In a CAN system, an arrangement is incorporated for making possible more efficient utilization of available band-width on the system's bus connection between, from and/or to modules incorporated in the system and/or reduction of accuracy requirements for clock functions utilized in the system. The system operates with communication on the bus connection that is in accordance with rules set up in the system and constitutes a combination of event-driven and time-controlled communication functions. The said functions are, together with a rule change in the time-controlled communication function, arranged to achieve the said making more efficient and/or reduction. The rule change is arranged to bring about deliberate collisions between messages appearing on the bus connection. In this way, the bandwidth utilization, the clock function and the system's general construction and function can be simplified according to the requirements imposed.