GSDML Getting Started
Simple Instructions for Creating a Device Description Data (GSD) File for PROFINET Page 5/48
2 Introduction
The GSD for Profibus field devices (Status 2005) has now a history of more than ten years. The
original designation "Device Description Data" has in the meantime been internationalized to "Generic
Station Description". However, the new name can’t obscure the fact that some GSD rules are no
longer up to date.
The GSD allows for a textual description of some attributes of a Profibus field device (electronic data
sheet). However, the hierarchical structure of a field device was only shown one-dimensional –in the
form of a list. On the one hand, this provides for a clear representation of the key words included
there, but also requires a (mental) conversion step for mapping the key words to the device model. .
In comparison to the PROFIBUS model, the PROFINET IO device model has an additional hierarchy
level when addressing the I/O data -that of the submodules- since a "level“ description of these field
devices would lead to an additional complexity regarding the mapping.
By introducing the GSDML (General Station Description Markup Language), the feature of XML based
documents to generate any hierarchical levels was used to map the hierarchical device model as
unchanged as possible.
The result is a description language that is able to describe over several levels the attributes of a
device family. When the XML schematics representation was generated, the attempt was made to
include as much as possible of the GSD semantics, but to also, where it was advisable and
necessary, to redesign the mapping.
Note on Terminology
GSDML is one language to describe PROFINET IO field devices. By using this language, a GSD
(General Station Description) is generated in turn. For that reason, it is correct to refer to a "GSD file"
although it is structured in XML notation.
When the term "GSD" or "GSD file" is used in this document, it always refers to the form based on the
XML If the keyword-based GSD is referred to, it will be mentioned explicitly.
2.1 What is New
Compared with the keyword-based GSD, the following are essential changes regarding the XML-
based GSD, in addition to the syntactical change because of XML:
The "Device Access Point" (DAP) is described explicitly for the GSDML. For the GSD on the
other hand, only the DP slave is described as a whole. The result of adding the DAPs is that
almost all parameters of the device are described at the DAP element.
A GSDML document can contain any number of DAP definitions. This allows for generating a
file for a device family (and not only for individual field devices). The advantage is obvious,
particularly to field devices that have a modular configuration. The description of the modules
can be maintained centrally in one GSD file – the generation and update effort is clearly
reduced in comparison to a keyword-based GSD since there, the module descriptions are
present redundantly and have to be kept identical in the different files 'manually’.
A GSDML document can maintain any number of foreign language texts in one file. This leads
to a further reduction of the number of required files since in the keyword-based GSD, a
separate file is required for each language.
Add to this the capabilities that result in using the XML standard: validation of XML files by means of
schematic description and transformation into other formats by means of XLS.
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