The present invention relates to a system for performing a co-simulation and/or emulation of hardware and software. The system includes a hardware simulator with an integrated hardware model, a hardware and/or software environment for controlling the hardware simulator and performing a software simulation and/or a direct software application, at least one synchronization facility within the hardware model for indicating a request from the hardware and/or software environment, a receiver for setting the synchronization facility into a predetermined state, and a controller for switching the hardware simulator between a free-running state and a request-handling state.