Spectral RTL Test Generation for Microprocessors

We introduce a method of test generation for microprocessors at the RTL using spectral methods. Test vectors are generated for RTL faults, which are the stuck-at faults on inputs-outputs of the different modules/registers in the circuit, and the vectors are analyzed using Hadamard matrices for Walsh functions and the random noise level at each primary input. This information then helps generate vector sequences. At the gate-level, a fault simulator and an integer linear program (ILP) compact the test sequences. RTL test appraisal also helps reveal the hard-to-test parts of the circuit. An XOR observability tree was used to improve the testability of those parts. We give results for a simple accumulator-based processor named Parwan. The RTL spectral vectors produced higher coverage in shorter CPU times as compared to a gate-level ATPG