| Integration of INTERBUS Into Profinet IO |
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Due to its technical properties and the support of numerous automation suppliers, Profinet IO is set to become the global communication standard for realtime Ethernet. The decision of the Automatisierungs-Initiative Deutscher Automobilhersteller (AIDA, Automation Initiative for German Automotive Manufacturers) to use Profinet with integrated operator safety features wherever this provides technical and commercial benefits for a specific application will also contribute to the further acceptance of the system across many sectors. However, for reasons of investment protection, the introduction of Profinet IO in automation solutions is likely to be a gradual process. It is therefore important that existing INTERBUS systems can be integrated effectively into the Ethernet protocol. The Profinet IO system could also be called "Ethernet as a fieldbus" because the user sees the fieldbus devices in the same way as in conventional fieldbus systems. The use of Profinet IO provides access to the following advantages of the Ethernet communication system:
These advantages must be balanced against the following INTERBUS system functions, which are popular with users but are not yet provided by Profinet IO:
The combination of INTERBUS and Profinet IO offers all of the listed advantages in one automation solution. It also protects investments in INTERBUS products and solutions, and creates a future-proof migration path from fieldbus-based to Ethernet-based communication. However, the entire solution must be seamless and consistent without losing any of the key properties of the individual systems. A special device, the proxy, has therefore been developed to provide the network transition between INTERBUS and Profinet IO.
The Profinet IO Device Model The Profinet IO device model helps users to understand the various concepts involved in the integration of INTERBUS into Profinet IO. The model describes how the functions of an actual field device are viewed by Profinet IO. This view must be the same for all field devices in a network to enable communication regardless of the manufacturer or device type.
In the Profinet IO system, every field device is represented as an IO device. This type of device does not necessarily correspond to the physical component: for example, one field device can contain several logical IO devices. The IO device in turn defines slots in which modules can be integrated, which comprise at least one submodule that represents the actual functions. The Profinet IO network provides the following services:
Members of the INTERBUS Club and members of the "INTERBUS Integration" working group of the Profibus User Organization have used the device model to develop various concepts for the optimal mapping of the INTERBUS system in Profinet IO.
Integration Concepts
Following consideration of the advantages and disadvantages of the various integration models, the first step is to work on the specification of the modular concept. Modular Integration
Slot 1 of the Profinet IO device model is reserved for the INTERBUS master. The cyclic process data channel, which is used for status messages and control registers, can be used to request the status of the INTERBUS system and to execute a special action such as connecting and disconnecting devices. All events, which do not affect a specific slot, such as general parameterization errors, are mapped to the channel diagnostics of slot 1. Every diagnostic event is sent to the control system using a corresponding diagnostic alarm. All INTERBUS slaves connected to the master use slots 2 and above. The order of the slots must correspond to the structure of the INTERBUS system. Empty slots are not permitted. The cyclic process data of a slot is assigned directly to the input and output data of the individual INTERBUS slaves, while the Profinet IO parameters are used for setting device-specific data (e.g., ID code or process data length) and for mapping device-specific PCP parameters. A key feature of the INTERBUS system is its excellent diagnostic properties. All diagnostic messages are therefore available as Profinet IO channel diagnostics and sent to the control system using diagnostic alarms. The control system then displays the diagnostic event in plain text.
Configuration Aspects Profinet IO devices are described in GSDML (Generic Station Description Markup Language), which is a further development of GSD (Generic Station Description) used in the Profibus system. The file must include the slots of an IO device as well as all the modules, which can be integrated in the slots. Since the slaves of the INTERBUS system are mapped to the modules of the IO device during fieldbus integration, the GSDML file for the proxy should also include all INTERBUS devices available on the market. This is neither practical nor useful. Instead, the file contains universal modules with INTERBUS parameters that can be set by the user. In addition, modules from the FDCML files for INTERBUS slaves can be inserted in the GSDML file for the proxy. FDCML (Field Device Configuration Markup Language) used for the INTERBUS system is also based on XML technology, is multilingual, and has comprehensive description options for INTERBUS devices.
The GSDML file for the proxy enables the user to set up the INTERBUS system in any programming software using the Profinet IO configurator, by simply inserting the modules into slots 2 and above according to the bus configuration. In PC Worx automation software from Phoenix Contact, INTERBUS is configured directly via FDCML files. GSDML files are not required. The INTERBUS system is parameterized during control system startup. Separate configuration in an additional software tool is no longer required, which makes startup much easier.
Summary The modular integration of INTERBUS into Profinet IO offers the user the option of combining the specific advantages of both systems to form a single seamless solution that is tailored to the relevant application. Key features of the concept include minimal runtime losses, the use of standard software for configuration, and the direct configuration of the INTERBUS system in the control system. In addition, the comprehensive diagnostic properties of the fieldbus system can be integrated easily into the world of Profinet IO.
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