Siemens SIMATIC ET 200S Manual page 588

Glossary
Programmable controller
A programmable controller is a programmable logic controller consisting of at least
one CPU, various input and output modules, and operator interfaces.
Provider-Consumer principle
On the PROFINET I/O, unlike PROFIBUS DP, both partners are independent
providers in the transmission of data.
Real time
Real time means that a system processes external events in a defined time.
Determinism means that a system responds predictably (deterministic).
Both requirements are important in industrial networks. PROFINET meets these
requirements. PROFINET is therefore designed as a deterministic real-time
network as follows:
• Transmission of time-critical data between different stations over a network in a
defined time interval is guaranteed.
PROFINET offers an optimized communication channel for real-time
communication: Real Time (RT).
• The time of transmission can be determined exactly (prediction).
• It ensures that smooth communications can take place in the same network via
other standard protocols, such as industrial communication for PC/programming
device.
Reference potential
Potential from which the voltages of the circuits involved can be observed and/or
measured.
Reversing starter
A reversing starter is a → motor starter that determines the direction of rotation of
a motor. It consists of a circuit breaker and two contactors.
Segment
The bus line between two terminating resistors forms a segment. A segment
contains 0 to 32 → bus nodes. Segments can be interconnected by means of
RS 485 repeaters.
SELV
Protective Extra Low Voltage = safe low voltage
Glossary-8
ET 200S Distributed I/O System
EWA-4NEB 780602402-12