Modified Geffe Test Pattern Generator for Built-in Self-test

Various linear finite state machines have been widely used as pseudo-random test pattern generators for Built-in Self-test. These generators are inexpensive to use as they have the advantage of low hardware overhead. However, the Geffe generator, a classic type of nonlinear finite state machines, hasn´t been frequently studied or used in similar applications. It is known that a Geffe generator when used as a pattern generator for digital system testing gives improved fault detection. Unfortunately, the area overhead involved is sufficiently high, thus such a generator becomes impractical for Built-in Self-test design. We propose a possible redesign of the Geffe generator. This redesign has very sharply reduced area overhead. More importantly, the fault simulation results show it can lead to fault coverage, which is comparable to the original Geffe generator.