R8A20210BG データシートの表示（PDF） - Renesas Electronics

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コンポーネント説明

メーカー

R8A20210BG

Network Address Search Engine (9 M/18 M-bit Full Ternary CAM)

Renesas Electronics 

R8A20211BG/R8A20210BG (MARIE_Blade)

⎯ Load Data Register (LDR)

Load Data Register (LDR) is used as the write data source in order to operate Move. See the figure 6.

The Load Data command loads the DQ data into the LDR first, and then operates the Write TCAM with this

LDR (source register). Please refer to another section for details.

1. Load Data

Entry to be transferred

2. Reset All Bits to "0"

LDR

3. Write TCAM

Destination

TCAM Array

Move Sequence

Load data to the LDR

→ Reset the original data to "0"

→ Data from LDR to Write TCAM

Figure 6 Move

10. Pseudo Learn

MARIE_Blade does not support an ordinary Learn function required by LAN switch for example. However, with a

combination of DSR and ASR, Pseudo Lean can take the place of Learn. A search key resulting in a miss is stored

into the DSR. Then Pseudo Learn can be achieved by operating Write TCAM with the DSR. Furthermore, search

for empty entries can be added into this process. In this case, the data to be input must contain an entry flag bit.

There is an example of 72-bit Normal Search. The user must select MSB [71] DQ data as the empty entry flag bit,

and set it to be [even, odd] = [0, 1] respectively (1 bit consists of even and odd). If there is any empty entry

indicating [1, 0], it means all data are occupied. In other words, all data in the TCAM must be [0, 1] after reset, and

bit-1 [71] must be always [even, odd]= [1,0] during the Write TCAM.

After setting a rule likewise, the procedure follows…

(1) When a search miss occurs, store the search miss key into the DSR

(2) Stop searching when the DSR is full of search miss keys

(3) Search only the DQ MSB with GMSR

(Search key, DQ [71] = 0, detects empty entries)

(4) Store the hit address of (3)

(5) Do the Write TCAM with (1) DSR data and (4) ASR address

The Write Delete Entry command can facilitate to reset empty entry bits. This command resets all bits in the

assigned entry to be [even, odd] = [0,1].

Search key

DQ

Search Miss

DX

DSR

Pseudo Learn

TCAM Array

What is Pseudo Learn?

Normal Search → Search Miss → Store Search Miss Key into DSR

→ Write TCAM with data in DSR

If it is not clear where an empty entry is, search sequence for empty

entry is needed.

Figure 7 Pseudo Learn

Rev.1.00 Feb 21, 2005 page 6 of 14

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