Glossary
Glossary-17
S7-400 and M7-400 Programmable Controllers Hardware and Installation
A5E00069481-04
User Memory
The user memory contains logic blocks and data blocks of the user program. The
user memory can either be intergrated in the CPU or can be plugged in on memory
card or memory submodules. In general, however, the user program is executed
from the work memory (RAM) of the CPU.
User Program
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
Varistor
Voltage-dependent resistor
W
Warm Restart
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.
Work Memory
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.
