Siemens SIMATIC ET 200S Operating Instructions Manual page 158

Glossary
PROFINET device
A PROFINET device always has at least one Industrial Ethernet connection. In addition, a
PROFINET device can also have a PROFIBUS connection and even act as a master with
proxy functionality. In exceptions, a PROFINET device can also have a several PROFIBUS
connections (for example CP 5614).
Provider-consumer principle
In a PROFINET IO both partners are independent providers in sending data, in contrast to
PROFIBUS DP.
Real time
Real time means that a system processes external events within a defined time.
Determinism means that a system responds in a predictable (deterministic) manner.
Both requirements are important for industrial networks. PROFINET satisfies these
requirements. Thus, as a deterministic real-time network, PROFINET is designed as follows:
● The transfer of time-critical data between different stations via a network is guaranteed
● To this end, PROFINET has an optimized communication channel for real-time
● The time of transfer can be accurately determined.
● It is ensured that seamless communication can take place in the same network by means
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 coupled via RS 485 repeaters.
SELV
Safety Extra Low Voltage
158
within a defined interval of time.
communication: real time (RT): Real time (RT).
of other standard protocols, such as industrial communication for programming
device/PC.
Operating Instructions, 08/2008, A5E00515771-06
ET 200S