M7010R View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'M7010R' PDF : 67 Pages View PDF
M7010R
SEARCH PROCEDURE FOR 32-BIT WIDE PREFIXES
The Global Mask Register is used for 32-bit wide
data paths as follows:
Writing a '1' in the Global Mask Register allows
data to be written into the M7010R. A '0' in the Glo-
bal Mask Register disallows data modification. In-
formation is written into the left half of the 68-bit
word Search Engine as long as space for 34 bits
of data is available and then into the right half of
the Search Engine. 32-bit data can be entered in
two cycles.
es a match, then in that case, the left half is a high-
er priority. So if only one unique match exists in a
particular system, then a match on the left side
may alleviate the need to do a search on the right
half of the Data array.
Figure 15. Global Mask Register Patterns
Register 0
111 1000 0
The first step is to write into two of the eight Global
Mask Registers with the patterns shown in Figure
15. Writing this data using Global Mask Register 1
allows the left half of the data array to be com-
pletely filled.
Register 1
000 0111 1
Figure 16 shows Bits 67 through 36 in the left sec-
tion of the data array representing 32-bits of data.
Bits 35 and 34 shown separately can be defined
by the user for table management. In this applica-
tion 34-bit operation occurs in each half-section of
the Data and Mask arrays of the Search Engine.
The left half is filled first, then the right. Not all lo-
cations have to be filled.
SEARCH operations are performed twice, once on
the left half and then on the right half. Note that a
'1' in the Global Mask register enables a compare
during a SEARCH operation and a '0' forces a
match condition regardless of the state of the data
bit.
Bits
67 3433 0
AI04277
Figure 16. Storing left half of a Data or Mask
Array
The SEARCH throughput for 34-bit operations is
half of the 68-bit operations. A search is performed
by using the Global Mask Register “0” for the left
half of the 68-bit, then another search is performed
using Global Mask Register 1 for the right half of
the 68-bit word. The order is important, as the left
half has a higher priority than the right half.
Bits 67 36 35 34 33
2 10
For example, if a search on the left half produces
a match and a search on the right half also produc-
AI04278
22/67
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