Siemens SIMATIC ET 200AL, System Manual

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Glossary
Communication
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Function Manual, 05/2021, A5E03735815-AJ
Modbus RTU
R emote T erminal U nit; Open communications protocol for serial interfaces based on a
master/slave architecture.
Modbus TCP
T ransmission C ontrol P rotocol; Open communications protocol for Ethernet based on a
master/slave architecture. The data are transmitted as TCP/IP packets.
Network
A network consists of one or more interconnected subnets with any number of devices.
Several networks can exist alongside each other.
NTP
The N etwork T ime P rotocol (NTP) is a standard for synchronizing clocks in automation
systems via Industrial Ethernet. NTP uses the connectionless UDP transport protocol for the
Internet.
OPC UA
OPC U nified Automation is a protocol for communication between machines, developed by
the OPC Foundation.
Operating states
Operating states describe the behavior of a single CPU at a specific time.
The CPUs of the SIMATIC standard systems have the STOP, STARTUP and RUN operating
states.
The primary CPU of the redundant system S7-1500R/H has the operating states STOP,
STARTUP, RUN, RUN-Syncup and RUN-Redundant. The backup CPU has the operating states
STOP, SYNCUP and RUN-Redundant.
Operating system
Software that allows the use and operation of a computer. The operating system manages
resources such as memory, input and output devices and controls the execution of programs.
PG
→ Programming device
PNO
→ PROFIBUS user organization