A guide to Profibus and Profinet industrial fieldbus networks

Profibus was created in 1989 by a consortium of companies and institutions. According to Profibus International, Profibus is now the world's most popular fieldbus in discrete manufacturing and process control. It is mature, proven technology for supporting modern automation systems, with over 20million installed devices. By continuously enhancing the technology, Profibus International aims to ensure that Profibus remains a dominant fieldbus. An ongoing commitment from some of the world's major automation suppliers ensures that investments today are fully protected for the lifetime of any plant. Profibus is said to be unique in offering a fully integrated platform for discrete and process applications, which is a major benefit in the process industries where upstream, mainstream and downstream processes have to work together. Industries using Profibus range from critical petrochemical operations and high volume robotic manufacturing plants, right across the spectrum to food and drink, and water/waste treatment plants.

Technology Overview

Profibus is described by Profibus International (PI) as the most universal fieldbus for plant-wide use across all sectors of the manufacturing and process industries, and the fieldbus having worldwide best economic success. Independent market studies have confirmed Profibus as the market leader today and predicted high growth rates for the future (contact PI for more information).

One of the most important advantages of using fieldbuses in the automation is reduced installation efforts. For example, using Profibus instead of conventional 4-20mA cabling can save an estimated 43 per cent of costs, made up of savings in engineering time, assembly time and hardware costs.

Profibus Basics

The key fieldbus technologies are today included in the standards IEC 61158 and IEC 61784. Profibus is an integral part of these standards.

Profibus is an open, digital communication system with a wide range of applications, particularly in the fields of factory and process automation. Profibus is suitable for both fast, time-critical applications and complex communication tasks. The application and engineering aspects are specified in the generally available technical documents of Profibus International. This fulfils user demand for manufacturer independence and openness and ensures communication between devices of various manufacturers.

Building on a very efficient and extensible communications protocol, coupled with the development of numerous application-oriented profiles and a fast growing number of devices, Profibus began its advance, initially in factory automation and, since 1995, in process automation. Today, Profibus is a fieldbus world market leader.

Profibus has a modular design (Profibus Tool Box) and offers a range of transmission and communication technologies, numerous application and system profiles, as well as device management and integration tools. Profibus therefore covers the diverse and application-specific demands from the field of factory to process automation, from simple to complex applications, by selecting the adequate set of components out of the tool box.

Profibus protocols

Profibus DP (Decentralized Peripherals) is available in three versions, DP-V0, DP-V1 and DP-V2, with each having its own special key features. All versions of DP support the implementation of both mono-master and multi-master systems.

Version DP-V0 provides the basic functionality of DP, including cyclic data exchange, station, module and channel-specific diagnostics and four different interrupt types for diagnostics and process interrupts, and for the pulling and plugging of stations.

Version DP-V1 contains enhancements geared towards process automation, in particular acyclic data communication for parameter assignment, operation, visualisation and interrupt control of intelligent field devices, parallel to cyclic user data communication. This permits online access to stations using engineering tools. In addition, DP-V1 has three additional interrupt types: status interrupt, update interrupt and a manufacturer-specific interrupt.

Version DP-V2 contains further enhancements and is geared primarily towards the demands of drive technology. Due to additional functionalities, such as isochronous slave mode and lateral slave communication (DXB) etc, DP-V2 can also be implemented as a drive bus for controlling fast movement sequences in drive axes.

The Profibus PA (Process Automation) Devices profile defines all functions and parameters for different classes of process devices that are intrinsically intelligent and can execute part of the information processing or even the overall functionality in automation systems. The PA device profile version 3.0 includes device data sheets for pressure and differential pressure, level, temperature, flow rate, valves and actuators, analysers, and analogue and digital inputs and outputs.

More Information can be found on the Profibus website

PROFIdrive

The most recent DP-V2 functions, namely 'clock cycle synchronisation' and 'slave-to-slave communication', have been added to suit the needs of electric drive applications.

Profibus now permits the highly dynamic distribution of signals among networked drives, enabling distributed automation structures to be realised economically by means of intelligent drives. Digital servo drives can now be synchronised via Profibus, and the position control loop can be closed via the bus.

For more details on PROFIdrive, see the Drives & Motion section of the Profibus website.

PROFIsafe

PROFIsafe has been developed following a comprehensive examination of application scenarios by numerous safety experts from well-known companies. It can be used for a wide variety of high-integrity applications (for example, in the case of processing industries, the lowest loss making output, and in the case of manufacturing industries, reaction times in milliseconds).

See more details of PROFIsafe

Profinet

Profinet is an open standard for Industrial Ethernet and is said to be suitable for all automation technology requirements. With Profinet, systems can be implemented for factory and process automation, safety applications, and for the entire range of drive technology right up to clock-synchronised motion control.

Profinet also enables investments to be protected, by integrating fieldbus systems like Profibus, DeviceNet, and Interbus without changes having to be made to existing devices.

The use of open standards, simple operation and the integration of existing system segments has driven the definition of Profinet from the beginning. Profinet is standardised in IEC 61158 and IEC 61784.

The continual further development of Profinet offers users a long-term perspective for the implementation of their automation tasks.

For plant or machine builders, the use of Profinet is claimed to minimise the cost of installation, engineering, and commissioning. For plant operators, Profinet enables simple system extensibility and high system availability due to autonomously running system segments.

The establishment of certification now ensures a higher standard of quality for Profinet products.

More about Profinet is available at the Profibus website.

The Profibus and Profinet community

Profibus & Profinet International (PI) is the international industrial communications community responsible for Profibus and Profinet. PI has more that 1400 member companies around the world developing and supplying products, services and systems. A searchable database of compatible products is available on the Profibus website.

The PI commitment to openness and standardisation ensures there is a wide choice of interchangeable products. This stimulates innovation and ensures best-in-class performance, competitive prices and major whole-life asset benefits for all users

For more information about PI see www.profibus.com