Siemens Simatic S7-300 Technical Data Manual page 224

Glossary
Chassis ground is the totality of all the interconnected passive parts of a piece of equipment
on which dangerous fault-voltage cannot occur.
GSD file
The properties of a PROFINET device are described in a GSD file (General Station
Description) that contains all the information required for configuration.
Just as in PROFIBUS, you can integrate a PROFINET device in STEP 7 using a GSD file.
In PROFINET IO, the GSD file is in XML format. The structure of the GSD file complies with
ISO 15734, the worldwide standard for device descriptions.
In PROFIBUS, the GSD file is in ASCII format.
Hub
In contrast to a switch, a hub sets itself to the lowest speed at the ports and forwards the
signals to all connected devices. A hub is also not capable of giving priority to signals. This
would lead to a high communication load on Industrial Ethernet.
See Switch
Industrial Ethernet
Industrial Ethernet (formerly SINEC H1) is a technology that allows data to be transmitted
free of interference in an industrial environment.
Due to the openness of PROFINET, you can use standard Ethernet components. We
recommend, however, that you install PROFINET as Industrial Ethernet.
See Fast Ethernet
Instance data block
The STEP 7 user program assigns an automatically generated DB to every call of a function
block. The instance data block stores the values of inputs / outputs and in/out parameters, as
well as local block data.
Interface, MPI-capable
See MPI
Interrupt
The CPU's operating system knows 10 different priority classes for controlling user program
execution. These priority classes include interrupts, e.g. process interrupts. When an
interrupt is triggered, the operating system automatically calls an assigned OB. In this OB
the user can program the desired response (e.g. in an FB).
Interrupt, cyclic interrupt
A cyclic interrupt is generated periodically by the CPU in a configurable time pattern. A
corresponding OB will be processed.
Glossary-8
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05