Abstract:
In a method for transmitting data over a fieldbus of process automation technology with a field device in which a first application program for a first fieldbus protocol runs, the data of a second application program for a second transmission protocol are mapped onto the first fieldbus protocol and transmitted as fieldbus telegrams.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method for transferring data via a fieldbus of process automation technology. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a method for transferring data via a fieldbus of process automation technology, as such method is defined in the preamble of claim  1 . 
     In process automation technology, field devices are frequently used, in order to control the flow of an industrial process. 
     To this end, process variables are registered with the help of sensors, and controlled variables are controlled with the help of actuators. 
     Field devices for determining flow rate, fill level, pressure difference, temperature, etc. are generally known. They serve for registering the corresponding process variables flow rate, fill level, pressure, temperature, etc., and are most often arranged in the immediate vicinity of the process components of concern. 
     Examples of actuators are controllable valves, which control the flow rate of a liquid or gas in a section of pipeline. 
     The field devices are frequently connected via a fieldbus with a control unit, which controls the total process flow. In the control units, the measured values of the individual sensors are evaluated and the appropriate actuators are actuated. 
     Often, fieldbusses are also connected with superordinated communication networks, which serve for data communication with control systems and with company and/or office equipment. In this way, an integrated communication is possible within a company, from the field level into the various company levels. Besides a bounded communication in the local networks LAN, with appropriate connection, also a worldwide communication via the Internet WAN is possible. 
     In the control systems, process flow is monitored and visualized. Error reports are recorded there. From the control system, direct access to the individual field devices is also possible. This enables querying and modification of parameter values and configuration data. Additionally, diagnosis functions can also be called-up from the control system. 
     Recently, in process automation technology, systems have also become know, in the case of which the fieldbus is dispensed with, and the field devices are connected directly with a superordinated communication network. The most wide spread network is Ethernet with TCP/IP. Via this, a compatibility within various company levels and, beyond this, also outside of the company, is possible with the Internet. 
     Via the company network, emails and process data can, in this way, be transmitted simultaneously. 
     The superordinated company networks based on Ethernet work according to the client/server principle. Fieldbusses, in contrast, work according to the publisher/subscriber principle. The protocols are correspondingly designed. 
     The strengths of Ethernet with TCP/IP lie in the monitoring/parametering of plants, or plant parts, as the case may be. For control with distributed intelligence, fieldbusses are, in contrast, better suited. 
     At present, in the case of fieldbusses, no method for data transmission is known, which is capable of meeting both requirements. 
     SUMMARY OF THE INVENTION 
     An object of the invention is, therefore, to provide a method for data transmission via a fieldbus of process automation technology, which is suited both for control tasks and also for monitoring tasks. 
     This object is achieved by a method which comprises the steps of:
         a method for transmitting data via a fieldbus of process automation technology, comprising the steps of:   providing a field device in which a first application program runs for a first fieldbus protocol, which exchanges data with the fieldbus according to the first fieldbus protocol in fieldbus telegrams via a fieldbus interface of the field device; and   providing a second application program in the field device for a second transmission protocol, protocol data of which are mapped onto the first fieldbus protocol and transmitted as fieldbus telegrams.       

     An essential idea of the invention is to map the protocol data of a second transmission protocol onto the fieldbus protocol, so that such can then be transmitted via the fieldbus. 
     In a simple manner of putting the invention into practice, the data field in the frame of the fieldbus telegram contains a frame of a second transmission protocol. 
     In order to be able to distribute the data in the field device application-specifically, there is provided in the field device a distributor module, which analyzes the incoming fieldbus telegrams and forwards them, depending on their content, to the appropriate application or applications. 
     In the case of the fieldbus system, such is, for example, a Profibus®, or a Foundation Fieldbus®, system. 
     Advantageously, the second transmission protocol corresponds to the wide spread TCP/IP-standard. 
     In a simple manner, a Web-server can, in this way, be implemented in the field device. 
     In order to enable communication with the telecommunication networks present worldwide, a packaging gateway is provided, which maps the protocol data of the second transmission protocol into the fieldbus protocol, or, as the case may be, unpacks such in the opposite direction. 
     An essential advantage of the invention resides in the fact that, for the querying and configuring of field devices, special tools are no longer necessary. Access is possible by means of standard browsers (Netscape Navigator®, Internet Explorer®). At the same time, the advantages of conventional fieldbusses can continue to be used in the method of the invention. 
     For the parametering and configuring of field devices, various tools are available. A suitable tool is e.g. the configuring and parametering program CommunWin 2 of the firm Endress+Hauser. The functionality of the field devices to be operated is made known in these operating tools with the help of so-called device descriptions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in greater detail on the basis of an example of an embodiment illustrated in the drawing, the figures of which show as follows: 
         FIG. 1  hardware-software-structure of a field device of the invention; 
         FIG. 2  network with operating device and a plurality of field devices in schematic presentation; and 
         FIG. 3  structure of a fieldbus frame. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 2  shows an operating device B connected via a plurality of networks with various field devices F 1 , F 2 , F 3  and F 4 . Serving as a first network connection between the operating device B and a converter unit U is a conventional communication connection T. This communication connection T can be a WAN Wide-Area-Network (Internet), LAN Local-Area-Network (intranet), or a direct Internet protocol connection. This connection is provided via the known services GSM, UMTS, PSTN, ISDN, Ethernet, etc. 
     Emanating from the converter unit U are two fieldbusses A and B leading to the field level, with three field devices F 1 , F 2 , F 3  in the one case and a field device F 4  in the other. Additionally connected to fieldbus A is a control unit S (e.g. a programmable logic controller PLC). The field devices F 1 , F 2 , F 3  communicate via fieldbus A with the control unit S, which evaluates the measured values of the individual field devices and appropriately actuates actuators (not shown). 
       FIG. 1  shows the hardware-software-structure of a field device (F 1 , F 2 , F 4 ) of the invention on the basis of the field device F 1  selected by way of example. (Field device F 3  is a conventional field device.) Field device F 1  is connected with fieldbus A via a fieldbus interface FS. A distributor module VM, which is connected after the fieldbus interface FS, distributes protocol data P 1  and P 2  either to the communication stack ST 1  or ST 2 , as the case may be. Connected after the two stacks ST 1  and ST 2  are the respective applications A 1  and A 2 . Application A 1  is connected to a measurement pickup interface MS. Between the applications A 1  and A 2 , a data exchange is possible. Conventional field devices, such as the field device F 3 , have only the fieldbus interface FS, the communication stack ST 1  and the fieldbus application A 1 , as well as the measurement pickup MS. 
       FIG. 3  shows a fieldbus frame FR 1  with a normal data field, or with a frame of another transmission protocol. By way of example, a Profibus frame is shown, which contains a TCP/IP frame. The Profibus frame FR 1  is composed of a plurality of data fields: SD 3  Start Delimiter; DA Destination Address; SA Source Address; FC Function Code; Data; FCS Frame Check-Sum; and the End Delimiter ED. The data field Data can contain e.g. normal measured values, or also a TCP/IP frame with the corresponding data. 
     The functioning of the invention will now be explained in further detail. 
     The fieldbus application A 1  can communicate in the usual way with the control unit S via the fieldbus A. The data provided from the fieldbus application A 1  are packaged with the help of the fieldbus stack ST 1  and issued onto the fieldbus A via the distributor module VM and the fieldbus interface FS. The distributor module VM forwards the fieldbus frame FR 1 , which contains normal fieldbus data, to the fieldbus interface FS without change. Incoming telegrams are analyzed in the distributor module as to whether fieldbus data P 1  or protocol data P 2  of another, second transmission protocol are contained in the data field. In the one case, the protocol data are forwarded to the fieldbus stack ST 1 , in the other case to the communication stack ST 2 . The data then go either to the fieldbus application A 1  or to the application A 2 . The application A 2  can include e.g. a Web-server, or an OPC-server. Of course, field devices can exchange data corresponding to the first or second protocol. Thus, corresponding applications in the respective field devices can communicate very easily with one another. 
     The functioning of the converter unit U will now be described in greater detail. The converter unit U, which serves as a packaging gateway, packages the TCP/IP protocol data into the fieldbus protocol and forwards such to the appropriate fieldbus A or B, as the case may be. Correspondingly, fieldbus telegrams from the fieldbus are unpacked and forwarded as TCP/IP telegrams to the corresponding communication connection T. The converter unit U can be connected with one or more fieldbusses, which work, especially, also on the basis of different protocols. Equally, one or more different networks working on the basis of the second transmission protocol can be connected to the converter unit U. 
     With the operating device B, therefore, a simple access to the desired field devices is possible. Via a Web-browser, the field devices F 1 , F 2  or F 4 , as the case may be, can be configured and parametered from the operating device B. A significant advantage of the invention is that the operating device B can directly access HTML-pages stored in the field devices F 1 , F 2  or F 4 , as the case may be. The operating device B requires no special device description of the field device which is to be operated. 
     With the help of the present invention, it is possible to install TCP/IP applications in field devices, without having to make changes in the existing fieldbus. Field devices without TCP/IP applications and field devices with TCP/IP applications work independently of one another. A significant advantage of the invention is that TCP/IP applications can communicate over a two-wire connection with a widely removed operating device. Such field devices can also be used simply in explosion-endangered areas (EX-areas). 
     The converter unit can also serve as firewall and provide various services for the field devices F 1 , F 2 , F 4  on the basis of the second transmission protocol. 
     Additionally, the converter unit can also serve as router between the various connected networks.