ISO 17356-3:2005 defines the OSEK/VDX Operating System API, establishing a standardized interface for embedded automotive software to ensure task management, resource handling, and portability between ECUs. The standard covers key OS functionalities, including task management, interrupt handling, event mechanisms, and alarms. You can find the official document at ISO Store.
ISO 17356-3 is the international standard that defines the OSEK/VDX Operating System (OS) for road vehicles. It provides a standardized Application Program Interface (API) for a real-time, multitasking operating system specifically designed for distributed embedded control units (ECUs). Core Purpose and Scope
The standard establishes a uniform environment for automotive control software, focusing on portability and resource efficiency.
Target: Single-processor operating systems in embedded control units.
Portability: It allows application software modules to be transferred between different ECUs with minimal changes by standardizing service calls and constants. iso 17356-3 pdf
Hardware Efficiency: Designed to run on low-end hardware, including 8-bit microcontrollers, with minimal RAM and ROM consumption. Key Technical Features
ISO 17356-3 details several critical components of a real-time operating system:
Task Management: Concepts for task states, activation, and priority-based scheduling.
Resource Management: Uses the Priority Ceiling Protocol to prevent priority inversion during task synchronization. ISO 17356-3:2005 defines the OSEK/VDX Operating System API,
Interrupt Processing: Rules for integrating hardware interrupts with the task scheduler.
Static Configuration: Unlike general-purpose OSs, all system objects (tasks, alarms, resources) are defined at system generation time, eliminating dynamic overhead during runtime.
Conformance Classes: Four classes define varying levels of functionality to allow scaling the OS based on the specific ECU requirements.
Error Checking: Two modes are provided—Standard (for production efficiency) and Extended (for enhanced plausibility checks during development). Relationship to OSEK/VDX and AUTOSAR OSEK/VDX (2004-2005) was the original consortium standard
| Class | Tasks | Events | Resources | Alarms | Multiple activations | Scheduling | |-----------|-----------|------------|---------------|------------|--------------------------|----------------| | BCC1 | Basic | No | No | No | Yes (max 1 queued) | Non-preemptive | | BCC2 | Basic | No | Yes | No | Yes (multiple queued) | Mixed/Preemptive | | ECC1 | Extended | Yes | No | No | Yes (max 1 queued) | Non-preemptive | | ECC2 | Extended | Yes | Yes | Yes | Yes (multiple queued) | Mixed/Preemptive |
Many engineers confuse the ISO version with the original OSEK/VDX documents. Here is a critical distinction:
While the content is nearly identical, only the ISO 17356-3 PDF carries the legal weight of an ISO standard. In regulated industries, you must reference the ISO version, not the legacy OSEK documents.
Because ISO 17356 is essentially the international standardization of the original OSEK/VDX consortium documents, the technical content is largely identical to the freely available "OSEK OS 2.2.3" specification.
While the ISO 17356-3 PDF is the official legal document, the OSEK OS 2.2.3 PDF is often available for free through academic repositories or partner consortiums. For general technical study, they are often interchangeable, but for official certification and compliance audits, the ISO document is required.
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