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Section 2 Transmission Technology
PROFIBUS is an industrial communication system that uses a range of media such
as copper cable, fibre optics or wireless, with bit-serial transmission for coupling
smart field devices to a control system.
This chapter describes the transmission technologies mostly used in connection with
the AC 800M Controller. PROFIBUS provides different transmission technologies,
based on international standards such as IEC 61158 and IEC 61784, which
describes the digital data communications for measurement and control in fieldbus
networks.
RS485 Transmission Technology
RS485 is the most commonly used transmission technology for PROFIBUS DP. It
uses a shielded twisted pair copper cable and enables transmission rates up to 12
Mbit/s. Because of its simply installation it is cost-effective and requires no expert
knowledge.
The bus structure allows adding or removing of field devices as well as step by step
commissioning without influencing the system. Later extensions have no impact on
devices that are already working on the bus. RS485 is scalable in its transmission
rate from 9,6 kbit/s up to 12 Mbit/s, which is set in the PROFIBUS master.
AC 800M and CI854(A)
In connection with the AC 800M Controller, the Communication Interface
CI854(A) interacts as PROFIBUS master and builds up a PROFIBUS network with
RS 485 technology. Up to 12 CI854(A) modules can be placed at one AC 800M
Controller and each interface works as a single PROFIBUS master, which can be
configured with its own transmission rate. Supported transmission rates are 9.6;
19.2; 93.75; 187.5; 500; 1500; 3000; 6000 and 12000 kbit/s. Not support are the
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