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Field devices, decentralized periphery, subordinate
Controls, gateway to PROFIBUS PA
Figure 3-15
The figure shows a section of a typical PROFIBUS automation system. The control system
consists of two masters with distributed tasks.
The class-1 master recognizes the control and regulation tasks. The class-2 master enables
the operating and monitoring functions. Between the class-1 master and the field devices
there is a periodic exchange of measurement and settings data. The status information from
the field devices is transmitted parallel to this data, and evaluated in the class-1 master.
Parameterization of the field devices or the readout of additional device information is not
performed during periodic operation.
Besides periodic operation, one or more class-2 masters can access the field devices
asynchronously. Using this type of communication, additional information can be retrieved
from the devices or settings sent to them.
3.6.4
Properties
PROFIBUS PA enables the bidirectional communication of a bus master with field devices.
At the same time, the shielded two-strand wiring provides auxiliary power to the two-wire
field devices.
3.6.5
Profile
As an extension to the EN 50170 standard, the PROFIBUS user organization (PNO) defined
the functionality of the individual field device types in a so-called profile description. This
profile determines minimum functional requirements and optional extensions. The device-
internal "Device Management" provides the configuration tool of the control system with all
SIPART PS2 with PROFIBUS communication
Operating Instructions, 09/2007, A5E00127926-07
Class-1 master
(Klasse 1)
PROFIBUS DP
Functional principle of the PROFIBUS automation system
Class-2 master
PROFIBUS PA
Description
3.6 PROFIBUS PA
33
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