Siemens S7-400 Installation Manual page 299

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 Communication
Global data communication is a procedure with which global data are 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.
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
Glossary
Glossary-7