Siemens SIMATIC ET 200AL System Manual page 1995

Glossary
Standard mounting rail
Standardized metal profile to EN 50022.
The standard mounting rail is used for quick snap-on installation of network components,
such as OLM, repeaters, etc.
Subnet
Part of a network whose parameters must be synchronized with the devices
(e.g., with PROFIBUS). A subnet includes the bus components and all connected stations.
SynchronousCycle
Name for synchronous cycle interrupt OB in STEP 7.
Target-Rotation-Time (Ttr)
Bus parameter for PROFIBUS. The token is the send permission for a device on
PROFIBUS. A device compares a token rotation time it has measured with the Target-
Rotation-Time and controls the sending of frames with high priority or low priority based on
this comparison.
Terminating resistor
Component that terminates the ends of a data transmission line to prevent reflections in the
transmission medium.
Terminator
Terminating resistor of bus segments with transmission rates of 9.6 kbps to 12 Mbps. The
power supply is separate from the bus nodes.
TIA Portal
Totally Integrated Automation Portal
Topology
Structure of a network. Common structures are line topology, ring topology, star topology
and tree topology.
Transmission rate
Specifies the number of bits transmitted per second.
Watchdog
Mechanism for monitoring the readiness for operation.
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PROFIBUS with STEP 7 V13
Function Manual, 12/2014, A5E03775446-AC