Siemens SIMATIC S7-300 Hardware And Installation Manual page 237

User Program
The SIMATIC system distinguishes between the --> CPU operating system and
user programs. The latter are created with --> -->STEP 7 programming software,
using optional programming languages (LAD and STL). User programs are stored
in code blocks. data is stored in data blocks.
User memory
User memory contains --> code and --> data blocks of the user program. The user
memory can be integrated in the CPU or can be provided on plug-in memory cards
or memory modules. However, user programs are always executed from --> CPU
main memory.
Main Memory
Working memory is a RAM memory in the --> CPU accessed by the processor
during user program execution.
Automation system
An automation system in the context of SIMATIC S7 --> is a programmable logic
controller.
back-up Memory
The back-up memory provides a back-up of memory areas for the --> CPU without
a back-up battery. It backs up a configurable number of timers, counters, memory
bits, data bytes and retentive timers, counters, memory bits and data bytes).
Transmission rate
Rate of data transfer (bps)
Module Parameters
Module parameters are values which can be used to control the response of the
module. A distinction is made between static and dynamic module parameters.
CPU operating system
The operating system of the CPU organizes all functions and processes of the
CPU which are not associated with a special control task.
Operating mode
SIMATIC S7 PLC operating modes are: STOP, --> START-UP, RUN.
S7-300 Programmable Controller Hardware and Installation
A5E00105492-02
Glossary
13-3