The theory of signature testing for VLSI
J. Lawrence Carter · 1982
Several methods for testing VLSI chips can be classified as signature methods. Both conventional and signature testing methods apply a number of test patterns to the inputs of the circuit. The difference is that a conventional method examines each output, while a signature method first accumulates the outputs in some data compression device, then examines the signature - the final contents of the accumulator - to see if it agrees with the signature produced by a good chip. Signature testing methods have several advantages, but they run the risk that masking may occur. Masking is said to occur if a faulty chip and a good chip behave differently on the test patterns, but the signatures are identical. When masking occurs, the signature testing method will incorrectly conclude that the chip is good, whereas a conventional method would discover that the chip is defective.