Siemens SIMATIC S7-400 Hardware And Installation Manual page 280

Glossary
GD Element A GD element is created through assigning the global data to be
exchanged and is clearly identified in the global data table by the GD
identifier.
GD Packet A GD packet can consist of one or more GD elements which are
transmitted together in a message frame.
Global Data Global data are data which can be accessed from each logic block (FC,
FB, OB). These include bit memory M, inputs I, outputs Q, timers T,
counters C, and data blocks DB. Global data can be accessed either
absolutely or symbolically.
Global Data Global data communication is a procedure with which global data are
Communication transferred between CPUs (without communication function blocks
(CFBs)).
Ground The conductive mass of the ground whose potential can be assumed to
be zero at any point.
In the vicinity of ground electrodes, the ground may have a potential
other than zero. The term "reference ground" is often used in this
situation.
Ground (verb) To ground means connecting an electrically conductive part via a
grounding system to ground (one or more electrically conductive parts
that have good contact with the soil).
H
Hardware The hardware is understood to be the entire physical and technical
equipment of a programmable controller.
Hardware Interrupt Interrupt-triggering modules trigger a hardware interrupt in the case of
a certain event in the process. The hardware interrupt is signalled to
the CPU. In accordance with the priority of this interrupt, the
corresponding organization block is then executed.
Glossary-6
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S7-400 and M7-400 Programmable Controllers, Installation Manual
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