A data processing system ensures maximum reaction times. A novel and significantly improved way of ascertaining, checking and/or observing maximum reaction times in data processing systems includes complex or distributed, safe and/or nonsafe systems, particularly between a safe input signal and the corresponding safe output signal, in a flexible and universally applicable manner. Input and/or output data, which are present on the input side of users incorporated in the system, are read in synchronously during each data cycle and checked in relation to currency parameters, which are based on at least one data cycle and associated with the input and/or output data An error is identified in response to a defined discrepancy being reached between at least one currency parameter and a defined currency threshold, and a defined function, particularly a safety-oriented function, are triggered in response to identification of an error.