Optimization of retargeting for IEEE 1149.1 TAP controllers with embedded compression

We present a formal optimization technique that enables retargeting for codeword-based IEEE 1149.1-compliant TAP controllers. The proposed method addresses the problem of high test data volume and Test Application Time (TAT) for a system-on-chip design during board or in-field testing, as well as during debugging. This procedure determines an optimal set of codewords with respect to given hardware constraints, e.g., embedded dictionary size and the interface to the Test Data Register in the IEEe 1149.1 Std. A complete traversal of the spanned search space is possible through the use of formal methods. An optimal set of codewords can be determined, which is directly utilized for retargeting. The proposed method is evaluated using test data with high-entropy, which is known to be the least amenable to compression, as well as input data for debugging and Functional Verification (FV) test data. Our results show a compression ratio improvement of more than 30% and a reduction in TAT up to 20% compared to previous techniques.