Glossary
S7-300, CPU 31xC and CPU 31x: Installation
Glossary-14
Operating Instructions, Edition 08/2004, A5E00105492-05
PNO
See PROFIBUS International
Priority class
The S7 CPU operating system provides up to 26 priority classes (or "Program execution
levels"). Specific OBs are assigned to these classes. The priority classes determine which
OBs interrupt other OBs. Multiple OBs of the same priority class do not interrupt each other.
In this case, they are executed sequentially.
Process image
The process image is part of CPU system memory. At the start of cyclic program execution,
the signal states at the input modules are written to the process image of the inputs. At the
end of cyclic program execution, the signal status of the process image of the outputs is
transferred to the output modules.
Process interrupt
A process interrupt is triggered by interrupt-triggering modules as a result of a specific event
in the process. The process interrupt is reported to the CPU. The assigned organization
block will be processed according to interrupt priority.
Process-Related Function
See PROFINET Component
Product version
The product version identifies differences between products which have the same order
number. The product version is incremented when forward-compatible functions are
enhanced, after production-related modifications (use of new parts/components) and for bug
fixes.
PROFIBUS
See PROFIBUS DP
See PROFIBUS International
Process Field Bus - European fieldbus standard.
PROFIBUS DP
See PROFIBUS
See PROFIBUS International
A PROFIBUS with the DP protocol that complies with EN 500170. DP stands for distributed
peripheral I/O (fast, real-time, cyclic data exchange). From the perspective of the user
program, the distributed I/O is addressed in exactly the same way as the central I/O.