An Analytical Model of the CAN Bus for Online Schedulability Test

Controller area network (CAN) is a prioritybased bus that supports real-time communication. Existing schedulability analysis for the CAN bus is peformed at the design stage, by assuming that all message information is known in advance. However, in pratice, the CAN bus may run in a dynamic environment, where complete specifications may not be available at the design stage and operational requirements may change at system run-time. In this paper, we develop an analytical model that describes the dynamics of message transmission on the CAN bus. Based on this analytical timing model, we then propose an online test that effectively checks the schedulability of the CAN bus, in the presence of online adjustments of message streams. Simulations show that the online test can accurately report the loss of scheduability on the CAN bus.