Glossary-2
Primer: S7-300 Programmable Controller, Quick Start
C79000-G7076-C500-01
C
The CPU is the central module in the programmable controller consisting of
a control unit, arithmetic unit, memory, operating system, and interfaces to
the signal modules and function modules.
When a CPU starts up (for example, when the mode selector is moved from
STOP to RUN or when power is turned on), before cyclic program processing
starts (OB1), either the organization block OB101 (restart; only in the
S7-400) or OB100 (complete restart) is processed first. In a complete restart
the process-image input table is read in and the STEP 7 user program
processed starting with the first statement in OB1.
F
According to the International Electrotechnical Commission’s IEC 1131–3
standard, functions are logic blocks without static data. A function allows
you to pass parameters in the user program, which means they are suitable
for programming complex functions that are required frequently, for
example, calculations.
I
An instruction is part of a STEP 7 statement and specifies what the processor
should do.
L
In SIMATIC S7, a logic block is a block that contains part of the STEP 7 user
program. The other type of block is a data block which contains only data.
The following list shows the types of logic blocks:
S Organization block (OB)
S Function block (FB)
S Function (FC)
S System function block (SFB)
S System function (SFC)
Central Processing
Unit (CPU)
Complete Restart
Function (FC)
Instruction
Logic Block
Glossary
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