Tech Tip: How PROFIBUS PA Profiles Work

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Profile 3.0.2 defines the rules for PROFIBUS for Process Automation (PA). How can you use Profiles to your benefit in the Process Industry competition?

Profiles were created to define properties and behaviors as an abstraction layer for devices, device families, or entire systems. Using Profiles gives the PROFIBUS or PROFINET devices a common framework for operation.

PA Profile 3.0.2 has some features within it that were put there to give the power of flexibility to the customer. Unfortunately, these very user oriented features are not often talked about. PA Profile mode can allow us to make instruments generic. By using PA PROFIBUS_PA_ProfilesProfile mode a device can be replaced by a similar type device from an entirely different manufacturer.

General Station Description files (GSD), are files that describe all the features of the device so that the PLC/DCS configuration tool can set up communication between the PROFIBUS master and the slave devices. GSDs describe the features of the instrument such as baud rates supported, parameters that the device uses to determine how it should work, and possible I/O configurations that the user can specify. The essential difference for the user between Profile mode and Manufacturer’s mode is which GSD file the user chooses to represent their device in the PLC or DCS configuration.

PA Instrument Manufacturer mode GSD files describe the way a PROFIBUS Master (PLC or DCS) can communicate with the slave device using the data exchange cycle. Each GSD file is specific to the manufacturer’s particular instrument. Using the manufacturer’s GSD, the master can do data exchange with this slave from this manufacturer only.

PA Profile GSDs are generic files, defined by PROFIBUS and PROFINET International. They are available to be downloaded from the web at PA Profile GSDs describe the type of I/O the instrument supports rather than the device itself. For example, single input temperature transmitters can be accessed with the Transmitter Profile Transmitter 1 Analog In (4 bytes of analog input + 1 byte quality data). Actuators, Discrete Inputs, Discrete Outputs, Flow Transmitters, Analyzers and Multi-Variable Transmitters are defined as PA profiles as well.

The value of using Profile mode GSDs can be seen in operation when a failing device needs to be replaced. If the Master system was configured to communicate with the slave using the Manufacturer’s mode GSD, the failed unit must be replaced with the same type of unit, from the same manufacturer. If the Master was configured using the Profile GSD, the failed device can be replaced by a similar type device from an entirely different manufacturer. This gives the customer the ability to do a quick replacement with something they have in their parts locker, rather than waiting for a spare to be shipped to their site from the original vendor.

0ecc72bIf you have questions about using or implementing PA profiles, the fastest way to get up to speed is to contact us here at the PROFI Interface Center or a global PI Competence Center.

–John Swindall, PROFI Interface Center