Method and apparatus for testing a contents-addressable-memory-type structure using a simultaneous write-thru mode

Abstract

A method and apparatus for testing a contents-addressable-memory type structure using a simultaneous write-thru mode in an array is provided. The circuit to be tested has combinational logic and an array, and the array has bit cells and a logic cells. Each logic cell is uniquely associated with a bit cell such that an output of a bit cell provides an input to a logic cell, and each set of logic cells for an address of the array provides an output data vector from the array. Each cone of logic in the combinational logic receives an output data vector from an associated address in the array as an input data vector, and each cone of logic in the combinational logic is independent from other cones of logic in the combinational logic. A test vector is input to a write port of the array, and a set of logic cell input values are also input into the array. A test write-thru mode signal simultaneously asserts all write wordline signals of the array associated with the write port in order to write the test vector to all addresses of the array. Test vectors can then be applied simultaneously to all the cones in the combinatorial logic instead of having to apply them to one array address at a time, thereby making it feasible to test this combinatorial logic using standard logic testing techniques. The non-CAM compare type array operations are then tested using ABIST techniques.