Improving gate-level simulation accuracy when unknowns exist

Unknown values (Xs) may exist in a design due to uninitialized registers or blocks that are powered down. Due to X-pessimism in gate-level logic simulation, such Xs cannot be handled correctly, producing false Xs that result in inaccurate simulation values. To improve gate-level simulation accuracy when Xs exist, we first trace the fan-in cone of Xs to check whether they are real. For the Xs that are not real, we extract small sub-circuits responsible for creating the false Xs. We then generate auxiliary code to repair gate-level simulation by replacing the Xs with the correct values. Our experimental results on commercial designs show that the proposed methods are both effective and efficient. Categories and Subject Descriptors B.6.3 [Logic Design]: Design Aids—Simulation General Terms Algorithms, Design, Verification Keywords X-pessimism, Gate-level logic simulation, Formal methods

• Type: Journal
• Year: 2012
• Where: DAC
• Authors: Kai-Hui Chang, Chris Browy
• Keywords: Auxiliary Code, Computer Architecture, DAC 2012, Gate Level Simulation, Logic Simulation