Siemens SIMATIC ET 200AL, System Manual

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Glossary
Communication
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Function Manual, 05/2021, A5E03735815-AJ
Tree topology
Network topology characterized by a branched structure: Two or more bus nodes are
connected to each bus node.
Twisted-pair
Fast Ethernet via twisted-pair cables is based on the IEEE 802.3u standard (100 Base-TX). The
transmission medium is a shielded 2x2 twisted-pair cable with an impedance of 100 Ohms
(22 AWG). The transmission characteristics of this cable must meet the requirements of
category 5.
The maximum length of the connection between the terminal and the network component
must not exceed 100 m. The connectors are designed according to the 100Base-TX standard
with the RJ-45 connector system.
UDP
U ser D atagram P rotocol; communications protocol for fast and uncomplicated data transfer,
without acknowledgment. There are no error checking mechanisms as found in TCP/IP.
User program
In SIMATIC, a distinction is made between the CPU operating system and user programs. The
user program contains all instructions, declarations and data by which a system or process
can be controlled. The user program is assigned to a programmable module (for example,
CPU, FM) and can be structured in smaller units.
USS
Universal Serial Interface protocol ( U niverselles S erielles S chnittstellen-Protokoll); defines an
access method according to the master-slave principle for communication via a serial bus.
Web server
Software/communications service for data exchange via the Internet. The web server
transfers the documents using standardized transmission protocols (HTTP, HTTPS) to a Web
browser. Documents can be static or put together dynamically from different sources by the
web server on request from the Web browser.