Content-addressable Memory - Ternary CAMs

Ternary CAMs

Binary CAM is the simplest type of CAM which uses data search words consisting entirely of 1s and 0s. Ternary CAM (TCAM) allows a third matching state of "X" or "Don't Care" for one or more bits in the stored dataword, thus adding flexibility to the search. For example, a ternary CAM might have a stored word of "10XX0" which will match any of the four search words "10000", "10010", "10100", or "10110". The added search flexibility comes at an additional cost over binary CAM as the internal memory cell must now encode three possible states instead of the two of binary CAM. This additional state is typically implemented by adding a mask bit ("care" or "don't care" bit) to every memory cell.

Holographic associative memory provides a mathematical model for "Don't Care" integrated associative recollection using complex valued representation.