Enhanced technique for built-in self-test of sequential logic

A modified circular self-testing technique based on circular self test path (CSTP) is presented. While the original CSTP technique offered advantages such as low area overhead and simple control logic, the fault coverage achieved may be limited due to limit cycling and register adjacency issues. This paper presents a modification to CSTP, called flushing, to minimize the chances of limit cycles and also reduce the effects of register adjacency issues on the fault coverage. Results indicate that in many cases, flushing can increase fault coverage and prevent limit cycling in circuits with a low number of flip flops.