the purpose of illustrating

the timings, it is further assumed that there is only

one device with the matching entry in each block.

Figure 74, page 104 shows the timing diagram for

a SEARCH command in the 272-bit-configured ta-

ble consisting of 31 devices for each of the eight

devices in Block 0. Figure 75, page 105 shows the

timing diagram for a SEARCH command in the

272-bit-configured table of 31 devices for all devic-

es above the winning device in Block 1. Figure 76,

page 106 shows the timing diagram for the global-

ly winning device (the final winner within its own

and all blocks) in Block 1. Figure 77, page 107

shows the timing diagram for all the devices below

the globally winning device in Block 1. Figure 78,

page 108, Figure 79, page 109, and Figure 80,

page 110, respectively, show the timing diagrams

of the devices above the globally winning device,

the globally winning device, and the devices below

the globally winning device for Block 2. Figure 81,

page 111, Figure 82, page 112, Figure 83, page

113, and Figure 84, page 114, respectively, show

the timing diagrams of the device above the glo-

bally winning device, the globally winning device,

the devices below the globally winning device (ex-

cept Device 30), and last device (Device 30) for

Block 3.

# of devices

Max Table Size

Latency in CLK Cycles

1 (TLSZ = 00)

8K x 272-bit

2–8 (TLSZ = 01)

64K x 272-bit

9–31 (TLSZ = 10)

248K x 272-bit

HLAT

Number of CLK Cycles

000

001

010

011

100

101

110

111

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