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The most common misconceptions about IEC 61131-3


During its years of existence, the IEC 61131-3 standard has become one of the hottest topics in industrial automation. Users increasingly sees the benefits of the standard, although even today an amazing amount of misconceptions exist. Let me discuss with you the most common ones.

IEC 61131-3 is a European standard

The IEC 61131-3 standard is a world wide standard. It is accepted by an international body: the International Electrotechnical Commission, IEC. The convenor of this standard happened to be an American. Other members' countries included Germany, France, UK, Japan, and the Netherlands.

Initially it was seen primarily as a PLC standard, attracting the attention of the largest user and supplier area: Europe. Popularity in North America increased when the first "soft"-controllers were defined, being personal computers running a program that makes them behave like a PLC. The OMAC-paper is a prime example of this.

Many Japanese PLC suppliers started by adopting European PLC programming packages for the European market. However, today Japan is amongst the hottest markets for suppliers of programming packages.

IEC 61131-3 is only for the small suppliers

Members of the IEC 61131-3 task force are representatives of their countries. In practice they are employed by industrial control suppliers, often large suppliers.

Initially the IEC 61131-3 standard was strongly pushed by small and medium sized suppliers because they were more affected by the lack of standardisation. First, their customers felt insecure about relying on a proprietary solution from a small supplier versus a more represented, de-facto standard. By offering a product based on standards, the small suppliers felt they could offer a strong alternative.

Secondly small suppliers have a stronger need to co-operate, which is easier when partners adhere to standards.

However, users have to deal with different suppliers or want to have the flexibility to switch if necessary. Therefore they increasingly demand programming in IEC 61131-3. Tenders from governmental bodies and large industries are an example. And even the large suppliers see the need for co-operation.

Today, all large suppliers of PLC's have announced IEC 61131-3 compliant development systems and some of them are shipping products today.

Now there is one programming system for all controllers

From the user perspective this looks like the ideal situation: buying one programming system for any control platform. Like a kind of Windows for any PLC. Would it be ideal? This would result in one dominant player, like Microsoft. But how many users feel it would be good if Microsoft just had just a little bit more competition?

The world of industrial automation is different. Compare it to cars: in the early days there was very little standardisation. It hasn't been for long that it was very hard for someone used to a car with one kind of gear to drive a different model. Today cars are identical in their basic operation: the steering, the place of the accelerator and the brake pedals. Also most trailers can be hooked on, because the towing hook is standardised. Yet, cars still differ strongly in size, speed and features to serve different taste and wallets.

Certified IEC 61131-3 programming systems have an agreed degree of source code compatibility and have a similar look and feel. Yet they will differ in debugging features, speed, etc.

Talking about this standard has been so long, it just won't happen

This one could be heard in the early days after approval of the standard. I don't hear it anymore today. Seems like it happened.

The IEC 61131-3 standard is not optimal

The basic idea behind this statement is that any standardisation sets limits to application of the newest technologies. This would result in solutions that don't use available technology in the best possible way.

First of all, the IEC 61131-3 task force incorporated different languages in the standard, thus meeting the requirements of different application areas and geographical regions. The jungle in the fieldbus arena has been avoided in industrial control programming!

Secondly the "best" solution is not always the technical most advanced one. Familiarity, proven technology and ease of use are often just as important. Are "Wintel" (Windows/Intel) systems really technologically so much better than PowerPC's and other operating systems?

Industrial control systems are often controlling mission critical applications. By consequence the designers and users are even keener to stick to familiar systems versus state-of-the-art technology. Compared with traditional systems, the IEC 61131-3 standard is a major step ahead, not only in the languages, but also in the communications and software model.

Of course new requirements emerge. Systems will become more distributed with more parallel processing. Therefore new standards are under development, such as the function block standard IEC 1499. These standards will not replace IEC 61131-3 but work in conjunction.


The IEC 61131-3 standard is growing up. It is not yet fully mature, but it is alive and healthy. It is the kind of offspring that, building on its parents experience, will be doing better than they ever did. But it is not the perfect child. Perfect children don't exist. But it is a powerful representative of a new generation!