Glossary
Glossary-14
S7-400 and M7-400 Programmable Controllers, Installation Manual
C79000-G7076-C424-01
With SIMATIC a difference is made between the operating system of
the CPU and user programs. The latter are generated by means of the
STEP 7 programming software in the possible programming languages
(Ladder Logic, Statement List, Function Block Diagram) and are stored
in logic blocks. Data are stored in data blocks.
V
Voltage-dependent resistor
W
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), OB100 (complete restart) is processed first. In
a warm restart, the process-image input table is read in and the
STEP 7 user program processed starting with the first statement in
OB1.
The work memory is the RAM (Random Access Memory) in the CPU to
which the STEP 7 user program is automatically reloaded from the load
memory. The processor executes the program in the work memory in
RUN mode.
User Program
Varistor
Warm Restart
Work Memory
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