Expanding a Pool of Functional Test Sequences to Support Test Compaction
Irith Pomeranz · 2023
When a pool of functional test sequences is created for simulation-based verification of a design, the same sequences can be used as manufacturing tests to complement scan-based tests. Without otherwise changing the pool, earlier compaction procedures selected sequences or subsequences as manufacturing tests from a given pool. This article is based on the new observation that the pool can be compacted further if it is first expanded by adding new sequences. New sequences are obtained without performing test generation from pairs of sequences in the pool that reach common states. The new sequences preserve functional properties of sequences in the pool. They also combine fault detection capabilities of sequences from the pool, allowing faults to be detected at earlier clock cycles. The ability of the new sequences to contribute to test compaction is evaluated based on their effect on the clock cycles where faults are detected. The article describes a procedure that applies these concepts to a pool iteratively. Experimental results demonstrate significant reductions in the size of an already-compacted pool for benchmark circuits with pools that contain common states.