The associative memory comprises a simplified functional processing unit (SFPU), implemented by an LUT logic network, that implements simplified CAM function g, where g is the function derived from CAM function ƒ by replacing the value showing “invalid” with the don't care, an auxiliary memory that stores the inverse function ƒ−1 of said CAM function ƒ; and an output modifier that checks whether the output value of said SFPU is equal to the output value of the CAM function ƒ; wherein the SFPU produces the operational value (“tentative index value”) for the simplified CAM function g; the auxiliary memory produces the value of the inverse function ƒ−1 when the tentative index value is applied; the output modifier compares the input data with the value of the inverse function ƒ−1, and produces the output of said SFPU if they are the same, otherwise produces the signal showing the “invalid”.