Multiple fault detection in parity checkers

Parity checkers are widely used in digital systems to detect errors when systems are in operation. Since parity checkers are monitoring circuits, their reliability must be guaranteed by performing a thorough testing. In this work, multiple fault detection of parity checkers is investigated. We have found that all multiple stuck-at faults occurring on a parity tree can be completely detected using test patterns provided by the identity matrix plus zero vector. The identity matrix contains 1´s on the main diagonal and 0´s elsewhere; while the zero vector contains 0´s. The identity matrix vectors can also detect all multiple general bridging faults, if the bridgings result in a wired-AND effect. However, test patterns generated from the identity matrix and binary matrix are required to detect a majority of the multiple bridging faults which yield wired-OR connections. Note that the binary matrix contains two 1´s at each column of the matrix