Glossary
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
Manual, 09/2008, A5E02191071-01
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S7–300 backplane bus
The S7 300 backplane bus for module intercommunication, and power distribution to the
modules.
Software
Software refers to the entirety of all programs that are used on a computing system. The
operating system and user programs belong to this.
Startup
The START-UP operating mode forms the transition from STOP mode to RUN mode.
STEP 7
STEP 7 is the programming software of SIMATIC S7.
System blocks
System blocks are different from other blocks in that they are already integrated into the S7–
300 system and are available for already defined system functions. There are system data
blocks, system functions and system function blocks.
System function blocks (SFBs)
System functions are blocks without memory that are already integrated into the operating
system of the CPU and can be called up by the user whenever necessary.
System functions (SFCs)
System functions are blocks without memory that are already integrated into the operating
system of the CPU and can be called up by the user whenever necessary.
User program
The user program contains all instructions and declarations for processing the signals used
for controlling a system or a process. In SIMATIC S7 the user program is structured and
divided into small units, the blocks.
Variable
A variable is an operand (e.g. I 1.0) which can have a symbolic name and therefore also be
addressed symbolically.
Working memory
The working memory is a RAM storage unit in the CPU which the processor draws on when
running the user program.
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