An approach to message arbitration in hard real-time applications

The present paper concerns the problem dealing with shared resource utilization in the hard real-time environment. Message transmissions via a serial bus or message processing by a router are examples of shared resource requests in networks. Hard real-time request must be completed within a certain deadline. When multiple requests are appeared they spend a part of time waiting for the resource access. The time lost depends on the shared resource arbitration scheme. One of such schemes called the ldquolast lowest schemerdquo is discussed in the paper. The last lowest priority scheme represents a variant of the scheme. The round-robin scheme doesnpsilat provide different deadlines for different shared resource requestors, which is very important for the hard real-time applications. The method to avoid this disadvantage is suggested and evaluated in the paper. The arbitration scheme suggested can be implemented both in software and hardware. The article presents an implementation of the method in a distributed arbiter for a single wire serial bus.