An efficient functional coverage test for HDL descriptions at RTL

Until now, simulation has been the primary approach for the functional verification of register transfer level (RTL) circuit descriptions written in a hardware description language (HDL). A finite state machine (FSM) coverage test can find all the bugs in a FSM design. However, this is impractical for large designs because of the state explosion problem. In this paper, we modify the higher-level FSM models used in other applications to replace the FSM model in the FSM coverage test. The state transition graphs (STGs) can be significantly reduced in this model, so that the complexity of the test becomes acceptable even for large designs. This model can be easily extracted from the original HDL code automatically, with little computation overhead. Experimental results show that it is indeed a promising functional test for FSMs.