Abstract: A method for providing a test response for testing a function of a master unit of a synchronous serial data bus, the method including a step of monitoring and a step of providing. In the step of monitoring, a command bit sequence on a command channel of the data bus is monitored in order to detect a predetermined command from the master unit. In the step of providing, the test response is provided on a response channel of the data bus in response to a detected predetermined command, a response bit sequence of the test response being provided by using a response rule predefined in a short-term memory.