Siemens S7-400PLC Dokumentacja Strona 459

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Glossary
S7-400 Automation System Module Data
Reference Manual, Edition 09/2009, A5E00850736-06
459
A fiber-optic cable is a transmission medium made of glass or plastic fiber. Fiber-optic cables
are insensitive to electromagnetic interference and allow high data transmission rates.
Fiber-optic cable
The "force" function overwrites a variable (for example, memory bit, output) with a value
defined by the user.
At the same time, the variable is write-protected so that the value cannot be modified from
any other location (it cannot, for example, be overwritten by the user program). After
removing the programming device, this value is retained.
The write-protection is canceled only after invoking the "unforce" function, following which
the variable can once again be written with the value set by the user program.
The "force" function can, for example, be used during commissioning to set specific outputs
to the "ON" state for any length of time even if the logic operation in the user program is not
true (due to missing wiring at inputs).
A fiber-optic cable is a transmission medium made of glass or plastic fiber. Fiber-optic cables
are insensitive to electromagnetic interference and allow high data transmission rates.
Floating
In the case of floating I/O modules, the reference potentials of the control and load circuits
are electrically isolated from each other, for example, by optocouplers, relay contacts, or
transformers. The I/O circuits can be connected to a common potential.
FREEZE
Control command, inputs of the → DP slaves are frozen at their current values.
Function
According to IEC 1131-3, a function (FC) is a → logic block without → static data. A function
allows parameter passing in the user program. This makes them suitable for programming
commonly recurring complex functions such as calculations.
Function block
According to IEC 1131-3, a function block (FB) is a → logic block with → static data. An FB
has "memory" so that it is possible to access its parameters (for example outputs) from any
part of the user program.
Functional grounding
Grounding with the sole purpose of ensuring the intended function of the electrical
equipment. Functional grounding, short-circuits interfering voltages that would otherwise
have an unacceptable influence on the equipment.
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