A short history of standardization and CAN

Standards might be boring to read about, but we couldn’t do without them. Without standards modern civilization would be much more difficult, costly, and hazardous, because we didn’t standardize the fire hydrants.

By Holger Zeltwanger February 16, 2015

We all know that standards are boring to read, but we can’t work without them. It’s especially dull to read standards that were not made for your needs. For example, the ISO 11898 series is written for chipmakers who want to implement the Controller Area Network (CAN) protocol. Users should not read them. To save time, buy one of the helpful books on the topic or to search for articles and basic information on the Internet.

The CAN protocol has been internationally standardized since 1993 in the ISO 11898 standard. These days, all basic CAN standards are under review. The ISO 11898-1 standard will be upgraded to include the CAN FD protocol extension. The ISO 11898-2 high-speed transceiver standard and its younger sisters ISO 11898-5 (low-power mode) and ISO 11898-6 (selective wake-up transceivers) are going to be merged into a single ISO document to make them consistent and easier to maintain.

We do need a shared way of communication so that different implementations can exchange messages. The same is true for human languages. If we didn’t agree on paper and envelope formats as well as character sets, we couldn’t communicate through mail. There would be no normed keyboards and no letters that could be read without an interpreter. 

The history of standardization in a nutshell

Standardization is as old as interactions within larger human communities. The first Chinese emperor, Qin Shi Huang (260 to 210 BC), standardized not only the Chinese characters, but also the system of units and measurements as well as the currency and the width of cart axles.

War has often driven standardization. More than 2,500 years ago, Heraclitus stated: "War is the father and king of all." In the American Civil War (1861 to 1865), one of the reasons for the Union’s victory against the South was the standardization of its rail tracks. The problem was the difference in track gauges. The Confederate rail network was mostly in the broad gauge format; only North Carolina and Virginia had standard gauge lines. Southern railroads west of the Mississippi widely differed in gauge, making them isolated and disconnected. During the Civil War, the Union government recognized the military and economic advantages of having a standardized track gauge. The government worked with the railroads to promote use of the most common railroad gauge in the U.S. at the time, which measured 4 ft and 8½ in., a track size that originated in England. This gauge was mandated for use in the Transcontinental Railroad in 1864 and by 1886 had become the U.S. standard.

Another example of standardization during wars is standardized rifle parts, making them interchangeable between guns. This was a revolutionary idea from Thomas Jefferson and Eli Whitney, who was a mechanical engineer in the late 18th century. Likewise, the foundation of the predecessor of the DIN (German standardization body) in 1917 had a military background. The German industry wanted to optimize production during World War I (1914 to 1918) because it was in a material battle between Germany and France.

There are also civil examples of standardization benefits. In 1904, a fire broke out in Baltimore. Reinforcements from New York, Philadelphia, and Washington, DC, came to Baltimore to combat the flames. After they arrived, they realized that their fire hoses could not be connected to the fire hydrants. With the lesson learned, the U.S. started many standardization projects. In 1904, the ANSI (American National Standards Institute) was established. A few years earlier, the British Standardization Institute (BSI) had been founded as well.

An increase in international business that demanded worldwide standardization led to the birth of the IEC (International Electrotechnical Commission). Its inaugural meeting was held in 1906. Originally located in London (UK), the commission moved to its current headquarters in Geneva in 1948. A year earlier, 25 countries founded the ISO (International Standardization Organization) to deal with all the "non-electrical" standards. The ISO predecessor had already been established in 1926, but it was suspended during World War II. Today, the division of labor is more or less history, because electrical equipment is used in many industries and needs to be standardized. ISO standardizes electronics too, especially for the industries that have non-electrical roots. That is why CAN is standardized by the automotive technical committees of ISO; originally, cars were not defined as electric and electronics.

ISO is a voluntary organization whose members are recognized authorities on standards, with each one representing one country. Members meet annually at a General Assembly to discuss the ISO’s strategic objectives. The Central Secretariat coordinates the standardization activities and publishes the ISO standards. There are 250 technical committees and thousands of subcommittees, working groups, and task forces.

The IEC has a similar number of technical workers. Some 10,000 electrical and electronics experts from industry, government, academia, test labs, and others with an interest in the subject develop the standards. IEC standards have numbers in the range from 60000 to 79999. The IEC is made up of members, called national committees (NCs). Each NC represents its nation’s electro-technical interests. 

CAN-related standards in ISO and IEC

The CAN protocol was first described in a specification published by Bosch. Many people still use the terms "CAN 2.0A" and "CAN 2.0B" from back then. However, in 1993 the ISO 11898 standard was released, substituting all predecessors including the Bosch specification. The ISO standard comprised the CAN data link layer and CAN high-speed transmission. In 1995, the ISO 11898 standard was extended by an addendum describing the extended frame format using the 29-bit CAN identifier. Ten years after the publication of ISO 11898, the document was split into parts. The first part contained the data link layer and the physical signaling, while the second part standardized high-speed transmission. Fault-tolerant, low-power transmission went into ISO 11898-3. At the same time, ISO started the standardization of CAN-based truck-trailer communication. The results are specified in the ISO 11992 series, which includes its own physical transmission solution and a higher-layer protocol based on J1939. This series also specifies dedicated parameter groups (signals assembled to CAN messages). All these standards are published under the roof of the Technical Committee (TC) 22. Within this TC, there is also the ISO transport protocol standardized (ISO 15765-2), which serves as the base for several emission-related CAN-based diagnostic standards (ISO 15765-4). The ISO 14229-3 standard specifies unified diagnostic services (UDS) transmitted via CAN. Another CAN-related series is ISO 16844 standardizing tachograph communication for commercial vehicles. This standard is referenced by European regulations, but not much loved in the industry, especially not by truckers. They don’t like to be watched electronically.

Just after the year 2000, Bosch started to extend the CAN protocol by a time-triggered protocol. The question of whether this is a session layer or if it doesn’t fit in the OSI reference model at all remains unanswered. But it was standardized in ISO 11898-4 and is known as TTCAN. As of now, it has not made its way into the industry. Some chipmakers have implemented it, but it is not being used. The same happened to the ISO 15745-2-2 standard describing an XML-based framework for CAN-based networks; it too has never been used in industrial automation systems. I was personally involved in its development but understood little of what the IT experts were discussing. This is one of the standards that are just paperwork and eating memory space on computers. They are not really ecologically valuable, especially when considering the traveling. Anyway, standardization can sometimes be slow and eat up a lot of work time.

ISO TC 23 is the home of the ISO 11783 series (also known as Isobus), which standardizes the communication between tractor and agriculture equipment (so-called implements). This standard is based on the J1939 higher-layer protocol. The ISO 13628-6 standard describes the general requirements for subsea equipment using CAN networks to link sensors and meters to the subsea control unit. These CAN applications make use of the CANopen application layer and the related CiA 443 CANopen profile for SIIS level-2 devices.

In the IEC organization, there are also some CAN-related standards. First of all, the IEC 61375-3-3 standard has to be mentioned. It describes the CANopen-specific implementation of CAN networks within rail vehicles, locomotives, and coaches. This includes some physical layer specifications and some functions originally specified in CiA 301 and CiA 302. Another IEC standard, IEC 61800-7-201/301, specifies the CiA 402 CANopen profile for drives and motion controllers. Of course, there are also two European Cenelec standards related to CANopen: EN 50325-4 specifies the CANopen application layer, and EN 50325-5 describes the CANopen Safety protocol extension. Cenelec and CEN, the European standardization bodies, were established in 1973 and 1961, respectively. Today, they work in close cooperation with IEC and ISO, to avoid double standardization. Or in other words, they do not try to reinvent the wheel. 

No standards without sponsors and editors

To put it bluntly, all standardization activities are driven by the interests of individuals or companies—sometimes both. Bosch backs the current activities regarding the ISO 11898 series. The C&S Group performing the related conformance testing of CAN silicon supports all of the conformance test plans. Of course, the market-leading semiconductor manufacturers and some carmakers spend a lot of effort on pursuing CAN standardization.

The editor of ISO 11898-1 is Florian Hartwich from Bosch. There were many contributions from different experts during the development of the document, in particular from GM, Mercedes, and Renesas. The related CAN conformance test plan, standardized in ISO 16845-1, was edited by Andreas Meidrodt from the C&S Groups. His colleague, Christoph Wosnitza, does the paperwork for ISO 16845-2, the conformance test plan for ISO 11898-6 (selective wake-up CAN transceivers). Bernd Elend from NXP volunteers as editor of the harmonized high-speed transceiver standard (ISO 11898-2). Without these editors, who also spend some of their free time on editing the documents, the standards would not meet the deadlines established by the ISO rules.

Every ISO or IEC group needs a convener and a secretary. The secretary is typically a representative of a national standardization body. Volunteers for conveners are always welcome, because this position is unpaid. Sometimes there are political discussions and arguments about who gets which position, because no country or company should dominate in a group. Traditionally, Germany is strongly represented in automotive-related committees. Standardization not only has a technical dimension; it also has a political one.

Standardization is slow

The process of standardization is sometimes slow compared to the development of technology. Because of this, technology is often introduced first and standardized later. Standardization is slow because all parties should have the chance to comment on the provided drafts and proposals. On the positive side, the slow process avoids standardizing technology that disappears again soon. While in the beginning, I found it harrowing to wait, I have learned to be more relaxed and patient. For example, when we started to standardize the CAN FD protocol, only Bosch and some other experts actually developed the protocol. But while we were preparing the committee draft for voting, we received many valuable ideas and comments from other experts. In the end, this improved the CAN FD protocol and will increase its acceptance in the industry. Of course, the standardization process should not be so slow that the document is never published. Therefore, ISO and IEC establish project deadlines that have to be met.

Still, it is boring to read standards, especially if you are not familiar with the specific standardization language. But we need these formal rules on how to write standards. We need a standard that tells us how to create standards. One of the reasons is to avoid misunderstandings and misinterpretations when translating the standard into languages other than the two official ones: English and French.

– Holger Zeltwanger is managing director, CAN in Automation; edited by Anisa Samarxhiu, digital project manager, CFE Media, asamarxhiu@cfemedia.com 

Key concepts:

  • We all know that standards are boring to read, but we can’t work without them.
  • Standardization is not a new concept.
  • The process of standardization is sometimes slow compared to the development of technology. Because of this, technology is often introduced first and standardized later.

Consider this

Which standards do you encounter or work with in your job?


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