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Every class 1 master and all field devices with slave functionality that conform to the standard must be described by the manufacturer by means of a GSD file. The GSD file is a master file containing device data.  GSD stands for 'general station description'.


Project planning tools for the PROFIBUS-DP master to be included in the project interpret the content of slave GSD files and generate from it a master parameter set for the class 1 master that will be in charge of payload traffic.


A class 1 master uses information from the GSD files of connected slaves to determine the expansion level of the bus, which services are supported by the slave in question, and the form in which data is exchanged.


GSD files are required for project planning and commissioning. Every manufacturer of a PROFIBUS-DP class 1 master provides a project planning tool for the class 1 master that knows the internal data structure of both the class 1 master and the host system. When making the project, the necessary GSD files must be made known to the project planning tool. This usually takes place when the GSD files are copied onto the PC's hard disk. (A precise path indication can be obtained from the description of the project planning tool). When planning a system project, the project planning tool interprets GSD file data for the chosen field device. Plausibility checks are also carried out at this early stage to ensure that project planning data has the correct logical construction.


A GSD file may be present either once, as when its construction is language-neutral (*.gsd) or several times, as when it has been written in a particular local language. In this case, a separate GSD file should be used for each language and they should only differ from each other in their visible-string type parameters. Language-related GSD files differ in the last letter of their extensions (*.gs?).


Default (language-neutral): ?=d

German ?=g

English ?=e

French ?=f

Italian ?=i

Portuguese ?=p

Spanish ?=s


The following rules apply for GSD-file names:




signifying the following:

Abc_ =company identifier (here company Abc_), always 4 characters
0008 =Ident number 0008 assigned by the PNO , always 4 characters in hexadecimal
.gsd =default. Language-neutral GSD(E) file


The properties of a devices are described with key words and values.


For historical reasons, there are different revisions of GSD syntax with an increasing number of key words. The latest version today is (2017) Version 5. The first key word therefore indicates the version of the GSD file:


GSD_Revision = 1


Vendor_Name= "Company_ABC & Co"

Model_Name= "Modular I/O Station"

Revision= "Version 01"


The manufacturer's name, model name and revision of the device are limited to 32 characters as a visible string.


Revision_Number= 05


Version identifier for the DP device. The revision number here must match the revision number in the slave-specific diagnosis.




The ident number identifies the type of DP device. Every field device is characterized by an ident number allocated to it by PROFIBUS International. It creates a unique reference to the GSD file and therefore to the technical data of that field device. Variants of field devices, which can be described with a GSD file, can use the same ident number (for example modular devices). It is only possible to exchange data with a field device if the DP master identifies the DP slave uniquely with the ident number during system start-up (parameter setting telegram).


An ident number may be ordered from PROFIBUS International. It is also possible to view here a list of currently used ident numbers.


Protocol_Ident= 0   ;PROFIBUS-DP device


Protocol used by DP device.


16 to 255: vendor-specific


Station_Type= 0   ;PROFIBUS-DP Slave


DP device type

0: DP slave,

1: DP master (class 1)


Further information about key words may be found in the appropriate chapters:

Address changes for a DP slave

Configuration  of a DP slave

Setting the parameters of a DP slave

Isochronous data cycle

SYNC and FREEZE commands

Alarm handling


A list of GSD key words mentioned in this manual may also be found in the index.