Content addressable memory with longest match detect
US6370613B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 27, 1999 |
| Grant date | Apr 9, 2002 |
| Priority date | — |
| Expiry date | Jul 27, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C15/04
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A CAM system is provided for determining which data word in a CAM array exhibits the longest continuous, unmasked match with an input data value. The input data value is divided into non-overlapping subfields, thereby creating a series of keys, the first key of the series including either the least significant bit (LSB) or most significant bit (MSB) of the input data value. The CAM array is divided along columns into a similar series of non-overlapping sub-arrays corresponding to the subfields defined by the series of keys. A first CAM sub-array compares the first key with its stored rows of data bit values to generate a first match signal. The first match signal disables each row of the second CAM sub-array for which the corresponding row of the first CAM sub-array did not show a match. A second CAM sub-array then compares the second key with its enabled rows to generate a second match signal. The second match signal disables each row of the third CAM sub-array for which the corresponding row of either the first or second CAM sub-array did not show a match. This comparison process continues in sequence with the remaining keys and CAM sub-arrays. The row of the CAM array that shows…
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