Hardware Reference
In-Depth Information
12.1.2
OSEK/VDX
OSEK/VDX 1 is a joint project of many automotive industries that aims at the def-
inition of an industrial standard for an open-ended architecture for distributed con-
trol units in vehicles [OSE03]. The term OSEK means “ Offene Systeme und deren
Schnittstellen f ur die Elektronik im Kraftfahrzeug ” (Open systems and the correspond-
ing interfaces for automotive electronics); the term VDX means Vehicle Distributed
eXecutive .
The objective of the standard is to describe an environment that supports efficient uti-
lization of resources for automotive application software. This standard can be viewed
as an application program interface (API) for real-time operating systems integrated
on a network management system (VDX), which describes the characteristics of a
distributed environment that can be used for developing automotive applications.
The typical applications considered by the standard are control applications with tight
real-time constraints, high criticality, and large production volumes. To save on pro-
duction costs, there is a strong push toward code optimization, by reducing the mem-
ory footprint to a minimum and enhancing the OS performance as much as possible.
A typical OSEK system has the following characteristics:
Scalability . The operating system is intended to be used on a wide range of
hardware platforms (from 8-bit microcontrollers to more powerful processors).
To support such a wide range of systems, the standard defines four conformance
classes with increasing complexity. Memory protection is not supported at all.
Software portability . An ISO/ANSI-C interface between the application and the
operating system is adopted to simplify software portability. However, due to the
wide variety of hardware platforms, the standard does not specify any interface to
the I/O subsystem. This reduces portability of the application source code, since
the I/O system strongly impacts on the software architecture.
Configurability . Appropriate configuration tools proposed by the OSEK stan-
dard help the designer in tuning the system services and the system footprint.
Objects that need to be instantiated in the application can be specified through a
language called OIL (OSEK Implementation Language).
Static allocation of software components . All the kernel objects and the ap-
plication components are statically allocated. The number of tasks, their code,
the required resources and services are defined at compile time. This approach
simplifies the internal structure of the kernel and makes it easier to deploy the
kernel and the application code on a ROM.
1 OSEK/VDX: http://www.osek-vdx.org
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