The paper presents Truetime, a Matlab Simulink-based simulator for real-time control systems. Truetime makes it possible to simulate the temporal behavior of multi-tasking real-time kernels containing controller tasks and to study the effects of CPU and network scheduling on control performance. The simulated real-time kernel is event-driven and can handle external interrupts as well as fine-grained simulation details such as context switches. Arbitrary scheduling policies may be defined, and the control tasks may be implemented using C functions, M functions, or Simulink block diagrams. A number of examples that illustrate the use of Truetime are presented.