CAN Network with Time Triggered Communication
Florian Hartwich, Bernd F. Müller, Thomas Führer, Robert Hugel · 2000
The communication in the classic CAN network is event triggered; peak loads may occur when the transmission of several messages is requested at the same time. CAN’s non-destructive arbitration mechanism guarantees the sequential transmission of all messages according to their identifier priority. For hard real-time systems, a scheduling analysis of the whole system has to be done to ensure that all transmission deadlines are met even at peak bus loads. For a RTOS that is based on static cyclic scheduling of all tasks, system integration and composability are served when the communication on the CAN network also follows a synchronised schedule. The time triggered communication option of the forthcoming new edition of ISO11898-1 describes the prerequisites needed for the synchronisation of all nodes in the CAN network. Based on the synchronisation of the nodes, the time triggered communication facilitates also the establishment of a global time in higher-layer protocols. A higherlayer protocol above the unchanged standard CAN protocol is in the process of standardization by ISO TC22/SC3/WG1/TF6, as ISO11898-4. In parallel to the standardization process, Bosch has implemented the time triggered communication function into a CAN IP module that maintains the cyclic transmission schedule autonomously, not depending on software control. This paper describes a CAN network with time triggered communication consisting of CAN controllers with autonomous message scheduling.