Industrielle styresystemer - Wiki
The design of the technology modules with PROFIBUS is oriented toward the OSI layer model (Open Systems Interconnection Reference Model). Here, the communication process between two nodes is distributed over seven "layers", from layer 1 ("physical layer", trans-mission technology) to layer
7 (“application layer”, interface to the application). PROFIBUS uses layers 1, 2 and 7.
References between OSI model and PROFIBUS. The figure shows the definition of the seven OSI layers on the left and the implementation of PROFIBUS on the right.
The actual application process lies above layer 7 and is not part of the OSI model.