A method is provided for co-simulating a digital circuit using a simulation engine (45) which communicates with one or more first programming languages by means of a foreign language interface and which communicates directly with one or more second programming language. At least one first model (2, 3) or at least one first part of the digital circuit is provided in at least one high-level hardware description language which supports concurrent processes communicating with each other. The at least one first model is converted (50, 51) to at least one software model in the at least one first language. At least one second model (4, 5, 6) of at least one second part of the digital circuit is provided in the at least one second language