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15 Years of CAN
This article was published in "Control Engineering" and the CAN newsletter
In February of 1986, Robert Bosch introduced the CAN (Controller Area Network) serial bus system at the SAE congress in Detroit. It was designed to handle short messages (up to 8 bytes), support multi-master access (collisions get resolved by priority), and offer a high degree of reliability (15-bit CRC for every message). In Mid 1987, Intel delivered the first CAN chip, the 82526. Shortly thereafter, Philips Semiconductors introduced the 82C200 CAN controller. Today, about 20 chip manufacturers produce devices with CAN interfaces and almost every new passenger car manufactured in Europe is equipped with at least one CAN network. Also used in other types of vehicles, from trains to ships, as well as in industrial controls, CAN is one of the most dominating bus protocols. In 1999 alone, close to 60 million CAN controllers made their way into applications; more than 100 million CAN devices were sold in the year 2000.
Although CAN was originally developed to be used in passenger cars, the first applications came from other market segments. Especially in northern Europe, CAN was already very popular in its early days for textile and other machine control. In the early 1990s, the time was right to found a user’s group to standardize the different solutions. Beginning of 1992, Holger Zeltwanger, brought together users and manufacturers to establish the ‘CAN in Automation’ (CiA) international users and manufacturers association. One of the first tasks of the CiA was the specification of the CAN Application Layer (CAL). As CAN is a pure data link layer implementation, there were no standards on how to exchange data object on an application level. Although the CAL approach was academically correct and usable in industrial applications, it had a drawback: every user needed to design a new communication profile because CAL was a true application layer.
Since 1993, within the scope of the Esprit project ASPIC, a European consortium lead by Bosch had been developing a prototype of what should become CANopen, the CAL-based profile for internal networking of production cells. In 1995, CiA released the completely revised CANopen communications profile. The CANopen profile family also defines a framework for programmable systems as well as different device, interface and application profiles. This is an important reason why whole industry segments (e.g. printing machines, maritime applications, medical systems) decided to use CANopen during the late 1990s.
In the early 1990s there was an independent parallel development for a higher-layer communication profile: the engineers at the US mechanical engineering company Cincinnati Milacron started a joint venture together with Allen-Bradley and Honeywell Microswitch regarding a control and communications project based on CAN. However, after a short while, important project members changed jobs and the joint venture fell apart. As a result, Allen-Bradley and Honeywell continued the work separately. This led to the two higher-layer protocols ‘DeviceNet’ and ‘Smart Distributed System’ (SDS), which are quite similar, at least in the lower communication layers.
In early 1994, Allen-Bradley turned the DeviceNet specification over to the ‘Open DeviceNet Vendor Association’ (ODVA), which boosted the popularity of DeviceNet. Honeywell failed to go a similar way with SDS, which makes SDS almost an internal solution by Honeywell Microswitch. DeviceNet was developed especially for factory automation and therefore presents itself as a direct opponent to protocols like Profibus-DP and Interbus. Providing off-the-shelf plug-and-play functionality, DeviceNet has become the leading bus system in this particular market segment in the US.
With DeviceNet and CANopen, two standardized (EN 50325) application layers are now available using CAN, both addressing different markets. DeviceNet is optimized for factory automation and CANopen is especially well suited for embedded networks in all kinds of machine controls. This has made proprietary application layers obsolete; the necessity to define application-specific application layers is history (except, perhaps, for some specialized high-volume embedded systems).
Of course the semiconductor vendors who have implemented CAN modules into their devices are mainly focused on the automotive industry. Since the mid 1990s, Infineon Technologies (formerly Siemens) and Motorola have shipped large quantities of CAN controllers to the European passenger car manufacturers. As a next wave, Far Eastern semiconductor vendors have also offered CAN controllers since the late 1990s. Since 1992, Mercedes-Benz has been using CAN in their upper-class passenger cars. After Volvo, Saab, Volkswagen and BMW, now also Renault and Fiat use CAN networks in their vehicles.
Although the CAN protocol is now 15 years old, it is still being enhanced. Several enhancements regarding the approval for different safety-relevant and safety-critical applications can be expected for the higher layer protocols. Last year an ISO task force defined a protocol for a time-triggered transmission of CAN messages. The TTCAN extension will add another five to ten years to the total lifetime of CAN. When taken into account that CAN is still at the beginning of a global market penetration, even conservative estimates show further growth for this bus system for the next ten to fifteen years. This is underlined by the fact that the US and Far Eastern car manufacturers are just starting to use CAN in the serial production of their vehicles over the next few years. Furthermore, new potentially high-volume applications (e.g. entertainment) are in the pipeline – not only in passenger cars but also in domestic appliances.