Automatic error recovery in targetless logic emulation

Targetless logic emulation refers to a verification system in which there are no external hardware targets interfacing with the emulator. In such systems input stimuli to the DUT come either from a user provided vector file or a HDL testbench running on a software simulator and the DUT runs on hardware based logic emulator. Many users use such targetless environment for automated long-running verification tests consisting of huge sets of input stimuli, consequently an automatic recovery method is of significant interest in such systems. The automatic error recovery method shall be able to complete the emulation session gracefully skipping error points and subsequently report various errors and mismatch conditions for user debug. The paper presents a novel methodology and verification infrastructure based on periodic checkpointing, which provides a robust way of error condition detection, subsequent restoration of last saved system state and resume emulation run by skipping offending operations. It does not require any special hardware extension and provides a fully customizable checkpoint frequency selection scheme. It is seen to add only a minimal overhead on overall hardware emulation speed.