An Improved Cellular Automata-Based BIST Architecture for Sequential Circuits

C2BIST (Circular CA BIST) is a Built-In Self Test (BIST) architecture for Sequential Circuits based on Cellular Automata (CA). When CA cells implements suitable rules, this structure shows good test generation capabilities, reaching a very high Fault Coverage. The main characteristic of this approach is that the same CA is used for both generation and compaction, leading to a trade-off between attained Fault Coverage and area overhead more favorable than other BIST approaches. On the other side, the main problem is that the circuit, during the test phase, may early enter a loop, reducing the attained Fault Coverage. The paper analyzes this problem and proposes a solution based on the Partial Reset technique, that is able to break down cycles by exploiting the circuit flip-flops synchronous reset signal with a reduced area overhead with respect to the basic C2BIST architecture. Experimental results allow a quantitative evaluation of the effectiveness of this approach.