The following section is structured as follows:

• All­ge­mein
• Overview of Standards
• How are standards?
• Outlook

All­ge­mein

About communication systems of all types structured to describe the ISO, the so-called Open System Interconnection (OSI) layer model defined in ISO 1978th It is therefore usually referred to as ISO / OSI layer model. The model is the basis for understanding the different layers of the diagnostic communication, and is reused within the seminar, as illustrated.

Open System Interconnection (OSI) Schichtenmodell (ISO 1978)

At the lowest two levels are the layers that describe the actual bus system (layer 1 and 2). In the physical layer (1) describes how the signals are on the line, what signal levels they have, how they are coded, etc. The Data Link Layer (2) describes how composed of individual bits of all the messages and transmission errors seen etc.

The visible parts of the bus system, so the bus lines and connections, unfortunately, not directly part of the ISO 1978th We will refer to here as layer 0th

Above are a series of layers, which are essentially concerned with the question: "How the message passes from sender to receiver?". In the automotive technology plays in practice only the transport layer (4) a role. It deals with the question: "How to transfer larger blocks of data, although the underlying bus systems typically allow only small amounts of data in a single message?". So he is responsible for segmentation and Desegmentierung.

As an interface to the actual application - so the diagnostic tester - is the so-called Application Layer (7). He is ready for application services, such as the reading out of memory errors, prepared. What is typically the transmission of several messages in a row so require.

Each layer to try up to encapsulate the details of the underlying layers.

Overview of Standards

For the individual layers now exist a number of standards, we are not on the individuals want to take. The following tables provide an overview:

Standards for bus systems (layers 1 & 2)

The ISO 9141 is a standard that is the oldest diagnostic interface of European vehicles, the so-called K-Line defined. J1850 is an SAE standard, which was formerly used in American cars for the diagnostic interface. The bus systems CAN, FlexRay, MOST, LIN, etc. are specified in ISO and / or SAE standards. In some cases, but there are only quasi-standards that are defined by business consortia.

Standards for transport protocols (layer 4)

The same applies at the level of the transport protocols and at the level of the application layer. There are both ISO and / or SAE standards, and company-specific forms - sometimes independently, sometimes only versions of the official standards.

Standards in diagnostic protocols (layer 7)

Well above the ISO OSI layer model, there are a number of proposed standards, which are important for diagnostic applications. First of all, the proposals are to give the ASAM consortium. A consortium made up of vehicle manufacturers and suppliers, and deals mainly with the fields of diagnostics and application of vehicle systems. The most important for the diagnostics area, which is the consortium formed ASAM, ODX is safe, a standardized data format for the exchange of diagnostic data.

Standards in on-and off-board diagnostic applications

There are also proposals in the standard HIS consortium of OSEK / VDX or - especially important today - AUTOSAR, which are to implement, especially on the ECU side of meaning.

How are standards?

Why is it now that there are so many standards, which all together are relevant to diagnostic applications? Quite simply because in the vehicle technology exists no overarching body that defines all mandatory standards. But that these standards between the automakers and their suppliers have to be agreed. This sometimes lengthy process of discussion is shaped by different partially conflicting interests that must ultimately be harmonized. The result is either a reasonable average amount or the sum of the common interests of the people involved in the standardization committee.

A standard is the sum of the interests of those involved in the standardization committee

Therefore always found in standards mandatory and optional parts. Due to the different time schedules often are also different versions, sometimes draft version is being used, all must work together somehow.

Outlook

In the other parts of this seminar, we will now discuss the most important for the diagnosis of these standards. We begin in the ISO / OSI layer model at the bottom of the bus systems, our work on transport and diagnostic protocols then up to the application layer and close the seminar with an overview of the main ASAM standards from this topic.