Siemens Simatic S7-300, Hardware And Installation Manual, Page: 225 / 242

Glossary
S7-300 Programmable Controller Hardware and Installation
A5E00105492-01
12-5
External power supply
Power supply for the signal and function modules and the I/O connected to them.
FB
--> Function Block
FC
--> Function
Flash EPROM
FEPROMs are the same as electrically erasable EEPROMS in that they can retain
data in the event of a power failure, but they can be erased much more quickly
(FEPROM = Flash Erasable Programmable Read Only Memory). They are used on
--> Memory Cards.
Force
The "Force" function overwrites a variable (e.g. memory bit, output) with a value
defined by the S7 user. At the same time, this variable is write protected, thus
preventing modification by any other operation (including from the STEP 7 user
program). The value is retained after the programming device is disconnected. The
write protection can only be cleared with the "Unforce" function. The value
specified in the user program is then written back to the variable. For example,
during commissioning you can use the "Force" function to set specific outputs to
"ON" state for an indefinite time, even if the user program is not logically linked
(e.g. inputs are not wired).
Function block
According to IEC 1131-3, a function block is a --> code block that contains -->
static data. An FB allows parameters to be passed in the user program. Function
blocks are therefore suitable for programming complex functions, e.g. closed-loop
controls, mode selections, which are repeated frequently.
Functional grounding
Grounding which has the sole purpose of safeguarding the intended function of the
electrical equipment. Functional grounding short-circuits interference voltage which
would otherwise have an impermissible impact on the equipment.
Function
According to IEC 1131-3, a function is a --> code block that contains no --> static
data. A function allows parameters to be passed in the user program. Functions
are therefore suitable for programming complex functions, e.g. calculations, which
are repeated frequently.