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Profibus International (PI) is the international industrial communications community responsible for two of the most important technologies used in plant and process automation today: PROFIBUS - the most popular fieldbus for discrete manufacturing and process control and PROFINET - an 'Industrial Ethernet' solution supporting advanced plant automation strategies and helping them be merged easily into the enterprise and beyond.

PROFIBUS International
Support Centre
Haid-und-Neu-Str. 7
76131 Karlsruhe
Tel: +49 721 9658 590
Fax: +49 721 9658 589

PROFINET - Technical overview
PROFINET is the leading Industrial Ethernet standard for automation that includes plant-wide fieldbus communication, plant-to-office communication, and equipment-to-equipment integration. PROFINET can simultaneously handle standard TCP/IP transmissions AND real-time transmissions at sub-millisecond speeds. PROFINET embraces industry standards like Ethernet, TCP/IP, XML, and OPC. Using proxy technology it connects other fieldbuses in addition to PROFIBUS; thus protecting the existing investment in plant equipment and networks. PROFINET is more than a fieldbus - it's a means of integrating disparate control equipment without programming! Currently more than 100 engineers from at least 50 different companies are working in 20 distinct Working Groups to advance PROFINET.

PROFINET is the innovative open standard for Industrial Ethernet. PROFINET satisfies all requirements for automation technology. With PROFINET, solutions can be implemented for factory and process automation, for safety applications, and for the entire range of drive technology right up to clock-synchronised motion control.

Scaleable Communication
PROFINET uses Ethernet as well as TCP, UDP, and IP as the basis for communications. TCP/IP is the de-facto standard for communication protocols in the IT arena. But for interoperability, it is not enough just to establish a common communications channel between field devices based on TCP, UDP, and IP, because these standards merely represent the basis for data exchange. Additional protocols and determinations are thus needed on top of TCP or UDP, the so-called application protocols, which ensure the interoperability of applications. The interoperability of applications between field devices is only ensured when the same application protocol is being used. Typical application protocols are, for instance, SMTP (email), FTP (file transfer), and HTTP (Web).

The different application areas in industrial automation depend on a wide range of services for communications. These range from non-time-critical through real time capable to clock-synchronized. PROFINET offers therefore scalable data communications.

For non-time-critical processes, PROFINET uses Non Real Time communication (NRT) with the standard Ethernet mechanisms over TCP/IP or UDP/IP. This NRT communication follows the international standard IEEE 802.3. This is enough for most applications of process automation.

In industrial applications of factory automation, however, significantly stronger requirements for data bandwidth and for clock synchronization exist. Data exchange optimized for performance is called Real Time communication (RT), and the deterministic and clock-synchronised communications is called Isochronous Real Time (IRT), which enables clock rates of under 1 ms and a jitter precision of <1 Ás.

Distributed I/O with PROFINET IO
Distributed I/O (Remote I/O) is connected through PROFINET IO. Here, the familiar I/O view of PROFIBUS is retained, in which the user data from the field devices are periodically transmitted into the process model of the control system.

PROFINET IO describes a device model, consisting of places of insertion (slots) and groups of I/O channels (subslots). The technical characteristics of the field devices are described by the GSD (General Station Description) on an XML basis.

PROFINET IO distinguishes between three following device types:

  • IO-Controller: Controller on which the automation program is run
  • IO-Device: remotely assigned field device, which is assigned to an IO-Controller
  • IO-Supervisor: programming device/PC with commissioning and diagnostics functions

The engineering of PROFINET IO is done in the way familiar to system integrators from years with PROFIBUS. The decentralized field buses are assigned to one or more control systems during configuration. During engineering the IO-Device is to be configured to the actual system expansion based on the content in the GSD file. The IO-Device is simultaneously integrated, appropriately parameterized and configured into the PROFINET topology (1).

After completion of the engineering process, the installer loads the data for the expansion into the IO-Controller (2). The IO-Controller independently takes over data exchange with the IO-Device (3).

PROFINET CBA is a groundbreaking concept for industrial automation which fulfills the requirements of plant builders and operators for an system-wide and manufacturer-spanning engineering process. The PROFINET component model sees its real use in distributed automation systems. It is ideally suited for intelligent field devices with programmable functionality as well as controllers.

PROFINET CBA is based on the object-oriented modelling of technological modules. Based on the object model, machines and installations are structured in PROFINET in the form of technological modules. The functionality of the technological modules is encapsulated in uniform PROFINET components. From the outside, PROFINET components are accessed through uniformly defined interfaces. They can be arbitrarily connected in this way.

A distributed automation system designed in this way allows the modularization of plants and machines and therefore the reuse of segments of plants and machines. This significantly reduces engineering costs.

PROFINET based on a component model is described using a PCD (PROFINET Component Description). It is XML-based and can be generated either by the Component Generator of a manufacturer-specific configuration tool.

PROFINET CBA systems. The engineering differentiates between the programming of the control logic of the individual technological modules (component generation using manufacturer-specific configuring tools) and the plant configuration which determines the communication relationships between the technological modules (using a PROFINET Connection Editor). As last engineering step, the connection information and configuration data are downloaded to the PROFINET components with a simple mouse-click.

PROFINET specifies a model for the integration of existing PROFIBUS and other fieldbus systems like INTERBUS and DeviceNet. This allows the construction of arbitrarily mixed systems consisting of fieldbus- and Ethernet-based segments. Thus a smooth technology transition is possible from fieldbus-based systems to PROFINET.

The large number of existing fieldbus systems makes it necessary to support their simple integration into PROFINET for reasons of investment protection. The following cases are distinguished:

  • The system operator would like to be able to integrate existing installations into a newly installed PROFINET system easily.
  • The system and machine builder would like to use the established, documented device lines unchanged for PROFINET automation projects.
  • The device manufacturer would like to be able to integrate existing field devices into PROFINET installations without any costs of change.

Fieldbus solutions can easily and seamlessly be connected into a PROFINET system using proxies. The proxy functions as a representative of the fieldbus device on the Ethernet. It integrates the nodes connected to the underlying fieldbus system into the overlying PROFINET system. This allows the advantages of fieldbuses like high dynamics, locally exact diagnostics, and automatic system configuration to be used in the PROFINET world without settings in the devices. The transfer of system advantages simplifies planning due to well-understood workflows and the commissioning and operation using the complete diagnostic capabilities of the fieldbus system. Device and software tools are also supported in the usual manner and integrated into the management of the PROFINET system.

The proxy concept allows the device manufacturer to provide a high degree of investment protection to the plant and machine builder and end user.


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