System considerations for robust time and space partitioning in Integrated Modular Avionics

Developers face many difficult and unique challenges when designing Integrated Modular Avionics (IMA) systems employing robust time and space partitioning as defined by the ARINC 653 open standard. Several such IMA system design challenges are posed by common hardware features such as interrupts, Direct Memory Access (DMA), and system Input/Output (I/O), as they may produce unpredictable distortions that violate the constraints of time and space partitioning. Time and space partitioning must be deterministic in an ARINC 653-based IMA system in order to avoid aircraft certification concerns and incompatibilities with the standards and guidelines set forth in DO-178B. Methods for identifying, analyzing, and rectifying potential determinism issues in the IMA system are presented herein. A sample system employing Wind Riverpsilas VxWorks 653 real-time operating system is used to empirically demonstrate determinism issues and how to overcome them, resulting in a certifiable IMA system which effectively uses hardware resources.