Schedulability analysis of CAN with non-abortable transmission requests

The analysis of the real-time properties of an embedded communication system relies on finding upper bounds on the Worst-Case Response Time (WCRT) of the messages that are exchanged among the nodes on the network. The classical WCRT analysis of Controller Area Network (CAN) implicitly assumes that at any given time, each node is able to enter its highest priority ready message into arbitration. However, in reality, CAN controllers may have some characteristics, such as non-abortable transmit buffers, which may break this assumption. This paper provides analysis for networks that contain nodes with non-abortable transmit buffers, as well as nodes that meet the requirements of the classical analysis. The impact on message WCRTs due to a limited number of transmission buffers with non-abortable behaviour is examined via two case-studies.