Introduction - 2.6 English

Semi-Ternary CAM Search v2.6 LogiCORE IP Product Guide (PG319)

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2.6 English

The Semi-Ternary CAM Search LogiCORE IP (STCAM) implements an associative array data structure also known as a content-addressable memory. The STCAM stores (key, mask, priority, response) entries with arbitrary key, mask and response bit strings and allows for the retrieval of the response based on ternary matching of the lookup key. Ternary matching allows multiple entries to match the same lookup key. The entry with lowest priority is selected as the winner. The STCAM supports a limited number of unique masks, that is each mask is shared by multiple entries. This allows for a considerable logic and memory reduction compared to TCAMs. The STCAM is well suited for applications requiring efficient storage of entries using multiple, but a limited number of masks. For example, longest prefix matching of the IP address for IP forwarding tables or OVS mega-flow lookup tables.