Testable realizations for ESOP expressions of logic functions

Abstract

A new testable design method for arbitrary logic functions is presented. The method employs AND gate arrays and XOR gate trees to realize the ESOP (EXOR-sum-of-products) expressions of logic functions. This significantly reduces the delay as compared with using cascaded XOR gates. It is shown that only n+5 test vectors are required to detect any single fault in the circuit realizations, and these tests are independent of the logic functions being realized, where n is the number of input variables. Multiple fault defects in the circuit realizations are studied, and a multiple faults test set is given. The test set can be generated easily. The method proposed in this paper is more versatile than those based on other function expression forms, since the ESOP is the most general form and it can give a small number of product terms.