Wednesday, May 23, 2018

IAM Search

System Profiles

Profiles in automation technology define specific characteristics and behavior for devices and systems so that these are uniquely characterized (in classes or families) and are vendor-independent, thus supporting device interoperability and interchangeability on a bus.

Master Profiles for PROFIBUS describe classes of controller, each of which support a specific "subset“ of all the possible master functionalities, such as

  • Cyclic communications
  • Acyclic communications
  • Diagnosis, alarm handling
  • Clock control
  • Slave-to-slave communication, isochronous mode
  • Safety

 

System Profiles for PROFIBUS go a step further and describe classes of systems including the master functionality, the possible functionality of Standard Program Interfaces (FB in accordance with IEC 61131-3, safety layer and FDT) and integration options (GSD, EDD and DTM). Fig. 26 shows the standard platforms available today.

Master system profiles for PROFIBUSFig. 26: Master/system profiles for PROFIBUS

In the PROFIBUS system, the master and system profiles provide the much needed counterpart to the application profiles (Fig. 27):

  • Master and system profiles describe specific system parameters that are made available to the field devices,
  • application profiles require specific system parameters in order to simplify their defined characteristics.

System and application profiles in correlationFig. 27: System and application profiles (in correlation)

By using these profiles the device manufacturers focus on existing or specified system profiles and the system manufacturers can provide the platforms required by the existing or specified device application profiles.

PROFIBUS has realized a number of system profiles based on tried and tested applications in the field, (see Fig. 26). These are expected to be stipulated in specifications in the near future and extended by further profiles in keeping with future demands.

 

Standardized Function Blocks (Communication Function Blocks)

To realize manufacturer independent system profiles, it is necessary to specify, additionally to the already existing communications platform, an Application Programmer ´s Interface (API, Fig. 27), using standardized function blocks.

While application programmers can usually access cyclic communication data (MS0 channel) over the process image of a control system, in the past there was no system-neutral program interface for acyclic data. In view of the wide range of manufacturers and devices, standards are needed to be established in this area to enable integration of different field devices without specific communication knowledge in the application programs of different control systems. For this purpose, the PNO has now specified its guideline "Communication and Proxy Function Blocks according to IEC 61138-3". This guideline specifies function blocks in a "combinations of standards" that are based on the widely used standard IEC 61131-3 (programming languages) and also use the PROFIBUS-defined communication services of the IEC 61158.

The guideline defines communications blocks for Master Classes 1 and 2 as well as slaves and several auxiliary functions. The technological functionality of a field device can be addressed under a compact identification, which is used consistently by all blocks. All blocks also have a common concept for displaying errors with coding in accordance with IEC 61158-6.

The PLC manufacturers of the corresponding system classes/profiles offer these standard communication blocks ("Comm-FBs") in PLC-specific "IEC libraries". The field device manufacturers can respond by creating uniform proxy function blocks, which can be used with all control systems.

 

Application Programmer´s Interface (API)

In order to make it as easy as possible for application programmers to use the communication services, blocks or function calls are made available in the standard programming language libraries. Together with the FDT interface, the PROFIBUS "Comm-FBs" expand the Application Programmer's Interface as shown in Fig. 28.

Fig_028_Application_Programmers_Interface_API.pngFig. 28: Application Programmer´s Interface, API


Proxy Function Blocks

Proxy function blocks represent a technological device function by providing all the necessary input and output parameters at the block interface. These proxy function blocks are usually created once by the field device manufacturers and can be implemented in the control systems of the relevant system classes/profiles without any special adjustment (see Fig. 29).


Portable function blocksFig. 29: Portable function blocks

Go back to the header article PROFIBUS Technology and Application

Comments (0)Add Comment

Write comment

security code
Write the displayed characters


busy

Promotions

  • ...more

Disclaimer

Important: All images are copyrighted to their respective owners. All content cited is derived from their respective sources.

Contact us for information and your inquiries. IAMechatronics is open to link exchanges.

IAMechatronics Login