Generation of Two-Cycle Tests for Structurally Similar Circuits

VLSI design flows improve design parameters (performance, power, area, and testability) iteratively. Whereas the "shift left" trend implies that changes at the RTL are preferred for improving the design, it is sometimes necessary to make gate-level changes, e.g., because of layout changes or ECO. In an iterative design flow, repeated ATPG to evaluate the testability of a design after design changes have been made creates a bottleneck. The goal of this article is to address this bottleneck considering two-cycle tests for transition faults. The test generation procedure described in third article transforms an LOC test set generated for an earlier version of the design into an LOC test set for a new version without repeating the entire test generation process. To enable the transformation, it is necessary to find a mapping between the inputs and outputs of the earlier and new versions of the design, taking into consideration that RTL resynthesis may produce a new gate-level netlist, with new signal names and different input and output orders. To address two-cycle tests, the mapping is performed over two time frames of the design. Experimental results for industrial circuits with changes made at the RTL as well as gate-level demonstrate significant runtime gains with the test generation procedure described in this article.