An overview of ARINC 653 part 4

In 1996, ARINC 653 Part 1 (653p1) was published, which defines a standard Real-Time Operating System (RTOS) API called the APplication EXecutive (APEX). APEX defines mandatory RTOS services including the notions of time and space partitioning, and is targeted at large, complex Integrated Modular Avionics (IMA) systems. In 2012, ARINC 653 Part 4 (653p4) was developed, which defines a subset of 653p1 capabilities intended to address systems that do not require the size, complexity, or features of IMA systems. As such, 653p4 brings the benefit of 653p1-style standards compliance to more devices on aircraft, such as the majority of the Line Replaceable Units (LRUs) on next-generation aircraft. In this paper, we discuss ARINC 653p4 in contrast with 653p1.