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messer · Senior Joined: 08 Mar 2012 Posts: 2059 Location: Europe

For Profibus DP a set of communication services is defined in IEC 61158-5 [1].
The representation of these services in the application program is dependent of the various controllers and devices provided by different manufactures.
State of the art for the programming tip and programming languages in the area of the programmable controllers (PLC) is the international standard IEC 61131-3 [2].
This standard defines a set of language elements and mechanisms
(e.g. data types, function blocks) which are commonly applied in a well defined set of programming languages (e.g. Ladder Diagram, Structured Text).
Note: The IEC 61131-3 Standard is currently in a revision phase and the updated 2nd Edition of IEC 61131-3 is expected to be finally issued in 2001.
Since the vendors of PLCs and corresponding programming
tools will need a certain time to implement the new features of the 2nd edition of the IEC Standard this PNO specification restricts the required language features to the content of the 1st Edition of
IEC 61131-3.
The application of this specification can provide benefits for the following three
groups:
End users
want to implement applications (of programming and devices) using predefined
solutions and having a wide choice and independent mixture of various PLCs
and field devices (FD) on Profibus.
PLC manufacturers
want to offer the PLC series with a wide choice of field devices (FD) from various
manufactures.
Field device manufacturers
wants to have applied his FD easily with a wide choice of minimise the effort to
use these FD with different PLCs.
This specification has two parts:
The main part of this specification contains the definitions of a set of Communication
Function Blocks (Comm FB) for the Profibus DP communication using the
IEC 61131-3 programming language standard and the standard Profibus DP services.
This set of Comm FB shall be provided by the manufacturers of PLC and
intelligent field device for their IEC 61131 programmable controllers.
The second part of this specification presents informative "Guidelines for the application
of Communication Function blocks". The "Guidelines" should be applied
by field device manufactures to implement specific "Proxy Function Blocks" for
the integration of their field devices (e.g. weigh control, valve control) in the program
of the DP-Master. These Proxy FB can be offered to the IEC 61131 application
programmers.
http://www.pacontrol.com/download/PROFIBUS_Communication.pdf