ISO 17356-3:2005

Overview

ISO 17356-3:2005 - "Road vehicles - Open interface for embedded automotive applications - Part 3: OSEK/VDX Operating System (OS)" specifies a standardized real-time operating system (RTOS) API for automotive control units (ECUs). It defines a single-processor, multitasking OS concept for distributed embedded control units, focusing on a uniform environment that supports efficient resource utilization and portability of application software. The standard describes system services in an ISO/ANSI-C‑like syntax (interface only), not a particular product implementation.

Key Topics and Requirements

• Task management: concepts, task states, activation, scheduling policies and priority handling for real-time tasks.
• Interrupt processing: rules and mechanisms to integrate interrupt handling with task scheduling.
• Resource management: mutual exclusion and synchronization with the Priority Ceiling Protocol (including interrupt-level extensions) to avoid priority inversion.
• Event mechanism & messages: inter-task communication and event-driven control suited to automotive timing constraints.
• Alarms and counters: time-triggered services for periodic/one-shot actions and timing control.
• Error handling, hooks and debugging: standardized hook routines and two error-checking levels - extended status for development and standard status for production.
• Static configuration and scalability: system objects (tasks, resources, alarms) are generated at system-generation time (no dynamic creation) to minimize runtime overhead and support low-end 8-bit microcontrollers up to complex ECUs.
• Portability & API: identical service interface across processor families to support source-level portability of application modules.
• Documentation & system generation: implementation specifics and system generation aspects are covered in companion parts (e.g., ISO 17356-6).

Applications and Users

ISO 17356-3 is used when developing safety-critical, time-deterministic automotive software:

• Automotive OEMs and Tier-1 suppliers designing ECU software architectures.
• RTOS developers and implementers creating OSEK/VDX-conformant kernels.
• Tool vendors (system generators, static configurators) and integrators ensuring portable, deterministic behavior.
• Verification, testing and certification teams applying standardized hooks, error modes and conformance classes for validation.

Practical benefits include predictable timing, reduced integration effort, easy reuse of application modules across ECUs, and support for low-resource hardware.

Related Standards

• ISO 17356-1 (General structure, terms)
• ISO 17356-2 (Binding OS, COM and NM)
• ISO 17356-4 (Communication - COM)
• ISO 17356-5 (Network Management - NM)
• ISO 17356-6 (Implementation Language - OIL)
• OSEK/VDX and OSEKtime references for timing and configuration details

Keywords: ISO 17356-3:2005, OSEK/VDX Operating System, automotive RTOS, embedded automotive applications, ECU, real-time operating system, task scheduling, Priority Ceiling Protocol, alarms, interrupt handling, API, OIL.