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A CAM-based keyword match processor architecture

Author:Long Bu, John A. Chandy *Publisher:Microelectronics Journal 37 (2006)Presenter:Han-Chen ChenDate:2009/11/18

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Outline Introduction Architecture of Keyword match

processor Performance

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Introduction Pattern match :1. Software algorithms : slow 2. FPGA Base : must be reconfigured when change

keyword sets3. CAM Base : reliance on fixed size keys.

Presents a cellular automata based design that is more space efficient and can easily handle arbitrarily sized keywords .The architecture is flexible enough to allow for ‘approximate word’ matches as well.

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Introduction

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Architecture of Keyword match processor

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Architecture of Keyword match processor

CAM and PE arrayMotomura: 4 match signals form the CAM array in a 5*3 PE array, a n-colume CAM array requires 5n/4*3 PE array

=>Waste space

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Architecture of Keyword match processor

1.if Mt(i) = 1 and PEt (i, j) = 1 thenPEt+1 (i+1, j) = 1PEt+1 (i, j+1) = 1

2.if Mt(i) ≠ 1 and PEt (i, j) = 1 thenPEt+1 (i+1, j+1)=1PEt+1 (i, j+1)=1

3.for (1 ≥ d ≤ D-j )PEt (i+d, j+d)=1

Overall:PEt+1 (i, j)= PEt (i, j-1) + PEt (i-1, j) M∙ t(i-1) +

PEt (i-1, j-1) M∙ t(i-1) + PEt+1 (i-1, j-1)

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 0 0 0 0 0 0 0 0 0 0 0 0 0

Cycle10 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match signal

Input: CONE

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 1 0 0 0 0 0 0 0 0 0 0 0 0

Cycle2

C

0 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match signal

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 0 1 0 0 0 0 0 0 0 0 0 0 0

Cycle3

O

0 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match signal

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 0 0 1 1 0 0 0 0 0 0 0 0 0

Cycle4

N

0 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match signal

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 0 0 0 0 0 0 0 0 0 0 1 0 0

Cycle5

E

0 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match signal

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Architecture of Keyword match processor

U C O N N \0 H U S K I E S \0

0 0 0 0 0 1 0 0 0 0 0 0 0 1

Cycle6

Match signal

\0

0 1 2 3 4 5 6 7 8 9 10 11 12 13

rule 1

rule 2

rule 3

Match distance=2 Unmatch

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Architecture of Keyword match processor

Distance decoder:WM(i) = END M(i) (PE(i, 0)+PE(i, 1)+…+PE(i, D))∙ ∙

Match position finder:Find the previous word endOutput Match Position array (size n)

0 0 0 0 0 1 0 0 0 0 0 0 0 1

0 0 0 0 1 1 0 0 0 0 0 0 0 0

0 0 0 0 0 1 0 0 0 0 0 0 0 0

M(i) array

PE match array

Word Match array

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Architecture of Keyword match processor

Matched address output (MAO) logic Binary tree priority encoder structure To generate the matched address available

All need : p+q+2 cycles p: length of input stream ,q match times , 2 initial & process distance flags

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Architecture of Keyword match processor

Keyword match processor with no delimiters: add E(i) array 1:last character 0:otherwise

Subsequence keyword match:

1.if Mt(i) = 1 and PEt (i, j) = 1PEt+1 (i, j+1) = 1if(E(i) ≠ 1 ) PEt+1 (i+1, j) = 1

2.if Mt(i) ≠ 1 and PEt (i, j) = 1 PEt+1 (i, j+1)=1if(E(i) ≠ 1 ) PEt+1 (i+1, j+1)=1

3.for (1 ≥ d ≤ D-j )if(E(i+d-1) ≠ 1 ) PEt (i+d, j+d)=1

4.PEt (0,0)=1 if(E(i) = 1 )

PEt (i+1, 0)=1

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Performance•0.5μm 3-metal layer process: tCLK>tDD+tDD2MPF+tMPF =>tCLK>7.66 ns. leads to a maximum clock frequency of 130.5 MHz.Taking into account the setup times and propagation times of the registers, we have been able to comfortably run the circuit at 100 MHz. equal to 800Mb/s .• 0.1μm 3-metal layer process: 500MHZ , 4Gb/s

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Thanks for your

listening