Siemens SIMATIC ET 200AL, System Manual

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Glossary
Communication
Function Manual, 05/2021, A5E03735815-AJ
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Point-to-point connection
Bidirectional data exchange via communications modules with a serial interface between two
communications partners (and two only).
Port
Physical connector to connect devices to PROFINET. PROFINET interfaces have one or more
ports.
Primary CPU
If the R/H system is in RUN-Redundant system state, the primary CPU controls the process.
The backup CPU processes the user program synchronously and can take over process control
if the primary CPU fails.
Process image (I/O)
The CPU transfers the values from the input and output modules to this memory area. At the
start of the cyclic program, the CPU transfers the process image output as a signal state to the
output modules. The CPU then reads the signal states of the input modules into the process
image input. The CPU then executes the user program.
PROFIBUS
Pro cess Fi eld Bus - European Fieldbus standard.
PROFIBUS address
Unique identifier of a device connected to PROFIBUS. The PROFIBUS address is sent in the
frame to address a device.
PROFIBUS device
Device with at least one PROFIBUS interface either electrical (for example RS-485) or optical
(for example Polymer Optical Fiber).
PROFIBUS user organization
Technical committee dedicated to the definition and development of the PROFIBUS and
PROFINET standard.
PROFIBUS DP
A PROFIBUS with DP protocol that complies with EN 50170. DP stands for distributed I/O =
fast, real-time capable, cyclic data exchange. From the perspective of the user program, the
distributed I/O is addressed in exactly the same way as the centralized IO.