Reducing the Storage Requirements of a Test Sequence by Using One or Two Background Vectors

We describe a storage scheme for functional test sequences where a test sequence T is associated with a primary input vector B called a background vector. T is stored by storing only the differences between its test vectors and B . We describe a procedure for computing a background vector B for a given test sequence T. We also describe a procedure that modifies T so as to reduce its storage requirements with respect to B . We present experimental results demonstrating that the single background vector B, computed based on T, allows T to be modified such that a vast majority of its entries are equal to the corresponding entries of B. Consequently, storage of T reduces to storage of a small number of entries. We also extend the discussion to storage of T based on two background vectors. A second background vector provides more flexibility in storing T as a list of entries where it is different from its background vectors. This contributes to a further reduction in storage requirements for certain circuits.