Siemens Simatic S7-300 CPU 31xC Series Installation And Operating Instructions Manual page 255

Operating system
See CPU
The CPU OS organizes all functions and processes of the CPU which are not associated to
a specific control task.
Organization blocks
Organization blocks (OBs) form the interface between CPU operating system and the user
program. OBs determine the sequence for user program execution.
Parameters
1. Variable of a STEP 7 code block
2. Variable for declaring module response (one or several per module). All modules have a
suitable basic factory setting which can be customized in STEP 7.
There are static and dynamic parameters
Parameters, dynamic
Unlike static parameters, you can change dynamic module parameters during runtime by
calling an SFC in the user program, e.g. limit values of an analog signal input module.
Parameters, static
Unlike dynamic parameters, static parameters of modules cannot be changed by the user
program. You can only modify these parameters by editing your configuration in STEP 7, for
example, modification of the input delay parameters of a digital signal input module.
PC station
See SIMATIC PC Station
PG
See Programming device
PLC
See CPU
See PLC
Programmable controllers (PLCs) are electronic controllers whose function is saved as a
program in the control unit. Therefore, the configuration and wiring of the unit does not
dependen on the PLC function. A programmable logic controller has the structure of a
computer; it consists of a CPU with memory, input/output modules and an internal bus
system. The I/O and the programming language are oriented to control engineering needs.
A PLC in the context of SIMATIC S7 is a programmable logic controller.
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
Glossary
Glossary-13