Integrating the CAN and MUST access techniques in a single fieldbus

Even though the controller area network (CAN) protocol is particularly suitable to support communications in real-time environments, it may exhibit unfair behaviour under heavy traffic conditions. Medium-utilisation state tracking (MUST) is a novel technique which achieves fair round-robin access in CANs and requires few changes to the original protocol. Furthermore, it preserves full compatibility with the existing devices and applications developed for CANs. In this paper, the combined use of conventional CAN and MUST devices is analysed, and the performance improvements which can be obtained have been evaluated. In addition, some hints are given on possible implementations of the MUST technique in real CAN controllers.