Siemens SIMATIC ET 200M Operating Instructions Manual page 13

Product overview
1.1 What Are Distributed I/O Devices
Area of application
When a system is set up, it is common for the inputs to and outputs from the process to be
incorporated centrally in the automation system.
If there are inputs and outputs at considerable distances from the programmable controller,
there may be long runs of cabling which are not easy to follow, and electromagnetic
interference may impair reliability.
Distributed I/O devices are the ideal solution for such systems:
● the control CPU is located at a central location
● The I/O devices (inputs and outputs) operate locally on a distributed basis.
● the powerful PROFIBUS DP with high data transmission speed ensures that the control
● PROFINET IO
1.2 What is PROFIBUS DP?
What is PROFIBUS DP?
PROFIBUS DP is an open bus system in accordance with the standard
IEC 61784-1:2002 Ed1 CP 3/1 with the transmission protocol "DP" (DP is the abbreviation of
the German term "dezentrale Peripherie" (distributed I/O).
Physically, the PROFIBUS DP is either an electric network based on a shielded two-wire line
(RS 485) or an optical network based on a fiber-optic cable (FOC).
The transmission protocol "DP enables a fast, cyclic data exchange between the control
CPU and the distributed I/Os.
What are the DP master and DP slaves?
The DP master is the connecting link between the control CPU and the distributed I/Os. The
DP master exchanges the data via the PROFIBUS DP with the distributed I/Os and monitors
the PROFIBUS DP.
The distributed I/Os (= DP slaves) prepare the data of the encoder and the actuators on site
in such a way that they can be transmitted via the PROFIBUS DP to the control CPU.
ET 200M
Operating Instructions, 12/2008, EWA-4NEB780600602-08
CPU and the I/O devices communicate smoothly.
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