A design for testability technique for RTL circuits using control/data flow extraction

We present a technique for extracting functional (control/dataflow) information from register transfer level (RTL) controller/data path circuits and illustrate its use in design for hierarchical testability of these circuits. This testing procedure and design for testability (DFT) technique is general enough to handle RTL control flow intensive circuits like protocol handlers as well as data flow intensive circuits like digital filters. It makes the combined controller-data path highly testable and does not require any external behavioral information. This scheme has the advantages of low area/delay/power overheads (average of 3.2%, 0.9% and 4.1%, respectively, for benchmarks), high fault coverage (over 99% for most cases), very low test generation times (because it is independent of bit-width), and the advantage of at-speed testing. Experiments show a 2-to-4 (1-to-3) orders of magnitude test generation time advantage over an efficient gate-level sequential test generator (combinational test generator that assumes full scan).