ModelSim

ModelSim is a multi-language HDL simulator developed by Model Technology and now marketed by Siemens EDA (formerly Mentor Graphics). It is used to simulate and verify digital designs described in hardware description languages such as VHDL and Verilog, and in more recent versions SystemVerilog; it supports mixed-language designs, enabling co-simulation of modules written in different languages. The tool provides a graphical user interface and a command-line interface, a waveform viewer, and debugging facilities that include breakpoints, stepping, and signal tracing. It also offers code coverage analysis, assertion-based verification support, and interfaces for C/C++ through DPI.

ModelSim runs on Windows and Linux and can be driven by TCL scripts for automated testbenches. It is available in multiple editions, including a lightweight Personal Edition for education and experimentation, and more feature-rich commercial versions used by semiconductor engineers and IP developers. In practice, ModelSim integrates into HDL verification flows alongside other EDA tools and simulators, and can be used for unit tests, regression testing, and IP-level verification; it also supports co-simulation with third-party simulators and hardware acceleration in some configurations.

ModelSim originated from Model Technology, founded in the late 1980s; it was acquired by Mentor Graphics in 2003 and subsequently became part of Siemens EDA when Siemens acquired Mentor Graphics in 2017. It remains a widely used tool for HDL-based verification, particularly for projects requiring reliable VHDL and Verilog/SystemVerilog simulation and debugging.

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