The CAN Bus – general
A bus is always a bus – but there are ‘buses’ and ‘buses’!
In fact, from one bus to the next, the problems to be solved remain the same, but the different characteristics of the proposed fields of application modify the hierarchical order of the parameters to be considered, and result in the development of new concepts in order to find neat solutions to the difficulties encountered. Here is a quick list of the virtually unchanging problems encountered in bus and network applications:
- network access concepts, including, clearly, problems of conflict, arbitration and latency;
- deterministic or probabilistic aspects and their relationship with the concepts of real-time or event-triggered systems;
- the concept of network elasticity (‘scalability’);
- the security of the data carried, in other words, the strategy for managing errors including their detection, signalling and correction;
- questions of topology, length and bit rate;
- questions of physical media;
- radio-frequency pollution, etc.
1.1 Concepts of Bus Access and Arbitration
‘Distributed’ real-time control systems, based on an operating system located within a single processor, interconnected by a communication network with distributed processors, are currently providing a significant addition to ‘parallel’ systems.
In addition to the simple exchange of data, the processing must be synchronized, in other words, the execution must follow certain interrelated logical sequences. In these systems, the messages ...