Siemens SIMATIC Manual page 634

Glossary
Organization block
OBs form the interface between the CPU operating system and the user program. The
sequential order of user program execution is defined in the organization blocks.
Parameters
1. Tag of a → Code block
2. Tag used to set one or several properties of a module. Each module is supplied with
default parameters which users may edit in
PG
→ Programming device
Process image
The CPU saves the signal states of analog IO modules to a process image.
We distinguish between the process image of inputs (PII) and outputs (PIO). The input
modules read the process image of inputs (PII) before the operating system executes the
user program. The operating system transfers the process image of outputs (PIO) to the
output modules at the end of program execution.
Product version
Differentiates products of the same order number. The product version is incremented in the
case of upwards compatible enhancements of functionality, production-specific changes (use
of new components/parts), and fixes.
Programming device
A programming device (PG) is a special compact PC (Personal Computer) suitable for use in
industry. A PG is fully equipped for programming SIMATIC automation systems.
Reference junction
When operating thermocouples on analog input modules: point of known temperature
(for example, → compensating box.)
Reference potential
Potential from which the voltages of participating circuits are derived and measured.
Repeat accuracy
Denotes the maximum deviation between measured/output values, if the same input or
output signal is repeatedly set. Repeat accuracy refers to the rated range of the module, and
applies to its settled temperature state.
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STEP 7 .
Manual, 06/2017, A5E00105505-AJ
S7-300 Module data